Internal AM Distortion

AM distortion is defined as the square root of the ratio of the power contained in the harmonics of the demodulated AM waveform to the power of the fundamental component of the demodulated waveform.

This is essentially a total harmonic distortion (THD) measurement, and is made directly by the audio analyzer. The THD indicated by the audio analyzer includes the distortion added by the measuring receiver.

Required Test Equipment

Instrument	Critical Specifications for This Test	Recommended Model¹
Measuring Receiver	AM Demodulated Distortion (<50% AM) ≤ 0.3%	8902A
Audio Analyzer	Distortion (20 Hz to 20 kHz) < –80 dB2	8903B
Mixer3	RF/LO Freq. Range: 1 to 2800 MHz IF Frequency Range: 1.5 MHz RF 1 dB compression: +8 dBm RF/LO Freq. Range: 500 to 9000 MHz IF Frequency Range: 50 MHz	M/A-COM MDC-164
Local Oscillator3	Frequency Range: 800 to 2500 MHz Amplitude:16 dBm	E8267D

Refer to the main equipment list for alternate models.
The distortion accuracy of the 8903B is worse than the specified AM distortion of the DUT. Therefore, the indicated distortion must be greater than the specification by at least the amount of the 8903B distortion measurement accuracy.
Not used for ESGs with frequency range < 2 GHz.

Connections and Setup Procedures

All test equipment requires a 30 minute warm-up period to ensure accurate performance.
In the following test setup, direct cable and adapter connections are designated as solid lines. Changeable cable and adapter connections are designated as dashed lines.
Connect all test equipment as shown.
Connect GPIB cables to all GPIB-controlled test equipment.
While performing this test, follow all instructions on the controller display.

Measuring Receiver Calibration Setup

AM Distortion CW Frequency < = 1300 MHz Test Setup

AM Distortion CW Frequency > 1300 MHz