JPH07221698A - Cordless telephone system - Google Patents

Abstract

PURPOSE:To enable a slave machine and a master machine to perform high grade communication by controlling the switching of transmission power proportionally to the electric field intensity of a reception carrier and stably at either or both of the slave machine and the master machine. CONSTITUTION:The voltage value which is proportional to the level of the reception carrier in the reception signal from an antenna 1 is outputted by a RSSI circuit 17. In this case, because a reception electric field level is high when a master machine and a slave machine are in a comparatively close distance, the output voltage value of the RSSI circuit 17 becomes higher. Based on this output voltage, a transmission output control circuit 10 controls the coupling of a drive amplifier circuit 9 and a power amplifier circuit 11 to a loose coupling. By this control, transmission power is lowered. On the contrary, because the reception electric field level is small when the master machine and the slave machine are in a distant distance, the output voltage value of the RSSI circuit 17 becomes small, the transmission output control circuit 10 controls the coupling of the drive amplifier circuit 9 and the power amplifier circuit 11 to a close coupling. By this control, transmission power is increased.

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 which is applied to a multi-channel access (MCA) system or the like and which varies its transmission power in accordance with a received electric field strength level.

[0002]

2. Description of the Related Art Conventionally, this type of cordless telephone device has been
The received electric field strength level in the connection of the wireless line fluctuates depending on the distance from the base unit as the mobile unit moves. If the received electric field strength level is high due to this variation, cross modulation is likely to occur. Further, when the received electric field strength level is low, noise or the like is generated to deteriorate communication quality, and the wireless line is disconnected. Therefore, one or both of the slave unit and the master unit are controlled to adjust their transmission power in accordance with the received electric field strength level.

FIG. 3 is a block diagram showing the configuration of such a conventional cordless telephone device. In FIG. 3, this example has a master unit connected to an office line and a slave unit connected to this slave unit through a wireless line. Antenna 1
An antenna duplexer 2 for using the antenna 1 for both transmission and reception, and a reception RF circuit 3 including a high frequency (RF) amplifier for amplifying a reception signal, a mixer, a band pass filter (BPF) and the like are provided. There is. Furthermore, a reception audio (AF) including a demodulation circuit 4 that includes a limiter amplification circuit and a detection circuit to demodulate an audio signal from the intermediate frequency signal from the reception RF circuit 3, and a compander and a confidential circuit.
A circuit 5 and a reception voltage controlled oscillator (VCO) 6 for sending a local frequency signal to the reception RF circuit 3 are provided. In addition, the slave unit comprises a PLL circuit 7 for stabilizing the local oscillation signal from the reception VCO 6 and a PLL frequency synthesizer, determines a local frequency signal for reception according to the set channel, and transmits the signal. A transmission VCO 8 that transmits a frequency signal and a drive amplifier circuit 9 that amplifies the transmission frequency signal from the transmission VCO 8 are provided. Furthermore, the noise level judgment output corresponding to the received electric field level, that is, the received carrier (radio waves at the receiving frequency)
If there is no noise, a high noise level is shown, and if there is a received carrier, a transmission output control circuit 10 for controlling transmission power by a two-stage noise level determination output having a low noise level, and a drive amplifier circuit 9 Power amplifier circuit 11 for amplifying the transmission frequency signal of
And a control circuit 12 for setting the channel of the PLL frequency synthesizer and judging the presence / absence of a reception carrier by the noise level judgment output. In addition, a transmission AF circuit 13 including a compander and a confidential circuit, a receiver 14, a numeric keypad 15, a microphone 16, and a reception electric field level input from the antenna 1, and shows a high noise level when there is no reception carrier, Further, there is provided a level determination circuit 18 which outputs two voltage values which are two-stage noise level determination outputs of a low noise level when there is a reception carrier.

Next, the operation of this conventional example will be described. 3, the PLL circuit 7, the reception VCO 6, the transmission VCO 8 and the control circuit 12 determine the transmission frequency and the reception frequency so that the cordless telephone device has the same channel as that of the parent device. A transmission radio wave obtained by modulating a voice signal transmitted from the base unit is received by the antenna 1, and the voice signal is demodulated through the reception RF circuit 3 and the demodulation circuit 4. The reception AF circuit 5 processes the audio signal such as compander and secret communication, and outputs the audio signal from the receiver 14. The audio signal input from the microphone 16 is
The transmission AF circuit 13 performs processing such as compander and confidential communication, and the transmission VCO 8 performs modulation.
The signal is amplified by the drive amplifier circuit 9 and the power amplifier circuit 11 and transmitted from the antenna 1. In this case, the level determination circuit 18 outputs the noise level determination output corresponding to the presence or absence of the reception carrier in the reception signal input from the antenna 1 as two voltage values. When the noise falls below a predetermined level and the voltage value of the noise level judgment output becomes low,
It is determined that the level of the reception signal (reception carrier) from the antenna 1 has risen, and the transmission output control circuit 10 reduces the voltage applied to the drive amplification circuit 9 and the power amplification circuit 11. That is, the amplification degree is reduced and the transmission power is reduced. Further, when the voltage value of the noise level determination output from the level determination circuit 18 increases, it is determined that the reception carrier input from the antenna 1 has decreased, and the transmission output control circuit 10 causes the drive amplification circuit 9 and the power amplification circuit 11 to operate. Increase the applied voltage. That is, the amplification degree is increased and the transmission power is increased. Note that such a circuit is also provided in the master unit, and similarly to the slave unit, control is performed to increase or decrease the transmission power according to the presence / absence of a reception carrier.

As described above, even in the cordless telephone device of the conventional example, it is possible to increase or decrease the transmission power according to the presence or absence of the reception carrier in the reception signal.

[0006]

However, in the cordless telephone device of the conventional example, when the transmission power is controlled, the drive amplifier circuit 9 and the power amplifier circuit 11 are applied depending on the magnitude of the noise level, that is, the presence or absence of the reception carrier. In order to control the voltage, the transmission power can be switched only in two steps. Therefore, when the transmission power is switched in two stages, the operation of the drive amplifier circuit 9 is changed and the transmission VCO is changed.
The output impedance of 8 fluctuates greatly and the lock frequency also changes, and when locked, noise is superimposed on the transmitted radio wave and noise is generated in the received sound at the other party (slave unit or master unit) connected by the wireless line. There was a problem of doing.

The present invention solves such a conventional problem, and one or both of a slave unit and a master unit are in proportion to the electric field strength of a reception carrier and stably control switching of transmission power. It is an object of the present invention to provide an excellent cordless telephone device in which noise is not generated during transmission power switching control, and high-quality communication can be performed by a slave unit and a master unit.

[0008]

In order to achieve the above object, a cordless telephone apparatus according to claim 1 includes a transmission signal processing means for transmitting to one or both of a slave unit and a master unit through a wireless line. A reception signal processing means for receiving through a wireless line, a reception electric field strength level determining means for outputting a voltage value proportional to the electric field strength of the reception carrier in the reception signal received by the reception signal processing means, and the transmission signal processing means. And a transmission power control means for varying the transmission power in accordance with the voltage value from the reception electric field strength level determination means.

The cordless telephone device according to claim 2 is
The transmission signal processing means includes a drive amplification circuit and a power amplification circuit, and the degree of coupling when the transmission high frequency signal from the drive amplification circuit is input to the power amplification circuit corresponds to the voltage value from the reception electric field strength level determination means. In this configuration, the transmission power control means is provided with a variable capacitance diode that is variable.

The cordless telephone device according to claim 3 is
The transmission signal processing means is provided with a drive amplification circuit and a power amplification circuit, and the transmission power control means is provided with an amplification control circuit for varying the amplification degree of the drive amplification circuit in accordance with the voltage value from the reception electric field strength level determination means. It is configured.

A cordless telephone device according to claim 4 is
The reception electric field strength level determination means is configured to judge the reception electric field strength level of the reception carrier of the control channel in the multi-channel access method.

[0012]

According to the cordless telephone system of the present invention, the cordless telephone system according to claims 1, 2, 3 and 4 is based on a voltage value proportional to the electric field strength of the received carrier in the received signal received by one or both of the slave unit and the master unit. Therefore, the transmission power is changed. Therefore, one or both of the slave unit and the master unit are in proportion to the electric field strength of the reception carrier, and the switching of the transmission power is controlled stably, so that the generation of noise during the switching control of the transmission power is eliminated, and High-quality communication is performed between the device and the base unit.

[0013]

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. In the following figures and texts, the same components as those of the conventional example shown in FIG.

FIG. 1 is a block diagram showing the configuration of an embodiment of a cordless telephone device of the present invention. In FIG. 1, this example is a master unit connected to an office line and a slave unit connected via a wireless line. This slave unit has an antenna 1 and an antenna 1
The antenna duplexer 2 for both transmitting and receiving, and the receiving RF circuit 3 including a high frequency (RF) amplifier for amplifying a received signal, a mixer, a band pass filter (BPF) and the like.
And are provided. Further, a demodulation circuit 4 including a limiter amplifier circuit and a detection circuit for demodulating an audio signal from the intermediate frequency signal from the reception RF circuit 3, a reception audio (AF) circuit 5 including a compander, a secret circuit, etc.
The circuit 3 is provided with a reception voltage controlled oscillator (VCO) 6 which sends out a local frequency signal. In addition, a PLL circuit 7 that locks and stabilizes the frequency of the local oscillation signal from the reception VCO 6 and a PLL frequency synthesizer are configured in this slave unit, and a local frequency signal for reception according to the channel set by control is formed. And a drive amplifier circuit 9 for amplifying the transmission frequency signal from the transmission VCO 8 are provided. Further, a transmission output control circuit 10 for controlling the transmission power by a noise level determination output according to the reception electric field level, and a power amplification circuit 11 for amplifying the transmission frequency signal from the drive amplification circuit 9 to a specified power.
And a control circuit 12 that determines the presence / absence of a receiving carrier (radio waves at the receiving frequency) by setting the channel of the PLL frequency synthesizer and determining the noise level. Also, a transmission A equipped with a compander and a secret circuit
An F circuit 13, a receiver 14, a numeric keypad 15, a microphone 16, and a reception field strength level determination (RSSI) circuit 17 that outputs a voltage value corresponding to the reception field level input from the antenna 1 are provided. .

FIG. 2 is a circuit diagram showing a detailed configuration of the transmission output control circuit 10. In FIG. 2, this example shows a variable capacitance diode (variable diode) between the drive amplification circuit 9 and the power amplification circuit 11 that controls the amount of transmission frequency signal passing by varying the capacitance with the voltage value from the RSSI circuit 17. Cap) Vc is provided. Further, a capacitor C for impedance matching is provided on the input side of the variable capacitance diode Vc.
1 and a resistor R are provided. A DC blocking capacitor C2 is provided on the output side of the variable capacitance diode Vc.

Next, the operation of this embodiment will be described. 1 and 2, the PLL circuit 7 and the reception VCO
6, the transmission VCO 8 and the control circuit 12 determine the transmission frequency and the reception frequency so that the slave unit has the same channel as the master unit (not shown). A transmission radio wave obtained by modulating a voice signal transmitted from the parent device is received by the antenna 1, and the voice signal is demodulated through the reception RF circuit 3 and the demodulation circuit 4. The demodulated audio signal is processed by the reception AF circuit 5 such as compander and secret communication, and is output as audio from the receiver 14. Further, the sound signal input from the microphone 16 is processed by the transmission AF circuit 13 such as compander and confidential communication, and further modulated by the transmission VCO 8.
Further, it is amplified by the drive amplifier circuit 9 and the power amplifier circuit 11 and transmitted from the antenna 1. In this case, RSSI
The circuit 17 outputs a voltage value proportional to the level of the reception carrier in the reception signal from the antenna 1. in this case,
When the parent device and the child device are relatively close to each other, the received electric field level is high, and the output voltage value of the RSSI circuit 17 is high. Based on this output voltage, the transmission output control circuit 10 controls the coupling between the drive amplification circuit 9 and the power amplification circuit 11 to be loosely coupled, and this control reduces the transmission power. On the contrary, when the master unit and the slave unit are located at a long distance, the received electric field level is small, the output voltage value of the RSSI circuit 17 becomes small, and the transmission output control circuit 10 causes the drive amplifier circuit 9 and the power amplifier circuit 11 to operate. The coupling is controlled to be tightly coupled, and this control increases the transmission power.

This sparse / dense coupling control is performed by setting the capacitance of the variable capacitance diode Vc in the transmission output control circuit 10 to R.
This is performed by changing the output voltage value of the SSI circuit 17. Therefore, when the electric field level of the receiving carrier is large,
The output voltage value of the RSSI circuit 17 increases, the electrostatic capacitance of the variable capacitance diode Vc decreases, and the drive amplifier circuit 9 and the power amplifier circuit 11 are loosely coupled. As a result, the transmission frequency signal from the transmission VCO 8 input from the drive amplification circuit 9 to the power amplification circuit 11 is reduced, and the transmission power from the power amplification circuit 11 is reduced. In addition, when the electric field level of the reception carrier is small, the RSSI circuit 1
The output voltage value of 7 decreases, the capacitance of the variable capacitance diode Vc increases, and the drive amplification circuit 9 and the power amplification circuit 11 are tightly coupled. Therefore, the transmission frequency signal from the transmission VCO 8 input from the drive amplification circuit 9 to the power amplification circuit 11 increases, and the transmission power from the power amplification circuit 11 also increases.

As described above, according to this embodiment, the RSSI circuit 17 outputs the output voltage value proportional to the electric field level of the reception carrier, and the drive amplifier circuit 9 and the power amplifier circuit corresponding to the output voltage value. It is possible to control the coupling of 11 and to output a linear transmission power proportional to the received electric field level. Further, since the transmission power is linearly controlled, the change in operation of the drive amplifier circuit 9 is reduced, and the transmission V
The output impedance of CO8 does not change significantly.
That is, the change in the lock frequency of the transmission VCO 8 is eliminated, noise is not superimposed on the transmission radio wave, and noise is not generated in the reception sound at the other party (slave unit or master unit) connected by the wireless line. In other words, a high quality call becomes possible.

In this embodiment, the transmission high frequency signal of the drive amplifier circuit 9 and the power amplifier circuit 11 is pass-coupled by the variable capacitance diode Vc, but other examples are also possible. For example, without using the variable capacitance diode Vc, only the capacitor C2 is used for the drive amplifier circuit 9 and the power amplifier circuit 1.
It is also possible to use an amplification degree variable circuit which is coupled to the drive circuit 1 and which varies the amplification degree of the drive amplification circuit 9 in accordance with the output voltage from the RSSI circuit 17. This amplification degree variable circuit uses, for example, a transistor, and changes the base bias voltage by the output voltage from the RSSI circuit 17 to drive the drive amplification circuit 9. In addition, although the slave unit has been described in this embodiment, the master unit may be provided with a configuration for controlling the transmission power corresponding to the electric field strength level of the reception carrier as in this embodiment.

[0020]

As is apparent from the above description, the cordless telephone device according to the first, second, third and fourth aspects of the present invention has the electric field strength of the reception carrier in the reception signal received by one or both of the slave unit and the master unit. Since the transmission power is varied based on the proportional voltage value, one or both of the slave unit and the master unit are in proportion to the electric field strength of the receiving carrier, and the transmission power can be switched stably. In addition, there is an effect that noise is not generated during transmission power switching control, and high-quality communication can be performed by the slave unit and the master unit.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a detailed configuration of a transmission output control circuit of the cordless telephone device of the present invention.

FIG. 3 is a block diagram showing a configuration of a slave unit in a conventional cordless telephone device.

[Explanation of symbols]

 7 PLL circuit 8 Transmission VCO 9 Drive amplifier circuit 10 Transmission output control circuit 12 Control circuit 17 Reception electric field strength level judgment (RSSI) circuit Vc Variable capacitance diode

Claims (4)

[Claims] 1. A transmission signal processing means for transmitting to one or both of a slave unit and a master unit through a wireless line, a reception signal processing unit for receiving through a wireless line, and a reception signal received by the reception signal processing unit. And a transmission electric field strength level determination means for outputting a voltage value proportional to the electric field strength of the reception carrier, and transmission for varying transmission power from the transmission signal processing means in accordance with the voltage value from the reception electric field strength level determination means. A cordless telephone device comprising: a power control unit. 2. The transmission signal processing means includes a drive amplification circuit and a power amplification circuit, and the coupling degree at the time of inputting the transmission high frequency signal from the drive amplification circuit to the power amplification circuit is a reception field strength level determination means. 2. The cordless telephone device according to claim 1, wherein the transmission power control means is provided with a variable capacitance diode that is variable according to the voltage value from. 3. A transmission signal processing means includes a drive amplification circuit and a power amplification circuit, and transmits an amplification control circuit for varying the amplification degree of the drive amplification circuit in accordance with the voltage value from the reception electric field strength level determination means. The cordless telephone device according to claim 1, wherein the cordless telephone device is provided in the power control means. 4. The cordless telephone apparatus according to claim 1, wherein the receiving electric field strength level judging means judges the receiving electric field strength level of the receiving carrier of the control channel in the multi-channel access system.