JP3169469B2 - 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 provided with a noise detection circuit for detecting pulse noise and a variable bandwidth filter.

[0002]

2. Description of the Related Art FIG. 2 is a block circuit diagram of an example of a conventional receiver having a noise blanker circuit and a variable bandwidth filter section. In FIG. 2, a received signal received by an antenna 10 is amplified by a high-frequency amplifier circuit 12, supplied to a first mixer 14, and mixed with a first local oscillation signal from a first local oscillation circuit 16. . This first mixer 1
4 is supplied to a first intermediate frequency amplifying circuit 18, a first intermediate frequency signal having a predetermined frequency is extracted and amplified, and a noise blanker circuit 20 is provided.
To the noise gate 22. This noise gate 2
The first intermediate frequency signal that has passed through the second switch 2 is supplied to a plurality of filters 26a, 26b, and 26c that are connected in parallel via a first switch group 24 and have different pass bandwidths, respectively. The first intermediate frequency signal whose bandwidth has been limited after passing through the filter is further supplied to a second intermediate frequency amplifier circuit 30 via a second switch group 28 and amplified. Then, the first intermediate frequency signal amplified by the second intermediate frequency amplification circuit 30 is provided to the second mixer 32 and mixed with the second local oscillation signal from the second local oscillation circuit 34. . The frequency-converted second intermediate frequency signal output from the second mixer 32 is output to the demodulation circuit 3
6 and converted into a demodulated signal,
The signal is amplified at 8 and output as sound from the speaker 40.

In the noise blanker circuit 20, a part of the first intermediate frequency signal output from the first intermediate frequency amplifier circuit 18 is given to a noise amplifier 42. The noise amplifier 42 amplifies the first intermediate frequency signal and supplies the amplified signal to the noise detector 44. If the first intermediate frequency signal includes pulse noise or the like, the noise detector 44 outputs the magnitude of the pulse noise from the noise detector 44. A noise detection signal of a level corresponding to the output is output and supplied to the gate control circuit 46. And
The gate control circuit 46 extracts a noise detection signal having a level equal to or higher than a predetermined value from the noise detection signal, and turns on / off the noise gate 22 according to the extracted signal.
Controlled. Therefore, since the noise detection signal is extracted in accordance with the pulse noise and the noise gate 22 is turned off, the first intermediate frequency signal from which the pulse noise has been removed is output to the subsequent stage of the noise blanker circuit 20. Is done.

Then, the first and second switch groups 24, 2
Reference numeral 8 denotes a plurality of filters 2 based on a control signal output from the filter switching drive circuit 48 in response to the filter switching signal.
ON / OFF control is performed so that any one of 6a, 26b, and 26c is interposed in the signal line to be in a conductive state, and the other two are in a cutoff state. First and second switch groups 24, 28 and a plurality of filters 26a, 26b, 26c
The filter switching drive circuit 48 forms a variable bandwidth filter unit.

The pass band width of the bandwidth variable filter unit is automatically adjusted by a relative comparison between the level of the received signal at the target receiving frequency and the level of the received signal at the transmitting frequency of another station in the vicinity thereof, etc. Are appropriately set in accordance with the filter switching signal output from. Alternatively, based on the quality of the sound output from the speaker 40 by the user, the pass bandwidth of the bandwidth variable filter is appropriately switched and set by a manual operation in order to improve a decrease in intelligibility due to proximity interference or the like.

[0006]

In the above-mentioned conventional receiver, the first and second switch groups for switching the noise gate 22 for removing the pulse noise and the filters 26a, 26b, 26c. Each of the factors 24 and 28 is a factor that degrades the intermediate frequency signal and is not sufficiently satisfactory.

Furthermore, if the operation of each component is examined in detail for the purpose of downsizing the receiver, the noise gate 22 of the noise blanker circuit 20 and the first and second switch groups 24 and 28 are Both are switches that are interposed in the signal line of the first intermediate frequency signal and that are ON / OFF controlled, and it is found that they can be shared.

The present invention has been made in view of the above circumstances, and has as its object to provide a receiver capable of reducing the number of components while reducing factors for attenuating an intermediate frequency signal.

[0009]

In order to achieve the above object, a receiver according to the present invention comprises a noise detection circuit for detecting pulse noise contained in an intermediate frequency signal, and a plurality of filters having different bandwidths. A noise detection signal output from the noise detection circuit is equal to or more than a predetermined value in a receiver including: a bandwidth variable filter unit that adjusts an intermediate frequency signal pass bandwidth by conducting or blocking by ON / OFF control of a switch group. At the level of
It is configured to perform F control to shut off any of the filters.

[0010]

The switch group is turned off in accordance with the noise detection signal output from the noise detection circuit, so that the switch group prevents the passage of pulse noise. Therefore, the switch group has both a switch function for switching a filter and a noise gate function of a conventional noise blanker circuit.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block circuit diagram of an embodiment of a receiver according to the present invention. 1, the same circuit blocks as those in FIG. 2 are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 differs from FIG. 2 in the following. First, the first intermediate frequency signal output from the first intermediate frequency amplifier circuit 18 is directly supplied to the first switch group 24. Further, a part of the first intermediate frequency signal is supplied to the noise amplifier 42 of the noise detection circuit 50 instead of the conventional noise blanker circuit 20, and the amplified output is supplied to the noise detector 44. And the first
If the intermediate frequency signal contains pulse noise, etc.,
The noise detection signal output from the noise detector 44 is supplied to the filter OFF control circuit 52. Further, a noise detection signal having a level equal to or higher than a predetermined value is extracted from the noise detection signal by the filter
The signal is supplied to the filter switching drive circuit 54 as an F signal.
Therefore, when the OFF signal is supplied, the filter switching drive circuit 54 gives priority to the first and second filter switching signals.
And either or both of the switch groups 24 and 28 are turned off.

The noise detection circuit 50 is formed by a noise amplifier 42 and a noise detector 44 which are a part of the conventional noise blanker circuit 20.
Numeral 2 corresponds to the gate control circuit 46 of the noise blanker circuit 20, and its control target is only different.

In this configuration, the first intermediate frequency signal contains pulse noise, and the noise detection circuit 5
When a noise detection signal is output from 0, at least one of the first and second switch groups 24 and 28 is controlled to be OFF, so that the passage of pulse noise is prevented, and the same as the conventional noise blanker circuit 20 is performed. The first intermediate frequency signal from which the pulse noise has been removed is supplied to the second intermediate frequency amplifier circuit 30. Therefore, although the conventional noise gate 22 is omitted from the signal line, the same function as the conventional one is achieved. Then, the factor for attenuating the intermediate frequency signal can be reduced by the number of switches interposed in the signal line.

Further, the elimination of the noise gate 22 reduces the number of components, reduces the area required for the printed wiring board for the circuit configuration, and is suitable for downsizing the receiver.

In the above embodiment, the noise detection signal from the noise detection circuit 50
2, the noise detection signal may be directly supplied to the filter switching drive circuit 54, and the first and second noise detection signals may be supplied to the filter switching drive circuit 54 in accordance with the noise detection signal.
Any configuration may be used as long as at least one of the switch groups 24 and 28 is controlled to be OFF to prevent the passage of pulse noise.

[0017]

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

Since a switch for removing pulse noise from a signal and a switch for switching and setting filters having different passbands are shared, the number of switches interposed in a signal line is reduced. The factor for attenuating the intermediate frequency signal is reduced.

In addition, since the switch corresponding to the noise gate of the conventional noise blanker circuit is omitted by sharing,
The number of components is reduced, and the area required for the printed wiring board for the circuit configuration accompanying this can be reduced, which is suitable for downsizing the receiver.

[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 block circuit diagram of an example of a conventional receiver including a noise blanker circuit and a variable bandwidth filter unit.

[Explanation of symbols]

 Reference Signs List 18 first intermediate frequency amplifier circuit 24 first switch group 26a, 26b, 26c filter 28 second switch group 42 noise amplifier 44 noise detector 50 noise detection circuit 52 filter OFF control circuit 54 filter switching drive circuit

Claims (1)

(57) [Claims] 1. A noise detection circuit for detecting a pulse noise included in an intermediate frequency signal, and a plurality of filters having different pass bandwidths are turned on or off by controlling ON / OFF of a switch group to thereby pass the intermediate frequency signal pass bandwidth. And a bandwidth variable filter unit that adjusts, when the noise detection signal output from the noise detection circuit is at a level equal to or higher than a predetermined value, the switch group is turned off to control any of the filters. Characterized in that the receiver is also configured to shut off.