CHANNEL SELECTION METHOD FOR RADIO RECEIVER AND RADIO RECEIVER USING IT

PURPOSE: To surely select a channel at a high speed by scanning channels in a frequency band of a signal when the signal is detected in a 1st scanning step and shifting a frequency of a local oscillator so that a desired channel frequency specified in a 2nd scanning step comes to the center of the band. CONSTITUTION: An upper side threshold voltage V2 and a lower threshold voltage V1 are set as shown in a characteristic of a frequency discriminator 103. An output voltage of a discriminator 103 with respect to a center frequency F0 of the current IF band is set to V0, then the voltage V2 corresponds to a frequency between the F0 and F0+(one channel step), the voltage V1 corresponds to a frequency between the F0 and F0-(one channel step), the voltage V4 corresponds to a frequency between the F0 and F0+(1/2 channel step), and the voltage V3 corresponds to a frequency between the F0 and F0-(1/2 channel step). When an output voltage Vd of the discriminator 103 is discriminated between the voltages V1 and V0, a desired frequency is searched.