Iec 60315 4 1997

1.3.7 niveau de limitation à –3 dB niveau du signal d'entrée pour lequel le niveau de tension de sortie audio est inférieur de 3 dB à la valeur donnée pour un niveau élevé du signal d'en

Domaine d'application

This part of IEC 60315 applies to radio receivers and tuners designed for receiving frequency modulation broadcasting emissions, with nominal maximum excursions of ±75 kHz and ±50 kHz in ITU band 8 It primarily addresses measurement methods using RF signals applied to the receiver's antenna terminals The specified measurements and testing conditions are selected to enable comparison of results obtained by different observers and across various receivers Performance requirements are not specified in this standard.

Les essais et exigences de rayonnement et d'immunité ne sont pas inclus et sont décrits dans le CISPR 13 et le CISPR 20.

Définitions

Pour les besoins de la présente partie de la CEI 60315, les définitions suivantes s'appliquent.

The carrier frequency is defined as the average value of the instantaneous frequency or the frequency generated in the absence of modulation In an ideal modulation system, free from any DC component or nonlinear distortion, these two values are identical.

1.3.2 excursion de fréquence instantanée différence entre la fréquence instantanée du signal RF modulé et la fréquence de la porteuse

1.3.3 excursion de fréquence de crête valeur crête de l'excursion instantanée de fréquence

1.3.4 excursion crête à crête double de l'excursion de fréquence de crête.

To avoid confusion between peak frequency excursion and peak-to-peak frequency excursion, the peak-to-peak excursion is expressed, for example, as ±50 kHz.

NOTE – 2 ôL'excursion de frộquence crờte à crờteằ est gộnộralement abrộgộe en ôexcursionằ dans cette norme.

1.3.5 excursion maximale nominale du système excursion maximale de fréquence crête à crête (voir 1.3.4) spécifiée pour le système considéré

1.3.6 taux de modulation rapport entre l'excursion crête à crête du signal et l'excursion maximale nominale du système, généralement exprimé en pourcentage

NOTE – Cette définition découle d'une analogie directe avec le cas de la modulation d'amplitude.

The -3 dB limitation level indicates the input signal level at which the audio output voltage is reduced by 3 dB compared to the specified value for a high RF input signal level, ideally set at 80 dB(fW).

The amplification reserve indicates the attenuation, measured in decibels, of the volume control when set to achieve the nominal output voltage or power, constrained by distortion This is specified for a high level of RF input signal, ideally at 80 dB(fW).

NOTE – Cette caractéristique n'est pas définie pour un récepteur ou un syntoniseur non muni d'une commande de volume.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

CISPR 20: 1996, Limits and methods of measurement of immunity characteristics of sound and television broadcast receivers and associated equipment

ITU-R Recommendation 468-4: 1990: Measurement of audio-frequency

ITU-R Recommendation 559-2: 1990: Objective measurement of radio-frequency protection ratios in LF, MF and HF broadcasting

For the purposes of this part of IEC 60315, the following definitions apply.

The carrier frequency refers to the average of the instantaneous frequency or the frequency produced without modulation In an ideal modulation system, where there are no direct current components or non-linear distortions, the carrier frequency and the instantaneous frequency are identical.

1.3.2 instantaneous frequency deviation the difference between the instantaneous frequency of the modulated radio-frequency signal and the carrier frequency

1.3.3 peak frequency deviation the peak value of the instantaneous frequency deviation

1.3.4 peak-to-peak deviation twice the peak frequency deviation

NOTE 1 – To avoid confusion between "peak frequency deviation" and "peak-to-peak frequency deviation", peak-to- peak deviation is expressed as, for example, ± 50 kHz.

NOTE 2 – "Peak-to-peak frequency deviation" is generally abbreviated to "deviation" in this standard.

1.3.5 rated maximum system deviation the maximum peak-to-peak frequency deviation (see 1.3.4) specified for the system under consideration

1.3.6 modulation factor the ratio of the peak-to-peak deviation of the signal to the rated maximum system deviation, usually expressed as a percentage

NOTE – This definition arises by direct analogy with the case of amplitude modulation.

–3 dB limiting level the input signal level at which the audio-frequency output voltage level is 3 dB below the value at a specified high r.f input signal level, preferably 80 dB(fW)

The amplification reserve refers to the attenuation in decibels of the volume control when set to achieve the rated output voltage or power, which is limited by distortion This measurement is ideally taken with a specified high radio frequency input signal level, preferably at 80 dB(fW).

NOTE – This characteristic is undefined for a receiver or tuner without a volume control.

1.3.9 sensibilité à l'excursion de fréquence valeur de l'excursion nécessaire pour produire la tension ou la puissance de sortie nominale

(limitée par la distorsion), la commande de volume étant réglée au maximum, avec un niveau élevé du signal d'entrée RF, de préférence 80 dB(fW)

The maximum signal-to-noise ratio (SNR) is reached at sufficiently high RF input signal levels, where increasing the input signal does not lead to any further improvement in the SNR.

1.3.11 seuil stéréophonique niveau de signal d'entrée RF pour lequel le décodeur stéréophonique commence à fonctionner

NOTE – Une diminution marquée du rapport signal sur bruit est habituelle à ce niveau de signal, à moins que des circuits de diaphonie dépendant du niveau du signal soient incorporés.

1.3.12 seuil de l'indicateur stéréophonique niveau de signal d'entrée pour lequel l'indicateur visuel montre que le récepteur fonctionne en mode stéréophonique

NOTE – Ce niveau peut être identique ou non au seuil stéréophonique.

1.3.13 seuil du silencieux niveau de signal d'entrée pour lequel les circuits de mise en silence permettent au signal de sortie audio d'apparaợtre aux bornes de sortie

The threshold may vary for increasing and decreasing signal levels This hysteresis is typically intentional, as it prevents unsatisfactory operation with RF input signals that are at or near the threshold level.

The attenuation of the silencer leads to a reduction in the output audio level, selectively measured at 1 kHz This occurs when a 1 kHz modulated input signal is applied with the system's maximum nominal excursion, particularly during the silencing phase.

The sensitivity at 50 dB input RF signal level indicates a 50 dB increase in audio output under specified conditions (refer to section 2.3) This occurs when modulation transitions from zero (excluding the pilot signal for stereo mode measurements) to the standardized excursion value (see section 1.4.2.1).

Conditions normalisées de mesure

1.4.1 Mesures aux bornes de sortie audio

1.4.1.1 Niveau de sortie audio normalisé

The normalized audio output level serves as the reference output level for audio measurements, and it should be 10 dB lower than the nominal output voltage or power Additionally, a specific output voltage or power value can be selected from the following options: 500 mV, 1 W, 500 mW, 50 mW, 5 mW, or 1 mW, as outlined in IEC 60315-1.

Deviation sensitivity refers to the amount of deviation needed to achieve the rated output voltage or power, which is limited by distortion This is measured with the volume control set to maximum and under a specified high radio frequency (r.f.) input signal level.

The ultimate signal-to-noise ratio refers to the maximum value achieved when radio frequency (RF) input signal levels are sufficiently high, beyond which increasing the input signal level does not lead to any further improvement in the signal-to-noise ratio.

1.3.11 stereo threshold the r.f input signal level at which the stereo decoder begins to operate

NOTE – A marked decrease in signal-to-noise ratio is usual at this signal level unless signal-strength dependent cross-talk circuits are included.

1.3.12 stereo indicator threshold the input signal level at which the visual indicator shows that the receiver is operating in the stereo mode

NOTE – This level may or may not be identical to the stereo threshold.

1.3.13 muting threshold the input signal level at which the muting circuits allow the a.f output signal to appear at the output terminals

The threshold for signal levels can vary between increasing and decreasing signals This intentional hysteresis is designed to prevent poor performance when radio frequency (r.f.) input signals are close to the threshold level.

1.3.14 muting attenuation the reduction in a.f output, selectively measured at 1 kHz, due to an input signal modulated at 1 kHz at rated maximum system deviation, when muting occurs

The 50 dB quieting sensitivity refers to the radio frequency (RF) input signal level that results in a 50 dB increase in audio frequency (AF) output under specific conditions This measurement is taken when the modulation shifts from no modulation (excluding the pilot tone in stereo mode) to the standard deviation value.

1.4.1 Measurements at audio-frequency output terminals

1.4.1.1 Standard audio-frequency output level

The standard audio-frequency output level serves as the reference for audio-frequency measurements, set at 10 dB below the rated output voltage or power Alternatively, specific output voltage or power values such as 500 mV, 1 W, 500 mW, 50 mW, 5 mW, or 1 mW may be utilized, as outlined in IEC 60315-1.

La charge de substitution audio est une impédance physique déterminée (généralement résistive) utilisée pour charger les bornes de sortie audio, (voir CEI 60315-1).

When measuring audio output terminals, it is advisable to insert a band-pass filter between the output terminals and the measuring instrument, except when measuring low-frequency or ultrasonic components in the output voltage To accommodate standard impedances in this filter, the substitution load should be directly connected to the audio output terminals If the filter's insertion loss is significant, it must be considered when determining the results.

It is advisable to use the same filter for both monophonic and stereophonic receivers to prevent errors caused by pilot signal or subcarrier components at the receiver output The filter's bandwidth should range from 200 Hz to 15 kHz, with the relative attenuation at 1 kHz not exceeding 3 dB Below 200 Hz, the attenuation slope should approach at least 18 dB per octave At 19 kHz, the attenuation must be at least 50 dB, and above 19 kHz, it should be no less than 30 dB This filter effectively helps to ensure that measurement results are not influenced by hum.

Pour des mesures dans une bande d'une octave et d'un tiers d'octave, les filtres doivent être conformes aux exigences de la CEI 61260.

Le tableau 1 donne la liste des filtres audio utilisés pour les mesures dans cette norme.

Type de filtre Figure Référence Notes

Passe-bande de 200 Hz – 15 kHz 1 1.4.1.3 Avec réjection à 19 kHz

Passe-bande de 22,4 Hz – 15 kHz 2 2.2.1 Avec réjection à 19 kHz

Passe-bande de 200 Hz – 1,5 kHz 3 Figure 8 Avec réjection à 19 kHz

Passe-bas de 15 kHz Aucune 1.4.2.3 Pente d'affaiblissement de

Elimination de bande à 1 kHz 4 Figure 8 Voir aussi annexe A

Passe-bande de 1 kHz Aucune Figure 6 1 / 3 d'octave: CEI 61260

Pondération A Aucune Figure 8 Voir CEI 60651

Filtre de pondération pour mesure du bruit

Filtre de pondération pour bruit coloré 5 1.4.2.3 Compatible avec UIT-R

The normalized value of the excursion for measurements should align with the nominal maximum excursion of the system (RMSD) as specified in Table 2 The excursion must be reported alongside the results Measurements for lower excursions can be beneficial in certain situations; when conducted, the excursion used should be clearly indicated with the results.

The audio-frequency substitute load is a stated physical (usually resistive) impedance for terminating audio-output terminals, (see IEC 60315-1).

When measuring audio-frequency output terminals, it is recommended to use a band-pass filter between the output and the measuring instrument, unless the goal is to measure low audio-frequency and ultrasonic components To ensure practical impedance in the filter, the substitute load should be connected directly to the audio-frequency output terminals Additionally, any significant insertion loss of the filter must be considered when interpreting the results.

Using a consistent filter for both monophonic and stereophonic receivers is recommended to avoid errors caused by pilot-tone or subcarrier components in the output The filter should have a pass-band ranging from 200 Hz to 15 kHz, with an attenuation not exceeding 3 dB relative to 1 kHz within this range Below 200 Hz, the attenuation slope should reach at least 18 dB/octave, and at 19 kHz, the attenuation must be a minimum of 50 dB.

19 kHz it shall be at least 30 dB (see figure 1) This filter usually prevents the results of measurements from being affected by hum.

Filters for octave and third-octave band measurements shall comply with the requirements of IEC 61260.

Table 1 lists the audio-frequency filters which are used in measurements in this standard.

Type of filter Figure Reference Notes

200 Hz – 15 kHz band-pass 1 1.4.1.3 With 19 kHz notch

22,4 Hz – 15 kHz band-pass 2 2.2.1 With 19 kHz notch

200 Hz – 1,5 kHz band-pass 3 Figure 8 With 19 kHz notch

15 kHz low-pass None 1.4.2.3 60 dB/octave attenuation slope

1 kHz band-stop 4 Figure 8 See also annex A

1 kHz band-pass None Figure 6 1 / 3 -octave: IEC 61260

A-weighting None Figure 8 See IEC 60651

Weighting filter for measurement of noise

Weighting filter for coloured noise 5 1.4.2.3 Consistent with ITU-R

The standard value of deviation for measurements shall be the rated maximum system deviation (RMSD) given in table 2 The deviation shall be stated with the results.

Measurements at lower deviations are useful in some cases: where these are carried out the deviation used shall be stated with the results.

Tableau 2 – Valeurs normalisées de l'excursion

Mode/signal RMSD ±50 kHz RMSD ±75 kHz

When a single excursion value is referenced in the text, it pertains to a system with an RMSD of +75 kHz For a system with an RMSD of +50 kHz, the mentioned value is proportionally reduced.

Dans certains cas, la valeur RMSD = +50 kHz est donnée entre parenthèses: par exemple, (+ 50 kHz).

NOTE 2 – Les excursions relatives à des services supplémentaires (tels que SCA, RDS et ARI), suscep- tibles de varier selon les régions ou les pays de l'UIT, sont indiquées à l'annexe B.

The standardized modulation frequency must align with the normalized reference frequency of 1,000 Hz If necessary, alternative frequencies may be selected, preferably from the central frequencies of the third-octave bands listed in Table I of IEC 60315-1.

1.4.2.3 Modulation normalisée utilisant un bruit coloré

The noise modulation is designed to ensure that the noise spectrum resembles that of modern dance music from Western Europe, which is a particularly critical form of modulation in the event of interference from an adjacent channel.

The noise signal is generated using a Gaussian white noise generator, which is then processed through a weighting filter, as shown in Figure 5 This is followed by a low-pass filter with a cutoff frequency of 15 kHz and a slope of 60 dB/octave, and finally, it passes through an emphasis network set to either 50 µs or 75 µs, depending on the specific requirements.

Généralités concernant les mesures

1.5.1 Valeurs de tension et de courant

Sauf indication contraire, les termes tension, courant et autres font référence à des valeurs efficaces.

The characteristics of devices such as speakers and audio output lines, for which connectors are provided on receivers, are defined in terms of constant input voltage rather than constant input power, as outlined in IEC 60268-1 This definition applies not only to audio outputs but also to other outputs, such as intermediate frequency outputs and multiplex signal outputs Consequently, it is now commonly accepted to perform most measurements at the output terminals and express the results in terms of voltage across a substitution load From the measured voltage, it is possible to calculate the power, if applicable, using the following relationship:

2 l'indice 2 faisant référence aux bornes de sortie par opposition aux bornes d'entrée.

When the output signal is nearly sinusoidal, with distortion and noise components representing less than 10% of the signal, measurements can be taken using an average-sensitive voltmeter calibrated for effective value in sinusoidal signals If these conditions are not met, a true RMS voltmeter should be used unless otherwise specified.

When multiple output pairs are anticipated, the manufacturer must specify for each pair: a) the nominal value of the substitution load (refer to IEC 60315-1); b) whether the output pair should be connected to a substitution load when measurements are taken at a different output pair.

It is common practice to connect all speaker outputs to dummy loads, while outputs intended for other devices are only loaded during measurements at those terminals.

To ensure optimal performance, the receiver should be adjusted according to the manufacturer's guidelines when using the tuning indicator, reflecting the proper tuning method during operation.

In the absence of a functioning tuning indicator, the receiver should be manually tuned to the signal while monitoring the audio output on an oscilloscope The deviation should be gradually increased until audio distortion occurs, at which point the receiver must be adjusted for symmetrical clipping of the audio signal Additionally, the volume control should be adjusted to avoid overloading the audio-frequency section of the receiver.

If an alternative method of tuning is used, this shall be stated with the results.

1.5.1 Values for voltage and current

Unless otherwise stated, the terms voltage, current and so on refer to root mean square

Devices like loudspeakers and audio-frequency distribution lines are characterized by their output terminals on receivers, as defined in standards such as IEC 60268-1 These characteristics are based on constant input voltage rather than constant input power, which applies to various outputs, including audio-frequency, intermediate-frequency, and multiplex signal outputs Consequently, it is standard practice to conduct most measurements at output terminals based on the voltage across a substitute load This voltage can be used to calculate the power in the load using a specific formula.

2 where the suffix 2 refers to output terminals as opposed to input terminals.

For output signals that are predominantly pure sine waves, characterized by noise and distortion levels below 10%, average-reading meters calibrated in r.m.s values can be utilized for sinusoidal inputs In all other scenarios, it is essential to employ a true r.m.s meter unless specified otherwise.

When multiple pairs of output terminals are available, the manufacturer must specify the rated value of the substitute load for each pair, as outlined in IEC 60315-1 Additionally, it should be clarified whether the terminals in each pair should be connected to a substitute load during measurements taken at a different pair of terminals.

When conducting measurements, it is standard practice to connect all terminals designated for loudspeakers to substitute loads In contrast, terminals for other devices are only loaded during measurements at those specific terminals.

1.5.3 Présentation du niveau ou de la tension de signal RF

RF signal levels can be expressed in dB(fW), dB(pW), dB(mW), or in microvolts with a specified source or load impedance Table 4 illustrates the relationships between these values.

Tableau 4 – Présentation du niveau ou de la tension de signal RF

W dB(fW) dB(mW) à V dB( à V) à V dB( à V)

For information regarding environmental conditions, refer to section one of IEC 60315-1 Mechanical measurements and verifications can be conducted under any combination of temperature, humidity, and atmospheric pressure, within the limits specified in IEC 60315-1 Additionally, to prevent unintentional interference from external signals, it is advisable to perform measurements in a shielded enclosure or room (see also IEC 60315-3).

Avant d'enregistrer les résultats des mesures, il convient de maintenir le récepteur à l'essai pendant au moins 10 min dans les conditions normalisées de mesure (voir la CEI 60315-1).

The results of the various measurements discussed in this section may be affected by other properties of the receiver Therefore, it is advisable to first conduct the measurements outlined in IEC 60315-1, if applicable.

1.5.6 Matériel d'essai et précision des mesures

In general, this standard specifies the use of the simplest testing equipment that provides sufficiently reliable results However, it does not preclude the use of more complex equipment that may yield identical or even more reliable results.

1.5.3 Presentation of radio-frequency signal level or voltage

Radio-frequency signal levels can be expressed in various units, including dB(fW), dB(pW), dB(mW), or electromotive force (e.m.f.) in microvolts, depending on the specified source or load impedance The interrelationship between these values is detailed in Table 4.

Table 4 – Presentation of radio-frequency signal level or voltage

W dB(fW) dB(mW) à V dB( à V) à V dB( à V)

Explication des termes

The sensitivity of a receiver is a measure of its ability to detect weak signals and produce an audio output of usable amplitude and acceptable quality This sensitivity can be defined in relation to various output signal characteristics, including the signal-to-noise ratio and the output voltage or power, with the volume control set to maximum if available.

(voir 2.4); c) niveau de limitation (voir point a) de 2.7.1).

Pour les mesures de sensibilité, on utilise un circuit tel que celui décrit figure 8.

Rapport signal sur bruit (pondéré et non pondéré) et SINAD

The signal-to-noise ratio of a receiver, under specified conditions, is the ratio of the audio output voltage from the signal to that from random noise Noise can be measured using a bandpass filter with a 3 dB bandwidth ranging from 22.4 Hz to 15 kHz.

The measurement of sinusoidal signals can be performed using various methods: a true RMS voltmeter or an average-sensitive voltmeter calibrated for RMS values; the A-weighting method as defined in IEC 60651 with a true RMS voltmeter; a weighting filter and measuring device specified in Annex A of IEC 60315-1; or a bandpass filter with a 3 dB bandwidth ranging from 200 Hz to 15 kHz.

(voir figure 1) et d'un des appareils de mesure indiqués au point a) ci-dessus.

Ces différentes méthodes donnant des résultats significativement différents, il est essentiel que celle qui est utilisée soit clairement mentionnée avec les résultats.

Using the figure 8 setup, the receiver is placed in standardized measurement conditions, with S1 and S3 adjusted to positions that introduce the necessary filter and measuring device (refer to section 2.2.1) The reading on the corresponding voltmeter is recorded The modulation is then removed, and the voltmeter reading is noted again as before The signal-to-noise ratio is then equal to the ratio of the voltmeter readings.

This measurement can be repeated at different signal frequencies and various tone control settings, if applicable For measurements on stereo receivers, in stereo mode, the pilot signal modulation is maintained when the 1 kHz modulation is removed, if necessary.

The presence of a modulated signal can sometimes increase the noise level at the output of a frequency modulation receiver instead of reducing it This effect can be achieved by employing method 2.2.2.1, where, instead of removing the modulation, S2 is set to position 2 This configuration allows the fundamental frequency component of the modulation to be eliminated using a filter Consequently, the ratio indicated on the voltmeter reflects the relationship between the combined signal, noise, and distortion, and the noise plus distortion, known as the SINAD measurement.

Receiver sensitivity indicates its capability to detect weak signals and generate a usable audio output This sensitivity can be assessed based on various output signal characteristics, such as the signal-to-noise ratio, output voltage or power (with maximum volume), and the limiting level.

For sensitivity measurements a circuit such as that shown in figure 8 is used.

2.2 Signal-to-noise ratio (weighted and unweighted) and SINAD

The signal-to-noise ratio (SNR) of a receiver, under defined conditions, represents the ratio of the audio-frequency output voltage generated by the signal to that produced by random noise Noise measurement can be conducted using a band-pass filter with a 3 dB bandwidth ranging from 22.4 Hz to 15 kHz.

To accurately measure sound levels, one can utilize a true r.m.s meter or an average-responding meter calibrated for r.m.s values in relation to a sinusoidal signal Additionally, measurements can be taken using A-weighting as specified in IEC 60651 alongside a true r.m.s meter Another method involves employing the weighting filter and meter outlined in annex A of IEC 60315-1 Lastly, a band-pass filter with a 3 dB bandwidth ranging from 200 Hz to 15 kHz can be used in conjunction with either of the meters mentioned previously.

Since these different methods give significantly different results, it is essential that the method used be clearly stated with the results.

Using the circuit of figure 8, the receiver is brought under standard measuring conditions, with

In section 2.2.1, S1 and S3 are positioned to introduce the necessary filter and meter, with the corresponding voltmeter reading recorded Following this, the signal modulation is eliminated, and the voltmeter reading is noted again The signal-to-noise ratio is determined by the ratio of these voltmeter readings.

Measurements can be conducted at various signal frequencies and tone control settings In stereo receivers operating in stereo mode, pilot-tone modulation is preserved even when the 1 kHz modulation is eliminated.

In certain situations, a modulated signal can actually increase the noise output of an FM receiver By employing a specific method, instead of eliminating the modulation, the signal is adjusted to filter out the fundamental frequency of the modulation Consequently, the voltmeter readings reflect the ratio of the combined signal, noise, and distortion to the noise and distortion alone, which is known as the SINAD measurement.

Il convient de répéter les mesures pour d'autres valeurs d'excursion.

Pour la réception stéréophonique, les deux voies doivent être modulées en opposition de phase Chaque voie de sortie est mesurée à son tour, à l'aide du montage de la figure 8.

The curves illustrating the signal-to-noise ratio, expressed in decibels and plotted on a linear scale, are represented as a function of the input signal level, also expressed in decibels.

(par rapport à 1 fW, de préférence), et porté en abscisse sur une échelle linéaire.

La méthode utilisée (voir 2.2.2.1 ou 2.2.2.2) doit être clairement indiquée.

Pour la méthode simultanée, il est possible de tracer des ensembles de courbes avec l'excursion comme paramètre Un exemple est présenté à la figure 9 (voir aussi 2.7).

Sensibilité limitée par le bruit

For a receiver, the noise-limited sensitivity is the minimum value of the RF input signal level that produces a specified signal-to-noise ratio at the audio output In principle, it is advisable to use unweighted narrowband signal-to-noise ratios of 40 dB.

(50 dB pour des récepteurs haute fidélité) pour la méthode séquentielle, et de 30 dB pour la méthode simultanée.

Le niveau du signal de sortie audio de référence est celui produit par l'excursion maximale nominale du système.

Sensitivities are defined based on various signal-to-noise (and/or distortion) criteria as follows: a) noise-limited sensitivity (S/N ratio method); b) sensitivity for a 50 dB variation in audio signal; c) noise-limited sensitivity (SINAD ratio method).

The results can be derived from the measurements in section 2.2.2 It is advisable to measure the signal-to-noise ratio across a sufficient range of input signal levels to ensure that areas with abrupt changes in the signal-to-noise ratio are thoroughly investigated.

Les mesures peuvent être répétées pour différentes fréquences de signal d'entrée.

La sensibilité limitée par le bruit est portée en ordonnée sur une échelle linéaire, en décibels

The output is dependent on the input signal frequency, measured in megahertz and displayed on a linear scale along the x-axis An example illustrating this relationship is provided in Figure 10.

Des ensembles de courbes peuvent être tracés en prenant le rapport signal sur bruit comme paramètre La méthode de mesure utilisée (2.2.2.1 ou 2.2.2.2) doit être clairement indiquée.

The measurement should be repeated at other values of deviation.

For stereophonic reception, the two channels shall be modulated in phase opposition Each output channel is measured in turn, using the circuit of figure 8.

The article presents curves that illustrate the signal-to-noise ratio in decibels on a linear scale, plotted against the input signal level, also expressed in decibels (ideally referenced to 1 fW), on a linear scale.

The method employed (see 2.2.2.1 or 2.2.2.2) shall be clearly stated.

For the simultaneous method, families of curves with deviation as a parameter may be plotted.

An example is shown in figure 9 (see also 2.7).

The noise-limited sensitivity of a receiver refers to the lowest radio-frequency input signal level that achieves a designated signal-to-noise ratio at the audio-frequency output Typically, for the sequential method, an unweighted, band-limited signal-to-noise ratio of 40 dB is recommended, while high-fidelity receivers should aim for 50 dB In contrast, the simultaneous method should utilize a signal-to-noise ratio of 30 dB.

The reference audio-frequency output signal level is that produced by rated maximum system deviation.

Sensitivities are categorized based on different signal-to-noise criteria, including noise-limited sensitivity using the signal-to-noise (S/N) ratio method, 50 dB quieting sensitivity, and noise-limited sensitivity assessed through the SINAD ratio method.

To ensure a comprehensive analysis of the signal-to-noise ratio, it is essential to measure it at adequate input signal levels This approach allows for a thorough examination of rapid fluctuations in the signal-to-noise ratio, as outlined in section 2.2.2.

The measurement may be repeated at several input signal frequencies.

The noise-limited sensitivity is represented in decibels, ideally referenced to 1 fW, plotted against input signal frequency in megahertz Figure 10 illustrates an example of this representation Additionally, families of curves can be displayed with the signal-to-noise ratio as a parameter It is essential to clearly specify the measurement method utilized, referring to sections 2.2.2.1 or 2.2.2.2.

Sensibilité limitée par le gain

A receiver's sensitivity is said to be limited by gain when the audio output voltage (or power), measured selectively at the modulation frequency with a weak input signal, falls below the nominal output voltage or power constrained by distortion.

The receiver may generate a reference output voltage or power, such as 100 mV or 50 mW, even with a very low input signal However, this output can be significantly lower than the manufacturer's specified output level and may not be sufficient for proper operation with associated devices.

Limited gain sensitivity refers to the minimum value of the RF input signal, modulated by the standardized modulation signal (1.4.2.4), which generates the nominal output voltage or power, with the volume control, if available, set to its maximum value.

NOTE – On utilise une excursion et, proportionnellement, un niveau de sortie réduits pour éviter des effets de surcharge.

We employ the 2.2.2.2 method while keeping switch S2 in position 3 to measure only the fundamental frequency of modulation The input signal level is adjusted to achieve the nominal output level limited by distortion.

Cette mesure peut être répétée pour d'autres fréquences du signal d'entrée et en mode stéréo- phonique.

La sensibilité limitée par le gain est portée en ordonnée sur une échelle linéaire, en décibels

(de préférence par rapport à 1 fW), en fonction de la fréquence du signal d'entrée, exprimée en mégahertz, et portée en abscisse sur une échelle linéaire.

Des paires de courbes peuvent être tracées en fonctionnement monophonique et stéréo- phonique Un exemple est donné à la figure 11.

Sensibilité utilisable

The usable sensitivity of a receiver is determined by either noise-limited sensitivity or gain-limited sensitivity, depending on which of these two values represents the highest input signal level.

NOTE 1 – Si la sensibilité utilisable est égale à la sensibilité limitée par le bruit, c'est ce critère qu'il convient d'indiquer (voir 2.3.1).

NOTE 2 – Pour certains récepteurs, la distorsion due à une largeur de bande insuffisante, à des niveaux très faibles de signal d'entrée, peut constituer une limite pratique de la sensibilité utilisable.

The limited sensitivity due to noise and gain is measured using the specified methods outlined in this standard, and the results are then compared The usable sensitivity is defined as the higher input signal level of the two measurements.

A receiver is considered gain-limited when its audio-frequency output voltage or power, assessed at the modulation frequency with a small signal input, falls below the specified distortion-limited output voltage or power.

The receiver can generate a reference output voltage or power, such as 100 mV or 50 mW, even with a minimal input signal However, this output may fall significantly short of the manufacturer's specifications and may not be sufficient for proper operation with related equipment.

Gain-limited sensitivity refers to the minimum level of radio-frequency input signal, modulated with a standard signal, that generates the specified distortion-limited audio-frequency output voltage or power, assuming the volume control is set to maximum.

NOTE – A reduced deviation and proportionally reduced output level may be used to avoid overloading effects.

The 2.2.2.2 method is employed while maintaining switch S2 in position 3 to measure only the fundamental frequency of the modulation The input signal level is calibrated to achieve the specified distortion-limited output.

The measurement may be repeated at other input signal frequencies, and for the stereophonic mode.

The gain-limited sensitivity is plotted linearly in decibels (preferably referred to 1 fW) as ordinate, as a function of the input signal frequency plotted linearly in megahertz as abscissa.

Pairs of curves may be plotted for monophonic and stereophonic operation An example is shown in figure 11.

The usable sensitivity of a receiver is the noise-limited sensitivity or gain-limited sensitivity, whichever is the greater value of the input signal level.

NOTE 1 – If the usable sensitivity is equal to the noise-limited sensitivity, the criterion of the noise-limited sensitivity should be stated (see 2.3.1).

NOTE 2 – For some receivers, the distortion caused by insufficient bandwidth at very low input signal levels may present a practical limit to usable sensitivity.

The noise-limited and gain-limited sensitivities are evaluated using specified methods from this standard, and their results are compared The usable sensitivity is determined as the greater of the two input signal levels.

Curves are plotted with sensitivity limited by noise and sensitivity limited by gain represented on the y-axis in a linear scale measured in decibels (fW) The RF frequency is displayed on the x-axis in a linear scale measured in megahertz.

Il convient d'indiquer la méthode utilisée dans les résultats.

Sensibilité à l'excursion de fréquence

La sensibilité à l'excursion de fréquence d'un récepteur est définie en 1.3.9.

The standardized RF test signal is applied to the receiver, and the excursion is set to zero The volume control is then adjusted to the maximum, and the excursion is increased until the nominal output voltage or power is achieved.

La sensibilité à l'excursion de fréquence est indiquée comme étant l'excursion mesurée confor- mément au 2.6.2 La fréquence du signal doit également être indiquée.

Caractéristiques entrée-sortie

L'une des caractéristiques les plus importantes et les plus représentatives d'un récepteur est la relation entre la tension ou la puissance de sortie audio et la puissance disponible à l'entrée

RF, notamment si la tension ou la puissance de bruit en sortie audio (voir 2.2) est tracée en fonction du niveau de signal d'entrée, sur le même graphique.

A variety of receiver characteristics can be identified from such a graph, including: a) the -3 dB limit level; b) noise-limited and gain-limited sensitivities; c) the maximum signal-to-noise ratio (S/N); d) the gain reserve; e) frequency excursion sensitivity; and f) overload effects that were not highlighted by the measurements in section 5.2.

For stereo reception, the following characteristics can be determined: the signal-to-noise ratio (S/N) in stereophony, the stereo threshold, the threshold of the stereo indicator, the mute threshold, and the attenuation of the mute.

Ces termes sont définis en 1.3.

The article discusses the plotting of curves that represent noise-limited and gain-limited sensitivity, measured in decibels (fW) on the vertical axis, while the horizontal axis displays radio frequency in megahertz, both utilizing linear scales.

The method used should be stated with the results.

The deviation sensitivity of a receiver is defined in 1.3.9.

The standard radio-frequency test signal is applied to the receiver with the deviation initially set to zero The volume control is adjusted to maximum, and the deviation is gradually increased until the rated output voltage or power is achieved.

The deviation sensitivity is stated as being the deviation measured according to 2.6.2 The signal frequency shall also be stated.

A key characteristic of a receiver is the correlation between its audio-frequency output voltage or power and the available radio-frequency input power This relationship becomes particularly insightful when the audio-frequency noise output is plotted against the input signal level on the same graph.

A graph can reveal several key characteristics of the receiver, including the –3 dB limiting level, noise-limited and gain-limited sensitivities, the ultimate signal-to-noise (S/N) ratio, amplification reserve, deviation sensitivity, and overloading effects that may not be evident from the measurements in section 5.2.

For stereophonic reception, the following characteristics, among others, may also be determined: g) signal-to-noise (S/N) ratio in the stereo mode; h) stereo threshold; i) stereo indicator threshold; j) muting threshold; k) muting attenuation.

These terms are defined in 1.3.

Using the figure 8 setup, with S1 positioned at 3, the receiver is placed in standardized measurement conditions (refer to section 1.4.2.8) The RF input signal level is then lowered to a low value (for instance, 0 dB(fW)), and the audio output voltage or power is measured.

Le niveau du signal d'entrée RF est ensuite augmenté graduellement, en mesurant la tension ou la puissance de sortie à chaque pallier.

For measurements at low input signal levels where the signal-to-noise ratio is poor, S2 can be positioned at 3 to selectively measure the output voltage at 1 kHz This adjustment must be noted in the results After each increase in the input signal level, the receiver should be readjusted (refer to section 1.4.4.2) Any significant changes in tuning based on the input signal level should also be documented in the results.

If the receiver has an audio power amplifier, it can become overloaded if the input signal level exceeds 70 dB(fW) To prevent this, the volume control attenuation should be increased by a known amount whenever the output voltage or power approaches one-third of the distortion-limited nominal value.

Cette mesure peut être répétée pour d'autres valeurs d'excursion, notamment avec un rapport d'utilisation de 100 % en stéréophonie.

A curve is plotted by placing the available RF power level (preferably relative to 1 fW) on the x-axis using a linear scale, while the audio output voltage or power, expressed in decibels relative to a specified reference, is placed on the y-axis, also on a linear scale Corrections must be made for any increases in attenuation caused by volume control adjustments to prevent overloads Multiple sets of curves can be plotted for different excursion values, and individual curves can be displayed on the same graph for both monophonic and stereophonic reception, highlighting their respective signal-to-noise ratio characteristics.

Un exemple est donné à la figure 12.

Tiêu đề	Methods of measurement on radio receivers for various classes of emission – Part 4: Receivers for frequency-modulated sound broadcasting emissions
Trường học	Not specified
Chuyên ngành	Electrical and Electronics Engineering
Thể loại	International Standard
Năm xuất bản	1997
Thành phố	Geneva

Định dạng
Số trang	164
Dung lượng	1,15 MB