JPH05335980A - Receiver - Google Patents

Abstract

PURPOSE:To simplify the operation by controlling the receiver automatically in an optimum setting state in response to the reception state. CONSTITUTION:A reception signal received by one antenna 10 is converted to a 1st intermediate frequency signal via a 1st intermediate frequency amplifier circuit 18, the converted signal is divided into two, either of signal is converted to a 1st demodulation signal by a 1st demodulation circuit 36 via a broad band filter 22, a band width variable filter 26 and a 2nd intermediate frequency amplifier circuit 28, and the other signal is converted to a 2nd demodulation signal by a 2nd demodulation circuit 48 via a narrow band filter 24 and a 3rd intermediate frequency amplifier circuit 46. Moreover, the 1st and 2nd intermediate frequency amplifier circuits 18, 28 are controlled by an AGC means 32 with the 2nd intermediate frequency signal as an input. Then the amplitude fluctuation periods of 1st and 2nd demodulation signals are compared by a comparison control means 52 and the time constant of the AGC means 32 and the band width of the band width variable filter 26 are controlled automatically in an optimum setting state with respect to the reception state depending on the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver which is automatically controlled to an optimum setting state according to the condition of a received signal.

[0002]

2. Description of the Related Art A technique for switching and selecting any one of a plurality of IF band filters incorporated in a receiver according to the condition of a received signal is disclosed in Japanese Patent Laid-Open No. 3-187623. Briefly explaining this technique, the tuning frequency of the receiver is shifted to a predetermined range above and below the target reception frequency by the user, and the transmission frequency of another station in the vicinity of the target reception frequency is calculated from the level of the received signal obtained by shifting. The presence / absence of the signal is determined, and if the signal of the transmission frequency of the other station exists at a strong level, the narrow band IF band filter is selected, and if it does not exist, the wide band IF band filter is selected.

This technique is excellent in that the conventional user automates the manual selection and switching of the IF band filter based on the user's judgment by listening to the demodulated output of the target reception frequency from the receiver. Is. Then, by automating, distortion due to intermodulation can be removed.

[0004]

By the way, in the above-mentioned prior art, in order to determine the presence of the signal of the transmission frequency of the other station based on the level of the received signal of only that frequency, the reception of the target reception frequency is performed. The IF band filter is not selected by relative comparison between the signal and the received signal of the transmission frequency of another station close to the signal. As a result, even if the level of the reception signal of the target reception frequency is considerably higher than the level of the reception signal of the transmission frequency of the other station, if the reception signal of the transmission frequency of the other station exceeds the predetermined level, the narrow band If the IF band filter is selected, the sound quality is unnecessarily deteriorated. Also, although the level of the received signal of the target reception frequency and the level of the received signal of the transmission frequency of another station are relatively similar in magnitude, if both levels are low, a wideband IF band filter is selected, and There is a problem that modulation is likely to occur.

Further, in the above-mentioned prior art, no consideration is given to performing proper AGC control in response to a change in volume due to fading.

The present invention performs appropriate AGC control in response to fading which is not considered in the prior art, improves the clarity of the demodulation output of the target reception frequency depending on the presence or absence of interference signals, or improves the sound quality. It aims at proposing a receiver adapted to improve.

[0007]

In order to achieve such an object, in the receiver of the present invention, one antenna and a part of the received signal received by this antenna are passed through a wide band filter to obtain a first signal. A first demodulation signal in the demodulation circuit and a first reception system including AGC means, and a second demodulation circuit in which a part of the reception signal is passed through a narrow band filter to form a second demodulation signal And a comparison control means for comparing the amplitude fluctuation cycle of the first demodulated signal and the amplitude fluctuation cycle of the second demodulated signal and controlling the time constant of the AGC means based on the comparison result. , And are configured.

In the receiver of the present invention, one antenna and a part of the reception signal received by this antenna are first demodulated by the first demodulation circuit through the wide band filter and the bandwidth variable filter. A first reception system for converting the received signal into a signal, a second reception system for converting a part of the reception signal into a second demodulation signal by a second demodulation circuit through a narrow band filter, and a first reception system for the first demodulation signal. Comparison control means for comparing the amplitude fluctuation cycle and the amplitude fluctuation cycle of the second demodulated signal and controlling the bandwidth of the bandwidth variable filter based on the comparison result may be provided.

In the receiver of the present invention, one antenna and a part of the reception signal received by this antenna are converted into the first demodulation signal by the first demodulation circuit via the noise blanker and the AGC is performed. A first reception system including a means, a second reception system in which a part of the reception signal is converted into a second demodulation signal by a second demodulation circuit through a narrow band filter, and a noise detection signal of the noise blanker Amplitude fluctuation period of the second and the second
And a comparison control means for controlling the time constant of the AGC means based on the comparison result.

In the receiver of the present invention, one antenna and a part of the received signal received by this antenna are passed through the noise blanker and the bandwidth variable filter to the first demodulation circuit and the first demodulation circuit. A first reception system that is a demodulated signal, a second reception system that partially converts the reception signal into a second demodulation signal by a second demodulation circuit through a narrow band filter, and noise detection of the noise blanker. The amplitude variation cycle of the signal and the second
Comparison control means for comparing the amplitude fluctuation period of the demodulated signal and controlling the bandwidth of the bandwidth variable filter based on the comparison result.

Further, the receiver of the present invention uses the reception signal received by the antenna as a demodulation signal by the demodulation circuit through the noise blanker and the filter having a narrower bandwidth, and a reception system including AGC means, The amplitude fluctuation cycle of the noise detection signal of the noise blanker is compared with the amplitude fluctuation cycle of the demodulation signal, and the AGC is performed based on the comparison result.
And a comparison control means for controlling the time constant of the means.

Furthermore, the receiver of the present invention is a receiving system in which a reception signal received by an antenna is converted into a demodulation signal by a demodulation circuit through a noise blanker and a bandwidth variable filter having a narrower bandwidth, and the noise. A comparison control means for comparing the amplitude fluctuation cycle of the blanker noise detection signal and the amplitude fluctuation cycle of the demodulated signal and controlling the bandwidth of the bandwidth variable filter based on the comparison result. Is also good.

[0013]

[Operation] In the receiver according to claim 1, since the second demodulated signal obtained by the second receiving system passes through the narrow band filter, a signal of only the target receiving frequency is obtained, but the first receiving system Since the first demodulated signal obtained in (1) passes through the wide band filter, the signal of the target reception frequency and the signal of the transmission frequency of another station in the vicinity thereof are superimposed. And the first
And the amplitude fluctuation cycle of the second demodulated signal match, the signal of the transmission frequency of the other station does not exist and the interference signal does not exist. If they do not match, the interference signal exists. Can be determined. Therefore, by controlling the time constant of the AGC means according to the degree of coincidence of the amplitude fluctuation cycles, it is possible to suppress the level fluctuation of the demodulation output due to the intermodulation. Also, the first and second
If the amplitude fluctuation cycle of the demodulated signal is the same, and if the cycle is a predetermined length of several seconds or more, fading has occurred, and the level fluctuation of the demodulated output is suppressed by controlling the time constant of the AGC means. obtain.

In the receiver according to the second aspect, since the second demodulated signal obtained by the second receiving system passes through the narrow band filter, a signal having only the target receiving frequency can be obtained.
The first demodulated signal obtained in the first reception system is a signal in which the signal of the target reception frequency and the signal of the transmission frequency of another station in the vicinity thereof are superimposed according to the bandwidth of the bandwidth variable filter. Then, if the amplitude fluctuation periods of the first and second demodulated signals match, the interference signal does not exist, and if they do not match, it can be determined that the interference signal exists. Therefore, by controlling the bandwidth of the bandwidth variable filter according to the degree of coincidence of the amplitude fluctuation cycle, the bandwidth is widened without interference signals to improve the sound quality of the demodulation output of the target reception frequency,
If there is an interference signal, the bandwidth can be narrowed to improve the clarity of the demodulation output.

In the receiver according to claim 3, the first
The noise detection signal of the noise blanker provided in the reception system is a signal of the target reception frequency and a signal of the transmission frequency of another station in the vicinity thereof. Therefore, by controlling the time constant of the AGC means according to the degree of matching of the amplitude fluctuation cycle of the noise detection signal and the amplitude fluctuation cycle of the second demodulation signal and the frequency of the amplitude fluctuation cycle when they match, demodulation output due to interference or fading It is possible to suppress the fluctuation of the level.

Further, in the receiver according to claim 4,
If the amplitude fluctuation cycle of the noise detection signal and the second demodulation signal match, it is determined that there is no interference signal and the bandwidth of the variable bandwidth filter is widened to improve the sound quality. It can be determined that there is an interference signal or noise to narrow the bandwidth and improve the clarity of the demodulated output.

Further, in the receiver according to the fifth aspect, by setting the bandwidth of the filter narrower than the bandwidth of the noise blanker, the noise detection signal of the noise blanker is demodulated through the narrow bandwidth filter and demodulated. Signals other than the target reception frequency are contained more than signals. Then, if the amplitude fluctuation cycles of the noise detection signal and the demodulation signal match, there is no signal other than the target reception frequency, and if they do not match, it can be determined that there are many signals other than the target reception frequency.
Therefore, by controlling the time constant of the AGC means in accordance with the degree of coincidence of the amplitude fluctuation cycle and the frequency of the amplitude fluctuation cycle when they coincide with each other, the level fluctuation of the demodulation output can be controlled in the same manner as in claims 1 and 3. Can be suppressed.

Still further, in the receiver according to claim 6,
By controlling the bandwidth of the bandwidth variable filter according to the degree of matching of the amplitude fluctuation period of the demodulated signal obtained through the noise detection signal of the noise blanker and the bandwidth variable filter,
Similar to the second and fourth aspects, the intelligibility and sound quality of the demodulated output of the target reception frequency can be automatically controlled according to the reception situation.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the receiver of the present invention will be described below with reference to FIGS. FIG. 1 is a block circuit diagram of an embodiment of the receiver of the present invention, and FIG.
4 is a diagram for explaining the relationship between the bandwidths of the wide band filter and the narrow band filter of FIG. 3, FIG. 3 is a block circuit diagram of an example of the period detection circuit of FIG. 1, and FIG. 4 is an operation by the comparison control means of FIG. It is a flowchart explaining.

First, the structure will be described with reference to FIG. 1
The received signal received by the antenna 10 of the book is amplified by the high frequency amplifier circuit 12 and given to the first mixer 14, and is mixed with the first local oscillation signal from the first local oscillation circuit 16. The frequency-converted signal output from the first mixer 14 is supplied to the first intermediate frequency amplifier circuit 18, and the first intermediate frequency signal having a predetermined frequency is extracted and amplified and supplied to the distributor 20. The distributor 20 divides the first intermediate frequency signal into two, one of which is, for example, 20 KH.
a narrow band filter 2 having a bandwidth of z, and the other having a bandwidth of 3 KHz, for example.
Given to 4. As shown in FIG. 2, the bandwidth of the narrow band filter 24 is included in the bandwidth of the wide band filter 22.

The first intermediate frequency signal that has passed through the wide band filter 22 is applied to the second intermediate frequency amplifier circuit 28 via the variable bandwidth filter 26, amplified, and then applied to the second mixer 30. With that, a part of it is AG
It is given to the C means 32. In this second mixer 30,
The second local oscillation signal from the second local oscillation circuit 34 is given, the second intermediate frequency signal obtained by frequency-converting the first intermediate frequency signal is given to the first demodulation circuit 36, and the first demodulation circuit 36 is given. The demodulated signal is output. The first demodulated signal is amplified by the low frequency amplifier circuit 38 and output as a low frequency from the speaker 40. Further, a part of the first demodulated signal is given to the first period detection circuit 42, and a DC voltage signal according to the amplitude fluctuation period is given to the comparison calculation means 44 composed of a microcomputer or the like.

The first signal passed through the narrow band filter 24
The intermediate frequency signal of 1 is given to the third intermediate frequency amplifier circuit 46 to be amplified, and the amplified output is given to the second demodulation circuit 48 to output the second demodulated signal. The second demodulated signal is given to the second period detection circuit 50, and the DC voltage signal according to the amplitude fluctuation period is given to the comparison calculation means 44.

The first and second cycle detection circuits 42,
The comparison control means 52 is constituted by 50 and the comparison calculation means 44. Further, the bandwidth variable filter 26 is not limited to one in which a plurality of filters having different bandwidths are arranged in parallel and one of them is switched and selected by the signal of the comparison operation means 44, and a passband tuning circuit, an IF WIDTH circuit, or the like is used. The one used may be used. Furthermore, AGC means 3
Reference numeral 2 is a time constant based on the signal from the comparison calculation means 44 according to the signal level of the second intermediate frequency signal, and supplies the AGC signal to the first and second intermediate frequency amplifier circuits 18 and 28.

Then, the first and second cycle detecting circuits 42,
As shown in FIG. 3, an example of 50 is an edge detection circuit 54 that detects a rising edge or a falling edge due to amplitude fluctuation of a demodulated signal and outputs a pulse for each edge.
And a frequency-voltage conversion circuit 56 that outputs a DC voltage according to the frequency of these pulses, and outputs a DC voltage according to the amplitude fluctuation cycle.

Here, in a receiving situation in which the level of the signal of the transmission frequency of another station near the target reception frequency is low, and there is little disturbance noise or the like, there is no interference signal and intermodulation is less likely to occur, And the second demodulated signal show similar amplitude variations. In addition, if the signal level of the transmission frequency of another nearby station is high and there is a lot of disturbance noise or the like to cause intermodulation in the presence of interference signals, the amplitude fluctuations of the first and second demodulated signals will be different. They differ and the amplitude fluctuation periods do not match. Furthermore, if there is no interference signal but fading occurs, the amplitude fluctuation periods of the first and second demodulated signals match, but the periods become several seconds or longer.

The operation of the comparison control means 52 for automatically switching the receiver to the optimum setting state according to various reception conditions will be described with reference to FIG.

First, the first and second cycle detection circuits 42, 5
The difference between the two signals output at 0 is obtained by the differential amplification means of the comparison operation means 44, and the difference is squared to determine the degree of coincidence of the amplitude fluctuation periods of the first and second demodulated signals. Calculate (step). The squared calculation result becomes smaller as the amplitude fluctuation periods match, and the squared calculation result becomes larger as the amplitude fluctuation cycles do not match. Therefore, if the calculation result is large, the bandwidth is narrowed according to the value, and if the calculation result is small, the bandwidth is widened according to the value.
The variable bandwidth filter 26 is controlled by (step).
If the first and second amplitude fluctuation periods do not match and the calculation result is larger than the predetermined value (step), the comparison calculation means 44 controls the time constant of the AGC means 32 to decrease as the calculation result increases ( Step), and returns to the step. If it is determined in step that the first and second amplitude variation periods match, the length of the amplitude variation period is determined to detect the presence or absence of fading (step). If the amplitude fluctuation period is, for example, 2 seconds or less in this step, fading does not occur, and the time constant of the AGC means 32 is controlled according to the calculation result. Also, if the amplitude fluctuation cycle is 2 seconds or longer in the step, fading occurs. However, in the range of 2 to 4 seconds, the AGC can correspond to the fading cycle, and the amplitude fluctuation cycle is The longer the time, the smaller the time constant of the AGC means 32 is controlled in accordance with the amplitude fluctuation cycle (step), and the process returns to the step. Furthermore, if the amplitude fluctuation cycle is 4 seconds or more in step, the AGC cannot cope with the fading cycle and rather the amplitude fluctuation of the demodulation output is expanded, so the operation of the AGC means 32 is stopped. Then, the control is returned to the step (step). The length of the amplitude fluctuation cycle for determining whether or not fading has occurred is not limited to 2 seconds or 4 seconds as described above, and may be appropriately set from the viewpoint of hearing.

In this way, by comparing the amplitude fluctuation periods of the first and second demodulated signals, the reception status can be determined, and the receiver can be automatically switched to the optimum setting state according to the reception status. .. Therefore, the receiver of the present invention is more suitable than a receiver that manually switches the bandwidth of the bandwidth variable filter 26 and the time constant of the AGC means 32 manually by listening to the demodulated output of the target reception frequency and judging by the listener. , Its operation can be particularly omitted and it becomes simple.

Further, another embodiment of the receiver of the present invention will be described with reference to FIG. 5, circuit blocks that are the same as or equivalent to those in FIG. 1 are assigned the same reference numerals and overlapping description will be omitted. 5 is different from FIG. 1 in that a noise blanker 60 is provided instead of the wide band filter 22 of FIG. 1, and noise detection output from a noise detector 62 is used instead of the first demodulation signal. Signal is first
Is applied to the cycle detection circuit 42 and the output signal thereof is applied to the comparison calculation means 44. In the noise blanker 60, one of the first intermediate frequency signals divided by the distributor 20 is supplied to the noise gate 64 and the noise amplifier 66. The noise amplifier 66 amplifies the first intermediate frequency signal and supplies it to the noise detector 62, and the noise detector 62 outputs the noise detection signal. Then, this noise detection signal is supplied to the first period detection circuit 42 and the gate control circuit 68 having a threshold value. The gate control circuit 68 extracts the pulse noise included in the noise detection signal, and the noise gate 64 is turned on / off according to the extracted pulse noise.
The first intermediate frequency signal from which the pulse noise is removed by passing through the noise gate 64 is given to the variable bandwidth filter 26.

Here, in addition to the reception signal of the target reception frequency, the noise detection signal includes the transmission frequency of another nearby station and the reception signal due to disturbance noise. Therefore,
Amplitude fluctuation cycle of this noise detection signal and narrow band filter 2
4 is compared with the amplitude fluctuation cycle of the second demodulation signal consisting only of the reception signal of the target reception frequency, the receiver is set in the optimum setting state according to the reception condition, like the receiver shown in FIG. It is possible to automatically switch to.

In another embodiment of the receiver of the present invention shown in FIG. 5, the noise blanker 60 is used instead of the wide band filter 22 of the receiver shown in FIG. It is suitable to be applied to a receiver equipped with.

Still another embodiment of the receiver of the present invention will be described with reference to FIG. 6, circuit blocks that are the same as or equivalent to those in FIG. 5 are assigned the same reference numerals and overlapping description will be omitted.

6 is different from FIG. 5 in that the distributor 20, the narrow band filter 24, the third intermediate frequency amplification circuit 46 and the second demodulation circuit 48 in FIG. 5 are omitted, and the first intermediate frequency is omitted. The first intermediate frequency signal output from the amplifier circuit 18 is supplied to the noise gate 64 and the noise amplifier 66 of the noise blanker 60, and the first demodulation circuit 36.
That is, the first demodulated signal output from is supplied to the low frequency amplifier circuit 38 and the second period detection circuit 50. Moreover, the maximum bandwidth of the bandwidth variable filter 28 is set narrower than the bandwidth of the noise blanker 60.

In such a configuration, the noise detection signal has a larger number of transmission frequencies of other nearby stations other than the target reception frequency and the reception signal due to the disturbance noise as compared with the first demodulation signal due to the difference in bandwidth. May include. Therefore, by comparing the amplitude fluctuation cycle of the noise detection signal and the amplitude fluctuation cycle of the first demodulated signal,
Similar to the receiver shown in, the receiver can be automatically switched to the optimum setting state according to the reception situation.

In the description of the above embodiment, the comparison calculation means 44 performs software comparison calculation processing by using a microcomputer or the like, but the invention is not limited to this, and the comparison calculation means 44 is constituted by discrete components. Of course, it is also good. And, as a comparison calculation means, DSP
(Digital signal processor) may be used.
Further, it can be easily understood that the amplitude fluctuation cycles of the second and third intermediate frequency signals may be compared instead of performing the comparison calculation of the amplitude fluctuation cycles of the first and second demodulated signals. Let's see Similarly, instead of performing the comparison calculation of the amplitude fluctuation cycle of the noise detection signal and the second demodulation signal, the noise detector 6
It is also possible to compare the amplitude fluctuation cycle of the signal in the preceding stage of 2 and the amplitude fluctuation cycle of the third intermediate frequency signal. Further, in the above embodiment, the case of the single mode reception is described, but when the multimode switching reception function is provided, the pass band width of the narrow band filter 24 of the second reception system is changed according to the reception mode. May be appropriately controlled to be narrower than the bandwidth selected by the bandwidth variable filter 26 of the first receiving system.

[0036]

As is clear from the above description, the receiver of the present invention has the following special effects.

First, in the receiver according to claim 1, the amplitude fluctuation cycle of the received signal of the target reception frequency is compared with the amplitude fluctuation cycle of the received signal including the target reception frequency and the transmission frequencies of other stations in the vicinity thereof. As a result, it is possible to determine the reception status such as the presence of the interference signal or the occurrence of fading, and control the time constant of the AGC means or stop the operation of the AGC means. Therefore, the receiver is automatically adjusted to the optimum setting state according to the reception situation, and the operation is extremely simple.

Further, in the receiver according to the second aspect, the amplitude fluctuation periods are compared, and if there is no interference signal, the bandwidth of the variable bandwidth filter is widened to improve the sound quality. The width of the demodulated output can be narrowed to improve the clarity of the demodulated output, and the receiver is automatically adjusted to the optimum setting state according to the reception situation, and the operation is that simple.

Then, even in the receivers according to claims 3 and 4, like the receivers according to claims 1 and 2, the receiver is automatically adjusted to the optimum setting state according to the reception situation. , Easy to operate. Moreover, the noise detection signal of the noise blanker is used to determine the reception status, and is suitable for application to a receiver equipped with a noise blanker.

Further, even in the receivers according to claims 5 and 6, like the receivers according to claims 1 to 4, the receiver is automatically adjusted to the optimum setting state in accordance with the receiving condition. Easy to operate. Moreover, since the amplitude fluctuation cycle of the noise detection signal of the noise blanker and the demodulation signal are compared, a receiving system using a narrow band filter is not required, and a simpler configuration can be applied to a receiver equipped with a noise blanker. be able to.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of a receiver of the present invention.

FIG. 2 is a diagram illustrating a relationship between bandwidths of the wide band filter and the narrow band filter of FIG.

3 is a block circuit diagram of an example of the cycle detection circuit of FIG.

FIG. 4 is a flow chart for explaining the operation of the comparison control means of FIG.

FIG. 5 is a block circuit diagram of another embodiment of the receiver of the invention.

FIG. 6 is a block circuit diagram of still another embodiment of the receiver of the present invention.

[Explanation of symbols]

 10 Antenna 12 High Frequency Amplifier Circuit 14 First Mixer 18 First Intermediate Frequency Amplifier Circuit 20 Distributor 22 Wideband Filter 24 Narrowband Filter 26 Bandwidth Variable Filter 28 Second Intermediate Frequency Amplifier Circuit 30 Second Mixer 32 AGC Means 36 1st demodulation circuit 42 1st period detection circuit 44 Comparison calculation means 46 3rd intermediate frequency amplification circuit 48 2nd demodulation circuit 50 2nd period detection circuit 52 Comparison control means 60 Noise blanker 62 Noise detector 64 Noise gate

Claims (6)

[Claims] 1. A first reception including an antenna and a part of a reception signal received by the antenna, which is converted into a first demodulation signal by a first demodulation circuit through a wide band filter and which also includes an AGC means. System, a second receiving system in which a part of the received signal is converted into a second demodulated signal by a second demodulation circuit via a narrow band filter, an amplitude fluctuation cycle of the first demodulated signal, and the second And a comparison control means for controlling the time constant of the AGC means on the basis of the comparison result. 2. A first reception in which one antenna and a part of a reception signal received by the antenna are converted into a first demodulation signal by a first demodulation circuit through a wide band filter and a bandwidth variable filter. A system and a second demodulation circuit for converting a part of the received signal into a second demodulation signal through a narrow band filter
Control system for comparing the amplitude fluctuation cycle of the first demodulated signal and the amplitude fluctuation cycle of the second demodulated signal and controlling the bandwidth of the variable bandwidth filter based on the comparison result. And a receiver. 3. An antenna and a first reception that includes a part of a reception signal received by this antenna into a first demodulation signal by a first demodulation circuit via a noise blanker and includes an AGC means. System, a second receiving system in which a part of the received signal is converted into a second demodulated signal by a second demodulation circuit through a narrow band filter, an amplitude fluctuation cycle of the noise detection signal of the noise blanker, and the second And a comparison control unit that controls the time constant of the AGC unit based on the comparison result. 4. An antenna and a first reception in which a part of a reception signal received by the antenna is converted into a first demodulation signal by a first demodulation circuit via a noise blanker and a bandwidth variable filter. A system and a second demodulation circuit for converting a part of the received signal into a second demodulation signal through a narrow band filter
Comparing the amplitude fluctuation cycle of the noise detection signal of the noise blanker and the amplitude fluctuation cycle of the second demodulation signal, and controlling the bandwidth of the variable bandwidth filter based on the comparison result. A receiver comprising: a control unit. 5. A reception signal received by an antenna is converted into a demodulation signal by a demodulation circuit through a noise blanker and a filter having a narrower bandwidth, and a reception system including AGC means and a noise detection signal of the noise blanker. A receiver comprising: a comparison control unit that compares the amplitude fluctuation period with the amplitude fluctuation period of the demodulated signal and controls the time constant of the AGC unit based on the comparison result. 6. A reception system in which a demodulation circuit demodulates a reception signal received by an antenna through a noise blanker and a bandwidth variable filter having a narrower bandwidth, and an amplitude fluctuation of the noise detection signal of the noise blanker. A comparison control unit that compares a cycle and an amplitude fluctuation cycle of the demodulated signal and controls the bandwidth of the bandwidth variable filter based on the comparison result.