SI4721 datasheet(49/68 Pages) SILABS

49 / 68 page

AN388

Rev. 0.2

5.1. FM Transmit Testing Measurement Considerations

For the power meter measurements, the power loss of the connection between the power meter and TXO on the

RF daughtercard must be calibrated into the measurement. This calibration value should be added to the

measurement values returned from the Power Accuracy and Maximum Output Power measurements.

5.2. FM Transmit Testing Procedures

5.2.1. Maximum Voltage

Connect test equipment as shown in Figure 12.

Configure the transmitter:

Set frequency = 98.1 MHz.

Set Pilot state = ON.

Set (L–R)/2 State = ON.

Set Pre-emphasis = 75 µS.

Set Output Voltage = 115 dBuV.

Set Pilot modulation rate = 6.75 kHz.

Set audio modulation rate = 68.25 kHz.

Set maximum line input voltage = 636 mV.

Set line input attenuation = 60 k

.

Set dynamic range control = OFF.

Configure the power meter:

Zero and calibrate the power sensor.

Set the frequency = 98.1 MHz.

Configure the power supply:

Configure the power supply to output 5 V on channel 2.

Configure the power supply to output 3.3 V on channel 1.

Configure the modulation analyzer output:

Set AF output = unbalanced 1 and 2.

Set AF impedance = 20



Set AF tone 2 state = OFF.

Set AF tone 1 state = ON.

Set AF tone 1 frequency = 1 kHz.

Set AF tone 1 level = 449.65 mVrms for analog audio input or 990 mVrms for digital audio input.

Record measured power Pmeas, dBm.

Maximum Output Voltage (dBµV) = measured power (dBm) + 107 + 27.77 (dB)

*Note: 107 dB is a conversion factor from dBm to dBµV. When using the 2 pF and 50

circuit on the Si471x/2x EVB, 27.7 dB is

a correction factor at 98.1 mHz.

SI4721 Datasheet(PDF) 49 Page - Silicon Laboratories