JPH05291852A - Transmission power control circuit for dual mode radio communication equipment - Google Patents

Abstract

PURPOSE:To execute high quality radio communication at all times without causing deterioration in the radio characteristic even in the analog mode or the digital mode. CONSTITUTION:A 1st low pass filter 8a having a time constant suitable for the analog mode and a 2nd low pass filter 8b having a time constant suitable for the digital mode are provided in a gain control loop of the transmission power control circuit for the dual mode radio communication equipment provided with the digital mode and the analog mode for the radio communication system and implementing radio communication through the selection of the modes, and a changeover switch 9 is provided and it is controlled for the switching in response to the result of selection of the digital mode or the analog mode by a control circuit 30 to incorporate alternatively the low pass filter 8a or 8b into the gain control loop.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication device used in a mobile radio communication system such as a mobile / automobile radio telephone system or a cordless radio telephone device, and particularly to a transmission provided in a dual mode type radio communication device. The present invention relates to a power control circuit.

[0002]

2. Description of the Related Art Conventionally, as a mobile radio communication system, for example, a cellular type mobile / automobile radio telephone system has been operated. This type of system is, for example, as shown in FIG. 3, a control station CS connected to a wired telephone network NW.
And the wired lines CL1 to C for the control station CS, respectively.
A plurality of base stations BS1 to BSn connected via Ln
And a plurality of mobile stations PS1 to PSm. The base stations BS1 to BSn form radio zones E1 to En called cells in different areas. The mobile stations PS1 to PSm are connected to the base station of the cell in which the mobile station is located via an empty radio communication channel, and the base stations of the mobile stations PS1 to PSm are connected to the counterpart telephone terminal of the wired telephone network NW via the control station CS. Connected to. In addition, the mobile station P
When S1 to PSm move to another cell during communication,
The base station is switched under the control of the control station CS while continuing the communication. This action is commonly referred to as handoff.

In a radio communication device for a mobile station used in this type of system, generally, the transmission power of its own station is controlled based on the transmission power designation information notified from the base station BS when setting a radio communication channel. A circuit is provided. Figure 4
FIG. 3 is a circuit block diagram showing an example of the configuration. In the figure, a variable attenuator 1 is inserted in the transmission signal path. The variable attenuator 1 controls the power of the transmission signal, and the transmission signal whose power is controlled is amplified by the transmission power amplifier 2 and then transmitted from an antenna (not shown). A part of the transmission signal output from the transmission power amplifier 2 is input to the detector 4 via the directional coupler 3 and detected. Then, the detection signal output from the detector 4 is smoothed by the smoothing circuit 5 to remove unnecessary high frequency components, and then input to the comparison amplifier 6. The comparison amplifier 6 compares the signal level of the detected signal with the reference voltage level generated from the reference voltage generator 7 according to the transmission power designation information, and detects the error. This error signal is smoothed by the low-pass filter 8 having a predetermined time constant, whereby it becomes a gain control signal and is negatively fed back to the variable attenuator 1. Therefore, the attenuation amount of the variable attenuator 1 is variably controlled so as to make the error signal zero, so that the transmission power of the transmission signal is always controlled to a value corresponding to the reference voltage.

[0004]

By the way, a system adopting a dual-mode wireless communication system has been proposed as a portable / vehicle wireless telephone system. The dual mode is a system that uses both an analog mode and a digital mode. In the analog mode, the transmitting side FM-modulates and transmits a carrier wave with the audio signal and data, and the receiving side receives the modulated wave sent from the transmitting side and FM demodulates to reproduce the audio signal and data. It is a method. On the other hand, in the digital mode, a voice signal and data are first encoded on the transmitting side, a carrier wave is modulated by the encoded signal by a digital modulation method such as π / 4 shift QPSK method, and the signal is transmitted on the receiving side. In this method, the modulated wave sent from the transmitting side is received, digitally demodulated, and then the demodulated signal is decoded to reproduce the original voice signal and data. In the analog mode, each radio frequency is used as a radio communication channel, and in the digital mode, a plurality of time slots that are time-division multiplexed and transmitted for each radio frequency are used as radio communication channels.

However, the above-mentioned conventional transmission power control circuit has the following problems when the above dual mode is used. That is, the time constant of the low pass filter provided in the gain control circuit is generally set to a value suitable for communication in the analog mode. But,
When the transmission power control of the communication in the digital mode is performed by the transmission power control circuit having the time constant suitable for the analog mode, the time constant of the low-pass filter is remarkably small as compared with the data speed of the digital mode. There is a problem that the amplitude component is suppressed and the spectrum unnecessarily spreads as shown in FIG. This unnecessary spread of the spectrum has a bad influence such as interference on other adjacent wireless communication channels, which is extremely undesirable. Further, in the modulation method by the digital mode, since the data is added to the amplitude and the phase respectively, if the above-mentioned amplitude component is suppressed, the data cannot be correctly demodulated on the receiving side, and as a result, the error rate characteristic is deteriorated. It was happening.

On the other hand, in order to prevent the deterioration of various characteristics in the digital mode, it has been considered to set the time constant of the low pass filter of the transmission power control circuit to a value suitable for the digital mode. However, although the spectrum characteristic in the digital mode is certainly improved as shown in FIG. 5B by doing so, when the communication is performed in the analog mode in this state, the time constant is too large as compared with the signal frequency in the analog mode. Therefore, various characteristics are deteriorated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to always provide high quality without deterioration of radio characteristics in both analog mode and digital mode. Another object of the present invention is to provide a transmission power control circuit of a dual mode type wireless communication device capable of wireless communication.

[0008]

In order to achieve the above object, the present invention has a dual mode type wireless communication device having a digital mode and an analog mode as a wireless communication system, and selecting these modes for wireless communication. In the transmission power control circuit provided in, is inserted in the transmission signal path,
Variable gain means for variably outputting the transmission power and power of the transmission signal output from the variable gain means are detected, and the error is detected by comparing the detected value of this power with a reference value, Based on the detected error, a gain control signal for generating a gain control signal for bringing the error close to zero and controlling the gain of the variable gain means is provided, and a time constant varying means is provided. .. The time constant changing means variably sets the loop time constant inserted in the gain control means to a value preset according to the selection result of the digital mode and the analog mode.

[0009]

As a result, according to the present invention, the optimum loop time constant corresponding to each mode is set in the gain control means both when the analog mode is selected and when the digital mode is selected. It will be. Therefore, the transmission power is controlled by the optimum loop time constant in both the analog mode and the digital mode, which causes deterioration of radio characteristics such as suppression of amplitude component and unnecessary spread of spectrum. It is possible to perform high-quality wireless communication without any trouble.

[0010]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a circuit block diagram showing the configuration of a mobile station radio communication apparatus including a transmission power control circuit according to an embodiment of the present invention. The wireless communication device of this embodiment is a dual mode type device that uses both an analog mode and a digital mode.

First, in the state where the digital mode is set, the voice switch 20,
23 is connected to the speech code decoding circuit (SP-COD) 19. A wireless communication signal sent from a base station (not shown) is received by the antenna 11 and then the antenna duplexer (D
It is input to the receiving circuit (RX) 13 via the UP) 12. In the receiving circuit 13, the received wireless communication signal is mixed with the local oscillation signal generated from the frequency synthesizer (SYN) 14 and converted into an intermediate frequency signal. The received intermediate frequency signal is input to the digital modulation / demodulation circuit (MOD) 16. The digital modulation / demodulation circuit 16 performs digitization of the received intermediate frequency signal, demodulation processing, processing for establishing bit synchronization and slot synchronization, and the like. The signal related to the slot synchronization is input to the control circuit (CONT) 30. An equalizer (EQL) 17 is attached to the digital modulation / demodulation circuit 16. The equalizer 17 performs waveform equalization processing on the demodulated signal demodulated by the digital modulation / demodulation circuit 16.

The digital demodulated signal output from the digital modulation / demodulation circuit 16 is an error correction code decoding circuit (C
H-COD) 18 is input. The error correction code decoding circuit 18 performs error correction decoding processing on the digital demodulated signal. The digital demodulated signal output from the error correction code decoding circuit 18 is input to the voice code decoding circuit 19. The voice code decoding circuit 19 performs voice decoding processing of the digital demodulated signal and D / A conversion of the decoded reception signal, thereby reproducing the analog reception signal. The reproduced analog reception signal is supplied to the speaker 21 via the voice switch 20 and is output as loudspeaker from the speaker 21.

On the other hand, the voice transmitted by the speaker is the microphone 22.
After being collected by and converted into an analog transmission signal, it is input to the voice code decoding circuit 19 via the voice switch 23. The voice code decoding circuit 19 digitizes and codes the analog transmission signal, and the coded transmission signal is input to the error correction code decoding circuit 18 together with the control signal output from the control circuit 30. To be done. The error correction code decoding circuit 18 performs error correction coding on the coded transmission signal and control signal, and the output signal thereof is input to the digital modulation / demodulation circuit 16. In the digital modulation / demodulation circuit 16, the intermediate frequency signal is digitally modulated by the coded transmission signal and the control signal output from the error correction code decoding circuit 18, and the modulated intermediate frequency signal is input to the transmission circuit 15. .. As a digital modulation method, for example, π / 4 shift DQP
The SK method is used. The transmission circuit 15 includes a mixer and a transmission power control circuit. In the mixer, the modulated intermediate frequency signal is mixed with the local oscillation signal output from the frequency synthesizer 14 and frequency-converted into a transmission signal having a radio channel frequency. The transmission power control circuit controls the transmission power of the transmission signal output from the mixer. The radio transmission signal output from the transmission circuit 15 is transmitted to the antenna 11 via the antenna duplexer 12.
And is transmitted from the antenna 11 to the base station.

In the state where the analog mode is set, the voice switches 20 and 2 are instructed according to the instruction of the control circuit 30.
3 is connected to the analog voice processing circuit (A-AUD) 24. In the analog voice processing circuit 24, the reception intermediate frequency signal output from the reception circuit 13 is FM-demodulated, whereby the analog reception signal is reproduced. The analog reception signal is supplied to the speaker 21 via the voice switch 20 and is output from the speaker 21 in a loud voice. On the other hand, the speaker's transmitted voice is collected by the microphone 22 and converted into a transmitted voice signal, and then input to the analog voice processing circuit 24 via the voice switch 23. In the analog voice processing circuit 24, the intermediate frequency signal for transmission is FM-modulated by the analog transmission signal. The modulated intermediate frequency signal is input to the transmission circuit 15. In the transmission circuit 15, the modulated intermediate frequency signal is first frequency-converted by the mixer into a transmission signal of a radio channel frequency,
Further, the power is controlled by the transmission power control circuit. Then, the radio transmission signal output from the transmission circuit 15 is supplied to the antenna 11 via the antenna duplexer 12 and transmitted from the antenna 11 to the base station.

The console unit (CU) 25 is provided with switches such as dial keys and a transmission switch, and indicators such as a liquid crystal display (LCD) and a light emitting diode. The power supply circuit 26 generates a predetermined operating voltage Vcc based on the output voltage of the battery 27 and supplies it to each circuit.

By the way, the transmission power control circuit provided in the transmission circuit 15 is constructed as follows. FIG. 2 is a circuit block diagram showing the configuration. In the figure, the same parts as those in FIG. 4 are designated by the same reference numerals and detailed description thereof will be omitted.

In the figure, a first low-pass filter 8a and a second low-pass filter 8b are provided between the error amplifier 6 of the gain control circuit and the variable attenuator 1, and the first and the second low-pass filters 8a and 8b. There is provided a changeover switch 9 for selectively connecting the two low pass filters 8a and 8b. The time constant of the first low-pass filter 8a is set to a value suitable for wireless communication in the analog mode. The time constant of the second low pass filter 8b is set to a value suitable for wireless communication in the digital mode. The changeover switch 9 is, for example, a transistor switch. Then, the switching control signal S output from the control circuit 30 according to the set mode.
The switching operation is performed according to S, whereby the first low pass filter 8a and the second low pass filter 8b are selectively connected between the error amplifier 6 and the variable attenuator 1.

With such a configuration, when the analog mode is first designated by the base station as the wireless communication system, the control circuit 30 outputs the switching control signal SS for setting the analog mode, and as a result, the switching switch. 9 is the first
Is switched to the low pass filter 8a side. Therefore, the first low pass filter 8a is inserted in the gain control loop. Therefore, when the wireless transmission operation is started in this state, the error signal between the detected value of the transmission power output from the error amplifier 6 and the reference voltage value is transmitted via the changeover switch 9 to the first
Is input to the low pass filter 8a and is smoothed by the first low pass filter 8a. Then, the DC voltage obtained by the first low-pass filter 8a is supplied to the variable attenuator 1 as a gain control signal, whereby the attenuation amount of the variable attenuator 1 is variably controlled. Here, as described above, the time constant of the first low pass filter 8a is preset to a relatively small value suitable for the analog mode.
Therefore, the gain control of the variable attenuator 1 by the gain control loop, in other words, the variable control of the transmission power of the radio transmission signal is performed at the loop response speed optimal for the analog mode.

On the other hand, when the digital mode is designated by the base station as the wireless communication system, the control circuit 3
A switching control signal SS for digital mode setting is output from 0, and as a result, the switch 9 is switched to the second low-pass filter 8b side. Therefore, the second low pass filter 8b is inserted in the gain control loop. Therefore, when the wireless transmission operation is started in this state, the error signal between the detected value of the transmission power output from the error amplifier 6 and the reference voltage value is output to the second low pass filter 8b via the changeover switch 9. Input to the second low-pass filter 8
It is smoothed by b. Then, the DC voltage obtained by the second low pass filter 8b is supplied to the variable attenuator 1 as a gain control signal, whereby the attenuation amount of the variable attenuator 1 is variably controlled. Here, as described above, the time constant of the second low pass filter 8b is preset to a relatively large value suitable for the digital mode. For this reason,
The gain control of the variable attenuator 1 by the gain control loop, in other words, the variable control of the transmission power of the radio transmission signal is performed at the loop response speed optimal for the digital mode.

As described above, according to the present embodiment, when the analog mode is set, the transmission power is variably controlled according to the loop time constant suitable for the analog mode, and when the digital mode is set, it is suitable for the digital mode. The transmission power is variably controlled according to the loop time constant. Therefore, when the digital mode is set, the amplitude component of the transmission signal is transmitted to the receiving side without being suppressed, so that the receiving side can perform accurate demodulation with few errors. Further, it is possible to prevent unnecessary spread of the spectrum of the wireless transmission signal, and thereby prevent interference and interference with other adjacent wireless communication channels. Further, in the analog mode, variable control of the transmission power can be performed with good responsiveness, so that the transmission power can always be stably maintained at a predetermined value.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the first low-pass filter 8a for analog mode and the second low-pass filter 8b for digital mode are provided respectively, and these are switched by the change-over switch 9 to selectively form a loop. Although it is configured to be inserted, one filter including an active filter or the like may be provided and the time constant of this filter may be variably controlled by the control circuit.

In the above embodiment, the variable attenuator is used as the transmission power varying means, but a variable gain amplifier may be used instead. Further, the high frequency amplifier 2 may be configured by a variable gain amplifier and the amplification gain thereof may be variably controlled.

In addition, the insertion position of the low-pass filter in the gain control loop, the type of system to be applied, the configuration of the wireless communication device, the configuration of the variable gain means, the configuration of the gain control means, etc. Various modifications can be implemented without departing from the above.

[0025]

As described above in detail, according to the present invention, the variable gain means inserted in the transmission signal path for varying and outputting the transmission power, and the power of the transmission signal output from the variable gain means. Is detected, the detected value of the power is compared with a reference value to detect the error, and a gain control signal for bringing the error close to zero is generated based on the detected error to generate the variable gain means. In addition to the gain control means for controlling the gain of, the time constant varying means is provided, and the loop time constant inserted in the gain controlling means is changed by the time constant varying means to select the digital mode and the analog mode. According to the above, the value is variably set to a preset value.

Therefore, according to the present invention, there is provided a dual mode type wireless communication device which can always perform high quality wireless communication without deterioration of wireless characteristics in both analog mode and digital mode. A transmission power control circuit can be provided.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a configuration of a wireless communication device including a transmission power control circuit according to an embodiment of the present invention.

2 is a circuit block diagram showing a configuration of a transmission power control circuit provided in a transmission circuit of the wireless communication device shown in FIG.

FIG. 3 is a schematic configuration diagram showing an example of a cellular mobile radio communication system.

FIG. 4 is a circuit block diagram showing a configuration of a conventional transmission power control circuit.

FIG. 5 is a diagram showing an example of spectrum characteristics in a digital mode.

[Explanation of symbols]

 1 ... Variable attenuator 2 ... Transmission power amplifier 3 ... Directional coupler 4 ... Detector 5 ... Smoothing circuit 6 ... Comparison amplifier 7 ... Reference voltage generator 8a ... First low-pass filter 8b ... Second Low-pass filter 9 ... Switching switch 11 ... Antenna 12 ... Antenna duplexer 13 ... Reception circuit 14 ... Frequency synthesizer 15 ... Transmission circuit 16 ... Digital modulation / demodulation circuit 17 ... Equalizer 18 ... Error correction code decoding circuit 19 ... Voice code decoding circuit 20, 23 ... Voice switch 21 ... Speaker 22 ... Microphone 24 ... Analog voice processing circuit 25 ... Console unit 26 ... Power supply circuit 27 ... Battery 30 ... Control circuit SS ... Switching control signal

Claims (1)

[Claims] 1. A transmission power control circuit provided in a dual mode type wireless communication device, comprising a digital mode and an analog mode as a wireless communication system, and selecting these modes to perform wireless communication. The variable gain means for varying and outputting the transmission power and the power of the transmission signal output from the variable gain means are detected, and the detected value of this power is compared with the reference value to detect the error. And a gain control means for controlling the gain of the variable gain means by generating a gain control signal for making the error close to zero based on the detected error, and a loop inserted in the gain control means. And a time constant varying means for variably setting a time constant to a preset value according to the selection result of the digital mode and the analog mode. Transmission power control circuit for dual-mode wireless communication device.