Ghost measurement by waveform synthesis

A television ghost is measured by synthesizing the ghost waveform demodulated by an in-phase synchronous demodulator. For this purpose, the calculated in-phase and quadrature demodulated waveforms of known transmitted waveforms are prepared at the receiving site. A ghost path is constructed by a software simulator where a ghost waveform is synthesized by changes in the ghost parameters consisting of the amplitude, phase and time delay. The ghost parameter in which a synthesized ghost waveform in the simulator equals the demodulated ghost waveform is the ghost parameter itself of a real ghost path. The steepest descent method is used to optimize the ghost parameter in the simulator. The proposed ghost measurement method uses only a synchronous demodulated waveform. Therefore, as compared with the conventional method using quadrature demodulated waveforms, the circuit scale is small, and it is possible to avoid measurement errors caused by phase fluctuations in the quadrature demodulator.