JPH065227U - Radio receiver - Google Patents

Abstract

(57) [Summary] [Object] To provide a radio receiver having a simple circuit configuration and capable of removing adjacent channel interference with good response. A noise level discriminating means 13 for discriminating that noise at the time of signal reception of a current receiving station exceeds a predetermined value,
A counter 12 that detects the passage of a predetermined period from when the noise level exceeds a predetermined value, and a predetermined frequency above and below the current reception frequency when the noise level exceeds a predetermined value or when the predetermined period elapses. When the difference between the electric field strength at that time and the electric field strength at the time of receiving the current reception signal is judged to be a predetermined value or more, the adjacent interference judgment means 14 for judging the degree of adjacent interference based on the difference in electric field strength, and the adjacent interference judgment means The intermediate frequency control means 16 for changing the intermediate frequency to the one with less interference based on the determination of 14, and the filter switching control for selectively switching the intermediate frequency bandwidth to the narrow bandwidth side based on the determination of the adjacent interference determination means 16. Means 17 and.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a radio receiver, and more particularly to a radio receiver with reduced adjacent channel interference.

[0002]

[Prior art]

 In order to reduce adjacent channel interference, conventional radio receivers track the center frequency of the intermediate frequency filter and control the band of the filter according to the reception condition.

[0003]

[Problems to be solved by the device]

 However, according to the above-described conventional radio receiver, the intermediate frequency filter section becomes very complicated, and a large-scale circuit is required. There was also the problem of being late.

An object of the present invention is to provide a radio receiver having a simple circuit configuration and capable of removing adjacent channel interference with good response.

[0005]

[Means for Solving the Problems]

 The radio receiver of the present invention is a radio receiver equipped with an electric field strength detection means, a frequency synthesizer capable of adjusting an intermediate frequency, and an intermediate frequency filter having a selectable intermediate frequency bandwidth, when receiving a signal from a current receiving station. Noise level discriminating means for discriminating that the noise level exceeds a predetermined value, timer means for detecting that a predetermined period has elapsed from when the noise level exceeds the predetermined value, and the noise level exceeding the predetermined value. Or when the predetermined period of time has elapsed, the upper and lower predetermined frequencies of the current receiving station frequency are searched, and it is determined that the difference between the electric field strength level at the search frequency and the electric field strength level of the current receiving station at the time of receiving the signal is a predetermined value or more. At this time, the adjacent disturbance discrimination means for discriminating the degree of adjacent disturbance based on the difference in the electric field strength level, and the intermediate circuit based on the discrimination by the adjacent disturbance discrimination means And a filter switching control means for selectively switching the intermediate frequency bandwidth to the narrow bandwidth side based on the discrimination of the adjacent disturbance discrimination means. To do.

[0006]

[Action]

 According to the radio receiver of the present invention, when the noise level determining means determines that the noise level at the time of signal reception from the current receiving station exceeds the predetermined value, or the noise level exceeds the predetermined value. When it is detected by the timer means that a predetermined period has passed, a predetermined frequency range above and below the current receiving station frequency is searched, and the electric field strength level at the searched frequency and the electric field strength level at the time of signal reception of the current receiving station. When the difference between and is greater than or equal to a predetermined value, the degree of adjacent interference is determined by the adjacent interference determination means based on the difference in the electric field strength level, and the intermediate frequency is determined by the intermediate frequency control means based on the determination by the adjacent interference determination means. It is changed to the one with less interference, and the intermediate frequency bandwidth is selectively narrowed based on the discrimination of the adjacent disturbance discrimination means by the filter switching control means. Is switched to the side, adjacent-channel interference is removed or is reduced.

[0007]

【Example】

 Hereinafter, the present invention will be described with reference to examples. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The radio receiver of the present embodiment cooperates with the front end 1 and the front end 1 to act as a local oscillator for converting to an intermediate frequency, and a PLL configuration in which the intermediate frequency is finely adjustable. , An intermediate frequency filter 3 that receives the intermediate frequency signal output from the front end 1 and that switches between wide band and narrow band, and an intermediate frequency amplifier circuit 4 that amplifies the output from the intermediate frequency filter 3. It includes a detection circuit 5 for detecting the output of the intermediate frequency amplification circuit 4, a stereo demodulation circuit 6 for stereo demodulating the detection output, and a mute circuit 7 for muting the stereo demodulation output to convert the received signal into an intermediate frequency signal. It performs the reception function of detecting and reproducing in stereo.

Further, the radio receiver of this embodiment is provided with an electric field strength detection circuit 8 for detecting the electric field strength from the output of the intermediate frequency amplifier circuit 4, and a noise detection circuit 9 for detecting the noise level from the detection output. .

Furthermore, in the radio receiver of this embodiment, the output from the reception frequency designating means 20, the electric field strength signal detected by the electric field strength detection circuit 8 and the noise level signal detected by the noise level detection circuit 9 are provided. When the noise frequency detected by the noise level detection circuit 9 is equal to or higher than a predetermined value, the output frequency of the frequency synthesizer 2 is set so as to receive the broadcast of the reception frequency designated by the reception frequency designating means 20. , Or when the noise level exceeds a predetermined value and a predetermined period has elapsed, the output of the frequency synthesizer 2 is changed to search the received frequency, and the electric field strength detected by the electric field strength detection circuit 8 is above the predetermined level. When there is, it is determined that there is interference, and the intermediate frequency is changed based on the level of electric field strength in the direction without interference. In addition to the intermediate frequency control, there is provided a microcomputer 10 for performing switching control of the intermediate frequency filter 3 and mute control for performing a mute operation via a mute circuit 11 during search control, intermediate frequency control and filter switching control.

Therefore, in addition to the RAM 11 that stores the electric field strength value detected by the electric field strength detection circuit 8, the microcomputer 12 functionally functions as an interval counter that constitutes a timer unit for performing a search at predetermined intervals. Based on the electric field strength level detected by the electric field strength detection circuit 8 (hereinafter referred to as a counter) 12, the noise level judgment means 13 for judging whether the noise level detected by the noise level detection circuit 9 is a predetermined value or more. Adjacent interference determination means 14 for determining the degree of adjacent interference, search control means 15 for searching the reception frequency based on the output of the noise level determination means 13 or the output of the counter 12, and the determination of the adjacent interference determination means 14. An intermediate frequency control means 16 for changing the intermediate frequency based on Filter switching control means 17 for selectively switching the bandwidth of the intermediate frequency filter based on the discrimination of No. 4 and mute control means 18 for controlling the muting circuit 7 during search control, intermediate frequency control and filter switching control. ing.

The operation of the present embodiment configured as described above will be described with reference to the flowchart of FIG.

During reception of a broadcast from a broadcasting station having a reception frequency designated by the reception frequency designating means 20, it is determined whether or not the noise level detected by the noise level detecting circuit 9 exceeds a predetermined value. If the level exceeds the predetermined value, it is determined that interference has occurred, the counter 12 is reset (step S17), and after step S17, the electric field strength level at the current reception frequency is It is stored in the area a of the RAM 11 (step S 1).

When it is determined in step S15 that the noise level is equal to or lower than the predetermined value, it is not determined that interference has occurred, and it is determined whether the counter 12 has overflowed (step S16), and it is determined that overflow has occurred. At this time, the counter 12 is reset (step S17), and then step S1 is executed. When it is determined in step S16 that the counter 12 has not overflowed, the counter 12 is set (step S14), and then step S15 is executed.

Therefore, when the noise level exceeds a predetermined value, or when a predetermined period set by the counter 12 has elapsed, step S1 is executed and the mute control means 18 controls the mute circuit 7. The mute state is set (step S2). Following step S2, the search control means 15 starts the search of the reception frequency. That is, the frequency division ratio of the frequency divider that constitutes a part of the frequency synthesizer 2 is controlled to a frequency division ratio of one step lower to control a frequency reception state one step lower (step S3), and detection at the reception frequency is performed. The electric field strength level is stored in the area b of the RAM 11 (step S4).

Subsequent to step S4, the frequency division ratio of the frequency divider forming part of the frequency synthesizer 2 is controlled to be one step higher than the frequency division ratio for the received frequency in step S1. Is controlled to the frequency receiving state (step S5), and the detected electric field strength level at the receiving frequency is stored in the area c of the RAM 11 (step S6). Therefore, the reception frequency is searched for in steps S3 and S5, and the electric field strength level at the reception frequency by the search is stored in steps S4 and S6.

Subsequent to step S6, the electric field strength levels stored in the areas a, b and c of the RAM 11 are compared by the adjacent disturbance discriminating means 14 so that only one side, that is, the upper or lower receiving frequency is received. It is checked whether there is interference (step S7). This check is determined by whether or not the difference between the electric field strength level stored in the area a of the RAM 11 and the electric field strength level stored in the areas b and c of the RAM 11 is larger than a predetermined value. When it is determined that one of the electric field intensity levels stored in the area is higher than the electric field intensity level stored in the area a of the RAM 11, it is determined that there is interference on only one side.

If it is determined in step S7 that there is interference on only one side, the difference in electric field strength level is compared with a predetermined interference level to determine whether the interference level is large, medium, or small, and the interference level is determined. Steps S9 to S11 are executed based on the large, medium, and small. When it is determined that the interference level is low, the intermediate frequency is finely adjusted in the direction of decreasing the interference (step S9), the mute by the mute circuit 7 is released (step S13), and then step S14 is executed. . Therefore, when the disturbance is small, the fine adjustment of the intermediate frequency substantially eliminates the disturbance.

When it is determined in step S8 that the interference level is medium, the intermediate frequency is changed by 10 kHz in the direction in which the interference is reduced, and the intermediate frequency filter 3 is controlled to be switched to the narrow band filter side (step S10). Next, step S13 is executed. Therefore, the interference is substantially eliminated by changing the intermediate frequency by 10 kHz when the interference is medium and narrowing the band of the intermediate frequency filter 3.

When it is determined in step S8 that the interference level is high, the intermediate frequency is changed by 20 kHz in the direction in which the interference is reduced, and the intermediate frequency filter 3 is controlled to be switched to the narrow band filter side (step S11). Next, step S13 is executed. Therefore, the disturbance is substantially eliminated by changing the intermediate frequency by 20 kHz when the disturbance is large and narrowing the band of the intermediate frequency filter 3. The change of the intermediate frequency in steps S9 to S11 is executed by changing the frequency division ratio of the frequency divider constituting a part of the frequency synthesizer 2.

When it is not determined that there is interference on only one side in step S7, the intermediate frequency filter 3 is switched to the wide band filter side without changing the intermediate frequency following step S7 (step S12), and then, Step S13 is executed. In this case, there is no interference or there is interference on both sides, and the intermediate frequency remains unchanged.

Next, another embodiment of the present invention will be described. This embodiment shows an example of a case where the preset frequency is called out. FIG. 3 is a flow chart for explaining the operation of another embodiment of the present invention.

When the preset frequency calling is started, the mute circuit 7 is controlled to the mute state (step S21), and the received preset channel reception frequency, the adjacent frequency one step below the preset channel reception frequency, and one step. Adjacent frequencies on the upper side are received, the electric field strengths at the time of receiving the respective frequencies are detected, and stored in the areas a, b, and c of the RAM 11 (steps S22 to S27).

After step S27, as in step S7, it is checked whether there is interference on only one side (step S28). When it is determined that there is interference on only one side, the same as steps S8 to S11. In addition, when the disturbance level is small, the intermediate frequency is finely adjusted to reduce the interference, and when the disturbance level is medium, the intermediate frequency is changed to 10 kHz and the intermediate frequency filter 3 is narrow band. When the interference level is switched to the filter side and the interference level is high, the intermediate frequency is changed to the direction in which there is less interference at 20 kHz, and the intermediate frequency filter 3 is switched to the narrow band filter side (steps S29 to S32), and interference is generated on only one side If it is not determined that there is, the intermediate frequency is not changed and the intermediate frequency filter 3 is set to a wide band as in step S12. It is switched (step S33).

By executing steps S30, S31, S32, and S33, the preset channel can be received, and then the mute is released in the same manner as in step S13 (step S34), and the process ends.

[0026]

[Effect of device]

 As described above, according to the present invention, when it is determined that the noise level at the time of receiving a signal from the current receiving station exceeds the predetermined value, or when the noise level exceeds the predetermined value, the predetermined period has passed. When it is detected, the frequency range above and below the current receiving station frequency is searched, and when it is determined that the difference between the electric field strength level at the searched frequency and the electric field strength level at the time of signal reception of the current receiving station is equal to or more than a predetermined value, the electric field strength The degree of adjacent interference is determined based on the level difference, the intermediate frequency is changed to the one with less interference based on the determination of the degree of adjacent interference, and the intermediate frequency bandwidth is selectively selected based on the determination of the degree of adjacent interference. Since switching to the narrow bandwidth side is performed, adjacent interference can be removed or reduced by changing the intermediate frequency and narrowing the intermediate frequency bandwidth.

Further, even when a predetermined time has elapsed since the noise level exceeded a predetermined value, the presence or absence of adjacent interference is checked and the adjacent interference is removed, so that it is possible to prevent the interference. There is also an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of one embodiment of the present invention.

FIG. 3 is a flowchart for explaining the operation of another embodiment of the present invention.

[Explanation of symbols]

 1 Front End 2 Frequency Synthesizer 3 Intermediate Frequency Filter 4 Intermediate Frequency Amplifier Circuit 5 Detection Circuit 6 Stereo Demodulation Circuit 7 Mute Circuit 8 Field Strength Detection Circuit 9 Noise Detection Circuit 10 Microcomputer 11 RAM 12 Counter 13 Noise Level Discrimination Means 14 Adjacent Disturbance Discrimination Means 15 Search control means 16 Intermediate frequency control means 17 Filter switching control means

Claims (1)

[Scope of utility model registration request] 1. A radio receiver comprising electric field strength detecting means, a frequency synthesizer capable of adjusting an intermediate frequency, and an intermediate frequency filter having a selectable intermediate frequency bandwidth, wherein a noise level at the time of receiving a signal from a current receiving station. Noise level determining means for determining that is above a predetermined value,
Timer means for detecting the passage of a predetermined period from when the noise level exceeds a predetermined value, and searching for a predetermined frequency above and below the current receiving station frequency when the noise level exceeds the predetermined value or when the predetermined period has elapsed. An adjacent interference determining means for determining the degree of adjacent interference based on the difference in the electric field strength level when the difference between the electric field strength level at the search frequency and the electric field strength level at the time of signal reception of the current receiving station is determined to be a predetermined value or more. An intermediate frequency control means for changing the intermediate frequency to a direction with less interference based on the discrimination of the adjacent interference determination means, and a filter for selectively switching the intermediate frequency bandwidth to the narrow bandwidth side based on the determination of the adjacent interference determination means. A radio receiver comprising a switching control means.