AN569 Datasheet, PDF (8/40 Pages) Silicon Laboratories – Si4831/35/36/20/24/25-DEMO BOARD TEST PROCEDURE

AN569
3.6. FM Audio Frequency Response
3.6.1. Description
Audio frequency response is the measure of linearity of output voltage vs. modulation frequency across the audio
band.
3.6.2. Conditions/Procedure
1. Connect test equipment as shown in Figure 1.
2. Configure the tuner in standard configuration.
3. Configure the audio analyzer:
a. Select Analyze.
b. Set Function = RMS Select.
i. Set Bandwidth = BP 3%.
ii. Set Units = dBV.
iii. Set Frequency Mode = FIX: 1 kHz.
4. Configure generator:
a. Set carrier frequency = 98 MHz.
b. Set RF level = 60 dBμV.
c. Select Stereo Modulation.
i. Set FM Deviation = 10.5 kHz.
ii. Set L = R.
iii. Set Source = LFGEN.
iv. Set LFGEN frequency = 1 kHz.
v. Set Pre-emphasis = 75 μs.
vi. Set Pilot = ON.
vii. Set Pilot Deviation = 6.75 kHz.
d. Enable modulation.
e. Enable carrier.
5. Audio 1 kHz level (dBV) = V1 kHz.
6. Configure audio analyzer frequency mode through RMS Select Function. Set Frequency Mode = FIX:
30 Hz.
7. Configure generator LFGEN frequency = 30 Hz.
8. Audio 30 Hz level (dBV) = V30 Hz.
9. Configure audio analyzer frequency mode through RMS Select Function. Set Frequency Mode = FIX:
15 kHz.
10. Configure generator LFGEN frequency = 15 kHz.
11. Audio 15 kHz level (dBV) = V15 kHz.
12. Audio frequency response (dB) equals the greater magnitude of (V30 Hz – V1 kHz) and (V15 kHz –
V1 kHz).
Note: If you test the band with De-emphasis 50 μs, you should Set Pre-emphasis = 50 μs.
3.6.3. Pass Criteria
The greater magnitude of (V30 Hz – V1 kHz) and (V15 kHz – V1 kHz) should be no more than 3 dB.
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