SI4721 datasheet(32/68 Pages) SILABS

32 / 68 page

AN388

Rev. 0.2

3.2. AM/Shortwave/Longwave Tuner Testing Procedures

The following procedures measure analog audio output. All audio measurments can be duplicated for digital audio

output where applicable. For audio analyzer settings in digital mode, refer to Section 6.1.

3.2.1. Sensitivity

Sensitivity of a receiver is a measure of its ability to receive weak signals and produce an audio frequency output of

usable magnitude and acceptable quality. Sensitivities may be defined with respect to many different

characteristics of the output signal. For the purposes of our testing, sensitivity is the minimum RF level required to

produce an audio output with a specified signal-to-noise and distortion ratio, 26 dB. Please note that the sensitivity

measurement is defined with respect to SINAD and not SNR. Descriptions for these two measurements will be

given in the following sections.

1. Connect test equipment as shown in Figures 6 or 7.

2. Configure the tuner:

a. Set frequency = 1 MHz. (10 MHz for shortwave and 216 kHz for longwave.)

b. Set volume = 63.

3. Configure the audio analyzer:

a. Select Analyze.

b. Set Function = THD+N / SINAD.

Set Measurement Mode = SINAD.

ii. Set Unit = dB.

iii. Set Filter = A-weighting.

iv. Set Frequency Limit Low = 300 Hz.

v. Set Frequency Limit High = 15000 Hz.

4. Configure generator #1:

a. Set carrier frequency = 1 MHz. (10 MHz for shortwave and 216 kHz for longwave.)

b. Select AM Modulation.

Set AM Modulation Depth = 30%.

ii. Set source = LFGEN.

iii. Set LFGEN frequency = 1 kHz.

c. Enable AM modulation.

d. Enable RF carrier.

5. Disable generator #2.

6. Adjust generator #1 RF level, VRF0, until audio analyzer SINAD = 26 dB ± 1 dB.

7. Sensitivity (µVrms) = VRF0.

SI4721 Datasheet(PDF) 32 Page - Silicon Laboratories