JPH0787000A - Multiple channel radio receiver - Google Patents

Abstract

PURPOSE:To stabilize received sound quality by setting the noise quantity of demodulated synthesized speech output of plural reception units for single speech path stored in a multiple channel radio receiver at a constant value in spite of the number of speech participants. CONSTITUTION:The number of speech participation reception units is counted by detecting tone detection output for tone squelch from the plural reception units 1a, 1b,..., 1n for single speech path. RSSI threshold values for the number of speech participation reception units stored in the memory of a microcomputer 17 in advance are read out, and they are compared with the output of a multiple channel A/D converter 15 which measures the electric field strength indicator output of each reception unit. Squelch operating points for the mute switches of all the reception units are updated by an addressable latch 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver of a base station wireless communication device of a communication system for premises work used at a production site or the like, and more particularly to a receiver for a plurality of single speech paths. The present invention relates to a multi-channel wireless receiving device that demodulates radio waves from mobile devices carried by a plurality of workers by receiving units of corresponding frequency channels and outputs a synthesized voice signal.

[0002]

2. Description of the Related Art A local radio system provided as a means for communication between workers on a premises includes a radio base station, a relay amplifier with an antenna distributed to the base station by wires, and a plurality of relay amplifiers. It is composed of a mobile device carried by a worker, and communication between workers is performed at any time centering on a radio base station via a relay amplifier. FIG. 6 is a configuration example diagram showing an outline of a conventional radio base station. In the figure, 20 is a radio base station, 21 is an antenna, 22 is a combiner / distributor, 23 is a multi-channel radio reception device, 24 is a transmission device, and 25 is a single channel reception implemented in the multi-channel radio reception device 23. It is a unit, and a plurality of units are provided corresponding to the number of channels of the mobile device. Reference numeral 26 is a variable resistor for adjusting the synthesized voice output level at any time. Reference numeral 28 denotes a bidirectional relay amplifier, each of which has an antenna 29 and is connected to the combining / distributing device 22 of the wireless base station 20 by a cable 27 such as a leaky coaxial cable or a coaxial cable.

As shown in FIG. 6, the radio base station 20 is equipped with a multi-channel radio reception device 23 and a transmission device 24, and radio waves transmitted from a plurality of mobile stations to the base station are: After being received and demodulated by the receiving units 25 of the corresponding channels of the multi-channel wireless reception device 23,
It is composed and output. The transmitting device 24 modulates a carrier wave using the synthesized voice output as a modulated wave and sends it to a plurality of mobile stations in a broadcast format. By constructing such a system, multiple workers carrying mobile devices can hear not only their own communication, but also the content of calls between other workers who are communicating at any time, so the entire campus The collaborative work of will proceed smoothly.

In the multi-channel radio receiver 23 in which a plurality of single-channel receiving units 25 are mounted, deterioration of spurious response caused by leakage or coupling from the assigned channel setting local oscillator of each receiving unit, Due to the intermodulation distortion that occurs as the number of mounted channels increases, carrier squelch and noise squelch often malfunction. Therefore, in the squelch control in the multi-channel wireless receiver, a tone squelch (Continuous Tone-Cortrolled Squelch System) is used.
． (Hereinafter abbreviated as CTCSS) has come to be used, and its details are specified by the Japan Electronic Machinery Manufacturers Association Standard (E
IAJ, 2017). That is, CTCSS is a simple type selective calling system used when radio waves of the same frequency or near frequencies are shared in the same area. Tone signals of subchannels set in a frequency band lower than the voice band are used as voice signals and data. At the same time, it is a system for sending out from the transmitting side, canceling the squelch of the receiver to which the tone signal is assigned, and performing a reception demodulation operation. The operation characteristics of CTCSS have high sensitivity (SI
Since NAD 9 dB or less) lacks the setting resolution, it is not suitable for setting the squelch operating point to, for example, S / N near 20 dB. Therefore, tone squelch is used to prevent the above-mentioned malfunction, but in order to set the squelch operating point, a field strength indicator (RSS1: Receiving Signale Stre
It is common to use carrier squelch that turns on / off the output of the receiving unit using ngth indicator) or noise squelch that uses the change in noise level, and set the operating point (threshold value). Is a fixed type that is preset by using a variable resistor or the like.

FIG. 7 shows a conventional single speech path receiving unit 2
5 is a diagram illustrating a circuit configuration example of FIG. In the figure, reference numeral 30 is a radio signal input terminal, and radio signals from a plurality of mobile stations received by the antenna 21 of the radio base station and the antenna 29 of the distributed bidirectional relay amplifier 28 are combined and distributed by the distributor 2.
It is distributed by 2 and input respectively. Reference numeral 31 is a reception demodulation unit that detects and demodulates a radio signal of a channel assigned to the reception unit, 32 is a mute switch, 33 is a squelch circuit, and 34 is a squelch level (RSSI threshold).
A setting variable resistor, 35 is a tone decoder, and 36 is an AND circuit. As shown in FIG. 7, in each single speech path receiving unit 25, the received electric field level is higher than the threshold value set in the squelch circuit 33, and the tone signal assigned in advance by the tone decoder 35 is detected. Only at this time, the gate of the mute switch 32 is opened to output the audio signal.

[0006]

As described above, in the conventional multi-channel radio receiving apparatus 23, the setting of the squelch operating point is a fixed type which is set in advance in each receiving unit, so that a plurality of stored single units are accommodated. When the number of participants in the one-way receiving unit 25 increases, the S /
There may occur a case where N becomes worse than the S / N at the time of a single call at the squelch operating point set for each receiving unit. Therefore, there is a problem that the call quality deteriorates as the number of participants in the call increases, and control suitable for practical use is not performed in terms of maintenance and management of the call quality. This will be described in more detail with reference to FIG. FIG. 2 is a diagram showing the relationship between the worst value of the signal-to-noise ratio S / N of the synthesized voice output with respect to the number N of receiving units which are mounted in the multi-channel radio receiving apparatus and whose squelch is released. Now, suppose that the squelch operating points of the plurality of single channel receiving units housed in the multi-channel wireless receiving device have an S / N of an audio output signal of 20 dB which is considered to be normally usable. Assuming that they are set in the vicinity, the number of receiving units N in which the communication path is opened by giving an input signal of the receiving electric field strength at which squelch is barely released to these receiving units.
And the S / N relationship of the synthesized voice outputs thereof is expressed by the following equation as shown by the curve in FIG.

[0007]

## EQU1 ## S / N (dB) = 20-10 logN

That is, when only one receiving unit is given an input signal of the received electric field strength that barely cancels the squelch, the S / N of the synthesized voice output of the multi-channel radio receiving apparatus is about 20 dB. Although it can be put to practical use enough, if the number of participants in the call increases and the squelch of 10 receiving units is barely released and the call continues,
The S / N ratio of the synthesized voice output deteriorates to about 10 dB, which makes it unusable for practical use. This is due to a problem in radio wave propagation that occurs due to the station placement relationship between the transmitting side and the multi-channel radio receiving device,
The indoor radio wave propagation occurs when it is not possible to set the service area, and the indoor radio wave propagation often causes a problem such as multipath fading. However, the conventional squelch control of the multi-channel wireless receiving device does not address such a problem, and thus there is a drawback that the call quality may be impaired, which is a problem in practical use.

The present invention has been made in view of the above circumstances, and the S / N deterioration of the synthesized voice output of these units increases as the number of participants of the single-channel receiving unit in the multi-channel radio receiver increases. Solves the conventional problem that the number of opportunities increases and the amount of S / N deterioration does not increase, and the practical lower limit of S / N of synthesized voice output is guaranteed even when the number of participants in the call of the receiving unit increases. It is an object of the present invention to provide a multi-channel wireless receiving device.

[0010]

According to a first aspect of the present invention for solving the above-mentioned problems of the prior art, a multi-channel radio receiving apparatus accommodating a plurality of receiving units for a single speech path is capable of performing full reception. It is characterized in that the squelch operating point of the unit is updated according to the number of call participation receiving units. This will be described in more detail with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing the relationship between the S / N of the voice output of the receiving unit and the electric field strength indicator RSSI output with respect to the magnitude of the input signal (R-IN) of the receiving unit. As described above, FIG. 2 shows the relationship of the S / N ratio of the synthesized voice output with respect to the number N of the receiving units, and the curve shows the S / N ratio of the synthesized voice output with respect to the number N of the receiving units in which the squelch is released. It represents the worst value relationship. Suppose now that the S / N of the synthetic speech output of a plurality of receiving units is
Is not less than the usual practical limit value of 20 dB, the S / N of the output at the squelch operating point of each receiving unit and the input signal of the received electric field strength that barely cancels the squelch are given. The relationship with the number N of receiving units talking with each other can be expressed by the following equation as shown by the curve in FIG.

[0011]

(2) S / N (dB) = 20 + 10 logN

That is, in order to prevent the S / N of the synthesized voice output of the receiving unit in the call of the multi-channel receiving device from falling below 20 dB, the squelch is released and the number N of the receiving units in the call is 0 or When the squelch operating point is 1, the S / N is 20 dB (point a in FIG. 1 and points a and b in FIG. 2).
If the number N of receiving units that participated in the call after the squelch is released is 16, for example, the squelch operating point is a point where the S / N is 32 dB (point b in FIG. 1, point c in FIG. 2).
Must be changed to. Further, when such a setting requires an excessively high call quality, resulting in an adverse effect of reducing the service area, and when there is an inconvenience, warm the setting slightly (for example, 6 dB) and The relationship between the output S / N at the squelch operating point of the receiving unit and the number N of receiving units to which the input signal of the received electric field strength at which the squelch is barely released is given, as shown in the curve of FIG. You may make it like a formula.

[0013]

## EQU3 ## S / N (dB) = 14 + 10 logN

According to a second aspect of the present invention for solving the above-mentioned problems of the conventional example, in a multi-channel radio receiving apparatus accommodating a plurality of receiving units of a single speech path, the squelch operating point of each receiving unit is The feature is that only the receiving units that are not participating in the call are updated when updating according to the number of receiving units participating in the call.
By doing this, the squelch operating point of the receiving unit that participated in the call while the number of receiving units participating in the call was small is fixed at the time of participation, and after that the change in the squelch operating point due to the increase in the number of participants in the call is affected. It is possible to provide a service form in which the call can be continued without being interrupted.

According to a third aspect of the present invention for solving the above-mentioned problem of the conventional example, in a multi-channel radio receiving apparatus accommodating a plurality of receiving units of a single speech path, the squelch operating point of the receiving unit When updating according to the number of participating reception units, the squelch operating point is changed by measuring the RSSI output when there is a detection output of CTCSS of the reception unit. Figure 1
2 will be described in more detail. Now, assuming that the S / N of the combined output of a plurality of receiving units does not fall below 20 dB, which is a normal practical limit value, when the number of receiving units operating the squelch is 0 or 1, The squelch operating point is controlled by measuring the RSSI output (point c in FIG. 1) when the S / N is 20 dB (point a in FIG. 1). For example, the S / N of the squelch operating point to be set when the number of participants in the call is 16 is 32 dB (see FIG.
(C point in Fig. 1 and c point in Fig. 1), the corresponding RS
By measuring the SI output (point d in FIG. 1), control for changing the squelch operating point becomes possible. Thus R
Since the squelch operating point is changed using the SSI output,
It has the characteristics that setting control can be performed over a wider range of received electric field strength than noise squelch, and that it is not affected by reception intermodulation by using CTCSS together.

Next, the operation of the present invention will be described. According to the first aspect of the present invention, when setting the maximum noise level of the synthetic voice output of the multi-channel wireless reception device, the squelch operating point of all the receiving units accommodated is opened (released) to make a call. Since squelch control is performed according to the number of receiving units in use, it is possible to perform squelch control without impairing the speech quality of synthesized voice output. Claim 2
According to the invention described, in the squelch control in the receiving unit of the multi-channel wireless receiving device, the squelch operating point is updated only to the receiving unit that does not participate in the call during which the squelch circuit is closed because there is no received signal. Even if a receiving unit with a low input field strength can participate in a call while the number of participants in the call is small, even if the number of participants in the call increases after that, the receiving unit that newly joined the call can Calls can continue without being affected by changes in the squelch operating point. According to the third aspect of the present invention, when performing squelch control in the receiving unit of the multi-channel wireless reception device, the squelch operating point is updated by the value obtained by measuring the RSSI output. This can be done, and by using tone squelch together, it is not affected by reception intermodulation.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a connection diagram showing a configuration example of a receiving unit accommodated in a multi-channel radio receiving apparatus of the present invention. In the figure, reference numeral 1 denotes a receiving unit, which is a receiving unit input section 2, a receiving unit connector section 3, and a receiving demodulating section 4.
, A mute switch 5, and a tone decoder 6 for detecting a tone squelch tone. The demodulation output of the reception demodulation unit 4 outputs an audio output 7 when the mute switch 5 controlled by the mute input 8 is released from the squelch operation. The tone detection output 9 of the tone decoder 6 is an RSSI output 10 for detecting the number of participants in a call and determining the squelch operating point corresponding to that number.
It is used for conditioning the start of measurement.

FIG. 4 is a block diagram of a multi-channel radio receiving apparatus showing an embodiment of the present invention. It should be noted that parts having the same configuration as in FIG.
The multi-channel radio receiving apparatus of the present embodiment includes a microcomputer 17 including a RAM and a ROM for controlling the entire apparatus, and a plurality of single channel receiving units 1.
a, 1b, to 1n, and audio output 7a of each receiving unit,
Variable gain amplifier 12 for adjusting the level of the synthesized voice output 16 of 7b, 7n, and mute inputs 8a, 8b, 8n for each receiving unit, for example, an addressable latch. 13, such as mute signal output means, tone signal input means such as a multiplexer (Multiplexer) 14 for receiving the tone detection outputs 9a, 9b, to 9n of the receiving units, and RSSI outputs 10a, 10 of the receiving units.
Connectors 11a, 11b, and 11n for connecting the receiving units 1a, 1b, and 1n to RSSI measuring means such as a multi-channel A / D converter 15 that digitally converts and measures analog signals of b and to 10n. Composed of and.

Updating of the squelch operating point, which is a characteristic part of this embodiment, will be described with reference to FIGS. 1, 2 and 4. The microcomputer 17 including the RAM and the ROM has an input signal R-IN when the squelch is released and the number of receiving units N during the receiving call and the signal-to-noise ratio S / N at the squelch operating point to be set are obtained. The relationship of RSSI threshold values corresponding to the levels is stored as a table as shown in the following Table 1, for example.

[0020]

[Table 1]

The method shown in Table 1 is used, for example, in the case where the signal-to-noise ratio S / N is not less than 20 dB in the sense of setting the combined maximum noise level of the multi-channel radio receiving device. Since it is necessary to set the squelch operating point that satisfies the expression of [Equation 2], if the number of receiving units in a call after releasing squelch is 16, the signal-to-noise ratio S / N at the squelch operating point to be set is set. Is c in FIG.
As shown by the dots, it is 32 dB, and RS at the magnitude of the input signal R-IN level of the receiving unit at this time is
The SI output is 56, as shown at point d in FIG. In this way, based on the table created in advance, RA
The microcomputer 17 including M and ROM uses the multi-channel A / D converter 15 to output RSSI outputs 10a, 1
The magnitudes of 0b and 10n are measured, and when the value is larger than the threshold value, the squelch is released (opened). The memory for storing Table 1 showing the RSSI threshold value may be one in the case of claim 1, but is provided corresponding to the receiving unit in the case of claim 2.

The squelch operating point is updated by RSS to be compared for each number N of receiving units which are in a call after squelch is released.
In addition to the above method using the table for obtaining the threshold value of I output, there is also a method of obtaining the threshold value of RSSI output by calculation processing. It is a method of obtaining the signal-to-noise ratio S / N at the squelch operating point to be set by the formula of [Equation 2] and directly obtaining the threshold value of the RSSI output to be compared from the value. As is clear from FIG. 1, in the region where the squelch setting is made, the input signal R-IN of the receiving unit, the signal-to-noise ratio S / N, and the RSSI output have a linear relationship, so Approximation formula (ax +
It goes without saying that the threshold of the RSSI output can be calculated from the signal-to-noise ratio S / N in b).

Next, the squelch control method of the multi-channel radio receiving apparatus of this embodiment will be described with reference to FIGS. 4 and 5. FIG. 5 is a flowchart showing the flow of squelch control of the present invention. In the figure, 100 to 111 are step numbers. In the squelch control method of the present invention, first, as an initial state, the setting memory of the number of participants in a call in the RAM area including the RAM and the ROM in the microcomputer 17 is set to 0 (step 100). Next, Table 1 described above
Sets the RSSI threshold to 45 (step 101). Tone detection output 9 of all receiving units 1a, 1b, to 1n mounted on the multi-channel wireless receiving device
a, 9b, to 9n are monitored by the multiplexer 14, and the presence or absence of the tone detection output is detected in step 102, and the reception unit having the tone detection output is measured by the multi-channel A / D converter 15. The RSSI output is compared to the RSSI threshold in RAM (step 103). When the measured value is larger than the RSSI threshold value of the RAM, the squelch of the receiving unit is opened (released) by the addressable latch 13 (step 105). Then, the process of updating the number of participants in the call in the RAM (step 110) and referring to the table, RSS
A process for updating the I threshold value (step 111) is performed.
For the receiving unit that has lost the tone detection output in step 102, a process of closing the squelch circuit (operating the squelch) (step 108) and a process of reducing the number of participants in the call (step 109) are performed, and similarly RA
The contents of M are also updated.

The microcomputer 17 including the RAM and the ROM is provided for all the receiving units installed.
Such processing is constantly executed at high speed to perform squelch control. When the update of the squelch operating point is applied only to the receiving unit whose squelch circuit is closed (squelch operating), the RSSI threshold when the squelch circuit is opened is stored in RAM for each receiving unit. Then, use it for comparison to close the squelch. Therefore, in the present embodiment, the microcomputer 17 including the RAM and the ROM uses the RSSI threshold value corresponding to the number of open reception units of the squelch circuit for the squelch control by referring to the table, so that the synthesized voice output The worst value of the signal-to-noise ratio (the lowest practical value) can be set.

In the case of updating the squelch operating point of only the receiving unit whose squelch circuit is closed, the disconnection of the call due to the increase in the number of participants in the call is prevented, and the squelch operating point is measured by the method of measuring the RSSI output together with CTCSS. By the determination, it is possible to perform squelch control over a wide range of received electric field strength that is not affected by reception intermodulation.

[0026]

According to the invention of claim 1, in the multi-channel radio receiver, the squelch operating point of the receiving units of the plurality of single communication paths to be accommodated is desired to be the number of receiving units with squelch open. By setting the lower limit value of the signal-to-noise ratio of the synthesized voice output calculated from the value of the signal-to-noise ratio, it is possible to prevent the deterioration of the communication quality. According to the invention of claim 2, the update of the squelch operating point is applied only to the receiving units which are not participating in the call and the squelch is closed. Since the call can be maintained without being affected by the change of the squelch operating point due to the increase of the call, there is an effect that an accurate call path control can be obtained.
According to the invention of claim 3, in the multi-channel radio receiving device, the CTSSS is also used, and the squelch operating point is updated by measuring the RSSI output for the channel having the detection output thereof. There is an effect that the squelch control can be performed for a wide range of received electric field strength.

[Brief description of drawings]

FIG. 1 S / N of input signal level and output of receiving unit
FIG. 3 is a diagram illustrating a relationship between the RS and the RSSI.

FIG. 2 is a diagram showing the relationship between the number N of receiving units in which squelch is operating and the worst value of S / N that changes due to addition of noise power.

FIG. 3 is a connection diagram showing a configuration of a receiving unit housed in the multi-channel wireless receiving apparatus of the embodiment of the present invention.

FIG. 4 is a connection diagram showing a configuration of a multi-channel wireless reception device according to an embodiment of the present invention.

FIG. 5 is a flowchart showing a flow of squelch control of the present invention.

FIG. 6 is a block diagram of a conventional radio base station.

FIG. 7 is a block diagram of a conventional receiving unit.

[Explanation of symbols]

1, 1a, 1b, to 1n Single channel receiver unit 2, 2a, 2b, to 2n receiver unit input unit 3, 3a, 3b, to 3n receiver unit connector unit 4 receiver demodulator unit 5 mute switch 6 tone decoder 7 , 7a, 7b, ~ 7n Audio output 8, 8a, 8b, ~ 8n Mute input 9, 9a, 9b, ~ 9n Tone detection output 10, 10a, 10b, ~ 10n Field strength indicator (RSSI) output 11a, 11b, ~ 11n Receiver unit connector 12 Variable gain amplifier 13 Addressable latch 14 Multiplexer 15 Multi-channel A / D converter 16 Synthetic voice output 17 Microcomputer including RAM and ROM 20 Radio base station 21, 29 Antenna 22 Synthetic distributor 23 Multi-channel Radio receiver 24 Transmitter 25 Single channel reception Knit 26 variable resistor 27 cable 28 two-way relaying amplifier 30 input terminal 31 receiving the demodulation unit 32 mute switch 33 squelch circuit 34 variable resistor 35 tone decoder 36 and circuit

Claims (3)

[Claims] 1. A multi-channel radio signal is received and demodulated for each channel by a plurality of single-channel receiving units, and the voice outputs of the plurality of single-channel receiving units are synthesized to produce a synthesized voice output. In the multi-channel wireless receiver configured to obtain, each of the plurality of receiving units, a receiving demodulation unit that demodulates and outputs a reception signal of a single speech path and outputs a reception field strength indicator, A tone decoder having a tone detection output for tone squelch from the demodulation output of the reception demodulator, and a mute switch for performing a squelch operation to turn on / off the demodulation output by an externally applied mute input and outputting an audio signal are provided. Tone input means for obtaining tone detection outputs from tone decoders of the plurality of receiving units, Mute signal output means for applying the mute input to the mute switch of the receiving unit, receiving electric field strength indicator measuring means for converting the received electric field strength indicators input from the plurality of receiving units into digital values and measuring the digital values. Memory means for storing in advance a table in which the threshold value of the reception electric field strength indicator for the number of participants in the call of the receiving unit is set so that the noise amount of the synthesized voice output becomes a predetermined value or less, and the number of participants in the call of the memory means With respect to the threshold value of the received electric field strength indicator and the measured value by the received electric field strength indicator measuring means, the received electric field strength indicator comparing means for measuring the received electric field strength indicator of the receiving unit of the tone detection output. The number of participants in the call each time. A multi-channel wireless reception device, comprising: a microcomputer for controlling the squelch operating points of the plurality of receiving units to be updated by comparing with a threshold value of a signal field strength indicator. 2. The microcomputer fixes the threshold value of the reception electric field strength indicator of the receiving unit participating in the call at the time when the squelch is released, and does not update the squelch operating point. 3. The squelch operating point is updated by changing the threshold value of the reception electric field strength indicator of the reception unit not participating in the call according to the number of participants in the call.
The described multi-channel wireless reception device. 3. The microcomputer according to claim 1, further comprising a tone squelch operation by a tone detection output input to the tone signal input means, and when the tone detection output is present, an output of the reception electric field intensity indicator is output. 2. The multi-channel radio receiver according to claim 1, wherein the carrier squelch operation is performed by comparing with a variable set value measured and stored in the memory.