HIGH FREQUENCY RECEIVING CIRCUIT

摘要

PURPOSE:To facilitate an easy adjustment of a noise index and to prevent the deterioration of the noise index, by providing a filter between a receiving terminal of a high frequency signal and a mixing circuit and furthermore setting a phase circuit between the filter and the mixing circuit. CONSTITUTION:The signal received through a receiving terminal 10 is applied to a filter 6 and converted into a signal of a prescribed frequency band to be applied to a phase circuit 8. The phase is adjusted through the circuit 8, and this phase-adjusted signal is applied to a mixer 2 to be mixed with the signal that is amplifier by an amplifier 4 and supplied from a local oscillator 5. Then an IF signal is fed to an IF amplifier 3, and the IF signal amplified by the amplifier 3 is delivered to a transmission line 20. If a receiving circuit has a preamplifier, this preamplifier is set between the circuit 8 and the mixer 2. Then the noise index is simply adjusted by the circuit 8. Thus the general noise index is improved.