| 摘要 |
PURPOSE:To realize automatic setting to an intermediate frequency that receives no disturbance of a disturbance signal, by applying the signal corresponding to the triple frequency signal simultaneously supplied to a local oscillator of the other side to a local oscillator or the like in case the spurious disturbance signal is mixed. CONSTITUTION:A means to extract the triple frequency signal of the intermediate frequency is provided to a frequency converting and amplifying circuit of heterodyne system. This triple frequency signal is applied to a local oscillator and a filter in case the spurious disturbance signal is mixed to ensure an automatic change of the intermediate frequency. For instance, the disturbance signal in the output signal L of a multiplier 1 is detected by a detector 21, and a switch 18 is turned on. On the other hand, the triple frequency signal in the output signal K of a multiplier 2 controls the intermediate frequencies produced from local oscillators 10 and 11 to a high or low level via nonreverse amplifiers 23 and 24 and in the form of a voltage signal R, and at the same time ensures a coincidence between the passes frequency of each filter and the intermediate frequency. |
