JP2002190712A - Array antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power efficiency of an array antenna system and to miniaturize the system by performing non linear distortion compensation on power amplifiers included in respective systems in the array antenna device and to form a highly accurate beam by compensating the linear dispersion of the power amplifier between the systems. SOLUTION: Distortion compensation characteristic adding parts 204 and frequency characteristic equalizing parts 202 are arranged for compensating non-linear distortion generated in the power amplifiers 206 of the respective systems and compensating frequency distortion in the respective systems. The parameters of the distortion compensation characteristic adding parts 204 and the frequency characteristic equalizing parts 202 are adaptively updated by feeding back the outputs of the power amplifiers 206 through distributors 207.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array antenna device which is used in a communication device of a radio communication system and has a nonlinear distortion compensator for compensating for nonlinear distortion generated in a transmission system.

[0002]

2. Description of the Related Art In a power amplifier included in a transmitter of a wireless communication system, nonlinear distortion occurs according to the amplitude of a transmission signal. This nonlinear distortion degrades transmission characteristics and causes adjacent channel interference. In order to reduce the non-linear distortion, a power amplifier having high linearity may be used, but a power amplifier that generates non-linear distortion is generally used in terms of power efficiency. Improvement in power efficiency leads to downsizing of the device and lower power consumption.

Conventionally, various methods such as feedforward, Cartesian loop, and predistortion have been proposed as methods for compensating for this nonlinear distortion.

FIG. 3 shows a configuration of a conventional nonlinear distortion compensator using a predistortion method. Reference numeral 301 denotes a transmission baseband signal, 302 denotes a distortion compensation characteristic adding unit, 303 denotes a frequency conversion unit, 304 denotes a power amplifier, and 305 denotes an antenna. In distortion compensation characteristic adding section 302, power amplifier 304 depends on the amplitude value of transmission baseband signal 301.
Are added to the transmission baseband signal 301. Then, the output of the distortion compensation characteristic adding section 302 is frequency-converted to an RF band in a frequency conversion section 303 and amplified to a desired level in a power amplifier 304. A linear signal whose distortion has been compensated appears at the output of the power amplifier 304 and is transmitted from the antenna 305.

[0005] On the other hand, as an antenna included in a transmitter of a radio communication system, an array antenna that controls directivity by arranging a plurality of antennas at equal intervals is known. By using the array antenna, a beam having a sharp directivity can be formed in an arbitrary direction, and the repetition distance of the same frequency can be shortened to increase the frequency use efficiency.

FIG. 4 shows a configuration of a conventional array antenna device. Reference numeral 401 denotes a transmission baseband signal, 402 denotes an amplitude / phase control unit, 403 denotes a frequency conversion unit, 404 denotes a power amplifier, and 405 denotes an antenna. Transmission baseband signal 4
Numeral 01 receives amplitude and phase control for forming a beam in a desired angle width and a desired direction in the amplitude / phase control unit 402. Then, the RF signal is
The signal is converted to a band, the output of the frequency conversion unit 403 is amplified to a desired level in the power amplifier 404, and transmitted from the antenna 405.

FIG. 4 shows a configuration in which a power amplifier is provided for each system. Alternatively, a configuration in which a common power amplifier is used and an amplitude / phase control unit is provided downstream of the power amplifier may be considered. In the latter case, only one power amplifier is required, but a high power and large power amplifier is required.

[0008]

In order to perform highly accurate beam forming in a conventional array antenna apparatus having a power amplifier in each system, each power amplifier needs to have high linearity. This is because, when nonlinear distortion occurs in each power amplifier, the amplitude level of each system fluctuates, making it difficult to obtain a desired beam characteristic. However, the use of a power amplifier with high linearity causes a reduction in power efficiency and an increase in the size of the device.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention uses a power amplifier that generates nonlinear distortion in each system of an array antenna apparatus and performs nonlinear distortion compensation on the power amplifier. . This improves the power efficiency of the entire array antenna device and reduces the size of the device,
By ensuring the linearity of the power amplifier between the systems, highly accurate beam forming is possible. In the present invention, in addition to the compensation for the nonlinear distortion generated in the power amplifier, the beam distortion with higher accuracy can be obtained by compensating for the frequency distortion generated in each system.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is an array antenna apparatus having a plurality of antenna elements and a plurality of power amplifiers, wherein all or a part of the power amplifiers are generated by the power amplifier. An array antenna device comprising a distortion compensation characteristic adding unit for compensating for nonlinear distortion, which is capable of improving power efficiency and reducing the size of the device and, at the same time, has the effect of obtaining highly accurate beam characteristics. Have.

According to a second aspect of the present invention, in the array antenna apparatus of the first aspect, the distortion compensation characteristic adding section of each system can selectively start or stop its operation according to transmission power. An array antenna device having a function similar to that of claim 1 and a function of reducing power consumption by stopping a nonlinear distortion compensating operation for a power amplifier in which distortion is small.

According to a third aspect of the present invention, in the array antenna apparatus of the first aspect, the power amplifiers of each system are power amplifiers having different maximum output values. In addition to having the same operation as that of the first aspect, by preparing a power amplifier suitable for the maximum transmission output value that differs depending on each system, there is an operation that enables further miniaturization of the device.

According to a fourth aspect of the present invention, in the array antenna apparatus of the first aspect, transmission power is controlled by performing gain control in a distortion compensation characteristic adding section of each system. This device has an operation similar to that of the first aspect, and has an operation of enabling high-accuracy transmission power control by performing transmission power control in consideration of nonlinear distortion generated in a power amplifier.

According to a fifth aspect of the present invention, there is provided the array antenna apparatus according to the first aspect, further comprising a frequency characteristic equalizing section for compensating frequency distortion in each system. In addition to having the same operation as that of the first aspect, the present invention has an effect of enabling more accurate beam forming by compensating for variations in frequency characteristics between systems.

[0015] The invention according to claim 6 is the invention according to claims 1 to 5.
The array antenna device according to any one of claims 1 to 3, wherein the distortion compensation characteristic adding unit of each system performs adaptive nonlinear distortion compensation using a feedback signal from a power amplifier. Items 1 to 5
In addition to the same operation as described above, the present embodiment has an effect of enabling a stable nonlinear distortion compensation operation even when the operating environment changes, such as temperature and power supply voltage.

According to a seventh aspect of the present invention, in the array antenna apparatus according to the fifth aspect, the distortion compensation characteristic adding section and the frequency characteristic equalizing section of each system adaptively utilize a feedback signal from a power amplifier. And a nonlinear distortion compensation and a frequency distortion compensation.
It has the effect of enabling stable nonlinear distortion compensation operation and frequency distortion compensation operation even with fluctuations in the operating environment such as temperature and power supply voltage.

An embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a block diagram of an array antenna apparatus according to a first embodiment of the present invention. 101 is a transmission baseband signal, 102 is a frequency characteristic equalizer, 103 is an amplitude / phase controller, 104 is a distortion compensation characteristic adder, 105 is a frequency converter, 106 is a power amplifier, 107 is an antenna, and 108 is compensation operation control. Part 10,
9 is a transmission power control signal.

The operation of the array antenna device configured as described above will be described with reference to FIG. First, the transmission baseband signal 101 is input to the frequency characteristic equalization unit 102, and compensation for frequency distortion generated in each system is performed. The frequency characteristic equalizer 102 can be configured by a transversal filter. The output of the frequency characteristic equalization unit 102 is subjected to amplitude and phase control required for beam forming in the amplitude / phase control unit 103, and the output of the amplitude / phase control unit 103 is input to the distortion compensation characteristic addition unit 104. In the distortion compensation characteristic adding section 104, the inverse characteristic of the nonlinear distortion generated in the power amplifier 106 is added to the input signal according to the amplitude value of the input signal. Distortion compensation characteristic adding section 104
Is a configuration in which a memory in which the inverse characteristic of the nonlinear distortion is stored in advance is prepared, and the inverse characteristic is read using the amplitude value of the input signal as an address.

The output of the distortion compensation characteristic adding section 104 is converted into an RF band signal in a frequency conversion section 105, and the output of the frequency conversion section 105 is amplified to a required level in a power amplifier 106. Then, a linear signal whose distortion has been compensated is output from the power amplifier 106, and the antenna 107
The transmitted signals are spatially combined to form a beam having a desired directivity.

On the other hand, the compensation operation control section 108 controls each distortion compensation characteristic adding section 104 based on the information of the transmission power control signal 109 to obtain a desired transmission power. This control changes the read address range of the memory in which the inverse characteristic of the power amplifier is stored according to the desired transmission power value, and multiplies the read coefficient value by a constant corresponding to the desired transmission power value. It is done by doing. When the distortion generated in the power amplifier 106 decreases due to the transmission power control and the nonlinear distortion compensation becomes unnecessary, the operation of the distortion compensation characteristic adding unit 104 of each system may be selectively stopped.
Further, the power amplifier 106 does not need to use the same power amplifier in each system, and a power amplifier that satisfies the maximum output value assumed in each system may be prepared in each system.

The above operation compensates for variations in linearity due to non-linear distortion of the power amplifier in each system, and variations in frequency characteristics between the systems, and enables an array antenna capable of highly accurate beam forming. A device is obtained. Further, by performing the nonlinear distortion compensation of each power amplifier, it is possible to improve the power efficiency and reduce the size of the device.

(Embodiment 2) FIG. 2 is a block diagram of an array antenna apparatus according to a second embodiment of the present invention. 201 is a transmission baseband signal, 202 is a frequency characteristic equalizer, 203 is an amplitude and phase controller, 204 is a distortion compensation characteristic adder, 205 is a quadrature modulator, 206 is a power amplifier,
Reference numeral 207 denotes a distributor, 208 denotes an antenna, 209 denotes a quadrature demodulation unit, 210 denotes a compensation operation control unit, and 211 denotes a transmission power control signal.

The operation of the array antenna device configured as described above will be described with reference to FIG. First, the transmission baseband signal 201 is input to the frequency characteristic equalization unit 202, and the frequency distortion generated in each system is compensated. The frequency characteristic equalizer 202 can be configured by a transversal filter. The output of the frequency characteristic equalizing section 202 is subjected to amplitude and phase control required for beam forming in an amplitude / phase control section 203, and the output of the amplitude / phase control section 203 is input to a distortion compensation characteristic adding section 204. In the distortion compensation characteristic adding section 204, the inverse characteristic of the nonlinear distortion generated in the power amplifier 206 is added to the input signal according to the amplitude value of the input signal. Distortion compensation characteristic adding section 204
Is a configuration in which a memory in which the inverse characteristic of the nonlinear distortion is stored in advance is prepared, and the inverse characteristic is read using the amplitude value of the input signal as an address.

The output of the distortion compensation characteristic adding section 204 is converted into an RF band signal in the quadrature modulation section 205, and the output of the quadrature modulation section 205 is amplified to a required level in the power amplifier 206. Then, a linear signal whose distortion has been compensated is output from the power amplifier 206, and the signal transmitted from the antenna 208 is spatially combined to form a beam having a desired directivity.

A part of the signal distributed by the distributor 207 is fed back and input to the quadrature demodulation unit 209. The quadrature demodulation unit 209 performs quadrature demodulation and outputs an IQ baseband signal, which is input to the distortion compensation characteristic adding unit 204 and the frequency characteristic equalizing unit 202. The distortion compensation characteristic adding unit 204 adaptively updates the inverse characteristic value of the nonlinear distortion stored in the memory using the IQ baseband signal. The frequency characteristic equalization unit 202 also adaptively updates the tap coefficients of the transversal filter using the IQ baseband signal.

On the other hand, the compensation operation control section 210 controls each distortion compensation characteristic adding section 204 based on the information of the transmission power control signal 211 to obtain a desired transmission power. This control changes the read address range of the memory in which the inverse characteristic of the power amplifier 206 is stored according to the desired transmission power value, and also sets a constant corresponding to the desired transmission power value to the read coefficient value. This is done by multiplying. When the distortion generated in the power amplifier 206 is reduced by the transmission power control and the nonlinear distortion compensation becomes unnecessary, the operation of the distortion compensation characteristic adding unit 204 of each system may be selectively stopped. Further, the power amplifier 206 does not need to use the same power amplifier in each system, and a power amplifier satisfying the maximum output value assumed in each system may be prepared in each system.

With the above operation, the variation in linearity due to the nonlinear distortion of the power amplifier between the systems and the variation in the frequency characteristics between the systems are adaptively compensated.
An array antenna device that can stably and highly accurately form a beam even when the operating environment such as temperature and power supply voltage fluctuates is obtained. Further, by performing nonlinear distortion compensation of the power amplifier of each system, it is possible to improve power efficiency and reduce the size of the device.

[0029]

As described above, according to the present invention, in an array antenna device having a power amplifier in each system, nonlinear distortion compensation is performed for nonlinear distortion generated in each power amplifier, thereby providing the entire array antenna device. In addition, the power efficiency can be improved and the size of the apparatus can be reduced, and at the same time, highly accurate beam forming can be realized by suppressing variations in linearity between systems.

[Brief description of the drawings]

FIG. 1 is a block diagram of an array antenna device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an array antenna device according to a second embodiment of the present invention;

FIG. 3 is a block diagram of a conventional nonlinear distortion compensator;

FIG. 4 is a block diagram of a conventional array antenna device.

[Explanation of symbols]

 101, 201 Transmission baseband signal 102, 202 Frequency characteristic equalization unit 103, 203 Amplitude / phase control unit 104, 204 Distortion compensation characteristic addition unit 106, 206 Power amplifier 107, 208 Antenna 108, 210 Compensation operation control unit 109, 211 Transmission Power control signal 105 Frequency converter 205 Quadrature modulator 207 Divider 209 Quadrature demodulator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Masayuki Orihashi 3-10-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture Inside Matsushita Giken Co., Ltd. (72) Akihiko Matsuoka 3-chome, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa No. 10 No. 1 Matsushita Giken Co., Ltd. F-term (reference) 5J021 AA05 AA06 DB01 FA05 FA17 FA26 FA32 GA01 HA05 5J090 AA01 AA41 CA21 CA36 CA92 FA17 GN03 GN06 KA16 KA53 KA55 KA68 MA11 SA14 TA01 5J091 AA01 KA55 KA55 KA68 MA11 SA14 TA01

Claims (9)

[Claims] A plurality of antenna elements; a plurality of power amplifiers connected to each of the plurality of antenna elements;
An array antenna device having a distortion compensation characteristic adding unit for compensating for non-linear distortion generated in a power amplifier for all or a part of the plurality of power amplifiers. 2. The array antenna apparatus according to claim 1, wherein the distortion compensation characteristic adding section selectively starts or stops its operation according to the transmission power. 3. The array antenna device according to claim 1, wherein the plurality of power amplifiers have different maximum output values. 4. The array antenna device according to claim 1, wherein transmission power is controlled by performing gain control in a distortion compensation characteristic adding unit. 5. The array antenna device according to claim 1, further comprising a frequency characteristic equalizer for compensating for frequency distortion. 6. The array antenna apparatus according to claim 1, wherein the distortion compensation characteristic adding section adaptively performs nonlinear distortion compensation using a feedback signal from the power amplifier. 7. The array antenna according to claim 5, wherein the distortion compensation characteristic adding section and the frequency characteristic equalizing section of each system adaptively perform nonlinear distortion compensation and frequency distortion compensation using a feedback signal from the power amplifier. apparatus. 8. A communication device comprising the array antenna device according to claim 1. 9. A wireless communication system including the communication device according to claim 8.