Transmitting and receiving apparatus capable of the suppression of the microphonic noise in digital transmission system

摘要

A transmitting and receiving apparatus has: modulating circuit for modulating an input digital data; first frequency converting circuit for converting a signal output from said modulating circuit into a signal of a predetermined frequency; amplifying/branching circuit for amplifying and branching a signal output from said first frequency converting circuit; second frequency converting circuit for converting a signal output from said amplifying/branching circuit, into a signal of a predetermined frequency; and demodulating means for demodulating a digital data from a signal output from said second frequency converting circuit, wherein each of said first and second frequency converting circuit comprises a PLL frequency synthesizer, said demodulating means has a carrier recovery section, and natural angular frequencies of said PLL frequency synthesizers are set to be equal to a maximum frequency of mechanical vibrations which are externally applied, or in a predetermined width above and below the maximum frequency, or a loop filter bandwidth of said carrier recovery section is set to be higher by a predetermined amount than the maximum frequency of mechanical vibrations which are externally applied.