Amplitude modulated high frequency signal detection device

Claim 1

A high frequency signal detection device to be used in an information playback system for playing back information from a record medium having a plurality of record tracks by means of a pickup, comprising: a first positive peak hold circuit responsive to a high frequency input signal from the pickup, for holding positive peaks of the high frequency input signal and having a first predetermined time constant; a second positive peak hold circuit responsive to said high frequency input signal, for holding positive peaks for the high frequency input signal and having a second predetermined time constant which is greater than said first predetermined time constant; a negative peak hold circuit responsive to the high frequency input signal, for holding negative peaks of the high frequency input signal; a difference circuit connected to said first positive peak hold circuit and said negative peak hold circuit, and for generating a difference signal between an output signal of said first positive peak hold circuit and an output signal of said negative peak hold circuit; and a comparator circuit connected to said difference circuit and said second positive peak hold circuit for comparing said difference signal with a signal corresponding to a peak hold output signal of said second positive peak hold circuit, and producing a comparator output signal as a detection signal of the high frequency input signal.