JPH0362631A - Repeating system for cordless telephone set - Google Patents

Abstract

PURPOSE:To install plural repeaters and to improve the utilizing efficiency of a radio frequency by using the repeating system of a cordless telephone set using a power line for a communication line between a line connector and a radio repeater. CONSTITUTION:When an incoming signal comes to a telephone circuit 16, the signal is detected by a control section 18 via a hybride circuit 17, a transmitter 14 is driven and the incoming signal is sent in a carrier f4 onto a power line 9. On the other hand, when the receiver 11 of a repeater 6 receives the carrier f4, the demodulation signal is sent to a control section 12 and when it is discriminated to be from a master station 13, a transmitter 7 radiates the incoming signal as a radio wave in a frequency f2 into air. The receiver 3 of a slave set 1 demodulates the radio wave and the control section 4 detects it to be the incoming signal of the master set 13, then a transmitter 2 radiates a reply signal in a frequency f1 as a radio wave. The receiver 8 of the repeater 6 receives it and the control section 12 detects it to be a reply signal from the slave set 1, then the transmitter 10 sends a reply signal in a frequency f3 onto the power line 9 attain communication enable state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a relay system for cordless telephones that expands the communication range using a wireless repeater.

(Prior Art) Examples of conventional relay systems for cordless telephones include the following (Japanese Unexamined Patent Publication No. 72422/1982).

In Japanese Unexamined Patent Application Publication No. 61-72422, the applicant of the above application proposed that a cordless telephone be equipped with a relay function, and that the transmission and reception frequency of the upper connection device and the transmission and reception frequency of the relay telephone on the lower side are different. This proposal proposes extending the communication range.

If the transmitting frequency of the connecting device of the cordless telephone on the telephone station side is fl and the receiving frequency is f2, then the cordless relay telephone on the opposite side has a transmitting frequency of f toward the connecting device.
2. The receiving frequency has a function of fl. In addition, in the section between the relay telephone and the frequency converter facing it, the transmitting/receiving frequency f1 is frequency-converted to f3, and f2 is frequency-converted to f4 to avoid radio wave interference. is the transmitting/receiving frequency f3 is fl, f4 is f
2, thus extending the communication range.

In addition to the relay function, the relay telephone has the functions of a conventional cordless telephone, so it can be used as a cordless telephone in the same way as a parent-child telephone.

In this case, while the relay telephone is talking to the central office, it sends a melody tone to the cordless telephone to notify the cordless telephone that the relay telephone is in use.

This relay method has been developed as described above.

(Problem to be solved by the invention) However, in such a conventional relay system for cordless telephones, since the connecting device and the relay telephone are connected wirelessly, a new relay radio frequency is required. There was a problem in that two waves were required for transmission and reception, resulting in a decrease in frequency usage efficiency.

In addition, the current Radio Law for cordless telephones stipulates that the transmission output must be within 10 mW, so the distance between the connecting device and the relay telephone cannot be more than 50 to 100 meters, and if the distance is longer than that, then One relay telephone is required, and along with this, two additional radio frequencies must be secured, which poses the problem of further deterioration of frequency usage efficiency.

Furthermore, when a power line is used as a signal transmission line as another signal transmission method, a problem arises in that noise generated in the power line deteriorates the quality of signal transmission.

Therefore, methods are being used to set the frequency of the signal carrier wave to 100 KHz or more, which lowers the noise level, or to use a transmission format that is resistant to noise, such as spread spectrum. However, as shown in Figure 14, the frequency is 500KHz.
However, the noise level is as high as 60 dBμV, and as the frequency increases further, a new problem arises: although the noise level decreases, the transmission loss of the power line increases.

In addition, in the signal transmission method using spread spectrum, the spread bandwidth is set to 100~
It is realistic to set it to 500KHz. However, if the noise spectrum exists uniformly within the spread band, the effect of improving S/N (receiving sensitivity), which is a characteristic of spread spectrum, cannot be expected much. In addition, since the signal power is spread within the spread band, the S/N decreases when focusing on a specific frequency within the band. Therefore, in order to ensure the S/N ratio at all frequencies within the spread band, there is a problem in that greater signal power is required than in the above system.

Further, there are other problems such as a beat disturbance between carrier waves in the carrier wave format as described above and a beat disturbance between harmonics of the carrier wave and the carrier wave of the cordless telephone.

This invention was made to solve these conventional problems, and provides a cordless telephone that solves the above problems by connecting a line connection device and a wireless repeater using a communication method using a power line carrier. The purpose is to provide a relay method for

[Configuration of the Invention (Means for Solving the Problem) In order to achieve the object, the present invention uses a power line as a communication line between a line connection device and a wireless repeater.

(Function) The cordless telephone relay system uses a power line as the communication line between the line connection device and the wireless repeater, making it easy to install multiple repeaters and improving the efficiency of radio frequency usage. It is also excellent, and at the same time, it is possible to obtain power for line connection equipment or wireless repeaters from the power line.

(Example) The present invention will be explained below based on the drawings.

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

Handset 1 has transmitter 2. It is composed of a receiver 3, a control section 4 for controlling both devices 2 and 3, and an antenna 5a.

The repeater 6 also includes an antenna 5b and a transmitter 7 for wirelessly connecting it to the handset 1. It is composed of a receiver 8 and a transmitter 10 for transmitting signals onto the power line 9, a receiver 11 for receiving signals from the power line 9, and a control section 12 for controlling the repeater 6.

In addition, a line connection device (hereinafter referred to as a master device) 13 includes a transmitter 14 and a receiver 1 for transmitting and receiving signals from the power line 9.
5, a hybrid circuit 17 for transmitting and receiving communication voice from a telephone line 16, and a control section 18.

Next, the operation of this embodiment will be explained based on the above configuration.

When there is an incoming signal on the telephone line 16, this signal is detected by the control section 18 via the hybrid circuit 17.

Next, the control unit 18 drives the transmitter 14, for example, 10
An incoming signal is sent onto the power line 9 using a carrier wave f4 of about 0 to 500 KHz.

On the other hand, the receiver 11 of the repeater 6 receives the carrier wave f4 on the power line 9.
When received, the demodulated signal is sent to the control unit 12, and when it is determined that this signal is from the base unit 13,
The incoming signal is radiated into the air by the transmitter 7 via the antenna 5b as a radio wave of frequency f2.

The receiver 3 of the handset 1 demodulates this radio wave, and when the control unit 4 detects that it is an incoming signal from the base unit 13, it sends a response signal of frequency f1 as a radio wave from the transmitter 2 via the antenna 5a. radiate.

When the receiver 8 of the repeater 6 receives this and the control unit 12 detects that it is a response signal from the slave unit 1, the transmitter 10
A response signal having a frequency f3 different from the frequency f4 of about 100 to 500 KHz is sent onto the power line 9.

The receiver 15 in the main unit 13 transmits the signal carrier f3 on the power line 9.
When the control unit 18 receives the response signal and confirms that it is a response signal from the handset 1, it connects the telephone line 16 via the hybrid circuit 17, and becomes ready to talk.

In the above explanation, we have described the case where there is an incoming call on the telephone line 16, but the same applies to the case where the call is made from the handset 1. A calling signal is sent from the handset 1, and the call is sent to the base unit 13 via the power line 9. When detected, an operation is performed in which the telephone line 16 is connected.

The embodiment of the present invention differs from the conventional relay system in that the power line 9 is used as a relay line.

As the power line 9, for example, a 100V electric light line that supplies power to a general household can be used as is.

As mentioned above, the power line output wave is usually 100~
Since the low frequency band of 500KHz is used, transmission loss is low, and the amount of secondary radiation from the power line is small, so if it is on the power line in the same transformer, communication can be performed well even if the distance is 100 meters or more where weak radio waves cannot reach. can do.

In addition, there is no need to install a dedicated relay line, and it is possible to connect an existing power line, that is, a 100V electric light line as a relay line by connecting it to an outlet in a general household, and operate the main unit and repeater. The necessary power can be taken in at the same time. Therefore, the installation location of the repeater can be easily changed as necessary.

It is also easy to connect another repeater 6a to the same power line to further expand the reach.

Furthermore, since only two radio waves, f and f2, are radiated into the air, there is an advantage that the efficiency of frequency utilization is higher than that of conventional relay lines that are made wireless.

Further, as a relay system in factories and the like, it is possible to use a power line as a relay line and obtain electric power to operate a repeater via a transformer, as in the above-mentioned case of a general household.

Here, a method of transmitting signals on the power line 9 will be explained.

The signal on the power line 9 has SSB (SingleSid
e Band) or DSB (Double 5
ide Band), the transmitter 10° 14 and receiver 11 of the repeater 6 and base unit 13
．． 15 is capable of transmitting and receiving those signal waves.

FIG. 2 shows an example of the configuration of the SSB transmitter used here.

Signals such as voice or data coming from the population are AFPS
N (Audio, Frequency Phase
The signal is converted into two signals with a phase difference of 90° in a 5-hift network circuit 19. At this time, in order to reduce the phase error in the transmission frequency band (for example, 300 to 3 KHz), PP5N (Po 1 y
A PhaseShift Network) circuit can be used.

The pole frequency fp of each section is fp-1/2πCR
The number of sections and the number of poles are selected so that the phase characteristics are flat within the transmission band.

The signals having a phase difference of 90° from each other are then sent to a balanced modulator 20.
is input in 21. On the other hand, the carrier wave with a frequency four times the target frequency obtained by the oscillator 22 is RFPSN (Rad
io Frequency Phase 5hif
t Network) 23 into two signals of target frequencies having a phase difference of 90 degrees, and each is sent to a balanced modulator 2.
It will be manually operated on 0.21.

FIG. 4 shows an example of an RFPSN circuit. D type flip
By utilizing the fact that data is transferred to the output at the rising pulse of the clock in the flop, two outputs with a phase difference of 90 degrees are obtained at the target carrier frequency.

FIG. 5 shows a double-balanced circuit as an example of the circuit of the balanced modulators 20 and 21.

The carrier wave suppressed by this balanced modulator 20.21 is
Since the in-phase components are canceled by the combiner 24, a single sideband suppressed carrier signal, ie, an SSB wave, is obtained.

As a method of generating SSB waves, it is possible to use a more general configuration method as shown in Figure 6, but this requires a filter that matches the carrier frequency to be used, and there are problems such as manufacturing cost and large size. However, the degree of freedom in device design is limited, such as the need to change the filter each time the carrier frequency is changed, or the need to perform frequency conversion.

The phase shift method described herein is not subject to the above-mentioned limitations, and is capable of constructing a stable SSB generator in a low frequency band of 100 to 500 KHz, which is the purpose of the present invention.

In order to superimpose the SSB signal on the power line 9, combine the transmitted signal and the received signal, and extract the received signal from the power line 9, a duplexer (transmission line duplexer) as shown in FIG. 7 is used. This is a so-called directional coupler that transmits and receives a common signal, that is, a transmit signal and a receive signal in this case, while maintaining sufficient isolation between the transmitter and the receiver.

Impedance matching with the power line is achieved using the transformer (
Indicated by symbol T. (Similarly below), resistor R1 and capacitor C are used, and isolation between transmitter and receiver is achieved by resistors R2 and R3.
It is determined by the ratio of

FIG. 8 is a graph showing the frequency characteristics of the amount of isolation between the transmitter and receiver when the resistance R1 is kept constant and the capacitance C is varied.

As shown in FIG. 8, it is obvious that there is an optimum value for the capacitance C, and that the isolation amount has a sharp frequency peak.

Therefore, a duplexer like the one shown in FIG. 7 cannot be used in the conventional system in which the frequencies are separated from each other in order to prevent interference between transmitters and receivers.

In addition, in conventional systems that use carrier waves, in order to achieve sufficient isolation by using a duplexer, it is necessary to make the transmitting and receiving frequencies close to or coincide with each other, but due to slight leakage of the transmitted signal to the receiver, It is not generally used because it produces a beat.

As for the configuration of the receiver, there is a method A shown in FIG.

In the figure, (a) represents BFO (Baa t F r i
q''/uency 0scilato: This is a product detector using an I signal 26 and a balanced modulator 25.

Moreover, in (b), an active filter 27 is placed in front of the product detector in order to improve the S/N ratio.

Furthermore, (C) uses a mechanical filter 28 in place of the active filter 27 in (b), and S
(C) is the best in terms of /N ratio, that is, sensitivity.

The SSB method and the DSB method have narrow transmission bands (~3 KHz for SSB and ~6 KHz for DSB), and are suitable transmission means in a noisy transmission environment in which voice is transmitted by power line carrier.

Furthermore, since the carrier wave is suppressed, all of the transmission power is transmitted information, which means that the amount of power consumed is lower than that of the carrier wave method or the spread spectrum method.

Furthermore, since it does not have a carrier wave, problems such as beat disturbances do not occur even if the transmitting and receiving frequencies are matched. In this case, f3 and f4 in FIG. 1 are f3-f4.

Next, the transmission output power of the transmitter will be explained.

If the thermal noise power input to the receiver is generally P,
P-KTB... (represented as 0.

In the formula, K: Boltzmann's constant T: Absolute temperature B: Bandwidth Therefore, if the S/N at the entrance of the receiver is (S/N)in, (S/N) in = S/P - S
/ K T B - (2) S: Signal input power If the noise power inside the receiver is Pn, then Nout-K
TB+PnB, and the S/N at the receiver output, that is, (S/N)out is (S/N)out-3/
(KT+Pn)B=13) Therefore, the S/N of the receiver,
That is, the sensitivity is related to the bandwidth B, and the smaller B is, the higher the sensitivity is.

If the noise figure of the receiver is NF, then G: Receiver gain (-3out/5in) (S/N) o
NF when u t-1 is obtained by substituting (S/N) into (4).The minimum value of the signal that can be captured at ) Sin-10uogKT+10101o+NF(d
Bm display) ... (6n (S/N) o u t -1, so SoutmN
.

ut therefore Nout-10 o gKT+10i o gB+NF
...(7) Here, receiver NF-10dB, bandwidth B-3KHz
, when the absolute temperature is T-300@, Nout--17
3,8 + 34.8 + 10 - -29 dBm On the other hand, the noise power induced in the power line is approximately -40 dBm (B-20 KHz) at 100 KHz as shown in Figure 14, and the noise from the power line is extremely weak compared to the internal noise of the receiver. big.

Here, assuming that the noise on the power line is uniformly distributed on the frequency axis, the noise power depends on the bandwidth, so B
=3KHz, the noise level is about -48dB.

An SSB wave (also a DSB wave) is a type of AM wave, that is, a method in which transmission information is superimposed on the amplitude, so the relationship between input and output is 1. FIG. 10 shows the state.

FIG. 10 is a graph showing the relationship between human output levels in SSB waves.

As a signal format of the conventional carrier wave system, an FM wave has been used, which has a high effect of reducing pulse noise and can expect a significant S/N improvement when (S/N) in>9 dB.

However, the bandwidth required for FM waves is 10-30KH.
Since it is wider than z, the noise power inputted to the receiver is large, and it is therefore necessary to increase the output power on the transmitting side.

Here, considering FM with a frequency displacement of ±10 KHz, the noise input power is -40 dBm, and the minimum input signal power is -31 dBm, which is 9 dB higher.

The FM improvement effect is 10 dB, the practical minimum received output S/N is 20 dB, and the maximum loss on the power line is 30 dB.
Assuming B, the transmission power when using FM waves is approximately 1
0 dBm is necessary.

On the other hand, in the case of SSB waves, if the frequency is B-3 KHz and all other conditions are the same as in the case of FM waves, the required transmission power will be about 2 dBm, which is 8 dBm lower than the FM waves. Therefore, the isolation design of the duplexer becomes easier.

Further, it is possible to use both signals of the same frequency in SSB waves and DSB waves. This is an effective feature when duplexer isolation is insufficient.

Next, a second embodiment of the present invention will be described based on FIG. 11.

This embodiment is to reduce the noise level when no signal is received in the first embodiment.

In conventional power line carriers, FM waves are used for analog transmission of audio and the like, and as described above, FM waves have advantages such as pulse noise and S/N improvement effects.

SSB waves and DSB waves do not have the effect of suppressing amplitude noise such as pulse noise, and since the carrier wave is suppressed, the noise when there is no signal may be annoying in practice. The following methods have been used to improve boat fishing.

■ Lower the noise figure (NF) of the receiver.

■ Add a noise blanker circuit ■ Optimize the time constant of AGC (automatic gain adjuster).

■ Add an audio squelch circuit.

However, regarding (2), even if the NF is lowered, the noise output Nout of the receiver cannot be reduced below the noise input. Regarding (2), although there is a reduction effect on pulse noise, the effect is small on white noise. Further, there is a problem that intermodulation characteristics deteriorate. Regarding (2), optimization that satisfies the time constant of various conditions is difficult due to the breathing phenomenon of the reproduced output and the followability of sensitivity to human input signals with a large dynamic range. Regarding (2), it is also difficult to operate when there is no signal between words, and if this is done, there is a problem in that the received sound is unnaturally intermittent.

The configuration and operation of this embodiment will be explained.

In FIG. 11, signals are exchanged with the power line 9 via two duplexers.

The received signals from the two duplexers are processed by a bandpass filter 31, for example, at IKHz, which is less affected by noise.
Bandwidth is limited to: Here, information only about the signal strength of the received signal is extracted and rectified by the wave detector 32, and the signal strength is converted into voltage. This voltage controls the bandwidth of the variable bandpass filter 30.

The received signal that has passed through the variable band filter 30 is mixed with a pseudo carrier wave from the BFO 26 in a balanced modulator 25, and its modulated output is extracted as a demodulated output.

In this embodiment, when the received signal strength is low, the S/N is improved by narrowing the passband of the variable band filter 30, and as the received signal strength increases, the passband width is widened to ensure transmission frequency characteristics. . Therefore, when there is a weak signal or no signal where noise is generally a concern, the band is restricted and the noise level is lowered, so that the substantial dynamic range is improved and the auditory quality is improved.

Here, the minimum bandwidth when performing band limitation is Bmir
+-300Hz and maximum bandwidth Bmax-3KHz, the receiver noise output from the power line is Bmax compared to Bmax.
At min, the value is 10 dB lower. Therefore, the S/N is 10
Improved by dB.

Next, an example of the configuration of the variable bandpass filter 30 will be described with reference to FIG.

In (a), the passband width of the crystal filter is varied by using a voltage-controlled variable capacitance as the grounded capacitance of the multi-element padded crystal filter.

(b) is an explanatory diagram showing a method of shifting the passbands of two bandpass filters 33 and 34 up and down to vary the total passband width when they are connected in series.

FIG. 13 shows this situation. The oscillation frequency of the voltage controlled oscillator 37 is varied up and down by an external control voltage,
In addition, in order to change the center frequency of the bandpass filter 34 relative to the bandpass filter 33, the two are mixed in a mixer 35.

Since the center frequency of the signal that has passed through the bandpass filter 34 is shifted from the original human input signal, a mixer 36 is used to restore the signal to the original signal. As the bandpass filters 33 and 34, a multi-element crystal filter or the like having steep characteristics can be used.

Another possible method is to control the CR value of the active filter using an external voltage if the frequency is low.

It has been explained above that using SSB waves is an effective means when using a power carrier line as a signal transmission line connecting the repeater 6 of the cordless telephone and the line connection device (base unit) 13.

It goes without saying that similar effects can be obtained using DSB waves.

In addition, the problems of the above signal format such as pulse noise and AG
AC35 with further improved C (automatic gain adjuster) characteristics
Signal formats such as B, WolfsonSSB, and RZSSB may also be used.

Conventionally, power line transportation does not require dedicated line facilities;
It is used in indoor intercoms, home automation systems, etc., but its carrier signal format is FM or spread spectrum, and AM has poor pulse noise and AGC characteristics.
system is not used. Another reason why SSB waves and the like are not utilized is that their circuits are complicated and their filters are expensive.

However, power line transport is a relatively low-frequency area in the telecommunications field, and filters are easy to manufacture, and circuit formats that do not require filters, such as PSN, can be used, and they operate stably. There are also advantages.

As explained above, in the relay system of the cordless telephone according to the embodiment of the present invention, the existing power line 9 is used as the communication line between the line connection device (base unit) 13 and the wireless repeater 6. This relay method eliminates the need to install a new dedicated line, makes it easy to change the installation location, allows multiple repeaters to be installed, and has excellent radio frequency usage efficiency. At the same time, the line connection device 13 or the wireless repeater 6 can be powered from the power line 9.

In addition, since the relay method uses a signal format that suppresses outgoing waves such as SSB waves, DSB waves, or variations thereof superimposed on the power line 9, a high degree of receiving sensitivity is obtained, and at the same time, power consumption is reduced. Even if the carrier frequencies in the up and down directions of the relay line are the same, it is now possible to prevent beat disturbances and the like from occurring.

Although one embodiment of the present invention has been described above in detail with reference to the drawings, the specific relay system is not limited to this embodiment, and may be modified without departing from the gist of the present invention. These also belong to the technical scope of the present invention.

[Effects of the Invention] As explained above, according to the present invention, since the cordless telephone relay system uses a power line as the communication line between the line connection device and the wireless repeater, it is easy to connect multiple repeaters. can be installed, has excellent radio frequency utilization efficiency, and at the same time can obtain power for the line connection device or wireless repeater from the power line.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a first embodiment of the present invention, Fig. 2 is an explanatory diagram showing the configuration of an SSB transmitter, and Fig. 3 is an explanatory diagram of a first embodiment of the present invention.
Figure 4 is a circuit diagram showing an example of a 5N circuit, Figure 4 is a circuit diagram showing an example of a PPPSN circuit, Figure 5 is a circuit diagram showing a double balanced circuit as an example of a balanced modulator circuit, Figure 6 is a general circuit diagram. FIG. 7 is a circuit diagram showing an example of a transmission line duplexer circuit. Figure 8 is a characteristic diagram showing the frequency characteristics of the isolation amount of the transmitter and receiver when the resistance is constant and the capacitance is varied.
FIG. 9 is an explanatory diagram showing an example of the configuration of the receiver, (a)
is a product detector with BFO and balanced modulator, (b)
(c) is a product detector with an active filter in front of it, (c) is a product detector with a mechanical filter in front of it, Figure 10 is a diagram showing the level relationship of human output in SSB, and Figure 11 is: FIG. 12 is an explanatory diagram of a second embodiment of the present invention, and FIG. 12 is a circuit and explanatory diagram showing a configuration example of a variable bandpass filter, and (a) is a circuit of a multi-element ladder type crystal filter that varies the passband width. figure,
(b) is an explanatory diagram showing a method of varying the overall passband by connecting two bands in series, Figure 13 is a diagram showing the operation of a variable band filter, and Figure 14 is a diagram showing the noise power generated in the power line. It is a diagram showing frequency dependence. 1...Slave unit 2...Transmitter 3...Receiver 4...Control unit 5a...Antenna of slave unit 5b...Antenna of repeater 6...Relayer 6a... Other repeater 7...
Transmitter 9...Power line 10...Transmitter 11...Receiver 12...Control unit 13...Line connection device (base unit) 1
4... Transmitter 15... Receiver 16... Telephone line 17... Hybrid circuit 18... Control section 19... AFPSN circuit 2
0... Balanced modulator 21... Balanced modulator 22...
・Oscillator 23...RFPSN circuit 24...
Combiner 25...Balanced modulator 26...BFO
27...Active filter 28...Mechanical filter 29...Duplexer 30...Variable band filter 31...Band pass filter 32...Detector 34...Band filter 36...Mixer router 33... Bandpass filter 35... Mixer 37... Voltage controlled oscillator

Claims (1)

[Claims] (1) A cordless telephone relay system that expands the communication range using a wireless repeater, characterized in that a power line is used as a communication line between a line connection device and the wireless repeater.