Thus at the time being, achieving the maximal possible Doppler performance is the responsibility for the radar circuits, which should ensure as much as possible tight control of magnetro
Trang 2In
de
4
4.1
Le
op
the
on
con
spa
the
coo
dim
sig
att
to
me
Th
is s
key
sho
in
fre
ov
me
Fig
RF Pulse Jitter
PRF
Supply Voltag
Current consu
Weight
Dimensions
able VI Parameter
the next section
scribed briefly
Magnetron ba
1 General consid
t us to remind br
perational mode i
e spectrum of RF
n the parameters
nceptually in loca
ace of signal para
e simplest case
ordinates of amp
mensions should
gnal in the space
tending the magn
provide a precise
easurement capab
he most evident b
simply to measu
y issue to imple
ould be provided
order to measur
equency is next i
verall radar perfo
easured
g 5 Typical block
r
ge min umption, max @ 28
rs of W band sho
n some design
ased radars – d deration
riefly that any m
s used; (ii) each R oscillation depen
of external micro ating the received ameters dependin
of non-coheren plitude and time r
be added In tru
of signal param netron utilization
e location of radi bilities of the rada but comprehensiv
re its parameters ement Doppler p
d with correspond
re its parameters important param ormance At first
k-diagram of mag
ns kHz
V
kg
ort pulse magnetr approaches used
design approac
agnetron based r
RF pulse is chara nds strongly on a owave circuits O
d signal as respec
ng of the radar m
nt pulsed radar respectively For uly coherent rada meters is known a
in the radars req iated signal in su
ar
ve method to ens
s It is the only w processing Thus ding circuits to sa
s like it is depicte meter, whose mea
t, it determines h
gnetron based rad
19”
on transmitter
d in the above
ches
radar is featured acterized by an ar
a shape of modula
On other hand, ra
ct to the radiated measurement capa this space is tw Doppler radar th
ar systems the exa
a priori Instead, quire introduction uch space and ext ure exact location way to get phase i each magnetron ample a small po
ed in Fig 5 The asurement accura how precisely a
dar
3 3…30 18…32 14.1
25
”, 5U unit
mentioned rada
as follows: (i) a p rbitrary phase; an ation voltage as w adar operation co one in a correspo abilities For exam
wo dimensional,
he phase and freq act location of ra the above peculi
n of specific appro tend its dimensio
n of the radiated information, whi
n based Doppler ortion of radiated
e magnetron osci acy affects strong target velocity c
ars are
pulsed
nd (iii) well as onsists onding mple in , with quency adiated iarities oaches ons, i.e
signal ich is a
r radar signal illation gly the can be
It does not require a great accuracy and may be implemented relatively easily Practically in the most cases no measurements are required at all due to a specified magnetron frequency deviation does not exceed a portion of percent in the worst case A different matter is a pulse-to-pulse frequency deviation This parameter introduces both non-coherent (noise) and regular components (spurs) into Doppler signal processing (see Fig 3) In part it determines the ability of the radar to resolve targets with different velocities and reflectivity
in the same range bin, e.g clouds in a strong rain or a moving target in presence of a much stronger reflection from a clutter As it has been exposed above, the magnetron frequency should be measured with accuracy of about 10-7 for a period of several hundred nanoseconds typically or even less, if a higher spatial resolution is required, in order to provide 70 dB spectral dynamical range for Ka band radar and the distance of 5 km The indicated accuracy is on the edge of contemporary technical capabilities or beyond them, not even to mention the situation inherent to very recent time Thus at the time being, achieving the maximal possible Doppler performance is the responsibility for the radar circuits, which should ensure as much as possible tight control of magnetron operational parameters – voltage, filament, loading etc, and, finally, its frequency stability In the nearest future due to
a dramatically fast progress in the development of data acquisition and processing hardware we expect that precise measurements of the parameters of the radiated pulse will
be a basic method defining radar resolution and instrumentation capabilities Some promising prospects concerned to this possibility will be discussed later (see Section 4.3.5 ) Below in this section we will try to analyze requirements to high performance magnetron based radar and discuss some methods to meet them
4.2 Transmitter
4.2.1 General consideration
As mentioned above the modern requirements to the radar performance cannot be met otherwise than designing the magnetron environment to ensure as much as possible stability and safety of its operation Therefore, the transmitter is probably the most valuable part of either magnetron based high performance radar Before we will proceed to discuss some design approaches used in the transmitters, let us make a simple calculation in order
to give an impression about how precisely its circuits should work Assume that the aforementioned value of pulse-to-pulse frequency stability ߜ݂Ȁ݂ of 10-7 should be provided The variations of the amplitude of voltage pulse across magnetron should not exceed value given by the following expression:
οܸ ೞ
ி ೡȉ ቀఋ
where ݂௦ is a magnetron oscillation frequency, ܨ௩௧ – a magnetron oscillation frequency pushing factor, ܴௗ - a dynamical resistance of the magnetron in an operational point, i.e the slope of its volt-ampere characteristic in this point Let us take into consideration Ka band magnetron and suggest that the magnetron frequency pushing factor is of 500 kHz/A – a very respectable value, inherent to a highly stable coaxial magnetron rather than any other type, and a dynamical resistance of 300 Ohms – a typical value for devices with 10-100 kW peak power Then the above expression gives an impressive value of about 2 V, or less than
200 ppm typically, for the required value of pulse-to-pulse amplitude instability of magnetron anode voltage! Note, that the indicated value should be ensured during the
Trang 3In
de
4
4.1
Le
op
the
on
con
spa
the
coo
dim
sig
att
to
me
Th
is s
key
sho
in
fre
ov
me
Fig
RF Pulse Jitter
PRF
Supply Voltag
Current consu
Weight
Dimensions
able VI Parameter
the next section
scribed briefly
Magnetron ba
1 General consid
t us to remind br
perational mode i
e spectrum of RF
n the parameters
nceptually in loca
ace of signal para
e simplest case
ordinates of amp
mensions should
gnal in the space
tending the magn
provide a precise
easurement capab
he most evident b
simply to measu
y issue to imple
ould be provided
order to measur
equency is next i
verall radar perfo
easured
g 5 Typical block
r
ge min umption, max @ 28
rs of W band sho
n some design
ased radars – d deration
riefly that any m
s used; (ii) each R oscillation depen
of external micro ating the received ameters dependin
of non-coheren plitude and time r
be added In tru
of signal param netron utilization
e location of radi bilities of the rada
but comprehensiv
re its parameters ement Doppler p
d with correspond
re its parameters important param ormance At first
k-diagram of mag
ns kHz
V
kg
ort pulse magnetr approaches used
design approac
agnetron based r
RF pulse is chara nds strongly on a owave circuits O
d signal as respec
ng of the radar m
nt pulsed radar respectively For uly coherent rada meters is known a
in the radars req iated signal in su
ar
ve method to ens
s It is the only w processing Thus ding circuits to sa
s like it is depicte meter, whose mea
t, it determines h
gnetron based rad
19”
on transmitter
d in the above
ches
radar is featured acterized by an ar
a shape of modula
On other hand, ra
ct to the radiated measurement capa this space is tw
Doppler radar th
ar systems the exa
a priori Instead, quire introduction
uch space and ext ure exact location
way to get phase i each magnetron ample a small po
ed in Fig 5 The asurement accura how precisely a
dar
3 3…30
18…32 14.1
25
”, 5U unit
mentioned rada
as follows: (i) a p rbitrary phase; an ation voltage as w
adar operation co one in a correspo abilities For exam
wo dimensional,
he phase and freq act location of ra the above peculi
n of specific appro tend its dimensio
n of the radiated information, whi
n based Doppler ortion of radiated
e magnetron osci acy affects strong
target velocity c
ars are
pulsed
nd (iii) well as onsists onding mple in , with quency adiated iarities oaches ons, i.e
signal ich is a
r radar signal illation gly the can be
It does not require a great accuracy and may be implemented relatively easily Practically in the most cases no measurements are required at all due to a specified magnetron frequency deviation does not exceed a portion of percent in the worst case A different matter is a pulse-to-pulse frequency deviation This parameter introduces both non-coherent (noise) and regular components (spurs) into Doppler signal processing (see Fig 3) In part it determines the ability of the radar to resolve targets with different velocities and reflectivity
in the same range bin, e.g clouds in a strong rain or a moving target in presence of a much stronger reflection from a clutter As it has been exposed above, the magnetron frequency should be measured with accuracy of about 10-7 for a period of several hundred nanoseconds typically or even less, if a higher spatial resolution is required, in order to provide 70 dB spectral dynamical range for Ka band radar and the distance of 5 km The indicated accuracy is on the edge of contemporary technical capabilities or beyond them, not even to mention the situation inherent to very recent time Thus at the time being, achieving the maximal possible Doppler performance is the responsibility for the radar circuits, which should ensure as much as possible tight control of magnetron operational parameters – voltage, filament, loading etc, and, finally, its frequency stability In the nearest future due to
a dramatically fast progress in the development of data acquisition and processing hardware we expect that precise measurements of the parameters of the radiated pulse will
be a basic method defining radar resolution and instrumentation capabilities Some promising prospects concerned to this possibility will be discussed later (see Section 4.3.5 ) Below in this section we will try to analyze requirements to high performance magnetron based radar and discuss some methods to meet them
4.2 Transmitter
4.2.1 General consideration
As mentioned above the modern requirements to the radar performance cannot be met otherwise than designing the magnetron environment to ensure as much as possible stability and safety of its operation Therefore, the transmitter is probably the most valuable part of either magnetron based high performance radar Before we will proceed to discuss some design approaches used in the transmitters, let us make a simple calculation in order
to give an impression about how precisely its circuits should work Assume that the aforementioned value of pulse-to-pulse frequency stability ߜ݂Ȁ݂ of 10-7 should be provided The variations of the amplitude of voltage pulse across magnetron should not exceed value given by the following expression:
οܸ ೞ
ி ೡȉ ቀఋ
where ݂௦ is a magnetron oscillation frequency, ܨ௩௧ – a magnetron oscillation frequency pushing factor, ܴௗ - a dynamical resistance of the magnetron in an operational point, i.e the slope of its volt-ampere characteristic in this point Let us take into consideration Ka band magnetron and suggest that the magnetron frequency pushing factor is of 500 kHz/A – a very respectable value, inherent to a highly stable coaxial magnetron rather than any other type, and a dynamical resistance of 300 Ohms – a typical value for devices with 10-100 kW peak power Then the above expression gives an impressive value of about 2 V, or less than
200 ppm typically, for the required value of pulse-to-pulse amplitude instability of magnetron anode voltage! Note, that the indicated value should be ensured during the
Trang 4ma
No
or
dia
hig
con
tha
ma
Fig
tra
the
4.2
Th
sta
ma
A
(PW
inh
pro
cha
uti
ba
uti
mo
ass
vo
mu
com
uti
fac
Fo
Do
de
PW
terval of data acc
ay vary within th
ow, when a refere
other, it is possib
agram of a transm
gh voltage powe
ntroller Let us le
at it handles oth
agnetron operatio
g 6 Block-diagra
ansmitter with re
e magnetron perf
2.2 High voltage
he high voltage p
ability, i.e Doppl
atter of the highes
switching mode
WM) converter, c
herent high effici
ovided by such s
aracteristics of P
ilization Our exp
sed radars demo
ilize operation in
ode Such approa
sists maximizing
ltage regulation l
ultiple to the p
mpletely the inf
ilization of a par
ctor corrector for
r information, th
oppler performan
veloped accordin
WM converter Fr
cumulation for Fo
he range from tens ence point for the ble to consider so mitter is depicted
er supply; (ii) a eave the latter un her units accordin onal mode as wel
am of magnetron emote control and formance, thus w
power supply
ower supply det ler performance o
st priority under
e power supply, cannot be alterna iency, small dime supply is lower g PWM converter m perience to devel onstrates a benefi either peak curre ach as well as the both rejection of loop Next, it is m pulse repetition fluence of rippl rticular pre-regul
AC powered sys
he line of Ka b nce (see Section
ng strictly to the rom our opinion,
ourier processing
s millisecond up
e magnetron tran olutions enabling
d in Fig 6 It incl modulator; (iii) nit beyond a mor
ng the procedure
ll as provides the
transmitter
d diagnostics abi
e would like to o
ermines essential
of whole radar T the development , based on the u ated to produce h ensions, and ligh generally than th may be improve lop the high volt
t of the following ent or close to it m
e usage of a frequ
f the input voltag mandatory to syn frequency of th les at PWM op ator is preferably tems is virtually band meteorologi 0) is equipped above recommen , such topology i
g As usual the d
to several portion nsmitter design is
g its consummatio ludes the followi
a filament pow
re detailed consid
es ensuring the m
ilities Other abo utline their desig
lly the short term Thus ensuring its
t
utilization of pu high voltage in m
ht weight Howev hat of linear regu
d to an extent a tage power supp
g rules At first, P mixed mode rath uency compensate
ge ripples and the nchronize PWM c
he radar, which erational frequen
y In this respect compulsorily
ical radar demo with the high ndations A flyba
is the most suita
duration of this in
ns of second
indicated in som
on A simplified ing essential unit wer supply; and deration, mentio most optimal an
ove units affect d
gn in more detail
m magnetron freq
s maximal stabili ulse width modu modern systems ver the voltage st ulators On other allowing its stand plies for the magn PWM converter s her than in pure v
ed high voltage d
e overall stability onverter at a freq eliminates prac ncy And at las
t, the usage of a onstrating a very voltage power s
ck topology is us ble to the high v
nterval
me way block-ts: (i) a (iv) a
n only
nd safe
directly
quency ity is a ulation due to tability hand, dalone netron should voltage divider
y of the quency ctically
st, the power
y solid supply sed for voltage
ap rad
is wi sw sup hig Fig hig op
4.2
In hig inc the de de sen mi cha ma mo me dra sho con pu No mu pu ma wh
Fig
plications with th dar systems or ev used The essent ithin a wide rang wing across the p pply voltage Th
gh voltage power
g 3 there is no r
gh voltage powe perational frequen
2.3 Modulator
this section we w
gh voltage mod cludes circuits to
e most cases a velopment Since viation of the p nsitivity Thus, b inimized Especia aracterized by a agnetrons requir odulation pulse t ean better! An op awn to ensure its ould be taken i nsiderable thresh ulse through the otice that at lowe uch greater as re ulse duration and agnetron perform hile a pulse repeti
g 7 Waveforms o
he output power ven airborne DC tial advance of su
ge of output pow primary winding
he above peculiar
r supply in a ma egular spurious
er supply at the ncy of PWM conv
will consider brief ulators used in form the pulse w near-rectangle s
e the magnetron pulse shape from both transients a ally it is importan rather short widt res a well contr
to facilitate runni pposite situation a
s appropriately s into consideratio hold current to pr magnetron may
er voltages the po espect to anode p
d higher pulse r mance Thus the ition rate greater
of voltage pulse a
r up to 1 kW and powered radars uch scheme is a wer as well as th
s of the high vo rities meet perfec agnetron based tr components cau harmonics of bo verter (folded)
fly some issues r high performan with a definite sh shape of RF pu frequency depen
m the rectangula and the distortio
nt for the millime
th of the output rollable voltage ing oscillation (O appears for the tr short duration H
on there It is d roduce RF oscilla
y be much longe ower of back bom power as indicat repetition rate th above issue shou than several kilo
across magnetron
d voltages up to 2
if an appropriate stable operation
he ability to prov oltage transforme ctly actual operat ransmitters As c sed by ripples of oth AC power l
elated to the dev nce radars In g hape across the m ulse is a target nds strongly on th
ar one results in
ns of flat part o eter wavelengths pulse On other h rate during the Okress, 1961) In th railing edge As u However, not only due to the magn ation as usual It
er than RF pulse mbardment of the ted in Fig 7 Evi
he stronger the a uld be always ta ohertz is required
n and RF envelope
20 kV for AC po
e step-up pre-reg with a capacitiv vide the output v
er much greater tional conditions can be easily seen
f the output volt line frequency an
velopment of up-t general the mod magnetron termin under the mod
he applied voltag
n a drop in the
of the pulse shou magnetrons, whi hand the most ty
e leading edge his case faster do usual a less atten
y shape of RF env netrons have a means that the c
as depicted in
e magnetron cath idently, the shor above effect affec aken into conside
e
owered gulator
ve load voltage than a
of the
n form tage of
nd the
to date dulator nals In dulator
ge, any radar uld be ich are ypes of
of the oes not ntion is velope rather current Fig 7 hode is rter RF cts the eration
Trang 5ma
No
or
dia
hig
con
tha
ma
Fig
tra
the
4.2
Th
sta
ma
A
(PW
inh
pro
cha
uti
ba
uti
mo
ass
vo
mu
com
uti
fac
Fo
Do
de
PW
terval of data acc
ay vary within th
ow, when a refere
other, it is possib
agram of a transm
gh voltage powe
ntroller Let us le
at it handles oth
agnetron operatio
g 6 Block-diagra
ansmitter with re
e magnetron perf
2.2 High voltage
he high voltage p
ability, i.e Doppl
atter of the highes
switching mode
WM) converter, c
herent high effici
ovided by such s
aracteristics of P
ilization Our exp
sed radars demo
ilize operation in
ode Such approa
sists maximizing
ltage regulation l
ultiple to the p
mpletely the inf
ilization of a par
ctor corrector for
r information, th
oppler performan
veloped accordin
WM converter Fr
cumulation for Fo
he range from tens ence point for the ble to consider so mitter is depicted
er supply; (ii) a eave the latter un
her units accordin onal mode as wel
am of magnetron emote control and
formance, thus w
power supply
ower supply det ler performance o
st priority under
e power supply, cannot be alterna
iency, small dime supply is lower g PWM converter m
perience to devel onstrates a benefi
either peak curre ach as well as the
both rejection of loop Next, it is m
pulse repetition fluence of rippl
rticular pre-regul
AC powered sys
he line of Ka b nce (see Section
ng strictly to the rom our opinion,
ourier processing
s millisecond up
e magnetron tran olutions enabling
d in Fig 6 It incl modulator; (iii)
nit beyond a mor
ng the procedure
ll as provides the
transmitter
d diagnostics abi
e would like to o
ermines essential
of whole radar T the development
, based on the u ated to produce h ensions, and ligh
generally than th may be improve
lop the high volt
t of the following ent or close to it m
e usage of a frequ
f the input voltag mandatory to syn frequency of th les at PWM op ator is preferably
tems is virtually band meteorologi
0) is equipped above recommen , such topology i
g As usual the d
to several portion nsmitter design is
g its consummatio ludes the followi
a filament pow
re detailed consid
es ensuring the m
ilities Other abo utline their desig
lly the short term Thus ensuring its
t
utilization of pu high voltage in m
ht weight Howev hat of linear regu
d to an extent a tage power supp
g rules At first, P mixed mode rath
uency compensate
ge ripples and the nchronize PWM c
he radar, which erational frequen
y In this respect compulsorily
ical radar demo with the high
ndations A flyba
is the most suita
duration of this in
ns of second
indicated in som
on A simplified ing essential unit wer supply; and deration, mentio most optimal an
ove units affect d
gn in more detail
m magnetron freq
s maximal stabili ulse width modu
modern systems ver the voltage st
ulators On other allowing its stand
plies for the magn PWM converter s
her than in pure v
ed high voltage d
e overall stability onverter at a freq eliminates prac ncy And at las
t, the usage of a onstrating a very
voltage power s
ck topology is us ble to the high v
nterval
me way
block-ts: (i) a (iv) a
n only
nd safe
directly
quency ity is a ulation due to tability hand, dalone netron should voltage divider
y of the quency ctically
st, the power
y solid supply sed for voltage
ap rad
is wi sw sup hig Fig hig op
4.2
In hig inc the de de sen mi cha ma mo me dra sho con pu No mu pu ma wh
Fig
plications with th dar systems or ev used The essent ithin a wide rang wing across the p pply voltage Th
gh voltage power
g 3 there is no r
gh voltage powe perational frequen
2.3 Modulator
this section we w
gh voltage mod cludes circuits to
e most cases a velopment Since viation of the p nsitivity Thus, b inimized Especia aracterized by a agnetrons requir odulation pulse t ean better! An op awn to ensure its ould be taken i nsiderable thresh ulse through the otice that at lowe uch greater as re ulse duration and agnetron perform hile a pulse repeti
g 7 Waveforms o
he output power ven airborne DC tial advance of su
ge of output pow primary winding
he above peculiar
r supply in a ma egular spurious
er supply at the ncy of PWM conv
will consider brief ulators used in form the pulse w near-rectangle s
e the magnetron pulse shape from both transients a ally it is importan rather short widt res a well contr
to facilitate runni pposite situation a
s appropriately s into consideratio hold current to pr magnetron may
er voltages the po espect to anode p
d higher pulse r mance Thus the ition rate greater
of voltage pulse a
r up to 1 kW and powered radars uch scheme is a wer as well as th
s of the high vo rities meet perfec agnetron based tr components cau harmonics of bo verter (folded)
fly some issues r high performan with a definite sh shape of RF pu frequency depen
m the rectangula and the distortio
nt for the millime
th of the output rollable voltage ing oscillation (O appears for the tr short duration H
on there It is d roduce RF oscilla
y be much longe ower of back bom power as indicat repetition rate th above issue shou than several kilo
across magnetron
d voltages up to 2
if an appropriate stable operation
he ability to prov oltage transforme ctly actual operat ransmitters As c sed by ripples of oth AC power l
elated to the dev nce radars In g hape across the m ulse is a target nds strongly on th
ar one results in
ns of flat part o eter wavelengths pulse On other h rate during the Okress, 1961) In th railing edge As u However, not only due to the magn ation as usual It
er than RF pulse mbardment of the ted in Fig 7 Evi
he stronger the a uld be always ta ohertz is required
n and RF envelope
20 kV for AC po
e step-up pre-reg with a capacitiv vide the output v
er much greater tional conditions can be easily seen
f the output volt line frequency an
velopment of up-t general the mod magnetron termin under the mod
he applied voltag
n a drop in the
of the pulse shou magnetrons, whi hand the most ty
e leading edge his case faster do usual a less atten
y shape of RF env netrons have a means that the c
as depicted in
e magnetron cath idently, the shor above effect affec aken into conside
e
owered gulator
ve load voltage than a
of the
n form tage of
nd the
to date dulator nals In dulator
ge, any radar uld be ich are ypes of
of the oes not ntion is velope rather current Fig 7 hode is rter RF cts the eration
Trang 6de
pa
the
ou
mo
uti
A
lin
bo
Fig
Th
con
als
cur
in
uti
(iii
bre
ov
pro
Ho
the
pu
du
sig
no
sen
ma
tra
uti
to
all
rad
ma
An
wi
fro
ow, when the ess
sign approaches
rts: (i) energy sto
e magnetron wit
utput and the ma
odulator types be
ilized practically
simplified
block-ne arranged as a p
th to store energy
g 8 Block diagram
he utilization of
ntrolled devices l
so thyristors or
rrents and voltag
general; and do
ilization of the ste
i) practically com
eakdown due to
verall complexity
obably the lowes
owever there are
e usage of a lum
ulse Next, it is pr
uration Further, t
gnificant distortio
onlinearity of ma
nsitivity from th
atching the impe
ailing edge of th
ilizing modulator
be used in the hi
mentioned disad
dar performance
agnetron based sy
nother type of hi
ith partial dischar
om the line mod
sential requireme
to meet them can orage; (ii) a switc thin definite tim agnetron; and (vi eing in use, a line exclusively in ma -diagram of a lin piece of cable or a
y and to form the
m of line modula line modulators like a hard tubes thyratrons, whic
ges (MOSFET vs
o not require a ep-up transforme mplete cancellati the total energy s and total cost o
t as compared wi
a number of serio mped element dela ractically impossi the inherent utili ons of the modu gnetron volt-amp
he voltage rate a edances of the d
he modulation pu
rs equipped with
gh performance r dvantages of the
e only and caus ystems
igh voltage modu rge (Sivan, 1994) dulator is only a
ents to the modu
n be discussed E
ch or switches, w
me intervals only i) protection and
e modulator and agnetron transmi
e modulator is d assembled from lu
e trailing edge of t
ator
provides the fo
or MOSFETs may
ch are rated fun thyristors compa precise shape o
er to match the im ion of the possib stored in the dela
of a transmitter ith other types
ous disadvantage
ay line leads us t ible to implemen ization of the tra ulator output pu pere characteristi across the magne delay line and th ulse Both nume
h a transformer pr radars On other line modulators
se no problems ulator used to dr The essential d
a small part of e
ulator circuits hav Either modulator which provides a y; (iii) circuits to
d decoupling circ
a modulator wit itters (Sivan, 1994 depicted schemati ump inductors an the pulse across m
ollowing advanta
y be used in the h ndamentally to arison); demonstr
of triggering pul mpedances of del ble magnetron d
ay line is limited
equipped with t
es of such type of
to oscillations ap
t smooth regulati ansformer results ulse especially du
ic as well as pos etron (Okress, 19
he magnetron d rical simulation revent us to reco hands it should b are important to
in a variety of rive magnetrons ifference of such energy accumula
ve been outlined, contains the foll applying voltage match the mod uits From a vari
th partial dischar 4)
ically in Fig 8 A
nd capacitors is u magnetron
ages: (i) not only high voltage swit work at much rate a greater effi se; (ii) the man
ay line and magn damage in the c All above result the line modulat
f modulator The ppear at flat part ing of the output
s in the introduct
ue to there is a ssible appearance 961) It makes d uring the leadin and the experie ommend such app
be accepted that a
o achieve the max simple and low
is so called mod
h type of the mod ated in an appro
, some lowing across dulator iety of rge are
A delay used as
y fully tch but higher iciency datory netron;
case of
t in the tor are first is
of the
t pulse tion of strong
e of its ifficult
ng and ence of proach almost ximum
w cost dulator dulator opriate
sto ma uti pu
A ba dis fre
is bia mo
a s
to
Fig
A po dis com ord res cho
a p mo com gen pa com pa wi on 200
A
in po con ad de
orage is used to f agnetron modula ilization of match ulse than the line m variety of varian sic configuration sadvantages prov equently than oth
a great advantag
as power supplie odulator design T stack of transistor drive each transi
a)
g 9 Schemes of th resistor or choke ower supply dur stortions of mag mponent with fr der to decrease sistor should be oke is used instea possibility to prod odulator supply v mponent, the out nerally, there are rameters taking mponent is bulk rts of the modula ith inductive deco nly if retrieving of 02)), such scheme simplified block-Fig 9.b The only ower supply and nceptually in this ditional resistor picted in Fig 9.b
form the output ators exclusively
hing circuitry con modulator
nts can be used t
ns are depicted vided by each o her configurations
ge for whichever
s for the modulat This issue is not s
rs connected in se stor independent
he modulator wit
e may be used to ing interval of p gnetron pulse du requency depend duration of the chosen small en
ad the resistor, th duce the output voltage Howeve tput pulse distort
e big constructiv into account it i
ky and characteri ator Thus we wo oupling in mode
f very short pulse
e may appear to b -diagram of the m
y capacitor may b storage capacito
s case Neverthel
to decrease the d
b by a dash line I
pulse A capacit Due to such typ nceptually it prov
to build the mod
in Fig 9 Let
of them The fir
s It is due to the hard tube based tor tube are grou
so important for eries Actually, a g tly on either the h
b)
th partial dischar
o decouple the s pulse formation
uring its front a dant impedance trailing edge of ough, which resu
he efficiency is be pulse with ampli
r due to the puls tions are higher in
ve difficulties to d
is under high pu ized by a rather ould not like to r ern high performa
es at a high repet
be the most optim modulator with a
be used both as t
r of the modulat less, as mentione duration of the o
It is difficult evid
tor is used as the
e of the modulat vides a much bet dulator with part
us consider br rst scheme is tr high voltage swi
d modulator In th unded also, simpl
a solid state swit galvanic decoupl high voltage switc
rge
switch from the o
In the case of r and flat part ar
is in the pulse the output puls ults in lower mo etter fundamenta itude, which is h
e formation netw
n the case of the c design a chargin ulsed voltage con large weight as recommend the u ance magnetron tition rate is requ mal choice
floating high vol the output capaci tor No decouplin
ed above if a high utput pulse traili dently to use a ha
e energy storage tor does not requ ter shape of the o tial discharge So riefly advantage aditionally used itch is grounded, his case a filamen lifying considerab tch, arranged usu ling is required an
ch is grounded o
c)
output of high v resistor utilizatio
re minimal due formation netwo
e the resistance odulator efficienc ally In addition th higher than the va work includes a re choke utilization
ng choke with req ndition As usua
s compared with utilization of mod based radars Pro uired (see (Belikov ltage switch is de itor of the high v
ng circuits are req
h PRF is suggest ing edge is requi ard tube in such
in the uire the output ome of
es and
d more which
nt and bly the ually as nyway
r not
voltage
on, the
to no ork In
of the
cy If a here is alue of eactive Next, quired
al such
h other dulator obably
v et al, epicted voltage quired ted, an ired as circuit
Trang 7de
pa
the
ou
mo
uti
A
lin
bo
Fig
Th
con
als
cur
in
uti
(iii
bre
ov
pro
Ho
the
pu
du
sig
no
sen
ma
tra
uti
to
all
rad
ma
An
wi
fro
ow, when the ess
sign approaches
rts: (i) energy sto
e magnetron wit
utput and the ma
odulator types be
ilized practically
simplified
block-ne arranged as a p
th to store energy
g 8 Block diagram
he utilization of
ntrolled devices l
so thyristors or
rrents and voltag
general; and do
ilization of the ste
i) practically com
eakdown due to
verall complexity
obably the lowes
owever there are
e usage of a lum
ulse Next, it is pr
uration Further, t
gnificant distortio
onlinearity of ma
nsitivity from th
atching the impe
ailing edge of th
ilizing modulator
be used in the hi
mentioned disad
dar performance
agnetron based sy
nother type of hi
ith partial dischar
om the line mod
sential requireme
to meet them can orage; (ii) a switc
thin definite tim agnetron; and (vi eing in use, a line
exclusively in ma -diagram of a lin
piece of cable or a
y and to form the
m of line modula line modulators like a hard tubes thyratrons, whic
ges (MOSFET vs
o not require a ep-up transforme
mplete cancellati the total energy s
and total cost o
t as compared wi
a number of serio mped element dela ractically impossi
the inherent utili ons of the modu gnetron volt-amp
he voltage rate a edances of the d
he modulation pu
rs equipped with
gh performance r dvantages of the
e only and caus ystems
igh voltage modu rge (Sivan, 1994)
dulator is only a
ents to the modu
n be discussed E
ch or switches, w
me intervals only i) protection and
e modulator and agnetron transmi
e modulator is d assembled from lu
e trailing edge of t
ator
provides the fo
or MOSFETs may
ch are rated fun thyristors compa
precise shape o
er to match the im ion of the possib stored in the dela
of a transmitter ith other types
ous disadvantage
ay line leads us t ible to implemen
ization of the tra ulator output pu pere characteristi across the magne delay line and th
ulse Both nume
h a transformer pr radars On other
line modulators
se no problems ulator used to dr
The essential d
a small part of e
ulator circuits hav Either modulator which provides a y; (iii) circuits to
d decoupling circ
a modulator wit itters (Sivan, 1994 depicted schemati ump inductors an
the pulse across m
ollowing advanta
y be used in the h ndamentally to
arison); demonstr
of triggering pul mpedances of del ble magnetron d
ay line is limited
equipped with t
es of such type of
to oscillations ap
t smooth regulati ansformer results ulse especially du
ic as well as pos etron (Okress, 19
he magnetron d rical simulation revent us to reco hands it should b
are important to
in a variety of rive magnetrons ifference of such energy accumula
ve been outlined, contains the foll applying voltage match the mod uits From a vari
th partial dischar 4)
ically in Fig 8 A
nd capacitors is u magnetron
ages: (i) not only high voltage swit work at much
rate a greater effi se; (ii) the man
ay line and magn damage in the c
All above result the line modulat
f modulator The ppear at flat part ing of the output
s in the introduct
ue to there is a ssible appearance
961) It makes d uring the leadin and the experie ommend such app
be accepted that a
o achieve the max simple and low
is so called mod
h type of the mod ated in an appro
, some lowing across dulator iety of rge are
A delay used as
y fully tch but higher iciency datory netron;
case of
t in the tor are first is
of the
t pulse tion of strong
e of its ifficult
ng and ence of proach almost ximum
w cost dulator dulator opriate
sto ma uti pu
A ba dis fre
is bia mo
a s
to
Fig
A po dis com ord res cho
a p mo com gen pa com pa wi on 200
A
in po con ad de
orage is used to f agnetron modula ilization of match ulse than the line m variety of varian sic configuration sadvantages prov equently than oth
a great advantag
as power supplie odulator design T stack of transistor drive each transi
a)
g 9 Schemes of th resistor or choke ower supply dur stortions of mag mponent with fr der to decrease sistor should be oke is used instea possibility to prod odulator supply v mponent, the out nerally, there are rameters taking mponent is bulk rts of the modula ith inductive deco nly if retrieving of 02)), such scheme simplified block-Fig 9.b The only ower supply and nceptually in this ditional resistor picted in Fig 9.b
form the output ators exclusively
hing circuitry con modulator
nts can be used t
ns are depicted vided by each o her configurations
ge for whichever
s for the modulat This issue is not s
rs connected in se stor independent
he modulator wit
e may be used to ing interval of p gnetron pulse du requency depend duration of the chosen small en
ad the resistor, th duce the output voltage Howeve tput pulse distort
e big constructiv into account it i
ky and characteri ator Thus we wo oupling in mode
f very short pulse
e may appear to b -diagram of the m
y capacitor may b storage capacito
s case Neverthel
to decrease the d
b by a dash line I
pulse A capacit Due to such typ nceptually it prov
to build the mod
in Fig 9 Let
of them The fir
s It is due to the hard tube based tor tube are grou
so important for eries Actually, a g tly on either the h
b)
th partial dischar
o decouple the s pulse formation
uring its front a dant impedance trailing edge of ough, which resu
he efficiency is be pulse with ampli
r due to the puls tions are higher in
ve difficulties to d
is under high pu ized by a rather ould not like to r ern high performa
es at a high repet
be the most optim modulator with a
be used both as t
r of the modulat less, as mentione duration of the o
It is difficult evid
tor is used as the
e of the modulat vides a much bet dulator with part
us consider br rst scheme is tr high voltage swi
d modulator In th unded also, simpl
a solid state swit galvanic decoupl high voltage switc
rge
switch from the o
In the case of r and flat part ar
is in the pulse the output puls ults in lower mo etter fundamenta itude, which is h
e formation netw
n the case of the c design a chargin ulsed voltage con large weight as recommend the u ance magnetron tition rate is requ mal choice
floating high vol the output capaci tor No decouplin
ed above if a high utput pulse traili dently to use a ha
e energy storage tor does not requ ter shape of the o tial discharge So riefly advantage aditionally used itch is grounded, his case a filamen lifying considerab tch, arranged usu ling is required an
ch is grounded o
c)
output of high v resistor utilizatio
re minimal due formation netwo
e the resistance odulator efficienc ally In addition th higher than the va work includes a re choke utilization
ng choke with req ndition As usua
s compared with utilization of mod based radars Pro uired (see (Belikov ltage switch is de itor of the high v
ng circuits are req
h PRF is suggest ing edge is requi ard tube in such
in the uire the output ome of
es and
d more which
nt and bly the ually as nyway
r not
voltage
on, the
to no ork In
of the
cy If a here is alue of eactive Next, quired
al such
h other dulator obably
v et al, epicted voltage quired ted, an ired as circuit
Trang 8configuration Instead, from our opinion, it is the most preferable scheme to utilize a solid
state high voltage switch
The push-pull scheme of the modulator is depicted in Fig 9, c It provides the tightest
control of the output pulse shape as well as the highest energy efficiency among the
schemes discussed before The expense for that is much more complexity in design as
compared to previous solutions It is one of the reasons why the modulators utilizing such
approach may be found in a very limited number of radars despite its evident advantages
Let us now discuss some issues concerned to the selection of an appropriate electronic
device to build the high voltage switch According to modern tendencies solid state devices
should be considered as first choice while designing any new electronic system Two types
of solid state devices, namely, MOSFETS, and IGBT may be used in magnetron modulators
Despite IGBT are superior generally to MOSFETs as respect to both maximal rated voltage
and current, as well as efficiency provided, they are characterized by a lower switching
speed and an attitude to a second-induced breakdown, which confines the overall reliability
of the modulator Thus, MOSFETs remain the only choice among solid state devices to use
in the magnetron modulators intended for high performance millimeter wavelength radars
featured by rather short operational pulse width
Hard tubes were historically the first devices used to build high voltage modulators in
radars They remain to be utilized widely until now despite a serious competition from solid
state devices A considerably greater robustness should be indicated as an essential reason
High voltage circuitry have a strong attitude to appearance of various local breakdowns,
leakages etc, which are difficult to control and prevent especially for long-term unattended
radar operation Such phenomena stress the modulator parts greatly Energy to destroy a
hard tube is on orders higher than that for any solid state device Next, the only tube can be
used practically always to build any modulator Instead the limitations for currently
available powerful MOSFETs in the maximal rated voltage, makes inevitable utilizing a
stack arranged from many transistors connected in series and, possibly, parallel in order to
achieve the modulator parameter being enough to drive the most magnetrons Utilization of
pulse transformer allows in principle to minimize number of the transistors used but, as
mentioned above, causes considerable pulse distortions Certainly there is a well-known
disadvantage of hard tubes, namely, a limited life time We dare to claim that it may be
considered as almost virtual at the time being The situation is very similar to that
mentioned above for the magnetrons A current state of cathode manufacturing as well
general state of vacuum technique makes expected lifetime of the modulator hard tubes of
several ten thousand hours very realistic These expectations were ascertained completely
by our experience of utilization of hard tube based modulators in the line of meteorological
radars (see Section 3) The above consideration allows us to make a conclusion that despite
of a strong competition from solid state devices, partially MOSFETs, hard tubes are keeping
their positions under development of modern magnetron based radars The only issue may
prevent using them in the modulators, namely, their commercial availability and
assortment, which decreases actually generally at the time being due to, essentially, a
shortage in demand from non-radar application Certainly we do not mean a fantastic
breakthrough in the development of high voltage, high power semiconductor devices,
which makes all hard tubes obsolete at one bout!
It should be noticed that the modulator may operates as either voltage or current source
The latter is conceptually better for any cross-field vacuum tube (Sivan, 1994) On other
hand the introduction of the current mode in the modulator makes its design more complex especially in the case if a short pulse length is required Our experience demonstrates that providing an appropriate stability of the high voltage power supply it is possible to achieve
a great magnetron performance even if the much simpler voltage mode is utilized in the modulator Nevertheless, the development of a modulator, operating in the current mode, remains the greatest challenge a designer faces from our opinion
4.2.4 Magnetron filament and protection circuits
As mentioned in Section 0, keeping an adequate condition of the cathode surface is the most important issue to prolong the magnetron lifetime It depends on the following factors: (i) cathode temperature; (iii) vacuum condition inside the magnetron; (iii) electron back bombardment
The cathode temperature depends both of a filament power applied and the power dissipated on the cathode due to its back bombardment This temperature should be kept within a rather narrow interval of several tens degrees typically Thus, the filament power supply should ensure a very tight control of the magnetron filament power as well as provide a dedicated procedure to regulate it depending on the parameters of the magnetron operational mode In the developed radars (see Section 0) the following proven principle is used The filament power supply comprises of two parts, low and high side ones correspondingly The low side part is simply PWM inverter equipped with either analog or digital controller The high side includes a high voltage decoupling transformer, a rectifier, and a dedicated controller It should be noticed that we consider that DC filament voltage should be used to supply magnetron filament due to in this case a possible alternating of the magnetron frequency is canceled The controller is used to measure both filament voltage and current and to transfer the corresponding data to the low side in a digital form An optical link is used for such communication The above approach provides accurate and independent measurement and control of the magnetron filament parameters
The vacuum conditions inside the magnetrons depend not only on quality of manufacturing
routine and materials it is made of Electrical breakdowns affect them strongly In general, it
is considered that the magnetrons demonstrate a rather strong attitude to the development
of breakdowns They may cause in addition direct magnetron damage if no current limiting
is provided by the modulator circuitry It is important for the millimeter wavelengths magnetrons especially due to such magnetrons are characterized by a rather delicate structure of cavities Hard tubes provide inherently such current limitation, which can be regulated moreover MOSFETs are featured similarly, but it is difficult to regulate a limit value due to the high voltage switch consists always of several devices connected in series
As a result, this limit is defined by the maximal rated current of the transistors used Certainly, there is a contradiction between the necessity both to limit the output current and
to ensure a minimal settling time of the output voltage of the modulator
Our experience demonstrates that there is a simple way to prevent possible worsening of the magnetron parameters due to breakdowns without a noticeable degradation in the shape of its output pulse Namely ferrite beads should be connected in series with the magnetron This effect may be explained as follows Breakdown in the magnetron appears usually in two stages The first stage caused by field emission from a tip located somewhere inside magnetron This stage runs very fast, typically during several nanoseconds It cause negligible damages of the magnetron internal parts, but initiates developing the next stage
Trang 9configuration Instead, from our opinion, it is the most preferable scheme to utilize a solid
state high voltage switch
The push-pull scheme of the modulator is depicted in Fig 9, c It provides the tightest
control of the output pulse shape as well as the highest energy efficiency among the
schemes discussed before The expense for that is much more complexity in design as
compared to previous solutions It is one of the reasons why the modulators utilizing such
approach may be found in a very limited number of radars despite its evident advantages
Let us now discuss some issues concerned to the selection of an appropriate electronic
device to build the high voltage switch According to modern tendencies solid state devices
should be considered as first choice while designing any new electronic system Two types
of solid state devices, namely, MOSFETS, and IGBT may be used in magnetron modulators
Despite IGBT are superior generally to MOSFETs as respect to both maximal rated voltage
and current, as well as efficiency provided, they are characterized by a lower switching
speed and an attitude to a second-induced breakdown, which confines the overall reliability
of the modulator Thus, MOSFETs remain the only choice among solid state devices to use
in the magnetron modulators intended for high performance millimeter wavelength radars
featured by rather short operational pulse width
Hard tubes were historically the first devices used to build high voltage modulators in
radars They remain to be utilized widely until now despite a serious competition from solid
state devices A considerably greater robustness should be indicated as an essential reason
High voltage circuitry have a strong attitude to appearance of various local breakdowns,
leakages etc, which are difficult to control and prevent especially for long-term unattended
radar operation Such phenomena stress the modulator parts greatly Energy to destroy a
hard tube is on orders higher than that for any solid state device Next, the only tube can be
used practically always to build any modulator Instead the limitations for currently
available powerful MOSFETs in the maximal rated voltage, makes inevitable utilizing a
stack arranged from many transistors connected in series and, possibly, parallel in order to
achieve the modulator parameter being enough to drive the most magnetrons Utilization of
pulse transformer allows in principle to minimize number of the transistors used but, as
mentioned above, causes considerable pulse distortions Certainly there is a well-known
disadvantage of hard tubes, namely, a limited life time We dare to claim that it may be
considered as almost virtual at the time being The situation is very similar to that
mentioned above for the magnetrons A current state of cathode manufacturing as well
general state of vacuum technique makes expected lifetime of the modulator hard tubes of
several ten thousand hours very realistic These expectations were ascertained completely
by our experience of utilization of hard tube based modulators in the line of meteorological
radars (see Section 3) The above consideration allows us to make a conclusion that despite
of a strong competition from solid state devices, partially MOSFETs, hard tubes are keeping
their positions under development of modern magnetron based radars The only issue may
prevent using them in the modulators, namely, their commercial availability and
assortment, which decreases actually generally at the time being due to, essentially, a
shortage in demand from non-radar application Certainly we do not mean a fantastic
breakthrough in the development of high voltage, high power semiconductor devices,
which makes all hard tubes obsolete at one bout!
It should be noticed that the modulator may operates as either voltage or current source
The latter is conceptually better for any cross-field vacuum tube (Sivan, 1994) On other
hand the introduction of the current mode in the modulator makes its design more complex especially in the case if a short pulse length is required Our experience demonstrates that providing an appropriate stability of the high voltage power supply it is possible to achieve
a great magnetron performance even if the much simpler voltage mode is utilized in the modulator Nevertheless, the development of a modulator, operating in the current mode, remains the greatest challenge a designer faces from our opinion
4.2.4 Magnetron filament and protection circuits
As mentioned in Section 0, keeping an adequate condition of the cathode surface is the most important issue to prolong the magnetron lifetime It depends on the following factors: (i) cathode temperature; (iii) vacuum condition inside the magnetron; (iii) electron back bombardment
The cathode temperature depends both of a filament power applied and the power dissipated on the cathode due to its back bombardment This temperature should be kept within a rather narrow interval of several tens degrees typically Thus, the filament power supply should ensure a very tight control of the magnetron filament power as well as provide a dedicated procedure to regulate it depending on the parameters of the magnetron operational mode In the developed radars (see Section 0) the following proven principle is used The filament power supply comprises of two parts, low and high side ones correspondingly The low side part is simply PWM inverter equipped with either analog or digital controller The high side includes a high voltage decoupling transformer, a rectifier, and a dedicated controller It should be noticed that we consider that DC filament voltage should be used to supply magnetron filament due to in this case a possible alternating of the magnetron frequency is canceled The controller is used to measure both filament voltage and current and to transfer the corresponding data to the low side in a digital form An optical link is used for such communication The above approach provides accurate and independent measurement and control of the magnetron filament parameters
The vacuum conditions inside the magnetrons depend not only on quality of manufacturing
routine and materials it is made of Electrical breakdowns affect them strongly In general, it
is considered that the magnetrons demonstrate a rather strong attitude to the development
of breakdowns They may cause in addition direct magnetron damage if no current limiting
is provided by the modulator circuitry It is important for the millimeter wavelengths magnetrons especially due to such magnetrons are characterized by a rather delicate structure of cavities Hard tubes provide inherently such current limitation, which can be regulated moreover MOSFETs are featured similarly, but it is difficult to regulate a limit value due to the high voltage switch consists always of several devices connected in series
As a result, this limit is defined by the maximal rated current of the transistors used Certainly, there is a contradiction between the necessity both to limit the output current and
to ensure a minimal settling time of the output voltage of the modulator
Our experience demonstrates that there is a simple way to prevent possible worsening of the magnetron parameters due to breakdowns without a noticeable degradation in the shape of its output pulse Namely ferrite beads should be connected in series with the magnetron This effect may be explained as follows Breakdown in the magnetron appears usually in two stages The first stage caused by field emission from a tip located somewhere inside magnetron This stage runs very fast, typically during several nanoseconds It cause negligible damages of the magnetron internal parts, but initiates developing the next stage
Trang 10brought by a local overheating, cooper sputtering, and further arcing This stage requires
much longer time to run but can cause significant degradation of the magnetron
performance
The ferrite beads demonstrate rather high impedance under transient conditions Thus, it
leads to fast decrease in the voltage across magnetron during the first stage of the
breakdown and prevents developing of the second stage Moreover the magnetron keeps
producing RF oscillations as usual There are some more benefits from the utilization of
ferrite beads They restrict the change rate of magnetron current resulting in a great
reduction of electromagnetic interferences and an increase to overall stability of the
transmitter operation In addition such beads may improve the output pulse shape
weakening the influence of stray circuit inductance and capacitance on the pulse front
formation It should be noticed that the usage of ferrite beads is practically mandatory if
MOSFET based high voltage switch is used in the modulator Such devices are characterized
by rather low rated �� ��� capability According to a numerical simulation and experimental
investigations, an excess in this value is an essential reason of transistors damage during
transients in the magnetron
At last, it should be noticed that there are evidences that influence of the cathode back
bombardment is not limited by thermal effects only as mentioned above Change in the
cathode surface condition has been fixed even after single pulses Probably it is due to a very
high value of instantaneous power of the back bombardment, which is about 10 % of anode
power at a nominal anode voltages and much more – up to 30 % - at lower voltages In order
to minimize effect of back bombardment it is necessity to keep the duration of the
modulation pulse trailing edge as shorter as possible (see Section 0)
4.3 Receiver
4.3.1 General consideration
The principles to develop receivers for the magnetron based radars are the same as for any
other systems Nevertheless, we would like to discuss below some design approaches,
which have proven their efficiency in a number of radars developed in the Institute of Radio
Astronomy of National Academy of Sciences of Ukraine
A simplified block-diagram of a full-featured double channel receiver used in the most
modern modifications of Ka band magnetron based meteorological radars (see Section 0) is
depicted in Fig 12 It may be considered as typical and reflecting the essential design
approaches At first, double frequency conversion is used in the receiver It makes the
receiver design more complex apparently, but simplifies greatly the design of local
oscillators as well as allows utilizing a simple filtration to reject image frequency The local
oscillator(s) should meet the following requirements: (i) cover wide enough frequency range
– typical values of possible frequency variation are 500 MHz for Ka band and 700…1000
MHz for W and G band magnetrons respectively; (ii) provide frequency tuning with a
relatively small step; and (iii) ensure a low phase noise with a fast roll-off beyond the band
of ����� 2� ����� 2� �, which corresponds to the unambiguous frequency range of Doppler
processing
Fig Th pro fix osc
If q fre Ne pu evi pro Ins illu fre dis (ii) ph pic Ne sys dir mu
g 10 Block-diagr
he latter is requi ocessing In the c xed frequency, wh cillator with freq quality of Dopple equency conversio ext point we wou ulse to the data ident way is to u ovides the highe stead a signal, le ustrated by Fig
equency only Th sadvantages: (i) a ) as usual the rece hase instability S
ck a sample of the evertheless it wa stems, which use rect comparison uch more design
ram of receiver fo ired to avoid an case of double fre hich makes its de quency multiplier
er processing pro
on simplifies its d uld like to discus acquisition uni use a separate do est possible perfo eaked through th
11 In this case his way is certai
an additional pha eiver circuitry op Several radars ha
e transmitted pul
as worse on sev
e a separate down
is hardly possib details than the m
or magnetron base
n increase in the equency conversi sign relatively sim
r provides enoug ovided by a radar design significant
s is a methods to
t to implement ownconverting ch ormance but req
he receiver protec newly introduce inly much simpl ase jitter may be i perates in a deep ave been develop lse up They dem veral decibels as nconverting chan ble due to the sy method of sampli
ed Doppler radar
e noise floor of ion the first local mple As usual a
gh performance le
r is not an issue, tly (Volkov et al,
o couple a sample coherence-on-re hannel as depicte quires additional ction circuitry, m
ed circuits opera ler but character introduced by an saturation, which ped by utilizing monstrated a solid
s compared wit nnel It should be ystems in consid ing transmitted p
r
coherence-on-re oscillator operat dielectrically stab evel for the most the utilization of 2007)
e of the transmitt eceiver processin
ed in Fig 10 Thi hardware to be may be used in th ate at the interm rized by the foll
n antenna environ
h may cause add the above appro
d Doppler perform
th the performan
e noticed actually deration distingu pulse
eceiver tes at a bilized
t cases single ted RF
ng An
is way
e used
he way mediate lowing nment; ditional oach to mance nce of
y that a uish in