JPH0555645U - AM stereo broadcast receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to prevent radio interference from adjacent channels that are broadcast at high output and stereo malfunctions. [Structure] Detects interference due to high-power broadcasting of adjacent channels, switches the filter of the intermediate frequency amplifier circuit from a wide band filter to a narrow band filter, and uses it.
By stopping the VCO operation by the VCO operation stop circuit of the stereo decoder, it is possible to prevent the interference and the stereo malfunction of the high output broadcast of the adjacent channel.

Description

[Detailed description of the device]     [0001]   [Industrial application]   The present invention relates to an AM stereo broadcast receiver, and particularly to prevent interference and stereo malfunction. The present invention relates to an AM stereo broadcast receiver that stops.     [0002]   [Prior Art]   A typical configuration example of a conventional AM stereo broadcast receiver is shown in FIG.   After the AM signal received via the antenna is amplified by the high frequency amplifier circuit 1, It is output to the mixing circuit 2. The mixing circuit 2 outputs the output signal from the high frequency amplifier circuit 1, Intermediate frequency tuned by mixing the output signals from the local oscillator circuit 3 The signal is sent to the intermediate frequency amplifier circuit 4. The intermediate frequency amplifier circuit 4 receives the received signal A band is selected based on whether it is a stereo broadcast or a monaural broadcast, and a band signal is amplified. In this way, the amplified signal is processed by the AM stereo decoder 7 in a predetermined stereo. Decoding processing is performed and L channel and R channel audio signals are output.     [0003]   [Problems to be solved by the device]   As described above, in the conventional AM stereo broadcast receiver, the reception frequency broadcast is broadcast. It is decided whether it is an O broadcast or a monaural broadcast, and based on this discrimination result The bandpass filter provided in the frequency amplification circuit is switched and used.   Although such a configuration does not cause any problem when receiving a broadcast of a desired frequency, Mixing and stereo malfunctions when high-power broadcasts from adjacent channels There is a problem that works will occur.     [0004]   Therefore, the purpose of this invention is to mix radio waves from adjacent channels that are broadcast at high output. To provide an AM stereo broadcast receiver capable of preventing a false signal and stereo malfunction. It is in.     [0005]   [Means for Solving the Problems]   In order to solve the above problems, the AM broadcast receiver according to the present invention is   An intermediate frequency signal is obtained by an intermediate frequency amplifier circuit from the received signal, and AM stereo decoding is performed. AM stereo broadcast reception that outputs L channel and R channel audio signals from D In the machine   Wideband filter and narrowband filter provided in the processing system of the intermediate frequency amplifier circuit With   A VCO stop circuit provided in the AM stereo decoder system,   In the normal reception state, the wideband filter is selected and the VCO stop The stop circuit is turned off, and the narrow band filter is activated in the abnormal reception state. And a changeover switch for turning on the VCO stop circuit, It is configured with.     [0006]   [Action]   In this device, interference such as high-power broadcasting of an adjacent channel is detected and the intermediate frequency is detected. Switch the filter of the wave amplification circuit from wideband filter to narrowband filter and use At the same time, the VCO operation stop circuit of the AM stereo decoder stops the VCO operation. By doing so, the interference of high-power broadcasting of adjacent channels and stereo malfunction can be prevented. Stop.     [0007]   【Example】   Next, this invention will be described with reference to the drawings.   FIG. 1 is a block diagram showing an embodiment of an AM broadcast receiver according to the present invention. Figure 1 In FIG. 2, the components having the same reference numerals as those in FIG. 2 indicate the components having the same function. You   The received signal amplified by the high frequency amplifier circuit 1 is fed to the local oscillation circuit in the mixing circuit 2. 3 is mixed with the local oscillation signal from 3 and converted into an intermediate frequency signal, and the intermediate frequency amplifier circuit 4 Sent to. The processing system of the intermediate frequency amplifier circuit 4 includes a narrow band filter 5 and a wide band filter. The filter 6 is connected via the changeover switches SW1 and SW2. Switching these Wideband filter 6 is selected during normal broadcast reception using switches SW1 and SW2 So that the narrow band filter 5 is selected when the interference from the adjacent channel occurs. Is configured. The output signal from the intermediate frequency amplifier circuit 4 is an AM stereo decoder. 7 is output. The AM stereo decoder 7 controls the voltage of the receiver system. The VCO stop circuit 8 for stopping the operation of the oscillator (VCO) is the changeover switch SW3. Connected through.     [0008]   Now, in the broadcast receiving state, during normal reception, the changeover switches SW1 and SW2 Switching control to select the wide band filter 6 of the intermediate frequency amplifier circuit 4 Reception processing is performed, and the changeover switch SW3 of the VCO stop circuit 8 is “OFF”. The VCO is in an operational state, and the AM stage is used for stereo broadcasting and monaural broadcasting. The Rheo decoder 7 generates L channel and R channel audio signals.   On the other hand, when there is interference from an adjacent channel, the changeover switches SW1 to SW1 The narrow band filter 5 of the intermediate frequency amplifier circuit 4 is selected by W3, and VC The O stop circuit 8 operates and the AM stereo decoder circuit 7 outputs a monaural L channel. The channel and R channel audio signals are output.     [0009]   [Effect of the device]   As described above, the AM stereo broadcast receiver according to the present invention is provided with an adjacent channel. The interference of the high-power broadcasting of the channel is detected, and the filter of the intermediate frequency amplifier circuit is wideband. Switching from bandpass filter to narrowband filter Since the VCO operation is stopped by the VCO operation stop circuit of the It is possible to prevent interference of high-power broadcasting of the channel and stereo malfunction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an embodiment of an AM stereo broadcast receiver according to the present invention. FIG. 2 is a configuration diagram of a conventional AM stereo broadcast receiver. [Explanation of Codes] 1 high frequency amplification circuit 2 mixing circuit 3 local oscillation circuit 4 intermediate frequency amplification circuit 5 narrow band filter 6 wide band filter 7 AM stereo decoder 8 VCO
Stop circuit

Claims (1)

[A utility model registration claim] In an AM stereo broadcast receiver which obtains an intermediate frequency signal from a received signal by an intermediate frequency amplifier circuit and outputs L channel and R channel audio signals from the AM stereo decoder, said intermediate frequency amplifier circuit A wideband filter and a narrowband filter provided in the processing system, a VCO stop circuit provided in the AM stereo decoder system, the wideband filter is selected in a normal reception state, and the VCO stop circuit is turned off. The AM stereo broadcast receiver is characterized by further comprising: a changeover switch for selecting the narrow band filter and for turning on the VCO stop circuit when in an abnormal reception state.