US 4,792,988 AGranted

Radio receiving circuit with a search tuning mechanism

AssigneeNihon Technical Kabushiki Kaisha

InventorsTamaki Ohashi, Toshiyuki Matsuda

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Abstract

A radio receiving circuit provided with a search tuning mechanism. A broadcasting radiowave signal is received during a search tuning operation, and a shift amount of frequency produced in frequency of an intermediate frequency amplifier output is experimentally determined within an inertia self-travelling time interval search tuning mechanism due to the mechanical inertia thereof from the moment at which a drive force applied to the search tuning mechanism is interrupted to the time when the mechanism temporarily positively stops its function. The drive force applied to the search tuning mechanism is interrupted at a frequency deviated by the shift amount in advance from a center frequency of a pass band width of the intermediate frequency amplifier circuit, whereby after the mechanism has self-travelled due to its own mechanical inertia force and when tuned to the center frequency of the received radiowave signal, the search tuning operation is suspended.

Claims14

Dependent claims

A radio receiving circuit with a search tuning mechanism, said radio receiving circuit including an intermediate frequency amplifier circuit, said search tuning mechanism having an inertia which determines an inertia travelling time during which the tuning mechanism travels after suspension of a drive force applied thereto, and including a control circuit which receives a part of an output signal from said intermediate frequency amplifier circuit, said control circuit comprising:

an oscillator circuit for producing an oscillating output oscillating at a center frequency in a pass band of said intermediate frequency amplifier circuit;
a mixing circuit for mixing and detecting the oscillating output of said oscillating circuit and the output signal of said intermediate frequency amplifier circuit;
and
a setting circuit which receives an output signal of said mixing circuit and which presets a predetermined amount of variation of frequency or predetermined shift width of frequency relative to the center frequency within the pass band of said intermediate frequency amplifier circuit so that said setting circuit produces an output signal effective to intermittently suspend the application of the drive force according to the output signal of said mixing circuit, said amount of variation of frequency or said shift width of frequency preset by said setting circuit corresponding to the inertia travelling time of said search tuning mechanism.

1 more element

Dependencies are inferred from the claim text.