| 摘要 |
PURPOSE:To easily realize a receiver capable of quaternary FSK reception by applying frequency conversion on an output from a conventional binary FSK direct conversion reception system by a low frequency signal. CONSTITUTION:A logic signal keeping a phase difference of pi /2 can be obtained by a low frequency oscillator 27 having center frequencies delta1 and delta2, a frequency converter 28, low-pass filters 30 and 31, and limiters 32 and 33. It is decided whether the frequency shift of reception waves of a Q2 signal and an 12 signal that are the outputs of the limiters 32 and 33 are the delta1 or the delta2 by an identification device 34 constituted similarly as an identification device 26, however, phase relation between the Q1 signal and the 11 signal is inverted by the frequency of the reception wave. Therefore, the output of the identification device is inverted based on the the (1) or the (0) of the output of the identification device 26. ln such a way, information representing the altitude of a frequency for a local oscillation frequency are outputted to a terminal 36, and identification information with respect to the delta1 and the delta2 are outputted to a terminal 37.
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