JP3165520B2 - Receiving machine - Google Patents

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 optimal setting according to the state of a received signal.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Hei 3-187623 discloses a technique for selecting one of a plurality of IF band filters incorporated in a receiver in accordance with the state of a received signal. Briefly describing 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 near the target reception frequency is obtained from the level of the received signal obtained by shifting. The presence / absence of the signal is determined. If a signal of the transmission frequency of another station exists, a narrow band IF band filter is selected, and if not, a wide band IF band filter is selected.

[0003] This technique is excellent in that a conventional user listens to a demodulated output of a target reception frequency from a receiver and automatically switches and selects an IF band filter based on the user's judgment. It is. Then, the distortion due to the intermodulation can be removed by automation.

[0004]

In the above prior art, the presence of a signal of a transmission frequency of another station is determined by the level of a received signal of only that frequency. The IF band filter is not selected by the relative comparison between the received signal of the other station and the received signal of the transmission frequency of the adjacent station. As a result, even if the level of the reception signal of the target reception frequency is relatively considerably higher than the level of the reception signal of the transmission frequency of another station, if the reception signal of the transmission frequency of the other station exceeds a predetermined level, the narrow band IF
There is a disadvantage that the band filter is selected and the sound quality is unnecessarily deteriorated. Also, the level of the reception signal at the target reception frequency and the level of the reception signal at the transmission frequency of another station are relatively similar in magnitude, but if both levels are small, a wideband IF band filter is selected, There is a problem that intermodulation is easily caused.

The present invention has been made in view of the circumstances of the related art, and has been made in accordance with a reception signal including a signal of a transmission frequency of another station adjacent to a target reception frequency obtained from a noise AGC means of a noise blanker. Optimum setting state according to the receiving condition based on the similarity of the level change of the control signal and the level change of the control signal of the AGC means according to the received signal of the target receiving frequency obtained through the filter having a narrower bandwidth. It is an object of the present invention to provide a receiver that is automatically controlled by a receiver.

[0006]

In order to achieve the above object, a receiver according to the present invention provides a receiver which receives a signal received by an antenna with a noise blanker which is narrower than a bandwidth in which a noise detection signal is output by the noise blanker. A demodulation circuit converts the signal into a demodulated signal via a bandwidth variable filter. The receiving system is provided with AGC means.
C means is provided, and the similarity between the level change of the control signal of the AGC means and the level change of the control signal of the noise AGC means is compared by comparison operation means, and the bandwidth of the bandwidth variable filter is compared by the comparison operation means. It is configured to control.

In the receiver of the present invention, a demodulated signal is received by a demodulation circuit through a noise blanker and a filter having a bandwidth narrower than a bandwidth in which a noise detection signal is output by the noise blanker. AGC means is provided in this receiving system, and the noise A
GC means is provided, and the similarity between the level change of the control signal of the AGC means and the level change of the control signal of the noise AGC means is compared by the comparison operation means, and the time constant of the AGC means is controlled by the comparison operation means. It may be configured as follows.

[0008]

[Operation] The noise detection signal of the noise blanker is obtained by superimposing the reception signal of the target reception frequency, the reception signal of the transmission frequency of another station in the vicinity of a wide range, and disturbance noise. The control signal output from the noise AGC means is such that the levels of these received signals are somewhat smoothed. The control signal output from the AGC means of the receiving system is a level of a received signal mainly having a target receiving frequency obtained through a filter having a bandwidth narrower than a bandwidth in which a noise detection signal is output by a noise blanker. Is somewhat smoothed. If the level changes of the control signals of the noise AGC means and the AGC means are similar and similar from the difference in the bandwidth, it is determined that there are few reception signals other than the target reception frequency and that the reception state has a sufficient S / N ratio. obtain.
Also, if the level changes are significantly different, it can be determined that there are many received signals other than the target received frequency and that there is an interference signal. Therefore, by controlling the bandwidth of the bandwidth variable filter, if the similarity is high, the bandwidth is widened to improve the sound quality of the demodulated output of the target reception frequency, and if the similarity is low, the bandwidth is narrowed. The clarity of the demodulated output of the target reception frequency can be improved.

If the similarity between the control signals of the noise AGC means and the AGC means is low, it is expected that intermodulation is caused by the presence of a strong interference signal. Therefore, by controlling the time constant of the AGC means based on the comparison result, if the similarity is low, the time constant of the AGC means can be reduced to increase the response speed, and the level fluctuation of the demodulated signal due to intermodulation can be suppressed. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the receiver according to the present invention will be described below.
This will be described with reference to FIGS. FIG. 1 is a block circuit diagram of an embodiment of a receiver according to the present invention, and FIG. 2 is a diagram illustrating the similarity of the level change of the control signal of the noise AGC means and the AGC means of FIG. FIG. 3 is a diagram showing a relationship between power bandwidths, and FIG. 3 is a diagram showing the similarity of the level change of the control signal between the noise AGC means and the AGC means in FIG.
FIG. 4 is a diagram showing a relationship between time constants to be adjusted by the C means, and FIG.
3 is a flowchart illustrating the operation of the comparison operation unit of FIG.

First, the structure will be described with reference to FIG. The received signal received by the antenna 10 is transmitted to the high-frequency amplification circuit 1
The signal is amplified by 2 and supplied to the first mixer 14 and 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 a first intermediate frequency amplifying circuit 18, where a first intermediate frequency signal having a predetermined frequency is extracted and amplified. Further, the first intermediate frequency signal output from the first intermediate frequency amplifier circuit 18 is supplied to the noise gate 22 and the noise amplifier 24 of the noise blanker 20.

The first signal that has passed through the noise gate 22
Is supplied to a second intermediate frequency amplifying circuit 28 via a variable bandwidth filter 26 and is amplified.
Of the AGC
Means 32 are provided. The second mixer 30 receives the second local oscillation signal from the second local oscillation circuit 34, and supplies the second intermediate frequency signal obtained by frequency-converting the first intermediate frequency signal to the demodulation circuit 36. And a demodulated signal is output. This demodulated signal is amplified by the low frequency amplifier circuit 38 and output from the speaker 40 as a low frequency. In addition,
The maximum bandwidth of the bandwidth variable filter 26 is set narrower than the bandwidth of the noise blanker 20.

The noise blanker 20 amplifies the first intermediate frequency signal by the noise amplifier 24 and supplies the amplified signal to the noise detector 42. The noise detector 42 outputs the noise detection signal, and the noise AGC means 44 serves as a threshold. The value is supplied to the gate control circuit 46 having a value. Then, the pulse noise included in the noise detection signal is extracted by the gate control circuit 46, and the noise gate 22 is ON / OFF-controlled in accordance with the extracted pulse noise, and passes through the noise gate 22 to output the pulse noise. Is supplied to the variable bandwidth filter 26. Further, the noise detection signal is somewhat smoothed by the noise AGC means 44 and output as a control signal. The control signal is supplied to the noise amplifier 24 to control the gain thereof, and the first A / D conversion circuit 48 Given to.

AGC means 3 to which the first intermediate frequency signal output from the second intermediate frequency amplifier circuit 28 is applied.
2, the control signal obtained by somewhat smoothing this signal is supplied to the high frequency amplifier circuit 12 and the first and second intermediate frequency amplifier circuits 18 and 28.
And its gain is controlled. In addition, AGC
The control signal of the means 32 is given to the second A / D conversion circuit 50. Then, the first and second A / D conversion circuits 48,
The digital values output from 50 are supplied to comparison operation means 52, respectively. As will be described later, the output from the first and second A / D conversion circuits 48 and 50 is compared and calculated by the comparison calculation means 52, and a signal for adjusting the bandwidth of the bandwidth variable filter 26 according to the result is obtained. And the AGC means 32
And a signal for adjusting the time constant.

Here, the noise detection signal of the noise blanker 20 is a signal obtained by superimposing a reception signal of a target reception frequency, a reception signal of a transmission frequency of another station in the vicinity of a wide range and disturbance noise. The control signal output from the noise AGC means 44 is such that the levels of these received signals are somewhat smoothed. Further, the second intermediate frequency signal is supplied to a bandwidth variable filter 26 having a bandwidth narrower than the bandwidth in which the noise detection signal is output from the noise blanker 20.
The control signal output from the AGC means 32 is a signal in which the level of these received signals is somewhat smoothed. Then, from the two control signals obtained from the reception signals having such different bandwidths, it is possible to determine the reception signal other than the target reception frequency and the degree of the presence of disturbance noise.
Therefore, if the level changes of the control signals of the noise AGC means 44 and the AGC means 32 are similar and similar, it can be determined that there is little signal other than the target reception frequency and that a reception state in which a sufficient S / N ratio can be obtained. If the level changes of the two control signals are significantly different, it can be determined that there are many signals other than the target reception frequency and that an interference signal exists. For this reason,
If the similarity of the level changes of both control signals is high, the bandwidth of the bandwidth variable filter 26 is widened as shown in FIG. 2 to improve the sound quality of the demodulated output of the target reception frequency, and as shown in FIG. The time constant of the means 32 is increased. If the similarity of the level change between the two control signals is low, the bandwidth of the variable bandwidth filter 26 is narrowed to improve the clarity of the demodulated output, and the time constant of the AGC means 32 is reduced to reduce the intermodulation. This suppresses a change in the volume of the demodulated output.

Next, the operation of the comparison operation means 52 for comparing and calculating the similarity of the level changes of the control signals of the noise AGC means 44 and the AGC means 32 will be described with reference to FIG.
First, a control signal is given to the variable bandwidth filter 26 and the AGC means 32 from the comparison operation means 52 to set a predetermined bandwidth and a predetermined time constant (step 1). Under this condition, the control signal of the noise AGC means 44 was sampled by the first A / D conversion circuit 48, and the control signal of the AGC means 32 was sampled by the second A / D conversion circuit 50. The digital value is provided to the comparison operation means 52 at a predetermined cycle, and the comparison operation means 52 reads and stores these values (step 2). The comparison operation means 52 includes a storage means having an appropriate capacity. Every time a new value is read and stored, the value is sampled immediately before and the previously stored value is read (step 3).
Then, the previous value is subtracted from the new value by the control signal of the noise AGC means 44 and the control signal of the AGC means 32 (step 4). Further, a product is obtained by multiplying the results of the two subtractions performed in step 4 (step 5). Further, the product is accumulated to obtain an added value (step 6). Step 2 is repeated until the accumulation in step 6 is performed a predetermined number of times, for example, 20 times.
Are repeated (step 7).

The noise AGC means 44 and A
If the control signal of the GC means 32 is increasing, the result of the subtraction in step 4 is positive, and if it is decreasing, it is negative. Then, the noise AGC means 44 and A
If the increasing / decreasing tendency of the control signal of the GC means 32 matches,
The product obtained by multiplication in step 5 is positive, and becomes negative if the increase / decrease trend is opposite. From this, it can be seen that the larger the value added by accumulation in step 6 is, the larger the noise AG
The increasing and decreasing trends of the control signals of the C means 44 and the AGC means 32 match, and it can be determined that the level fluctuations are similar. Further, it can be determined that the larger the added value is, the more the level fluctuations of both control signals are not similar and completely different.

Therefore, the bandwidth of the bandwidth variable filter 26 is adjusted in accordance with the relationship shown in FIG. 2 in accordance with the added value obtained in step 6 (step 8), and the bandwidth of the AGC means 32 is further adjusted in accordance with the added value. The constants are adjusted according to the relationship shown in FIG. 3 (step 9). In this way, when the bandwidth of the bandwidth variable filter 26 and the time constant of the AGC means 32 are adjusted according to the reception situation, the process returns to step 1 after waiting for a predetermined time (step 10). In order to accurately determine the reception situation, the bandwidth variable filter 26 is set to a predetermined bandwidth in step 1 and the AGC means 32 is set to a predetermined time constant. Stipulated appropriately.

In the above-described embodiment, the comparison operation means 52 performs software processing using a microcomputer or the like. However, the first and second A / D conversion circuits 48 and 50 are used.
And the comparison operation means 52 may be configured using one DSP (digital signal processor). Further, it is a matter of course that the comparison operation means 52 may be configured as a circuit so as to be processed by hardware using discrete components.

[0020]

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

First, in the receiver according to the first aspect, the similarity of the level change of the control signal between the noise AGC means and the AGC means is compared to determine the reception state, and the bandwidth is varied according to the result of the comparison calculation. The bandwidth of the filter is automatically adjusted, so if there is no signal other than the target reception frequency and there is no interference signal, the bandwidth is increased to improve the sound quality, and if there is an interference signal, the bandwidth is increased To improve the clarity of the demodulated output. As described above, the receiver is automatically adjusted to the optimum setting state according to the reception state, and the operation is extremely simple.

In the receiver according to the second aspect, if no interference signal exists according to the reception situation, the time constant of the AGC means is increased to output a faithful demodulated signal, and the interference signal exists. For example, the receiver is automatically adjusted to the optimum setting state so that the time constant of the AGC means is reduced and the strength of the demodulation output in intermodulation due to interference is eliminated, so that the operation is simpler.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a relationship between similarity of a level change of a control signal of the noise AGC means and a control signal of the AGC means of FIG. 1 and a bandwidth to be adjusted by a bandwidth variable filter.

FIG. 3 is a diagram showing a relationship between similarity of a level change of a control signal between the noise AGC means and the AGC means of FIG. 1 and a time constant to be adjusted by the AGC means.

FIG. 4 is a flowchart illustrating the operation of the comparison operation unit of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Antenna 12 High frequency amplifier circuit 14 1st mixer 18 1st intermediate frequency amplifier circuit 20 Noise blanker 22 Noise gate 26 Bandwidth variable filter 28 2nd intermediate frequency amplifier circuit 30 2nd mixer 32 AGC means 36 Demodulation circuit 44 Noise AGC means 48 First A / D conversion circuit 50 Second A / D conversion circuit 52 Comparison operation means

Claims (3)

(57) [Claims] A received signal received by an antenna is converted into a demodulated signal by a demodulation circuit through a noise blanker and a bandwidth variable filter having a bandwidth narrower than a bandwidth in which a noise detection signal is output by the noise blanker. An AGC means is provided in the system, a noise AGC means is provided in the noise blanker, and a similarity between a level change of the control signal of the AGC means and a level change of the control signal of the noise AGC means is compared by comparison operation means. A receiver configured to control a bandwidth of the variable bandwidth filter by an arithmetic unit. 2. A demodulation circuit converts a received signal received by an antenna through a noise blanker and a filter having a bandwidth smaller than a bandwidth in which a noise detection signal is output by the noise blanker. Providing means,
The noise blanker is provided with a noise AGC means.
The similarity between the level change of the control signal of the GC means and the level change of the control signal of the noise AGC means is compared by comparison operation means, and the time constant of the AGC means is controlled by the comparison operation means. Features receiver. 3. The receiver according to claim 1, wherein said comparison operation means calculates a difference between a newly sampled value of the control signal of said AGC means and a value sampled immediately before, The difference between the newly sampled value of the control signal of the noise AGC means and the immediately preceding sampled value is calculated, and the two differences are multiplied to obtain a product. A receiver, wherein the similarity between the level change of the control signal of the AGC means and the level change of the control signal of the noise AGC means is determined based on the magnitude of the added value.