JP2002353724A - Method for calibrating antenna transmission pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means that can calibrate a transmitter including a feeder and an antenna element while continuing the communication service. SOLUTION: An antenna signal processing section 106 composites a user signal with a calibration signal of a base band generated by a calibration signal generating section 110, an antenna transmission section 105 applied frequency conversion and amplification to the composite signal and outputs the resulting signal to a coupler 104. Part of transmission waves received by the coupler 104 is outputted to an adder 107 as a traveling-wave output. The transmission wave passing through the coupler 104 is fed to an antenna element 102 of an antenna array 101 via a feeder 103, part of the supplied power is given to the coupler 104 via the feeder 103 as a reflection wave from which a reflected wave output is given to the adder 107. The traveling wave and the reflected wave given to the adder 107 are received by a calibration signal reception section 108, where the traveling-wave and the reflected wave are converted into a base band, a calibration signal processing section 109 identifies the amplitude and the phase, a correction amount calculation section 111 calculates the correction value, which is given to an antenna signal processing section 106 as a calibration value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a means for calibrating a transmission directivity pattern in an adaptive array antenna base station apparatus.

[0002]

2. Description of the Related Art In recent years, cellular systems such as cellular phones have become widespread, and the demand for high-speed data communication has been growing. Therefore, it is essential to improve the frequency use efficiency, and CDMA (Code
Division Multi Accesses) and other methods with high frequency use efficiency are adopted.

[0003] As a method for further increasing the frequency efficiency, an adaptive array antenna method using a CDMA method has been devised. The adaptive array antenna transmitting apparatus is a technique for increasing the frequency use efficiency by controlling the directivity pattern to peak at a communication partner terminal or the null of the directivity pattern to a non-communication partner terminal. .

The adaptive array antenna transmitting apparatus includes a transmitting circuit corresponding to each antenna element arranged in an array, and controls a directional pattern by controlling phase and amplitude characteristics. If there is a characteristic difference in the phase and amplitude characteristics of the system, the transmission directivity pattern will be different from the desired one.

That is, the adaptive array antenna transmitting apparatus is a system that feeds a signal whose phase and amplitude are controlled to the antennas arranged in an array and controls the directivity and the radiation direction. It is preferable that the phase characteristics and the amplitude characteristics of the transmission circuits are uniform in order to accurately control the transmission characteristics. However, the phase characteristics and the amplitude characteristics of each transmission circuit vary.

Further, variations in amplitude characteristics and element delay amounts due to components such as semiconductors and filters used in a transmission unit change with time due to temperature, humidity, aging, etc., and the characteristics change accordingly. Since the variation in characteristics also changes, it becomes impossible to control the directivity and radiation direction accurately.

As a means for solving such a problem,
Japanese Patent Application Laid-Open No. 10-336149 discloses a measurement mode provided before starting communication, calculating a phase difference and an amplitude characteristic difference of each transmission circuit to obtain a calibration coefficient, and calculating a phase difference and a phase difference of a communication signal to be transmitted. A method is disclosed in which the amplitude is multiplied by a phase component and an amplitude component of a calculated calibration coefficient to compensate for characteristics, thereby controlling the array antenna apparatus to have an accurate directivity pattern.

[0008] In the invention described in the above publication, a spread signal in the same frequency band as a spread signal used for communication is used as a calibration signal in order to accurately compensate for characteristic fluctuations. Is switched from the antenna to the receiver for the calibration signal, and the calibration is performed.

FIG. 4 is a system diagram of a conventional CDMA transmitter provided with a calibration mechanism equivalent to that disclosed in the above publication.

In FIG. 4, in a communication mode, a user signal n is input to an antenna n signal processing unit (305-n), and this user signal n is orthogonally modulated and spread by the same spreading code. Signal processing unit (305-
n) are multiplied by complex (amplitude and phase) coefficients set individually for each antenna, and then converted to a high frequency by an antenna n transmission unit (304-n), and each antenna is fed via a feed line (303-n). Element (302-
sent to n).

On the other hand, in the calibration mode, the array antenna
Each antenna element (302-n) and the feeder line (303-n) in (301) are separated from each antenna n transmitting section (304-n). And
The antenna n signal processor (305-n) has a calibration signal generator (310-
n), a calibration signal n is input, and the calibration signal n is orthogonally modulated and spread by different spreading codes, and each antenna n signal processing unit (305-n ) Complex (amplitude and phase)
Set the coefficient.

The calibration signals n spread by the mutually different spreading codes are converted to high frequencies by the antenna n transmission units (304-n), respectively, added by the adder (306), and output by the adder (306).
The signal is input to the calibration signal receiving section (307) as a DMA-multiplexed high-frequency calibration signal. The CDMA-multiplexed high-frequency calibration signal is converted into a baseband signal by a calibration signal receiving unit (307), and is distributed to n, and is distributed to each calibration signal processing unit (308).
-n).

FIG. 5 is a detailed block diagram of a conventional calibration signal processing section (308-n). As shown in FIG. 5, in each calibration signal processing unit (308-n), the correlator (401) outputs a correlation value of only a specific calibration signal, and the delay profile estimating unit (402)
Generates a delay profile. Based on this delay profile, the path position of the calibration signal is detected by the path position detection circuit (403).

Normally, multipath does not occur in the system shown in FIG. Therefore, there is no problem if only one path can be detected. The detected path position is notified to the demodulator (404), and demodulation is performed based on the path position. The demodulated signal is in-phase adder (40
SIR (Signal to Interference Ratio) required in 5)
In-phase addition is performed until is obtained.

The amplitude and phase of the signal are specified by a calibration signal calculation unit (406), and respective correction values are calculated by a correction amount calculation unit (309) in FIG. 4, and each antenna n signal processing unit (305) -
The calibration is completed by inputting to n).

[0016]

In the above-described conventional calibration apparatus, when performing calibration, the feeder line and the antenna element must be separated from the antenna transmission unit, and calibration cannot be performed while performing communication services. was there.

In addition, since the feed line from the transmitting device is outside the calibration loop and is not subject to compensation, in the above-described conventional calibration device, the feed line to the antenna ahead of the antenna transmitting section and the antenna There was a problem that calibration including elements could not be performed.

An object of the present invention is to provide a means capable of performing the above-mentioned calibration while continuing a communication service without disconnecting a feeder line and an antenna element from an antenna transmitter.

It is another object of the present invention to enable highly accurate compensation including a feed line and an antenna element from an antenna transmitting section to an antenna.

[0020]

SUMMARY OF THE INVENTION The present invention provides an adaptive array antenna (adaptive antenna) transmitting apparatus using a code division multiple access (CDMA) system, wherein each antenna element of the array antenna is provided with the same spreading code. The spreading user signal and the spreading code for the user signal are different spreading codes, and the calibration signals spread by different spreading codes for the respective antenna elements are combined for each of the antenna elements. The calibration signal for each antenna element is extracted by extracting a part of the traveling wave transmitted to each antenna element and correlating the extracted traveling wave with a spreading code for each antenna element. Are independently demodulated, and based on the demodulated calibration signal for each antenna element, the transmission signal for each antenna element is demodulated. Against and adjusting the amplitude and phase characteristics.

The above adjustment is preferably performed when the directivity pattern for transmitting the user signal by the array antenna is a non-directional pattern. By taking this into consideration, it is possible to adjust the amplitude characteristic and phase characteristic of the transmission signal for each antenna element.

Further, the present invention detects a path length of a feed line to each antenna element and a cable loss by detecting two path timings due to a traveling wave and a reflected wave of a calibration signal output for each transmitter. It is characterized in that the amplitude characteristics and the phase characteristics of the entire transmission apparatus including the transmission device are compensated, and the transmission directivity beam can be accurately controlled.

According to the present invention, the amplitude and the amplitude of each transmitting section can be adjusted without changing the antenna and the calibrating device in order to perform the calibration.
Since the phase fluctuation can be calibrated, the calibration operation becomes easy. Further, by using the reflection at the antenna input end, it is possible to calibrate the amplitude and phase fluctuations of each transmitting device including the feeder line to the antenna with a simple configuration.

[0024]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a partially detailed block diagram of the embodiment of the present invention.

In FIG. 1, the antenna array 101 has N
The antenna elements (102-1 to 102-n) are arranged close to each other so that the antenna correlation is high.

The feed lines (103-1 to 103-n) are connected to the antenna elements (102-1 to 102-n) and the couplers (104-1 to 104-n), respectively. The couplers (104-1 to 104-n) are antenna n transmitting units
(105-1 to 105-n) and a part of the signal (reflected wave) reflected from the antenna elements (102-1 to 102-n) are output to the adder (107). Has functions.

The antenna n transmitting section (105-1 to 105-n) includes a low distortion power amplifier, a band-limited filter, a mixer, a local oscillator,
It is composed of LC (Auto Level Controller), quadrature modulator, analog / digital converter, etc., and has a function to convert the baseband signal coming from the antenna signal processing unit (106-1 to 106-n) into a high frequency transmission signal. .

The antenna signal processing units (106-1 to 106-n) include:
The user signal n and the calibration signal generator n (110-1 to 11
The calibration signal n from 0-n) is input. Each antenna signal processing unit (106-1 to 106-n), for the user signal n, all antenna signal processing units spread by the same spreading code,
The calibration signal n has a function of generating a baseband signal by spreading the calibration signal n using spreading codes different from each other and different from the spreading code used for the user signal n, and then combining the two. It also has a function of compensating for amplitude, phase, and the like by a correction signal input from the correction amount calculation unit (111).

The calibration signal generators (110-1 to 110-n) generate orthogonal code calibration signals required for the calibration operation and output the signals to the antenna signal processors (106-1 to 106-n). The adder (107) has the same number of inputs as n, and outputs the combined signal to the calibration signal receiving unit (108).
Output to

The calibration signal receiving unit (108) includes a low noise amplifier, a band limiting filter, a mixer, a local oscillator, a transmission / reception power detector, an AGC (Auto Gain Controller), a quadrature detector, a low-pass filter, and an analog / digital conversion. The output of the adder (107) as an input, amplification of an input signal, frequency conversion from a radio band to a baseband,
Performs quadrature detection and analog / digital conversion.

The output signal of the calibration signal receiving section (108) is distributed to n and input to the calibration signal processing sections (109-1 to 109-n). The configuration signal processing unit (109-n) has a configuration as shown in the detailed block diagram of FIG.
08) is input to the correlator (201) and the demodulator (204) of each constituent signal processing unit (109-n).

In FIG. 2, a correlator (201) converts a correlation of a desired calibration signal into a delay profile estimator.
(202), a delay profile is generated by the delay profile estimating unit (202), and is output to the path position detection circuit (203). The path position detection circuit (203) detects the path position of the traveling wave of the calibration signal and the path position of the reflection wave of the calibration signal from the delay profile and notifies the demodulator (204) of the path position.

The demodulator (204) receives information on the path position of the traveling wave of the calibration signal and the path position of the reflected wave of the calibration signal from the path position detection circuit (203), and demodulates the baseband signal at the path position. And outputs the traveling wave calibration signal and the reflected wave calibration signal separately. The output two signals are subjected to in-phase addition by the in-phase adder 1 (205) and the in-phase adder 2 (206), respectively, until a required SIR is obtained.

The outputs of the in-phase adder 1 (205) and the in-phase adder 2 (206) are input to a calibration signal calculator (207), and the amplitude and phase are specified. The correction amount calculation unit (111) inputs the amplitude and phase information from each calibration signal processing unit, calculates a correction amount, and notifies the antenna signal processing units (106-1 to 106-n) of the correction information. With the ability to

FIG. 3 is a waveform diagram for explaining a delay profile estimating operation in delay profile estimating section (202). Hereinafter, the operation of the present embodiment will be described with reference to FIGS.
3 will be described. For convenience of explanation, the antenna 1
The following description focuses on the calibration signals described above, but the same applies to the calibration signals of the antennas 2 to n.

The baseband calibration signal generated by the calibration signal generator (110-1) is transmitted to the antenna 1 signal processor (106-1).
After being spread by a spreading code different from the user signal, the signal is combined with the code-spread user signal. At this time, as the spreading code for spreading the calibration signal, different spreading codes are used in the respective antenna signal processing units (106-1 to 106-n).

The combined signal is sent to the antenna 1 transmitting section (105
The frequency is converted and amplified by -1) and output to the coupler (104-1). As the coupler, for example, a coupler having a coupling amount of 20 dB is used.

A part of the transmission wave input to the coupler (104-1) is output to the adder (107) as a traveling wave output. Coupler
The transmission wave passing through (104-1) is fed to the antenna element (102-1) of the antenna array (101) via the feed line (103-1).

Therefore, in the case of the present invention, the calibration signal is also CDMA.
The signal is multiplexed and radiated from the antenna element together with the user signal. However, since the spreading code used for the calibration signal is different from the spreading code used for the user signal, it affects the user signal. Never.

A part of the supplied power is again input to the power supply line (103-1) as a reflected wave. The return loss of each antenna is constant, and is 20 dB here. This reflected wave is input to the coupler (104-1) via the feed line (103-1), and is output to the adder (107) as a reflected wave output.

The traveling wave and the reflected wave input to the adder (107) are CDMA multiplexed by the adder (107), and are calibrated.
The signal is input to (108), converted into baseband by the calibration signal receiving unit (108), and then input to the calibration signal processing unit 1 (109-1).

The signal converted to the base band is supplied to the correlator (201) and the demodulator of each calibration signal processor 1 (109-1) shown in FIG.
(204). The correlator (201) extracts the correlation value of the antenna 1 calibration signal and outputs it to the delay profile estimating unit (202). The delay profile estimator (202) includes a correlator (20
From the correlation signal input in 1), a calibration signal delay profile of a traveling wave calibration signal and a reflection signal calibration signal is estimated, and the result is output to a path position detection circuit (203).

As shown in FIG. 3, the reflected wave always has a delay with respect to the traveling wave, and the amplitude is reduced by the return loss of the antenna and the loss of the coaxial feed line. Therefore, the path position detection circuit (203) sets the path with the first detected large amplitude as the traveling wave calibration signal, and the path with the second detected small amplitude as the reflected wave calibration signal as the path position of the demodulator (204).
Output to

The demodulator (204) demodulates the calibration signal of each of the traveling wave and the reflected wave converted into baseband based on the estimated value. The in-phase adder 1 (205) and the in-phase adder 2 (206) add the in-phase additions of the calibration signals of the traveling wave and the reflected wave to a required SIR (Signal to Interference Ratio).

Since the return loss of the antenna is known, the cable loss can be known from the ratio of the number of in-phase additions of the in-phase adder 1 (205) and the in-phase adder 2 (206).

The number of additions of the in-phase adder 1 (205) is x, the number of additions of the in-phase adder 2 (206) is y, and x: y = 1: 25.
If it is set to 1, y / x = 251. Therefore, the level difference A between the traveling wave and the reflected wave is A = 10 log (y / x) = 10 log (251) = 24 dB.

Since the return loss of the antenna is 20 dB, the loss in the cable is 24-20 = 4 dB. However, the reflected wave passes through the coaxial feed line twice as a traveling wave and a reflected wave. Is 4/2 = 2d
B.

Assuming that the length of the feed line (103-n) is 1, the reflected wave causes a 21 path difference from the traveling wave. Since the speed v at which the calibration signal travels through the power supply line (103-n) is constant, the time t required to travel the distance l is t = 1 / v. Therefore, the path length can be grasped by accurately measuring the delay 2t between the traveling wave and the reflected wave.

The above operation is performed in all the branches 1 to n, and by comparing them, the phase error and the amplitude error of each system, and the phase error and the amplitude error due to the line length error of the feed line can be accurately grasped. Can be done. Based on this, the correction amount is determined by the correction amount calculation unit (111), and the antenna 1 to n signal processing units are determined.
(106-1 to 106-n), the calibration is completed and each system can be compensated.

In the above embodiment, the coupler (104-1)
To 104-n) extract a part of the signal coming from the antenna n transmitting unit (105-1 to 105-n) and a part of the signal reflected from the antenna element (102-1 to 102-n). , Antenna element (102-1
~ 102-n) by extracting only a part of the traveling wave, demodulating a calibration signal from the extracted signal, and adjusting the amplitude characteristic and the phase characteristic of the transmission baseband signal for each antenna element. Calibration of the antenna signal processing unit and the antenna transmission unit can be performed in the same manner as in the conventional example without disconnecting the antenna and the feed line by the switch.

[0051]

According to the present invention, it is not necessary to switch the feed line from the antenna to the calibrating device in order to perform the calibration, so that the calibration can be performed while continuing the communication without interrupting the service.

Further, by using the reflected wave at the antenna input terminal, it is possible to compensate for the amplitude and phase fluctuations of each transmitting device including the feed line to the antenna with a simple configuration.

[Brief description of the drawings]

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

FIG. 2 is a partially detailed block diagram according to the embodiment of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the present invention.

FIG. 4 is a block diagram showing a conventional example.

FIG. 5 is a partially detailed block diagram of a conventional example.

[Explanation of symbols]

101, 301 Array antennas 102-1 to 102-n, 302-1 to 302-n Array antenna elements 103-1 to 103-n, 303-1 to 303-n Feeding lines 104-1 to 104-n Coupler 105 -1 to 105-n, 304-1 to 304-n Antenna 1 to n transmitters 106-1 to 106-n, 305-1 to 305-n Antenna 1 to n signal processor 107, 306 Adders 108, 307 Calibration signal receiving units 109-1 to 109-n, 308-1 to 308-n Calibration signal processing units 110-1 to 110-n, 310-1 to 310-n Calibration signal generation units 111, 309 Correction amount calculation units 201 , 401 correlator 202, 402 delay profile estimator 203, 403 path position detection circuit 204, 404 demodulator 205, 206, 405 in-phase adder 20 , 406 calibration signal calculator

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5J021 AA06 CA06 DB02 DB03 EA04 FA14 FA15 FA16 FA17 FA20 FA32 GA02 HA05 JA10 5K022 EE01 EE21 5K059 AA12 BB01 CC02 DD02 DD10

Claims (5)

[Claims] 1. A user signal spread with the same spreading code for each antenna element of an array antenna and a spreading code different from the spreading code for the user signal, and different for each antenna element. A calibration signal spread by a spreading code is combined with each antenna element and transmitted, and a part of a traveling wave transmitted to each antenna element is extracted, and each antenna is extracted from the extracted traveling wave. By taking a correlation by a spreading code for each element, the calibration signal for each antenna element is independently demodulated, and a transmission signal for each antenna element is based on the demodulated calibration signal for each antenna element. Characterized by adjusting the amplitude characteristic and the phase characteristic of the CD
A method of calibrating a transmission beam pattern of an adaptive array antenna transmission device using the MA system. 2. Extracting a traveling wave of a combined signal transmitted from each of said antenna elements and a reflected wave reflected from each of said antenna elements, detecting two path timings for said calibration signal, The amount of delay between timings,
2. The transmission beam pattern calibrating method for an adaptive array antenna transmitting apparatus using a CDMA system according to claim 1, wherein the calibration including the respective antenna elements is performed by detecting an amplitude difference between the two path timings. . 3. An array antenna including a plurality of antenna elements, a user signal spread by the same spreading code, and a spreading code different from the spreading code for the user signal, and each of the antenna elements has a different spreading code. Means for combining a calibration signal spread by a different spreading code with each of the antenna elements to generate a transmission baseband signal; converting the generated transmission baseband signal to a high frequency and transmitting the signal to each of the antenna elements Means for extracting a part of the traveling wave transmitted to each of the antenna elements and a part of the reflected wave reflected by each of the antenna elements; and for the extracted traveling wave and the reflected wave, Means for independently demodulating the calibration signal by correlating with a spreading code for each of the antenna elements; and Transmission beam pattern calibration method of adaptive array antenna transmitting apparatus using a CDMA system, characterized in that it comprises means for adjusting the amplitude and phase characteristics, the relative transmission baseband signals for each antenna element. 4. A plurality of antenna signal processing units for generating a transmission baseband signal by multiplying a user signal by the same spreading code and multiplying each by a separately set complex coefficient; In an adaptive array antenna transmitting apparatus using a CDMA system having a plurality of antenna transmitting units for converting to a radio frequency, and a plurality of feeder lines and antenna elements respectively connected to the plurality of antenna transmitting units, A calibration signal generation unit for inputting a calibration signal to the antenna signal processing unit; and the antenna transmission unit for outputting a part of a traveling wave output from the antenna transmission unit and a part of a reflected wave from the antenna element. And a plurality of couplers respectively connected between the feeder lines, and an adder for adding outputs of the plurality of couplers, A calibration signal receiving unit that converts the output of the adder into a transmission baseband signal; and a plurality of calibration signal processing units that receive the transmission baseband signal output from the calibration signal receiving unit and generate a calibration signal, respectively. A calibration signal from a plurality of calibration signal processing units is input, and a correction amount for correcting a complex coefficient value individually set to each of the plurality of antenna signal processing units is obtained and notified to the plurality of antenna signal processing units. A correction amount calculating unit, wherein the plurality of antenna signal processing units are such that, for the user signal, all antenna signal processing units are spread by the same spreading code, and the calibration signal is a different spreading code. And a function of generating the transmission baseband signal by combining the two with a spreading code different from the spreading code used for the user signal, and then combining the two. And
The plurality of calibration signal processing units have a function of demodulating the calibration signal by performing a correlation process in correspondence with one of a plurality of spread codes obtained by spreading the calibration signal, respectively. An adaptive array antenna transmitting apparatus using a CDMA system. 5. A correlator for inputting a transmission baseband signal output from the calibration signal receiving section and outputting a correlation value of the calibration signal processing section, and a delay profile based on the correlation value. A delay profile estimating unit that generates a calibration signal, a path position detection circuit that detects the path position of the traveling wave of the calibration signal and the path position of the reflection wave from the delay profile, and the path position information of the traveling wave of the calibration signal and the reflection wave. A demodulator that receives the path position information, demodulates the baseband signal at each path position, and outputs a traveling wave calibration signal and a reflected wave calibration signal, and inputs the traveling wave calibration signal and the reflected wave calibration signal, and A first and a second in-phase adder for performing in-phase addition until the SIR is reached, and an amplitude and a phase specified by the outputs of the first and the second in-phase adders to determine the correction amount calculating unit. The adaptive array antenna transmitting apparatus using a CDMA system according to claim 4, further comprising: a calibration signal calculation unit that outputs the calibration signal to the adaptive array antenna.