Spectrum analyser especially for TV signal analysis

摘要

The analyser includes two frequency converters (17,22). The frequency of a modulated signal at the input to the second frequency converter is wobbled, while the modulation frequency of the signal at the first frequency converter is held constant in order to determine the input signal frequency. The output signal from the first frequency converter is branched off to a demodulator (41) in order to monitor the demodulated signal (44). For TV signals the analyser can determine the in-band noise level during unmodulated interval, and the peak picture carrier signal. The signal-to-noise ratio is calculated and displayed.