JPH0445615A - Radio equipment - Google Patents

Abstract

PURPOSE:To relieve a defect such as the generation of noise from a speaker due to external noise or disabled transmission for a long time by outputting a squelch signal based on the result of comparison between a signal outputted from a level measuring circuit and a signal corresponding to a predetermined level. CONSTITUTION:A distributer 3 divides an intermediate frequency output of a radio receiver 1 to two band pass filters 2, 21. The band width of the BPF 21 is sufficiently smaller than that of the BPF 2 and the band is enough to limit external noise than that of the BPF 2. For example, when the band width of the BPF 21 is selected to be 1/10 of the band width of the BPF 2, the noise passing through the BPF 21 is improved by 10dB in comparison with the noise passing through the BPF 2. Thus, a squelch signal generating section 5 is affected almost the same degree even when external noise whose intensity is higher by 10dB is inputted to the section 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wireless device having a function of determining whether or not there is a radio wave generated from a wireless device of another station.

[Conventional technology]

In general wireless equipment, the received intermediate frequency is passed through a bandpass filter and the output is detected to obtain an audio signal, or furthermore, a data signal is obtained through a comparator. When determining whether or not to start up a station's wireless equipment and emit radio waves, or whether or not to output a received audio signal from a speaker, etc., there are radio waves generated from other station's wireless equipment. When using the judgment result of "no", this judgment was made based on the output of the same bandpass filter.

FIG. 2 is a diagram of an example of a conventional wireless device. In this conventional example, transmission and reception are performed on the same frequency.
It is a wave simplex type.

First, signal reception will be explained. The intermediate frequency output of the radio receiving device 1 passes through a bandpass filter 2 and is divided by a distributor 3 into a demodulator 4 and a squelch signal generator 5.

In the demodulator 4, the signal is amplified by a limiter amplifier 15, detected by an FM detector 16, and noise components are removed by a low-pass filter 17. The data is further set to “°0” by the comparator 18.
, the microcomputer 6 as a digital signal of “1”
is input to. On the other hand, for audio signals, switch 7
The power is amplified by the amplifier 8 and output from the speaker 9.

Further, the squelch signal generating section 5 is used to distinguish whether the received signal has any meaning in this wireless device.

In the squelch signal generating section 5, the level measuring circuit 19 measures the received electric field level of the output of the distributor 3 and converts it into a voltage. In the comparator 20, if the level measurement result is larger than a certain reference value (2), the received signal is considered to have meaning and this is communicated to the microcomputer 6.

When the microcomputer 6 learns that it is receiving data from the squelch signal generating section 5 at a sufficient level and receiving data from the demodulating section 4, it sends the received data to the operation display section 10. Alternatively, the microcomputer 6 is
If the output of the demodulator 4 is found to be not data while the signal is being received at a sufficient level, it is determined that the signal being received is audio, the switch 7 is closed, and the audio signal is sent to the speaker 9.
Output from

Next, signal transmission will be explained.

In response to the activation command from the operation display unit 10, the microcomputer 6 transmits data output by itself or an audio signal input from the microphone 11 using the wireless transmitter 14, if it is not receiving data. Amplifier 12 is used to amplify the signal from microphone 11 to a sufficient level.

If the output of the squelch signal generator 5 rises and the signal is being received, it means that radio waves of the same frequency are being used. Controlled by 6.

[Problem to be solved by the invention]

The conventional example shown in FIG. 2 described above has the drawback of being weak against external noise.6 The reason for this will be explained below.

First, the reference value V2 used in the squelch signal generator 5 is:
The value is selected to correspond to an electric field value that is approximately 5 to 10 dB higher than the receiving sensitivity of the local radio receiving device. If the value of V2 is increased more than this, the opposite effect will occur in that the service area for receiving and responding will become extremely small.

Therefore, if the external noise is sufficiently high and higher than the receiving sensitivity by about 10 dB or more, the measurement result will exceed the value of (2) and it will be considered that the signal is being received. As a result, the switch 7 is closed and noise is output from the speaker 9, or a disconnection occurs in which the wireless transmitter of the local station cannot transmit until the external noise disappears.

[Means to solve the problem]

The wireless device of the present invention includes a wireless receiving device, a distributor that divides the intermediate frequency received signal outputted by the wireless receiving device into two, and a first bandpass filter that passes the output of one of the distributors. a second bandpass filter whose bandwidth is sufficiently smaller than the bandwidth of the first bandpass filter and passes the other output of the distributor; and if the output of the second bandpass filter is equal to or higher than a predetermined level, a squelch signal is generated. and a demodulation section that demodulates the output of the first bandpass filter.

The squelch signal generating section compares a level measuring circuit that outputs a signal corresponding to the level of the output of the second bandpass filter, and a signal output from this level measuring circuit with a signal corresponding to the predetermined level. and a comparator that outputs the squelch signal based on the comparison result.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The basic difference between the embodiment shown in FIG. 1 and the conventional example shown in FIG.
The difference is whether the demodulator 4 and the squelch signal generator 5 use intermediate frequencies that have passed through different bandpass filters, or whether they use intermediate frequencies that have passed through the same bandpass filter.

First, the radio receiving device 1 is the same as in the conventional example of FIG. 2, and the bandpass filter 2 has the same bandwidth as that in FIG. 2. Further, 3 is a distributor, which divides the intermediate frequency output of the radio receiving device 1 into two bandpass filters 2 and 21. The bandpass filter 21 has a sufficiently smaller bandwidth than the bandpass filter 2, for example, about 1/3 to 1/10. Below, each part 4
20 are respectively the same as those in FIG.

Now, in the embodiment shown in FIG. 1, the bandpass filter 21 has a sufficiently smaller bandwidth than the bandpass filter 2. Therefore, external noise is sufficiently limited in terms of bandwidth compared to the bandpass filter 2. For example, if the bandwidth of the bandpass filter 21 is 1/10 of the bandwidth of the bandpass filter 2, the noise passing through the bandpass filter 21 is improved by 10 dB compared to the noise passing through the bandpass filter 2. Therefore, in the embodiment shown in FIG. 1, even if external noise that is 10 dB stronger is input, the squelch signal generating section 5 is only affected to the same extent as compared to the conventional example shown in FIG. 2.

Here, the bandpass filter 21 does not need to pass a signal through it like the bandpass filter 2, and is simply used to judge whether or not there is a radio wave from another station, so its bandwidth can be made as small as possible. It is possible to do so. Therefore, the influence of external noise can be sufficiently reduced. Of course, by limiting the band to a small value using the bandpass filter 21,
The band is limited not only by external noise but also by radio waves from other stations, but since it is distributed in the center of the spectrum in voice communication or general data communication, as long as that frequency is used as the center frequency of the bandpass filter 21, it is not practical. No problem.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to more accurately determine whether the radio waves are emitted from the wireless device of the other station without being affected by external noise, and it is possible to determine whether the radio waves are emitted from the wireless device of the other station, and to avoid the influence of external noise. Problems such as noise occurring or being unable to send data indefinitely are greatly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional wireless device. 1... Radio receiving device, 2... Bandpass filter, 3...
・Distributor, 4... Demodulator, 5... Squelch signal generator, 6... Microcomputer, 7... Switch, 8... Amplifier, 9... Speaker, 10... Operation Display unit, 11...Microphone, 12...Amplifier,
13... Combiner, 14... Wireless transmitter, 15...
- Limiter amplifier, 6... FM detector, ... low-pass filter, comparator, ... level measurement circuit, 20. comparator, 1... bandpass filter.

Claims (1)

[Claims] 1. A radio receiving device, a splitter that divides the intermediate frequency received signal outputted by the radio receiving device into two, and a first bandpass filter that passes the output of one of the splitters. , a second bandpass filter whose bandwidth is sufficiently smaller than that of the first bandpass filter and which passes the other output of the divider;
a squelch signal generating section that generates a squelch signal when the output of the bandpass filter is equal to or higher than a predetermined level;
A radio device comprising: a demodulator that demodulates the output of the first bandpass filter. 2. The squelch signal generation section includes a level measuring circuit that outputs a signal corresponding to the level of the output of the second bandpass filter, and a signal output from the level measuring circuit and a signal corresponding to the predetermined level. 2. The wireless device according to claim 1, further comprising a comparator that compares the squelch signal and outputs the squelch signal based on the comparison result.