A 180-nm CMOS RF Transmitter for UHF RFID Reader Khanh Nguyen Tuan Analog Group Integrated Circuit Design Research and Education Center ICDREC, Vietnam National University Ho Chi Minh-
Trang 1A 180-nm CMOS RF Transmitter for UHF RFID
Reader
Khanh Nguyen Tuan
Analog Group Integrated Circuit Design Research and Education Center
(ICDREC), Vietnam National University
Ho Chi Minh-City, Vietnam
E-mail: khanh.nguyentuan@icdrec.edu.vn
Cuong Huynh P.M
Department of Telecommunication, Faculty of Electrical
and Electronic Engineering Vietnam National University, University of Technology
Ho Chi Minh-City, Vietnam E-mail: hpmcuong@hcmut.edu.vn
Abstract— This paper presents the design of the RF
transmitter of RFID reader using 180-nm CMOS technology at
868 MHz The design of RF transmitter of RFID reader in this
paper includes up-conversion mixer, balun and class E of power
amplifier These results are maximum output power of 20.34
dBm, OP1dB of 19.3 dBm, PAE of 38.35% and power
consumption of 168.57 mW
Keywords—CMOS; UHF RFID Reader; transmitter; power
amplifier (PA) class E
I INTRODUCTION
Radio frequency identification (RFID) applications are
growing in many areas, such as object tracking systems, access
control and animal identification [1] The RFID reader can
access the information from the tag with the communication
network The RFID system operating at low frequencies (125
kHz or 13.56 MHz) are limited in their distances and data rates
With longer distance and higher data rates, the UHF frequency
band RFID system will be used And to meet the demand of
low cost, long battery life, the CMOS technology is believed to
be the most candidates toward the system on a chip (SoC)
In almost transceivers, the design of RF transmitters for
wireless applications has many challenges such as the number
of off-chip components, the tradeoff between the output power,
the efficiency and the required linearity [2]
This paper presents the design of the RF transmitter of
RFID reader integrated circuit (IC) using 180 nm CMOS
technology at 868MHz following the European
Telecommunications Standard Institute (ETSI EN 302 208) for
RFID at frequency 865 -868 MHz [3] Section II describes the
transmitter architecture Next, the design of PA, Mixer and
balun are provided in Section III Section IV provides the
simulation and layout results The conclusion of this paper is
presented in Section V
II TRANSMITTERARCHITECTURE
Passive tag is the most useful tag in RFID system because it
requires no battery, simple and low cost The communication
between the RFID reader and passive tag are shown in Fig 1
First, the transmitter of RFID reader sends a continuous wave
to the tag for power transfer By using the circulator which has
the isolation between transmitter and receiver, the reader need only one antenna The reader waits for a backscatter signal from the tag and then a connecting was established between reader and tag Next, the reader will send data modulated ASK signal following PIE to the tag, and tag will be returned signal modulated ASK following Miller or FM0 [3]
The choice of transmitter architecture is determined by number of oscillators, external filters, wanted and un-wanted emission… The architecture and frequency planning of the transmitter must be tradeoff with the architecture of the receiver in a transceiver for simple, low power, PLL architecture In direct conversion transmitter, the output carrier frequency is equal to the LO frequency, modulation and up-conversion occur in the same circuit (Fig 2) Direct conversion transmitter architecture is the best choice for high level of integration and system on chip [2]
Fig 1 Communication between RFID reader and passive tag
III CIRCUITSDESIGN The proposed transmitter architecture consists of I/Q up-conversion mixer, balun, driver (class A PA) and power amplifier (class E PA) (Fig 2) The transmitter adopts a direct up-conversion I/Q modulation
Fig 2 Direct Conversion transmitter architecture with I/Q modulation
This work
Trang 2A Power Amplifier
Figure 3 shows a schematic diagram of the two stages
single ended power amplifier The first stage is a class E power
amplifier at switching mode, which designed by Mr Sokal [4,
5] The cascode structure helps the class E have a good
isolation and voltage between the drain and the source is lower
3.56Vdd The bias voltage is approximate the threshold voltage
for good switching The second stage is a linear mode power
amplifier, class A which is designed with the bias voltage
larger than the threshold voltage Resistor R0 and capacitor C0
improve the stability of power amplifier
Fig 3 Schematic of power amplifier class E and driver class A
B Up-Conversion Mixer
The up conversion mixer which shown in Fig 4 is the
Gilbert architecture [6]
Fig 4 Schematic of up-conversion mixer with I/Q modulation
The cascode current mirror (N1 to N3) applied a constant
current for input stage (N4 and N5) [7] The input stage of I
and Q up-conversion mixer are combined to one stage for
simple and high level of integration The baseband signal (Vi)
are up-converted to 868 MHz (Vrf) when combined with an
ideal LO signal At the RF stage, the filter includes L1 and C1
are resonant at center frequency The on chip inductor L1 is
designed and optimized using IE3D EM simulator Resistor R4
and R5 improve the linearity of the mixer
C Balun
To transfer the differential signal from the output of the
mixer to single ended signal of the driver, a balun is proposed
Passive balun has no power consumption, but it takes a large
area because of the coupled spiral inductors Active balun has
very small chip area because it uses transistors There is a
tradeoff between the linearity and power consumption of this balun (Fig 5) [7, 8]
Fig 5 Schematic of active balun using transistor
IV SIMULATION RESULTS This transmitter of UHF RFID reader IC was designed using 180 nm CMOS technology The power, efficiency, gain and linearity are the important parameters of the transmitter The output power of mixer, balun and driver were careful designed for input of the PA To consider the parasitic of inductors, the on chip inductors which used in this paper were designed by IE3D software as figure 6
Fig 6 Onchip inductor designed by IE3D
After connecting all designs and simulation, the layout of them is shown in figure 7 In this layout, the on chip inductors
is exported from IE3D to Cadence by a gds file and the dimension of this transmitter is 2.75x0.87 mm2 All the component is on chip The output and inter stage matching circuits and radio frequency chokes (RFC) are off the chip
Fig 7 Layout of RF transmitter
Table I shows the summarized results in the comparison with the others from published CMOS PA paper With supply voltage of 1.8 V and 2.5 V, the PA has the maximum output power of 21.3 dBm, Power Added Efficiency (PAE) of 38.35%, OP1dB of 20.77 dBm and the Power consumption of
152 mW Figure 9 shows the relationship between PAE and Pout of PA in this paper by using a highly efficient nonlinear
PA combined with a linear PA
Off chip
Trang 3TABLE I SIMULATION RESULTS OF PA
Frequency 868MHz 915MHz 900MHz
Output
OP1dB 20.77dBm 14.5dBm 18.4dBm
PAE 38.35% 32.1% 35.4%
Power
PAPER
The simulation results show that the mixer provides -3.3 dB
of conversion gain and the input referred third order intercept
point (IIP3) of 11.7 dBm (Fig 10), output power at 1dB
compression point (OP1dB) of -5.127 dBm with power
consumption of 6.87 mW only
Fig 8 Output power and PAE of PA
Fig 9 Pout vs PAE of PA
Fig 10 IIP3 of up-conversion mixer
Results of balun have power gain of 17.71 dB and OP1dB
of -2.98 dBm (Fig 11) with power consumption of 9.7 mW
Fig 11 OP1dB of Balun
Finally, all of these blocks are integrated to the RF transmitter RFID reader These results are maximum output power of 20.34 dBm, OP1dB of 19.3 dBm (Fig 12) and power consumption of 168.57 mW in Table II
Fig 12 OP1dB of RF transmitter
The post layout simulation results of this paper are shown
in Table III:
Parameter OP1dB (dBm) Power (dBm) @ 868MHz
Mixer Post Layout Schematic -5.1 -10.89 - - Balun Post Layout Schematic -2.98 -4.48 - -
Technology 0.18μm 0.18μm 0.18μm 0.18μm
Power
consumption
-40 -30 -20 -10 0 10 20 -160
-140 -120 -100 -80 -60 -40 -20 0 20
Pin (dBm) 1st order 868.1MHz
1st order 3rd order
(11.7, 5.43)
IIP3 OIP3
-30 -25 -20 -15 -10 -5 0 6
8 10 12 14 16 18 20 22
Pin (dBm)
Pout
Output power at 1dB compression point (-16.48, 19.301)
1st order 868MHz
-12 -10 -8 -6 -4 -2 0
Pin (dBm)
Pout (-11.25, -2.98974)
(OP1dB) 1st order 868MHz
200.0M 400.0M 600.0M 800.0M 1.0G 1.2G 1.4G 1.6G
-30
-20
-10
0
10
20
Output Power (dBm) PAE (%)
Frequency(Hz)
(868000000, 20.918)
0 10 20 30
40
(868000000, 38.35)
-30 -20 -10 0 10 20
-5
0
5
10
15
20
25
30
35
Pout (dBm) (20.615689967376, 37.245661148089)
Trang 4200.0M 400.0M 600.0M 800.0M 1.0G 1.2G 1.4G 1.6G
-30
-20
-10
0
10
20
Frequency (Hz)
Output Power PA_Schematic Output Power PA_PostLayout
(868000000, 20.918) (868000000, 14.18)
Fig 13 Results of schematic and post-layout simulation of PA
Figure 14 shows the output signal output of each block
Fig 14 Signal waveform of each block in this paper
The results of corner and temperature of Balun, Mixer and
PA are shown in Fig 15, 16, 17, respectively
Fig 15 Results of corner and temperature OP1dB simulation of Balun
Fig 16 Results of corner and temperature OP1dB of Mixer
V CONCLUSION The RF transmitter of UHF RFID reader is designed using
180 nm technology The RF transmitter has 2.75x0.87 mm2 die size while consumes 168.57 mW, the maximum output power
of 20.34 dBm, OP1dB of 19.3 dBm and PAE of 38.35% Output waveform of PA is the ASK The results of Post Layout, efficiency, linearity will be improved and can be used for UHF RFID reader Besides, the external component will affect to all performance, especially the output power of PA It’s essential to quantify the effects that package parasitic will have on the circuit being designed
The author wish to thank Dr Cuong Huynh P.M for his advices and members of RFIC Group at Ho Chi Minh University of Technology for their helpful comments in this paper Thanks to Ministry of Science and Technology, Viet Nam and VNU HCM for the grant in the form of a state-level research project with Code number: DAKHCN.2011/DT-03
[1] Klaus Finkenzeller, RFID Handbook, 2nd ed., New York: Wiley, 2003 [2] Behzad Razavi “RF Transmitter Architectures and Circuits”, IEEE,
1999
[3] European Standard (Telecommunications series) RFID equipment operating in the band 865MHz to 868MHz with power levels up to 2W, ETSI EN 302 208- 1, V1.1.1
[4] Andrei Grebennikov, Nathan O Sokal, Switchmode RF Power Amplifiers, Linacre House, Jordan Hill, Oxford, UK, 2007
[5] Nathan O Sokal, Alan D Sokal, “Class E- A new class of high efficiency tuned single-ended switching Power Amplifier”, IEEE JSSC, June 1975
[6] Cuong Huynh, Microwave/RF Integrated Circuit Design, HCM University of Technology, Chapter 5, 2014
[7] Behzad Razavi, Design of Analog CMOS Integrated Circuits, McGraw Hill, New York, 2001
[8] Behzad Razavi, RF Microelectronics, 2nd edition, Prentice Hall, 2011 [9] Gao Tongqiang, et al, “Design and Analysis of a Highly Integrated CMOS Power Amplifier for RFID Reader”, IEEE, 2008
[10] HanKefeng, et al, “A 900 MHz, 21dBm CMOS linear power amplifier with 35% PAE for RFID readers”, Chinese Institute of Electronics,
2010
[11] Kyonggon Choi, et al, “CMOS DSB Transmitter with Low TX Noise for UHF RFID Reader System on Chip”, IEEE, 2010
[12] Jingchao Wang, et al, “A fully Integrated CMOS UHF RFID Reader Transceiver for Handheld Applications”, IEEE CICC, 2009
[13] Tongqiang Gao, et al, “A Novel CMOS Transmitter Front end for Mobile RFID Reader”, IEEE, 2009
Fig 17 Results of corner and temperature Pout and PAE of PA
-10
-5
0
Balun
1st order 868MHz
Pin (dBm)
OP1dB at 27C-tt -3.14dBm OP1dB at -44C-tt -3.063dBm OP1dB at 85C-tt -3.392dBm OP1dB at 27C-ss -7.27dBm (-11.131, -1.177)
(-12.19, -7.27)
(-12.21, -3.063)
(-11.4, -3.14) (-10.876, -3.392)
-30
-25
-20
-15
-10
-5
0
1st order 868MHz
Mixer
Pin (dBm)
OP1dB at 27C-tt -6.34dBm OP1dB at -44C-tt -6.774dBm OP1dB at 85C-tt -6.08dBm OP1dB at 27C-ff -3.466dBm OP1dB at 27C-ss -9.623dBm
(2.7028, -3.466)
(-0.543, -6.774) (2.197, -6.34)
(4.018, -6.08) (1.5945, -9.623)
-35
-25
-15
-5
0
10
20
30
40
PA
PAE (%)
Frequency (Hz)
Pout 27C-tt 20.51dBm PAE 27C-tt 36.08%
Pout -44C-tt 20.55dBm PAE -44C-tt 35.08%
Pout 85C-tt 20.306dBm PAE 85C-tt 34.109%
Pout 27C-ff 20.876dBm PAE 27C-ff 34.109%
Pout 27C-ss 20.08dBm PAE 27C-ss 37.76%
Baseband
Output Mixer I/Q
Output Balun
Input driver
Output PA