AN603

Rev. 0.3

5

3.3. FM Image Rejection

3.3.1. Description

The test measures the FM image rejection of the tuner.

3.3.2. 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 = THD+N / SINAD.

i. 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:

a. Set carrier frequency = 98 MHz.

b. Select FM Modulation.

i. Set FM Deviation = 22.5 kHz.

ii. Set Source = LFGEN.

iii. Set LFGEN Frequency = 1 kHz.

c. Enable modulation.

d. Enable carrier.

5. Adjust generator RF level, VRF1, until audio analyzer SINAD = 26 dB ±1 dB.

6. Record the RF level = VRF1.

7. Change generator carrier frequency to 97.744 MHz

8. Adjust generator RF level*, VRF2, until audio analyzer SINAD = 26 dB ±1 dB.

9. Image rejection (dB) = VRF2 – VRF1.

Note:

Maximum RF level setting for the R&S SML01 signal generator is 120 dBμV. You cannot increase the RF level beyond

this value. If you adjust generator RF level from VRF1 to 120 dBμV, the audio analyzer SINAD still can not get to the

SINAD = 26 dB ±1 dB, your image rejection will be better than 120 dBμV – VRF1.

3.3.3. Pass Criteria

FM Image rejection should be more than 40 dB.