JPH09200276A - Radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable direct communication between mobile stations by providing the non-linear distortion compensation of a transmission part without expanding circuit scale when performing digital linear modulation while using radio equipment for a system to perform the communication between mobile stations through a base station or to perform duplex or simplex communication. SOLUTION: Switchers 107-109 for diode switches, etc., are provided for switching a circuit at the output step of a power amplifier when inverting a transmission/reception frequency and without providing two pairs of feedback circuits and compensation circuits corresponding to transmission and reception frequency bands, a feedback/control loop for non-linear compensation is composed of a pair of feedback circuit 117 and compensation circuit 128 so that distortion compensation can be performed while including non-linear distortion generated at a power amplifier 118 and its switchers 107-109.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital linear modulation radio apparatus for performing communication (usually) between mobile stations via a base station, and by performing transmission / reception frequency inversion, communication between mobile stations without going through the base station. The present invention relates to a configuration of a non-linear distortion compensation system for a transmitter of a digital linear modulation radio that enables the above.

[0002]

2. Description of the Related Art As a wireless communication system used for general business, a communication system for performing simplex and duplex communication between mobile stations via a base station is widely known. This is shown in FIGS. In both figures, 1 is a base station, 2a,
2b, 2c and 3a, 3b represent mobile stations.

FIG. 4 shows an example of simplex communication, in which each mobile station 2a, 2
b and 2c transmit at carrier frequency f1 and receive at carrier frequency f2. Further, FIG. 5 is an example of duplex communication. When the mobile station 3a and the mobile station 3b communicate with each other, the mobile station 3a transmits at the carrier frequency f1, and the base station 1 converts the carrier frequency to f3 to make the mobile station. 3b. The mobile station 3b receives this f3 and transmits it at the carrier frequency f2. Similarly, the mobile station 3a performs duplex communication by receiving the transmission content of the mobile station 3b at f4. To simplify the explanation, these frequencies may be different in each mobile station depending on each communication system, but in the individual mobile station, the carrier frequency for transmission cannot be used as the reception frequency, and the carrier frequency for reception is Cannot be used as the transmission frequency. For this reason,
In a conventional wireless device using an analog modulation method such as FM modulation, a method of inverting the transmission / reception frequency and directly communicating between mobile stations is generally known.

On the other hand, recently, there are systems that employ digital linear modulation. FIG. 3 shows an example of the basic configuration of a mobile station radio used in such a system. The basic operation of this radio will be briefly described below. First, the operation of the transmission system will be described. The audio signal input from the microphone 601 is amplified by the low frequency unit 602, and the audio encoding unit 603.
Is converted into a digital signal. The encoded voice signal is digitally modulated by the digital modulator 604 by a system-specific method, and converted into I-phase (in-phase) and Q-phase (quadrature phase) signals. The compensation circuit 31 described later
After passing 0, the quadrature modulator 605 performs quadrature modulation and the power amplifier 309 amplifies the power to a predetermined power level. Generally, in digital linear modulation, non-linear distortion occurs due to amplitude and phase distortion of the power amplification section, the output spectrum of the power amplification section spreads out of a specified band, and leakage power to adjacent channels increases, which causes interference. The compensating circuit 310 is a circuit for suppressing the spread of the spectrum and improving the leakage power ratio, and the details will be described later. The amplified high-frequency signal passes through the isolator 306, the directional coupler 305, and the transmission-side bandpass filter 304 of the duplexer 301, and then the antenna 1
01, and is received by the base station.

Next, the operation of the receiving system will be described. The transmission wave from the base station is received by the antenna 101, passes through the reception filter 303, and is amplified by the reception high frequency unit 608.
After being converted to the reception intermediate frequency by the mixer 609,
The demodulation section 611 demodulates and reproduces as received data.
The received data is decoded by the audio demodulation unit, further converted into an audio signal, amplified by the low frequency unit 613, and output from the speaker 619 as a received audio signal. Here, the local signal for the quadrature modulation and reception unit mixer is supplied from the synthesizer unit 606. In addition, 615 is a control part which controls a radio | wireless machine, 616 is an operation and a display part. As is well known, the local signal input to the quadrature modulator 605 needs to be input with signals that are out of phase with each other by π / 2 radians (90 °).
It is realized by providing 7. Recently, an IC with a built-in 90 ° phase shifter is commercially available and can be easily realized.

Next, the above-mentioned compensation circuit will be described. Generally, the spectrum of a linearly modulated wave spreads due to the non-linear distortion generated in the transmission path of the power amplifier 309 or the like,
It interferes with the band of a communication channel that is in close proximity (eg, 12.5 kHz, 25 kHz detuning, etc.). As a countermeasure, a part of the transmission output is taken out by using a coupling circuit such as the directional coupler 305, fed back to the compensation circuit 310 via the feedback circuit 308, compared with the modulated wave signal of the digital modulator 604, and transmitted. There is known a Cartesian-controlled negative-return type compensation method that reduces leakage power to an adjacent band by correcting a difference between a signal and a feedback signal, that is, an amplitude and a phase difference. That is, in this method, Cartesian control is used in which the radio frequency fed back in the feedback circuit 308 is quadrature demodulated and processed in the compensation circuit 310 as I-phase and Q-phase signals. Regarding such a compensation method, as an example in the case of using π / 4 shift QPSK as linear modulation, I
EEE Journal on selected a
reas in communications, v
ol. SAG-5, No. 5 June, 1987
p. p. 890-895.
g. 7 p. In 892, a Cartesian control negative feedback type principle block diagram is shown. Although not included in this principle block diagram, as an example, in a commercial digital radio device that requires a strict regulation such that a leakage power ratio to an adjacent channel is -50 dBc or less, load fluctuation of a transmission output stage is required. On the other hand, a circuit configuration in which the isolator 306 is provided in the output stage of the power amplification unit is required to stably compensate the nonlinear distortion. Heretofore, an example of the general basic operation of a digital linear modulation wireless device has been described. As described above, a radio device using digital linear modulation requires a feedback circuit and a compensation circuit for compensating for the non-linear distortion of the power amplification section. Note that the duplexer 301 is required when performing duplex communication, but in a system that uses only simplex communication, transmission and reception are performed alternately, so a transmission and reception filter corresponding to the band puff filters 304 and 303 should be provided. But good.

As described above, the radio equipment for communicating between mobile stations via the base station does not have a means for directly communicating between mobile stations due to its structure, and it is out of the control range of the base station or the base station. There is a drawback that communication cannot be performed when a station failure occurs. For this reason, in a conventional analog-modulated radio, as a means for performing direct communication between mobile stations, the transmission frequency and the reception frequency of one radio are inverted, the signal path of the transmission / reception unit is switched, and the reception wave is transmitted through a transmission filter. A method is known in which communication between mobile stations is directly performed by inputting the input signal and outputting a transmission wave via a reception filter. On the other hand, in a wireless device that uses constant amplitude modulation such as conventional FM modulation as a modulation method in this way, interference with adjacent channels due to nonlinear distortion of the power amplification unit does not affect the power amplification unit. A class C amplifier is adopted, and the compensation circuit as described above is unnecessary. Therefore, in general, there are radio systems in which the transmission and reception bands are apart from each other by several MHz or several tens of MHz. However, in the conventional analog modulation radio, the transmission / reception frequency is simply inverted and the signal path of the transmission / reception unit is switched between the mobile stations. It was possible to communicate directly.

[0008]

On the other hand, in a digital radio device using linear modulation, in order to invert the transmission frequency and the reception frequency, it is necessary to provide the non-linear distortion compensation circuit of the power amplification section as described above. However, there is a problem in that distortion compensation cannot be sufficiently performed simply by inverting the transmission / reception frequency. That is, for example, the transmission / reception interval is several M
When they are separated by more than Hz, there is a difference in the amplitude and phase characteristics of the power amplifier, the quadrature modulator, the quadrature demodulator used in the feedback circuit, and other circuits that make up the compensation control loop. Cannot be compensated for. Therefore, it is necessary to provide a control loop for compensation for each transmission / reception frequency band and perform a compensation operation corresponding to changes in amplitude and phase difference. In particular, in the compensation method in which the amplitude distortion and the phase distortion are detected by using the training signal and the compensation amount is controlled, when the transmission / reception frequency is inverted, the compensation control loop is independently configured to respond to both frequency bands. Is required. As a method of this, it is possible in principle to form a control loop for nonlinear distortion compensation by providing two independent systems of a feedback circuit and a compensation circuit. However, this configuration method has drawbacks that the circuit scale becomes large and the cost also increases. The present invention eliminates such drawbacks and provides a direct communication between mobile stations by realizing a control loop for compensating the nonlinear distortion of the power amplification section with a simpler circuit configuration in a digital linear modulation radio device. Is.

[0009]

In order to achieve the above-mentioned object, the present invention, as a first means, first provides a switching device at the output stage of a power amplifier to branch a transmission line to invert the frequency of transmission and reception. The transmission wave can be output through the duplexer in any frequency band.

Generally, as an example, a power amplifier in the 400 MHz band can operate in the frequency band between transmission and reception intervals of about 20 MHz.

As a second means, a coupler such as a directional coupler is provided in each of the branch paths of the power amplification section described above, and a switching device for selecting the output of these two directional couplers is provided. A control loop is provided, which is input to the compensation circuit via the feedback circuit. As a result, although the feedback circuit and the compensation circuit have one system, it is possible to configure two systems of compensation control loops. Here, an isolator is generally provided in the output stage of the power amplifier in order to stabilize the compensating operation against a load change, but it is not necessary in principle. When the isolator has a wide band characteristic that covers the transmission / reception interval band, the number of the isolators can be reduced to one by switching the branch shown in the first means at the output stage of the isolator.

Further, as a third means, a switching circuit is also provided in the receiving section for inverting the transmission / reception frequency, and the switching circuit is configured so that the transmitted wave is not directly input to the receiving section.

As a result, even when frequency inversion is performed, by providing the above switching circuit, a return loop for compensating for non-linear distortion that responds to two frequency bands can be provided with one return circuit and a compensation circuit. Can be configured. Further, since the return loop is configured by including the switcher, it is possible to perform the compensation including the nonlinear distortion generated by the switch in addition to the nonlinear distortion generated by the power amplifier.
Therefore, the compensation performance is not deteriorated by switching the transmission circuit. On the other hand, since the switching of the receiving circuit operates so that the transmission wave is not directly input, the incoming wave can be received without being disturbed or interfered with by its own transmission wave, so that direct communication between mobile stations becomes possible.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows an embodiment in which a broadband isolator covering a transmission / reception interval is used. Here, in the embodiments, an example of the configuration of the high-frequency unit, which is the main point of the present invention, is shown. That is, the basic operation of the transmitter and the microphone 601 to the digital modulator 604 in the conventional example of the digital radio shown in FIG. 3 is the same in this embodiment. In the receiving section, the basic operation is the same as that of the embodiment from the mixer 609 onward, from the receiving intermediate frequency section to the output of the speaker 619. Furthermore, the synthesizer section 60
Operations and configurations of the control unit 615, the control unit 615, and the operation display unit 616 are also the same as those in the conventional example of FIG. 3, and thus the description thereof is omitted in FIGS. 1 and 2.

The operation will be described below. Transmission input terminal 126
Corresponds to the output of the speech encoding unit 603 shown in the conventional example of FIG. This transmission signal is digitally linearly modulated by the digital modulation unit 604 and is output as I-phase and Q-phase output signals from the compensation circuit 11.
9 is input. After being quadrature-modulated by the quadrature modulator 128 and further amplified by the power amplifier 118, the isolator 1
16 is input. As described above, the transmission wave increases the leakage power to the adjacent channel band, for example, the bands such as 12.5 kHz and 25 kHz, whose spectrum is spread due to the non-linear distortion of the power amplifier 118. Isolator 116
Is branched and connected to the switches 107 and 108. The switches can be, for example, diode switches, but in FIG. 1 these switches have terminals 112 and 114 on and terminals 113 and 115 off.

The switches 109, 112, 114, 204, 20 composed of diode switches are used here.
An example of Nos. 8 and 122 is shown in FIG. In FIG. 6, for example, pin diodes are used for D1 and D2, and switches SW1 and SW
When 2 is on the power supply + Vc side and the ground side, respectively, D1 is turned on and D2 is turned off, so that the terminals 501 to 112 are in a conductive state and the terminals 501 to 113 are disconnected, so that the transmission path can be switched. C and R are capacitors,
Reference numeral 505 denotes a control input terminal of SW1 and SW2.

Next, the transmitted wave is input to the directional coupler 105 through the terminal 112, and is transmitted from the antenna 101 through the bandpass filter 104 of the duplexer 102. The output of the directional coupler 105 is output from the switch 109 to the terminal 11.
Since it has been switched to the 0 side, it is returned to the compensation circuit 119 via the return circuit 117. Compensation circuit 119 operates as described above to reduce the non-linear distortion due to amplitude and phase distortion compared to the transmitted input signal. The point to be noted here is that the control / feedback loop of the compensation circuit 119 is configured to include the switches 107 and 109.
The point is that it is possible to perform non-linear compensation including the non-linear distortion generated in the diode of the switch.

On the other hand, the incoming received wave is input from the antenna 101, and the bandpass filter 103 of the duplexer 102 is input.
To the switch 108. Since the terminal of the switch 108 is connected to 114, the received wave is amplified by the receiver amplifier 120. After passing through the bandpass filter 124 through the terminal 122 of the switch 121, it is converted into an intermediate frequency by the mixer 609, further amplified by the reception intermediate frequency section, and then demodulated. The operation after the mixer is the same as that of the conventional example shown in FIG.

At this time, the transmission wave is not input to the reception amplifier 120 because the terminal 115 of the switch 108 is off, and does not directly interfere with the reception circuit.

The bandpass filters 124 and 12
5 is not always necessary due to the required attenuation characteristic of the device, and accordingly, the switching device 121 can be omitted.

When performing direct communication between mobile stations, the mobile station on the other side needs to invert the frequency of transmission and reception to perform transmission and reception.

The operation of the mobile station at this time will be described below.
In this mobile station, the switches 107, 108 and 109 are switched to the terminals 113, 115 and 111, respectively. The received wave passes through the bandpass filter 104 of the duplexer 102 and then is input to the receiving amplifier 120 via the terminal 113 of the switch 107. Switch 121
Is switched to the terminal 123 side, input to the bandpass filter 125 having the same pass band as the received wave, and after performing the required band limitation, it is input to the subsequent stage circuit as described above and subjected to detection demodulation. When this mobile station transmits, the transmitted wave passes through the isolator 116 because the isolator 116 uses the transmission and reception bands as a pass band, and then the terminal 112 of the switch 107 is turned off and the terminal 115 side of 108 is turned on. It is input to the bandpass filter 103 of the duplexer 102 via the coupler 106 and output from the antenna 101. At this time, the switch 109 is turned on at the terminal 111 side, a part of the transmission output is fed back to the return circuit 117, and the compensation circuit 119 performs non-linear distortion compensation. Note that such control is performed by the control of a control unit (not shown), and each switching device 1
09, 112, 114 and 121 work together.

Even when the transmission / reception frequency is inverted in this way, although the feedback circuit and the compensating circuit have one system, by performing the signal path switching operation, two independent control loops for distortion compensation are provided. The effect equivalent to that can be given.

As described above, in a digital linear modulation radio device or a duplex communication radio device that communicates via a base station, it becomes possible to realize the nonlinear distortion compensation function of the transmission output without significantly increasing the circuit scale. , Effective for direct communication between mobile stations.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, the pass band of the isolator is several MH.
This is an example in the case where it is narrower than z, that is, the transmission / reception interval. The output of the power amplifier 118 is branched into two by providing a switch 204, and one output is an isolator having a transmission frequency ft, for example, a center frequency of 360 MHz as a pass band.
An isolator having a reception frequency fr, for example, a center frequency of 378 MHz as a pass band is provided on the other signal path. Here, as an example, the transmission / reception frequency is separated by 18 MHz. Similarly, the bandpass filter 104 of the duplexer 102 is arranged so as to have a band for passing the transmission frequency ft, and the bandpass filter 103 is arranged so as to have a band for passing the reception frequency fr. It should be noted that ft is the received wave and ff is the transmitted wave in the mobile station whose transmission / reception frequency is inverted.

As in the first embodiment, a part of the transmitted wave is taken out through the directional coupler 105 or 106, the signal path is selected by the switch 109, and the signal is returned to the return circuit 117. Further, the compensation circuit 119 performs non-linear distortion compensation. Thus, since the switch is included in the feedback loop,
It is possible to compensate for the non-linear distortion of the power amplification unit including the non-linear distortion generated in the switch, and the switching can be performed without deteriorating the leakage power ratio to the adjacent channel.

Further, when the switch 203 is switched to the terminal 204, the terminal 208 of the switch 206 is off, so that the transmission wave can be prevented from leaking into the receiving amplifier 120 of itself. When the transmission wave is switched so as to pass through the bandpass filter 104, the radio wave transmitted from the mobile station of the other party passes through the bandpass filter 103 of the duplexer 102 as an incoming reception wave,
It is input to the terminal 207 of the switch 206, and then amplified by the reception amplifier 120. The operation thereafter is the first embodiment.
Is the same as

[0028]

According to the present invention, in a digital linear modulation radio used for a system for communicating between mobile stations via a base station or a system for duplex or simplex communication, nonlinear distortion compensation of a transmitter is performed. It is possible to configure a feedback / control loop for distortion compensation with one system by switching without providing two systems independently for the feedback circuit or the compensation circuit for. When inverting the frequency between mobile stations and performing direct communication, a circuit format was conceivable in which two systems of a feedback circuit and a compensation circuit of the transmission unit were provided to form a control loop for compensation. Can be reduced, which is effective for downsizing and cost reduction of equipment. Further, even when the transmission / reception frequency band is apart from, for example, 10's MHz to several 10 MHz, non-linear distortion compensation corresponding to the frequency band can be performed, so that the performance of the leakage power ratio is not deteriorated.

Even when the output signal path and the feedback path are switched by using a switch such as a diode switch, since the diode switch is included in the compensation control loop, the nonlinear distortion generated in the switch itself is prevented. It has the advantage that it can be compensated. As for the isolator, it is possible to use only one isolator by adopting a wide band isolator which covers the transmission / reception band, although it depends on the embodiment. Furthermore, since the receiving section has a configuration in which the signal path is switched so that the transmitted wave is not input to its own receiving circuit, the incoming wave can be received without causing interference due to the transmitted wave.

As described above, according to the present invention, by adding a small number of circuits such as a switch, the non-linear distortion compensation function of the power amplification section can be effectively operated even when the transmission / reception frequency is inverted. It is possible to realize the direct communication function between the mobile stations of the wireless device of the small size and the low price.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram of a conventional digital wireless device.

FIG. 4 is a configuration diagram showing an example of duplex communication between mobile stations via a base station.

FIG. 5 is an example of simplex communication between mobile stations via a base station.

FIG. 6 is a circuit diagram showing an example of a configuration diagram of a switch.

[Explanation of symbols]

101 antenna, 102 duplexer, 105 directional coupler, 106 directional coupler, 107, 108, 109
Diode switcher, 116 Isolator, 11
7 return circuit, 118 power amplification section, 119 compensation circuit, 120 reception amplifier, 121 diode switcher, 126 transmission data input terminal, 127 reception intermediate frequency output terminal, 201, 202 isolator, 203, 206
Diode switcher, 301 duplexer, 305 directional coupler, 306 isolator, 307 receiving amplifier, 308 return circuit, 309 power amplifier, 310
Compensation circuit, 311 Reception band pass filter, 604
Digital modulation unit, 128 quadrature modulation unit, 610 reception intermediate frequency unit, 609 mixer unit, 611 demodulation unit, 60
7 90 ° phaser, 606 synthesizer section, 502
503 pin diode, 1 base station, 2a, 2b, 2
c, 3a, 3b mobile stations

Claims (1)

[Claims] 1. In a wireless device that directly communicates between mobile stations by inverting the transmission and reception frequencies, a digital modulator that modulates a transmission signal into a digital signal of an I component and a Q component, and a compensation circuit in the next stage. , A quadrature modulator for quadrature modulating I and Q digital signals of the next stage, a power amplifier for the next stage, and at least two bandpasses of different frequency bands in the duplexer for supplying the output of the power amplifier to the antenna A filter, a diode switch circuit that selectively supplies the output of the power amplifier to the bandpass filter, a directional coupler connected between the diode switch and each of the bandpass filters, and the directional coupling. And a diode switch that selects any one of the capacitors and a loop that supplies a signal selected by the diode switch to the compensation circuit. Radio digital linear modulation scheme and having a circuit.