JP2002135141A - Receiving set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiving set of very high convenience, which enables automatically setting of squelch level (reference voltage) so as to be able to control the output power from a speaker, according as to whether environmental noises are radiated. SOLUTION: While providing a central processing unit, the receive enables watching of a noise detection voltage and enables to control the reference voltage, that is, the receiver, using the central processing unit, determines whether circumstance noises are radiated, by watching the noise detection voltage which is detected by a detector, when the wireless set is operating, and sets the reference voltage according to whether circumstance noises have been radiated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver such as a portable radio, and more particularly to a squelch level setting circuit used in a receiver.

[0002]

2. Description of the Related Art As an example of a conventional receiver, a manually operated squelch level setting circuit will be described with reference to FIG. FM including squelch level setting circuit in FIG.
FIG. 2 is a block diagram of a receiver (a wireless device of a single superheterodyne receiving system). 2, an intermediate frequency amplifier, 3 a demodulator, 4 an audio signal processing circuit, 5 an audio power amplifier,
6 is a speaker, 7 is a switch, 8 is a band-pass filter, 9
Is a comparator, 10 is a detector, 11 is a reference voltage, and 12 is AG
3 shows a C circuit. 7 to 11 are squelch level setting circuits.

When a receiver receives a signal, the signal is frequency-converted from a reception frequency to an intermediate frequency, and then amplified by an intermediate frequency amplifier 2. At this time, even if the signal level fluctuates, the AGC circuit 12 controls so that the output level from the intermediate frequency amplifier 2 becomes constant. After that, the output signal from the intermediate frequency amplifier 2 is input to the demodulator 3 and converted into a demodulated signal, and the demodulator 3 outputs the demodulated signal. The demodulated signal is input to the speaker 6 via the audio signal processing circuit 4 and the audio power amplifier 5.

FIG. 4 shows the received signal level versus sound output characteristics of this receiver. As shown in FIG. 4, this receiver outputs a demodulated signal containing noise. If the level of the received signal is high enough, the noise is hidden in the demodulated signal and is almost inaudible. However, when the level of the received signal decreases, the level difference between the demodulated signal and noise disappears, and the AGC circuit 1
Due to the effect of 2, the sound is output from the speaker 6 with excessive noise. Therefore, the squelch circuit is
, A component in the noise band is extracted by a band-pass filter 8 from a part of the output, and the noise is detected by a detector 9 and converted into a DC voltage. Then, based on the result of comparison between the converted DC voltage and the reference voltage 11 by the comparator 9, by controlling the opening and closing of the switch 7, the connection or disconnection of the audio power amplifier 5 is controlled, and the speaker with excessive noise 6 is prevented from outputting sound.

[0005]

In the above-mentioned conventional FM receiver, depending on the operating environment (whether or not there is a device that emits radio waves such as OA equipment in the surroundings), environmental noise (radiation from a device that emits radio waves such as OA equipment) may occur. Noise caused by
May be equal to the reception frequency or the intermediate frequency. In this case, due to the influence of environmental noise, the receiver may perform the same operation as when the signal is received. In the case where the receiver performs the same operation as when receiving a signal, if the mobility of the receiver is high, the reception state changes every moment, so that the level of environmental noise seen from the receiver appears unstable. When the level of the environmental noise fluctuates in the range shown in FIG. 4 for the receiver, the speaker opens when the level is high, and excessive noise is output at the same time as the level becomes low. However, the operation of the squelch circuit immediately causes the speaker to be turned off. Try to close. However, since the squelch level setting circuit also has a delay factor due to the noise detection time, there is a drawback that, although momentary, excessive noise must be heard though it is annoying. In some cases, in order to repeat this series of operations, there is a disadvantage that the user must listen to the beat of noise (noise that is output momentarily but repeatedly).

Therefore, in order to overcome these problems, it is necessary to reset the reference voltage according to the operating environment. However, in the conventional receiver, the reference voltage is reset by manual operation, which is troublesome, and has a disadvantage that it cannot follow the fluctuation of environmental noise due to the operating environment.

Therefore, in the present invention, the squelch level (reference voltage) is automatically set so that the output from the speaker can be controlled depending on whether or not environmental noise is radiated. It is an object of the present invention to provide a receiver having a squelch level setting circuit having a high squelch level.

[0008]

According to the present invention, in order to achieve the above object, a central processing unit is connected to a detector and a reference voltage output unit, and the central processing unit monitors a noise detection voltage and sets a reference voltage. The control is performed. During operation of the wireless device, the central processing unit constantly monitors the noise detection voltage detected by the detector to determine whether or not environmental noise has been radiated.The central processing unit determines the reference voltage based on the determination result. By controlling, the squelch level (reference voltage) can be automatically set according to the operating environment.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A receiver including a squelch level setting circuit according to one embodiment of the present invention will be described with reference to FIGS.

First, an outline of the operation of the receiver according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram of a receiver (single superheterodyne receiving wireless device) including a squelch level setting circuit according to the present embodiment. 1
A central processing unit, 2 an intermediate frequency amplifier, 3 a demodulator, 4 an audio signal processing circuit, 5 an audio power amplifier, 6 a speaker, 7 a switch, 8 a bandpass filter, and 9 a comparator. Reference numeral 10 denotes a detector, reference numeral 11 denotes a reference voltage, and reference numeral 12 denotes an AGC circuit. 1 and 7 to 11 are squelch level setting circuits.

When a receiver receives a signal, the signal is converted from a reception frequency to an intermediate frequency and then amplified by an intermediate frequency amplifier 2. At this time, even if the signal level fluctuates, the AGC circuit 12 controls so that the output level from the intermediate frequency amplifier 2 becomes constant. After that, the output signal from the intermediate frequency amplifier 2 is input to the demodulator 3 and converted into a demodulated signal, and the demodulator 3 outputs the demodulated signal. The demodulated signal is input to the speaker 6 via the audio signal processing circuit 4 and the audio power amplifier 5.

On the other hand, only the noise component is extracted from the output of the demodulator 3 by the band-pass filter 8, and the noise component is extracted by the detector 1
The value detected at 0 and converted to a DC voltage is the central processing unit 1
To monitor. At this time, the central processing unit 1 also controls the reference voltage, and compares the reference voltage value with the detection voltage value, and when the detection voltage value is equal to or lower than the reference voltage value, environmental noise is radiated. Then, the reference voltage is adjusted and set to be lower than the detection voltage value. Then, according to the result of comparing the newly set reference voltage and the detection voltage by the comparator 9, the switch 7 of the audio power amplifier 5
By controlling the opening and closing of the loudspeaker, it is possible to prevent a sound from being output from the speaker 6 in a state where excessive noise is placed.

Next, the setting of the squelch level (reference voltage) by the central processing unit will be described with reference to FIG. FIG. 3 shows a characteristic diagram of the detection voltage and the reference voltage. FIG.
The horizontal axis represents the received signal level, and the vertical axis represents the noise detection voltage. The bold line is a graph showing the relationship between the received signal level and the noise detection voltage, and the dotted line is the reference voltage. When the noise detection voltage is higher than the reference voltage, the squelch level setting circuit operates and the switch 7 of the audio power amplifier 5 is turned off, so that no sound is output from the speaker 6. At this time, if it appears that the received signal level has risen due to the influence of environmental noise, the noise detection voltage drops. When the value of the noise detection voltage becomes equal to the reference voltage, the central processing unit 1 sets the reference voltage to a value lower than the noise detection voltage.

As described above, by always performing the processing (monitoring of the noise detection voltage and control of the reference voltage) in the central processing unit 1, real-time setting of the squelch level (reference voltage) can be performed automatically. become. Therefore,
It becomes easy to follow a change in environmental noise due to a change in the operating environment.

[0015]

According to the present invention, even if the operating environment of the wireless device changes, the squelch level (reference voltage) can be automatically reset according to whether or not environmental noise is radiated. Therefore, it is possible to provide a receiver having a very convenient squelch level setting circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiver including a squelch level setting circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a receiver including a squelch level setting circuit as an example of the related art.

FIG. 3 is a characteristic diagram showing a relationship between a detection voltage and a reference voltage of the squelch level setting circuit according to one embodiment of the present invention.

FIG. 4: Received signal level versus sound output characteristics

[Explanation of symbols]

1: central processing unit, 2: intermediate frequency amplifier, 3: demodulator, 4: audio signal processing unit, 5: audio power amplifier,
6: speaker, 7: switch, 8: band-pass filter,
9: comparator, 10: detector, 11: reference voltage, 12: A
GC circuit.

Claims (1)

[Claims] 1. A noise level detecting means, a squelch level output section, a comparator for comparing a noise level with a squelch level, and controlled by the comparator to turn off when the noise level is higher than the squelch level. A receiver including a speaker, comprising: a central processing unit that receives the noise level and controls the squelch level; and when the environmental noise is radiated and the noise level changes below the squelch level, the squelch A receiver wherein the level is automatically set to be low and the speaker is turned off.