Measurement of AM to PM conversion in medium wave AM transmitter

A method for measuring AM (amplitude modulation) signal distortion caused by AM to PM (phase modulation) conversion at the output of an AM radio transmitter is presented. A novel type of measuring instrument is also presented for testing the phase distortion which may occur in an AM radio transmitter when an AM modulation signal is applied. The down-converted AM signal is first divided into the inphase and orthogonal-phase components, and these signals are processed by an operational circuit to obtain phase distortion, which is the angle between the orthogonal-phase and inphase components. A phase angle of 10 degrees or more is detected in the prototype version.<
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