SI4743 データシートの表示（PDF） - Silicon Laboratories
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SI4743 Datasheet PDF : 68 Pages
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AN388
2.3.6. SNR
The signal-to-noise ratio of a receiver, under specified conditions, is the ratio of the audio frequency output voltage
due to the signal to that due to random noise. The noise may be measured using different filtering techniques. The
technique used in this document is the A-weighting filter. Weighting filters are used to determine the loudness of
sounds, particularly noise. A-weighting filter is commonly used to emphasize frequencies around 3–6 kHz, where
the human ear is most sensitive, while attenuating very high and very low frequencies to which the ear is
insensitive. The aim is to ensure that measured loudness corresponds well with subjectively perceived loudness.
A-weighting is only really valid for relatively quiet sounds and for pure tones.
1. Connect test equipment as shown in Figures 1, 2, or 3.
2. Configure the tuner in standard configuration.
3. Configure the audio analyzer:
a. Select Analyze.
i. Set Input DISP = RMS.
ii. Set Units = dBV.
iii. Set Function = THD+N / SINAD.
Set Measurement Mode = LEVEL NOISE.
Set Units = dBV.
Set Filter = A-weighting.
Set Frequency Limit Low = 300 Hz.
Set Frequency Limit Upper = 15000 Hz.
4. Configure generator #1:
a. Set carrier frequency = 98.1 MHz.
b. Set RF level = 60 dBµV.
c. Select FM Modulation.
i. Set FM Deviation = 22.5 kHz.
ii. Set source = LFGEN.
iii. Set LFGEN frequency = 1 kHz.
d. Enable modulation.
e. Enable carrier.
5. Disable generator #2.
6. Record SNR (dB) = Input RMS(dBV) – Level Noise (dBV).
Rev. 0.2
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