JP3157282B2 - 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 in which the bandwidth of an intermediate frequency signal or a low frequency signal 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 the user conventionally listens to the sound reproduced from the receiver and automatically switches and selects the IF band filter based on the user's judgment. . Then, the distortion due to the intermodulation can be removed by automation.

[0004]

In the above-mentioned prior art, the clarity of the reproduced sound is improved in accordance with the state of the received signal, or the sound quality of the reproduced sound is improved. However, it requires an operation to shift the tuning frequency of the receiver from the target reception frequency.

The inventor of the present invention has proposed that if a received signal has only a target receiving frequency, the period of increase or decrease of the amplitude of the sound is, for example, 0.1
Focusing on the fact that the frequency becomes substantially constant at Hz, 0.2 Hz, 0.3 Hz, and the like, the present inventor has conceived that the reception state can be determined from the amplitude fluctuation period of the received signal. If the receiving condition is determined from the amplitude fluctuation period of the received signal, the operation of shifting the tuning frequency of the receiver as in the above-described related art is unnecessary.

The present invention has been made in view of the above circumstances, and determines a reception state from an amplitude fluctuation cycle of a reception signal, and controls a bandwidth of an intermediate frequency signal or a low frequency signal according to the reception state. It is an object of the present invention to provide a receiver.

[0007]

In order to achieve the above object, in a receiver according to the present invention, a reception signal received by an antenna is converted into a demodulation signal by a demodulation circuit via a variable bandwidth filter, and the demodulation signal of the demodulation signal is output. An amplitude variation cycle is detected by a cycle detection circuit, and the bandwidth of the bandwidth variable filter is controlled by a central processing unit in accordance with the amplitude variation cycle.

In the receiver of the present invention, a received signal received by an antenna is converted into a demodulated signal by a demodulation circuit via a noise blanker and a variable bandwidth filter, and the amplitude fluctuation cycle of the noise detection signal of the noise blanker is set to a period. The bandwidth of the variable bandwidth filter may be detected by a detection circuit and controlled by the central processing means in accordance with the amplitude fluctuation cycle.

In the receiver of the present invention, a received signal received by an antenna is converted into a demodulated signal by a demodulation circuit through a wide-band filter, and the demodulated signal is amplified through a tone adjustment filter. The amplitude fluctuation period may be detected by a period detection circuit, and the bandwidth of the tone adjustment filter may be controlled by the central processing unit in accordance with the amplitude fluctuation period.

Further, in the receiver according to the present invention, a received signal received by an antenna is converted into a demodulated signal by a demodulation circuit through a noise blanker, and the demodulated signal is loudspeaked through a tone adjustment filter, and the noise of the noise blanker is reduced. The amplitude fluctuation cycle of the detection signal may be detected by a cycle detection circuit, and the bandwidth of the tone adjustment filter may be controlled by a central processing unit according to the amplitude fluctuation cycle.

[0011]

In the receiver according to the present invention, if the amplitude fluctuation cycle of the demodulated signal is substantially constant and substantially the same as the voice amplitude fluctuation cycle, the level of the reception signal at the target reception frequency is high and sufficient S / N ratio, and if the amplitude fluctuation period is shorter than the voice amplitude fluctuation period, it can be determined that an interference signal exists. Therefore, by controlling the bandwidth of the bandwidth variable filter according to these reception conditions, if the reception conditions are good, the bandwidth is widened to improve the sound quality of the reproduced sound, and if there is an interference signal, the bandwidth is improved. The width can be narrowed to improve speech clarity.

In the receiver according to the second aspect of the present invention, 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 near the wide band thereof, and disturbance noise. Things. Therefore,
From the amplitude fluctuation period of the noise detection signal, the reception state can be determined in the same manner as the amplitude fluctuation period of the demodulated signal. In addition, the noise detection signal has a wider band than the demodulated signal, and the influence of a reception signal other than the target reception frequency can be reliably determined.

Further, in the receiver according to the third aspect, if the amplitude fluctuation period of the demodulated signal is unstable and longer than the amplitude fluctuation period of the voice, it can be determined that the reception condition includes wideband noise, and By narrowing the bandwidth of the adjustment filter to attenuate and suppress treble, the clarity of the reproduced sound can be improved.

Further, in the receiver according to the fourth aspect, the reception condition can be determined from the amplitude fluctuation period of the noise detection signal of the wideband noise blanker, and the tone adjustment filter is controlled and reproduced according to the reception condition. Clarity can be improved.

[0015]

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 illustrates an example of an operation performed by the central processing unit in FIG. 1 to determine whether or not the amplitude fluctuation period is constant. FIG. 3 is a flowchart illustrating an example of an operation performed by the central processing unit in FIG. 1 to determine whether the amplitude fluctuation period is long, equal, or short. FIG. 4 is a flowchart illustrating the central processing in FIG. 6 is a flowchart illustrating an example of an operation of controlling the bandwidths of the bandwidth variable filter and the tone adjustment filter in accordance with the amplitude fluctuation period by means.

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 amplification circuit 18, and a first intermediate frequency signal having a predetermined frequency is extracted and amplified, and supplied to a bandwidth variable filter 20. Can be The intermediate frequency signal that has passed through the bandwidth variable filter 20 is provided to a second intermediate frequency amplifier circuit 22 where it is amplified, and the second mixer 2
4 and a part thereof is provided to the AGC means 26. A gain control signal is supplied from the AGC means 26 to the first and second intermediate frequency amplifier circuits 18 and 22.
The second local oscillator circuit 2 is provided in the second mixer 24.
8, a second local oscillation signal is supplied, a second intermediate frequency signal obtained by frequency-converting the first intermediate frequency signal is supplied to the demodulation circuit 30, and a demodulated signal is output. This demodulated signal passes through the tone adjustment filter 32, is amplified by the low frequency amplifier circuit 34, and is output from the speaker 36 as sound. A part of the demodulated signal is supplied to the period detection circuit 38, and a signal corresponding to the amplitude fluctuation period is supplied to the central processing unit 40. The cycle detection circuit 38 outputs an edge detection circuit 42 each time a rising or falling edge of a demodulated signal is detected, and a frequency voltage conversion circuit 44 that outputs a DC voltage corresponding to the frequency of these pulses.
And a DC voltage corresponding to the amplitude fluctuation cycle is output. Then, a signal for switching the bandwidth between a wide band and a narrow band is provided to the variable bandwidth filter 20 and the tone adjustment filter 32 from the central processing unit 40.

It should be noted that the bandwidth variable filter 20 has two filters having different bandwidths centered on the first intermediate frequency signal arranged in parallel, and one of them can be switched and selected by the control signal of the central processing means 40. However, it is not limited to this,
A circuit using a passband tuning circuit, an IF WIDTH circuit, or the like may be used. In addition, it is assumed that the bandwidth of the variable bandwidth filter 20 can be set to a wide band such as 20 KHz as an example. The tone adjustment filter 32 is selectively switched between a narrow bandwidth in a high-cut state in which high-frequency parts are attenuated and a wide bandwidth in which high-frequency parts are not attenuated.

An example of the operation for determining whether or not the amplitude fluctuation period is constant in such a structure will be described with reference to FIG. First, N DC voltages output from the cycle detection circuit 38 are sampled within a predetermined time (step), and an average value of the N sampled values is calculated (step). Then, the level difference between the average value and the sampling value is calculated for each sampling value (step), and the absolute value of the difference is compared with the magnitude of a predetermined reference value (step). A ratio smaller than the reference value is calculated (step). And this ratio is, for example, 80%
If this is the case (step), it can be determined that the amplitude fluctuation period is constant, and if it is less than 80%, it can be determined that the amplitude fluctuation period is unstable.

Next, an example of an operation for determining whether the amplitude fluctuation period is longer, almost the same, or shorter than the amplitude fluctuation period of the voice will be described with reference to FIG. First, the DC voltage output from the cycle detection circuit 38 is sampled for M times within a predetermined time (step), and a level is compared with a reference value corresponding to the voice amplitude fluctuation cycle for each sampling value (step). Further, a ratio at which the sampling value is smaller than the reference value is calculated (step). Here, assuming that the level of the DC voltage output from the cycle detection circuit 38 is lower as the amplitude fluctuation cycle is longer, and the DC voltage level is higher as the amplitude fluctuation cycle is shorter, if the sampling value is smaller than the reference value, , Indicates that the amplitude fluctuation period is long. Therefore, if the ratio is, for example, 60% or more, it is determined that the amplitude fluctuation cycle tends to be longer than the amplitude fluctuation cycle of the voice, and it is determined that the amplitude fluctuation cycle is substantially the same in the range of 40 to 60%. If it is less than this, it can be determined that the amplitude fluctuation cycle tends to be short.

Further, an example of the operation for controlling the bandwidths of the variable bandwidth filter and the tone adjustment filter will be described with reference to FIG. First, it is determined whether the amplitude fluctuation period is constant or unstable by the operation of FIG. 2 (step 1). If the amplitude fluctuation period is constant, the operation of FIG. 3 causes the tendency of the amplitude fluctuation period to be longer than the amplitude fluctuation period of the voice. It is determined whether they are almost the same or shorter (step 2). If the amplitude fluctuation cycle is unstable in step 1, it is determined whether the amplitude fluctuation cycle is longer or shorter than the voice amplitude fluctuation cycle (step 3). In this step 3, the ratio in the operation in FIG. 3 may be determined according to whether the ratio is less than 50% or more than 50%. Then, in step 2, if it is determined that the amplitude fluctuation period is substantially the same as the amplitude fluctuation period of the voice,
The reception signal of the target reception frequency is large, and the reception signals other than the target reception frequency are small and the reception condition is a sufficient S / N ratio. The bandwidth of the bandwidth variable filter 20 is set wide (step 4), and the tone adjustment filter is set. The bandwidth of 32 is set wide (step 5), the receiver is set to a state where sound can be reproduced with excellent sound quality, and the process returns to step 1. On the other hand, if it is determined in step 2 that the amplitude fluctuation period is short, it indicates a reception situation in which an interference signal exists, and the bandwidth variable filter 20
Is narrowed (step 6), the level of the reception signal of the target reception frequency included in the demodulated signal is made relatively higher than the level of the reception signal other than the target reception frequency, and the intermodulation due to the interference signal is suppressed. . Then, the bandwidth of the tone adjustment filter 32 is set wide (step 7), and the process returns to step 1. Further, if it is determined in step 2 that the amplitude fluctuation period is long, it is a single signal interference state or a reception state in which continuity noise is present, and these factors are identified by other determination means. Bandwidth variable filter 20
Alternatively, one of the bandwidths of the tone adjustment filter 32 is set to be narrow and the other is set to be wide (step 8).
Return to If it is determined in step 3 that the amplitude fluctuation period is short, it means that there is interference, and steps 6 and 7 are performed.
And returns to step 1. And then step 3
If it is determined that the amplitude fluctuation period is long, it is a reception situation in which broadband noise exists, and the bandwidth of the bandwidth variable filter 20 is set wide (step 9), and the bandwidth of the tone adjustment filter 32 is set narrow. Then, the process returns to step 1 as a setting state in which the sound called “shear” is removed by attenuating and suppressing the treble portion of the sound to improve the clarity of the sound.

Here, by narrowing the bandwidth of the bandwidth variable filter 20, the reception signals other than the target reception frequency are omitted from the intermediate frequency signal, and the level of the reception signal of the target reception frequency is improved. Moreover, the overall level of the received signal is reduced by an amount corresponding to the elimination of the received signal other than the target reception frequency, the suppression by the gain control of the AGC means 26 is reduced, and the reception signal of the target reception frequency is amplified with a higher gain. Level improves. In addition, the bandwidth of the tone adjustment filter 32 is narrowed to attenuate and suppress high-frequency portions, so that the demodulation circuit 3
Noise generated after 0 can be suppressed, and the S / N ratio improves.
Since the level of the received signal supplied to the AGC means 26 does not change, the gain control does not change, and the volume of the entire sound is reduced and the relative level of the sound is improved by the suppression of the treble,
It will be easy to hear.

According to the receiver of the present invention, the receiving condition is identified from the amplitude fluctuation period of the demodulated signal as described above.
The receiver can be automatically set to an appropriate setting state.

Further, another embodiment of the receiver according to the present invention will be described with reference to FIG. 5, the same or equivalent circuit blocks as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. 5 is different from FIG. 1 in that the first intermediate frequency signal output from the first intermediate frequency amplification circuit 18 is connected to the noise gate 52 of the noise blanker 50.
To the bandwidth tunable filter 20 via
The period detection circuit 38 uses a noise blanker 5 instead of the demodulated signal.
That is, a noise detection signal output from the zero noise detector 54 is provided. The noise blanker 50 is configured so that the first intermediate frequency signal is
6 and given. The noise amplifier 56 amplifies the first intermediate frequency signal and supplies the amplified signal to the noise detector 54, which outputs a noise detection signal. The noise detection signal is supplied to the period detection circuit 38 and to the gate control circuit 58 having a threshold value. The pulse noise included in the noise detection signal is extracted by the gate control circuit 58, and the noise gate 52 is turned ON / OFF according to the extracted pulse noise,
The first intermediate frequency signal from which the pulse noise has been removed through the noise gate 52 is supplied to the bandwidth variable filter 20.

Here, the noise detection signal includes, in addition to the reception signal at the target reception frequency, the transmission frequency of another station adjacent in a wide band and the disturbance signal if there is disturbance noise. Therefore, the amplitude fluctuation cycle of the noise detection signal is affected by the reception signal of the transmission frequency of another nearby station and disturbance noise. Therefore, the reception state can be determined from the amplitude fluctuation period of the noise detection signal, similarly to the receiver shown in FIG.
The bandwidth of 0 and the tone adjustment filter 32 can be automatically switched to the optimum setting state.

The other embodiment of the receiver of the present invention shown in FIG. 5 is suitable for application to a receiver having a noise blanker 50.

In the description of the above embodiment, a microcomputer or the like is used as the central processing means 40. However, the cycle detection circuit 38 may be processed by a microcomputer or the like. Then, a circuit including these components is called a DSP
(Digital signal processor). Further, the detection of the amplitude fluctuation period in the receiver shown in FIG. 1 may be performed in a state where the bandwidth variable filter 20 is controlled to a predetermined bandwidth. In this case,
The detection of the amplitude fluctuation period may be performed at every predetermined period. Further, it is determined whether or not the amplitude fluctuation period shown in FIG. 2 is constant, and whether the amplitude fluctuation period is long, the same or short, as shown in FIG. 3, and further, the variable bandwidth filter 20 and the tone adjustment shown in FIG. The operation of controlling the bandwidth of the filter 32 is not limited to the above-described embodiment, but may be any operation that can achieve a desired purpose.

[0027]

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 bandwidth of the intermediate frequency signal is controlled in accordance with the reception condition determined from the amplitude fluctuation period of the demodulated signal, and the receiver is automatically controlled in accordance with the reception condition. Is adjusted to the proper setting state, and the operation is simpler. Moreover, the determination of the reception status is based on the amplitude fluctuation cycle of the demodulated signal, and there is no need to appropriately shift the tuning frequency as in the conventional technique, and the circuit configuration is simple accordingly.

In the receiver according to the second aspect, since the reception state is determined from the amplitude fluctuation period of the noise detection signal of the noise blanker, the receiver is suitable for application to a receiver having a noise blanker.

Also in the receiver according to the third and fourth aspects, the bandwidth of the tone adjustment filter is controlled in accordance with the reception condition, the receiver is set to an appropriate setting state, and the "sharing" of the broadband noise is performed. "Can be automatically removed and the operation is simple.

[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 flowchart illustrating an example of an operation performed by a central processing unit in FIG. 1 to determine whether an amplitude fluctuation period is constant.

FIG. 3 is a flowchart illustrating an example of an operation performed by the central processing unit in FIG. 1 to determine whether the amplitude fluctuation period is long, the same, or short.

FIG. 4 is a flowchart illustrating an example of an operation of controlling the bandwidths of the bandwidth variable filter and the tone adjustment filter in accordance with the amplitude variation period by the central processing unit in FIG. 1;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Antenna 20 Bandwidth variable filter 30 Demodulation circuit 32 Tone adjustment filter 38 Period detection circuit 40 Central processing means 50 Noise blanker 54 Noise detector

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/10 H04B 1/16 H04B 1/26

Claims (5)

(57) [Claims] 1. A signal received by an antenna is converted into a demodulated signal by a demodulation circuit via a variable bandwidth filter, and an amplitude fluctuation period of the demodulated signal is detected by a period detection circuit. A receiver configured to control a bandwidth of the variable bandwidth filter by an arithmetic unit. 2. A received signal received by an antenna is converted into a demodulated signal by a demodulation circuit via a noise blanker and a variable bandwidth filter, and an amplitude fluctuation cycle of a noise detection signal of the noise blanker is detected by a cycle detection circuit. A receiver characterized in that the central processing means controls the bandwidth of the variable bandwidth filter according to the amplitude fluctuation period. 3. A received signal received by an antenna is converted into a demodulated signal by a demodulation circuit through a wide-band filter, and the demodulated signal is loudspeaked through a tone adjustment filter. And a central processing means for controlling the bandwidth of the tone adjustment filter in accordance with the amplitude fluctuation period. 4. A received signal received by an antenna is converted into a demodulated signal by a demodulation circuit through a noise blanker, and the demodulated signal is loudspeaked through a tone adjustment filter. A receiver which is detected by a period detection circuit and configured to control the bandwidth of the tone adjustment filter by a central processing unit in accordance with the amplitude fluctuation period. 5. The receiver according to claim 1, wherein the central processing means determines whether the amplitude fluctuation period is constant and / or the amplitude fluctuation period is longer than, equal to, or shorter than a predetermined reference value. A receiver characterized in that the bandwidth of the variable bandwidth filter or the tone adjustment filter is controlled in accordance with the degree of change.