JPH07203522A - Cordless telephone system - Google Patents

Abstract

PURPOSE:To attain the connection of a radio line without disturbance by surely and speedily executing the carrier sensing of a control channel at the time of sending an outgoing and incoming call signal and an outgoing and incoming call answering signal in advance of the connection of the radio line at master and slave stations. CONSTITUTION:In advance of the connection of the radio line, a noise squelch circuit 10 executes carrier sensing by receiving a radio wave corresponding to the control channel in order to confirm whether the control channel to use is idle or not. From among FM demodulation signals obtained by demodulating reception signals, a variable band band pass filter fetches the band signal of a frequency 29 to 31kHz. A comparator 12 compares this signal with a reference noise set in advance and when the noise of a single frequency component like a beat sound is generated within the fetched signal, a microcomputer part 16 controls a band control part 17 to change the band to be frequency 35 to 37kHz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless telephone device for carrying out carrier sense for confirming an empty control channel from a demodulated signal.

[0002]

2. Description of the Related Art In this type of cordless telephone apparatus, a slave unit goes off-hook when a call is made and sends a call signal to a master unit.
The master unit in the standby state detects the call signal from the slave unit and sends a call response signal to the slave unit. When the base unit detects a ringing signal from the line during an incoming call, it sends an incoming call signal to the child unit, and the child unit in the standby state detects the incoming call signal from the parent unit and responds to the parent unit with an incoming call response. Send a signal. The transmission and reception of signals with the master unit and the slave unit are performed on the control channel. In order to confirm the free channel of the control channel, carrier sensing is generally performed in a noise squelch circuit, and the noise squelch circuit is arranged in each radio unit of the master unit and the slave unit.

An FM demodulated signal obtained by demodulating a radio wave coming from an antenna is input to the noise squelch circuit. Figure 3
FIG. 4 is a block diagram showing a configuration of a noise squelch circuit in a conventional cordless telephone device. In FIG. 3, the noise squelch circuit 1 includes a bandpass filter for extracting a frequency band (several tens KHz) which is a band not affected by a voice signal (frequency is 300 Hz to 3 KHz) from the input FM demodulated signal. A (BPF) 2 and a rectifier 3 for converting the component obtained by the bandpass filter 2 into a DC level are provided.

Further, a comparator 4 for comparing the DC level of the rectifier 3 with a preset reference noise level,
A carrier detect circuit 5 that outputs the value of the comparator 4 and a microcomputer (MPU) 6 that controls the operations of the comparator 4 and the carrier detect circuit 5 are provided.

Next, the operation of this conventional example will be described. FIG. 4 is a flow chart showing a processing procedure at the time of carrier sense of the control channel in the operation of the conventional example.

In FIGS. 3 and 4, the noise squelch circuit 1 is provided. For example, in order to confirm the vacancy of the control channel to be used in the slave unit, the radio wave corresponding to the control channel is received to perform carrier sensing (step). (Indicated by S in the figure) 1).

[0007] The FM demodulated signal demodulated from the received signal has a band not affected by the voice signal, for example, a frequency of 29
The band of ˜31 KHz is taken out through the bandpass filter 2 (step 2). The extracted signal component is converted into a DC level by the rectifier 3 (step 3). Then, the DC level is compared with a preset reference noise level (threshold value) (step 4).

High level (H) by the comparator 4
Alternatively, the low level (L) is determined and output to the carrier detect circuit 5 (step 5). If the value from the comparator 4 is high level (H), the carrier detect circuit 5 outputs a signal indicating that the channel is in use. That is, a signal with carrier is output, and if the value is low level (L), the channel is empty (no carrier).
The signal determined to be is output. Therefore, even if the control channel is not used for a call, if noise of a single frequency component such as a beat sound is generated within the pass band of the band pass filter 2 due to the influence of an interfering wave, etc. The squelch circuit 1 determines that the channel is in use. That is, it can be determined that there is a carrier. Therefore, even if noise occurs, it is not recognized as an empty channel, and the carrier sense operation can be performed without mistake.

As a proposal for improvement of this kind, JP-A-4-267
The "free channel determination method" disclosed in Japanese Patent No. 660 and the "cordless telephone device" disclosed in Japanese Patent Laid-Open No. 4-91439 can be mentioned. JP-A-4-267
In the example of Japanese Patent No. 660, the high frequency noise and the carrier of the cordless telephone are distinguished from each other based on the level of the DC voltage by demodulation and the output state of the noise squelch circuit. Japanese Patent Laid-Open No. Hei 4
In the example of Japanese Patent Publication No. 91439/1993, carrier sensing for three frequency bands is performed at one time to shorten the search time.

[0010]

However, in the conventional cordless telephone device shown in FIG. 3, the pass band of the band pass filter 2 is in a constant frequency region. For example, it is a fixed band with a frequency of 29 to 31 KHz. Also, by law,
The emission time of the radio wave of the control channel is set within 4 seconds for the master unit and within 1.3 seconds for the slave unit (when the control signal is transmitted subsequently to the calling signal). Therefore, when noise is generated in the pass band of the band pass filter 2 due to the influence of an interfering wave, etc., when the wireless line is connected between the master unit and the slave unit, the noise squelch circuit 1 always operates on the channel. There is a problem in that it is determined that the device is in use (with carrier), the wireless line cannot be connected by the control channel between the child device and the parent device within the specified time, and there is a problem in use. Further, although the example of the publication distinguishes high-frequency noise from the carrier of a cordless telephone and shortens the search for carrier sense, noise and carrier cannot be reliably distinguished when the high-frequency noise level is high. It is considered that the carrier sense cannot be shortened.

The present invention is intended to solve such a conventional problem and to provide a control channel for transmitting and receiving an incoming / outgoing call signal, an outgoing / incoming call response signal, etc. prior to the connection of the radio lines of the master station and the slave station. An object of the present invention is to provide an excellent cordless telephone device in which carrier sense is performed more reliably and quickly, disturbance is prevented, and reliable wireless line connection is possible.

[0012]

In order to achieve the above object, the cordless telephone apparatus according to claim 1 includes a noise squelch circuit for performing carrier sensing for confirming an empty control channel from a demodulated signal as a base unit and A cordless telephone device provided in a slave unit, wherein the noise squelch circuit extracts a predetermined frequency band in a demodulated signal when confirming the vacancy of a control channel, and a noise component included in the output signal of the variable band filter. And a comparison means for comparing with a reference noise level in the frequency band, and when the result of comparison by the comparison means has a noise component level larger than the reference noise level, the frequency band of the variable band filter is changed to another frequency band. And a band control means for performing control.

According to another aspect of the cordless telephone apparatus of the present invention, the band control is performed when the variable band filter extracts a band signal having a frequency of 29 to 31 KHz and the extracted band signal includes at least a single frequency component of a beat sound. Means for setting the band of the variable band filter at a frequency of 35 to 37 KHz
This is a configuration for performing control to change to.

[0014]

The cordless telephone apparatus according to claims 1 and 2 of this configuration is a variable band filter, and has, for example, frequencies 29 to 3.
When a 1 KHz band signal is extracted and the extracted band signal includes at least a single frequency component of the beat sound, the band of the variable band filter is set to, for example, the frequency 35.
Control to change to ˜37 KHz is performed. Therefore,
When noise is generated in the pass band of the variable band filter due to the influence of an interfering wave or the like, it is no longer determined that the channel is in use. In other words, it becomes possible to connect to the wireless line within the specified time without determining that there is a carrier, and the outgoing / incoming call signal, the incoming / outgoing call response signal, etc. are transmitted prior to the wireless line connection of the master station and the slave station. In this case, carrier sense of the control channel is performed more reliably and quickly.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cordless telephone device of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a cordless telephone device of the present invention. In FIG. 1, the noise squelch circuit 10 has a variable band for extracting a frequency band (several tens KHz) signal which is not affected by a voice signal (frequency 300 Hz to 3 KHz) from the input FM demodulated signal based on a control signal. Comparator 1 that compares the signal level of the band pass filter (BPF) 11 and the variable band band pass filter (BPF) 11 with a preset reference noise level.
2 and a rectifier 13 for converting the comparison signal from the comparator 12 into a DC level. Further, a comparator 14 that compares the DC level from the rectifier 13 with a reference noise level, a carrier detect circuit 15 that outputs a level signal having a value corresponding to the output signal from the comparator 14, a comparator 14 and a carrier detect circuit 15 For controlling the operation of the
U) 16 and a band control unit 17 that performs control for changing the pass band of the variable band band pass filter 11 to another frequency band when it is determined that noise is generated by the comparator 12. There is.

Next, the operation of this embodiment will be described. FIG. 2 is a flow chart showing a processing procedure at the time of carrier sense of the control channel in the operation of the embodiment. In FIG. 2, prior to connecting the wireless line, the noise squelch circuit 10 receives a radio wave corresponding to the control channel and performs carrier sense in order to confirm the vacancy of the control channel to be used (step 11).

A band of the received FM demodulated signal which is not affected by the voice signal, for example, a frequency of 29 to 31 KHz.
Is taken out through the variable band bandpass filter 11 (step 12). The extracted signal is compared with a reference noise level set in advance by the comparator 12 (step 13).

As a result, if no noise of a single frequency component such as a beat sound is generated in the extracted band (step 14: No), the rectifier 13 converts the component to a DC level (step). 15). And
The DC level is compared with a predetermined reference noise level (step 16), the high level (H) or the low level (L) is determined by the comparator 14 and output to the carrier detect circuit 15 (step 17).

If, as a result of the processing in step 13, noise of a single frequency component such as a beat sound is generated in the taken out band (step 14: Yes), the microcomputer 16 causes the band control unit 17 to operate. Is controlled (step 18) to change the pass band of the variable band pass filter 11 to a frequency within a range not affected by the audio signal, for example, a frequency band of 35 to 37 KHz (step 1).
9).

As described above, in this embodiment, the noise component contained in the FM demodulated signal subjected to the band limitation of the variable band bandpass filter 11 at the time of carrier sensing of the control channel is set as the reference noise within the preset same band. When compared with the level, the pass band is changed when it is larger than the reference noise level, and the pass band of the variable band pass filter 11 for extracting a predetermined frequency band from the FM demodulated signal is changed within a range that does not affect the audio signal. . Therefore, when a wireless line is connected between the master unit and the slave unit, if noise is generated in the pass band of the variable band pass filter 11 due to an interference wave or the like, it is determined that the channel is in use. Disappear. That is, it is no longer determined that there is a carrier. As a result, carrier sense of the control channel is performed reliably and promptly when sending and receiving an incoming and outgoing call signal, an incoming and outgoing call response signal, etc. prior to the connection of the radio line of the parent station and the child station. Connection of the wireless line by the control channel can be done within the specified time (radio wave emission time of the control channel frequency by law, within 4 seconds for the master unit, within 1.3 seconds for the slave unit) Become.

[0021]

As is apparent from the above description, the cordless telephone device according to the first and second aspects uses the variable band filter to extract the band signal having the frequency of 29 to 31 KHz, and the extracted band signal. In the case where at least a single frequency component of the beat sound is included in the variable band filter, control is performed to change the band of the variable band filter to, for example, a frequency of 35 to 37 KHz. If noise is generated due to the influence, it will not be determined that the channel is in use. That is, it becomes possible to connect to the wireless line within the specified time without determining that there is a carrier, and the outgoing / incoming call signal, the incoming / outgoing call response signal, etc. are transmitted prior to the wireless line connection of the master station and the slave station. In this case, there is an effect that the carrier sense of the control channel can be performed more reliably and quickly.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration in an embodiment of a cordless telephone device of the present invention.

FIG. 2 is a flowchart showing a processing procedure at the time of carrier sense of a control channel in the operation of the embodiment.

FIG. 3 is a block diagram showing a configuration of a noise squelch circuit in a conventional cordless telephone device.

FIG. 4 is a flowchart showing a processing procedure at the time of carrier sense of a control channel in the operation of the conventional example.

[Explanation of symbols]

 10 noise squelch circuit 11 variable band bandpass filter (BPF) 12 comparator 13 rectifier 14 comparator 15 carrier detect circuit 16 microcomputer (MPU) 17 band control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H04M 1/00 N 7605-5K H04B 7/26 109 D

Claims (2)

[Claims] 1. A cordless telephone device having a master unit and a slave unit with a noise squelch circuit for performing carrier sensing for confirming an empty control channel from a demodulated signal, wherein the noise squelch circuit confirms an empty control channel. In this case, the variable band filter for extracting a predetermined frequency band from the demodulated signal, the comparison means for comparing the noise component contained in the output signal of the variable band filter with the reference noise level within the frequency band, and the comparison means are compared. A cordless telephone device, comprising: band control means for performing control to change the frequency band of the variable band filter to another frequency band when the noise component level is higher than the reference noise level. 2. The variable band filter has frequencies 29 to 3
When the band signal of 1 KHz is taken out and the band signal taken out contains at least a single frequency component of the beat sound, the band control means controls the band of the variable band filter to a frequency of 35 to 37 KHz. The cordless telephone device according to claim 1, wherein: