JPH02309703A - Adaptive antenna system - Google Patents

Abstract

PURPOSE:To remove an unnecessary wave other than a desired communication signal from an antenna input in a high frequency range by providing a storage device where a digital signal outputted from an A/D converter fast is stored temporarily, inputting the stored signal at calculation intervals of a load calculating means, and calculating and outputting a load value. CONSTITUTION:Outputs x1(n),..., XM(n) of respective A/D converters 11 are stored on the storage device 6. Then the operation is repeated until (b) samples, i.e., x1(n+b),..., xM(n+b) are stored on the storage device 6. The necessary number (b) of sample data is stored on the storage device 6 previously. when sample data that a load calculating means 5 requires are stored on the storage device 6, the load calculating means 5 calculates a load. The sample data input from the respective A/D converters 11 to the storage device 6 is interrupted. Then the load calculating means 5 inputs one sample data from the storage device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an adaptive antenna device, and particularly to an improvement in a signal removal device for removing unnecessary waves other than communication signals in a high frequency band.

[Conventional technology]

FIG.
ROCREDINGS OF THEIERE VOL
"Adaptive Antenna Systems" (ADAPTIV) by B, WIDROW, et al., published in 1967).
E ANTENNA S'/STEMS) is a configuration diagram of a conventional adaptive antenna shown in FIG. 10 is a bandpass filter connected to each receiver 9; 11 is an A/D converter connected to each bandpass filter 10; l is an A/D converter connected to each receiver 9;
A complex multiplier that multiplies the output signal of the D converter 11 by the load control value that is the output signal of the load calculation means 5; 2 is a complex adder that takes the sum of the output signals of each complex multiplier 1; 4 is a complex adder that calculates the sum of the output signals of each complex multiplier 1; a reference signal generator that generates a reference signal that is a strongly correlated signal; 3 a complex subtracter that calculates the difference between the reference signal generated by the reference signal generator 4 and the output signal of the complex adder 2; 5;
is a load calculation means that inputs the output signals of the M A/D converters 11 and the output signal of the complex subtracter 3 and calculates a load control value. In addition, in the figure, s (B indicates the desired wave, J
(t) indicates unnecessary waves, x, (n), ...
, X14 (n) indicates a digital signal that is the output signal of the A/D converter 11, W+ (n), =-,
w, (n) indicate the output signal of the load calculation means 5, xl,
(n) + ”'+ The output signal of the subtracter 3 is shown, and y(n) is the output signal from the complex adder 2. Also, n is a factor indicating the time of the digital signal.Next, the operation will be explained.

The signal received by each antenna element 8 is sent to a receiver 9 through a bandpass filter 10 . The input signal X(n): x passes through the A/D converter 11 and enters the unnecessary wave removing means 7.

(n), −, x, 4 (n). The input signal X is a load control value W(n-1): w, (n), which is calculated by the load calculation means 5 using the input signal X(n-1) one sample before.
..., X14 (n) and is multiplied by each complex multiplier 1. Multiplied signal X' (n): X'+
(n), ++・, X', 4 (n) is complex adder 2
The total sum y (n) is obtained by

X' (n) =X (n-1) ・W (n-1
) ”・(1)y (n) =)(', (n) +・
.--X' Jl (n) -(2) The output signal y (n) of the complex adder 2 is taken out as the output of the adaptive antenna and is also manually input to the complex subtracter 3.

The complex subtracter 3 inputs the output y (n) of the complex adder 2 and the reference signal d (n) output from the reference signal generator 4 that generates a signal having a strong correlation with the desired wave S (t), y
Take the difference between (n) and d (n). The error signal ε(n), which is the output signal of the complex subtracter 3, is input to the load calculation means 5.

ε (n)-d (n)-y (n)
...(3) The load calculation means 5 calculates the load control value W(n) so that 1ε(n)I'' becomes the minimum.The load control value W(n) is ideally 1ener-Hopf. It is found by solving the equation of .Now, Wiener
When the load control value obtained by solving the equation of −11 opf is defined as W, W is expressed by the following equation.

W=R-ku, P...(
4) Here, R is a correlation matrix of the received signal, and P is a correlation vector between the received signal and the reference signal. In general, the following formula % Formula % H: Hermitian conjugate
The operation when using the east-Mean-3quare) algorithm is shown. The LMS algorithm is (7
) is shown in the formula.

W(n+1)=W(n)+ 2 ・u ・e (n)
・X(n) ”(7) μ: Parameter 22 μ is a parameter that controls the convergence speed and stability of the LMS algorithm. e (n) is the output of the complex subtractor 3. LMS algorithm As shown in equation (7), the n+1-order weight value is the n-order antenna input signal X (n) and the error signal e(n).

Estimated from the load value W(n).

When operating this algorithm in a high frequency band, it is necessary to increase the rate at which the A/D converter 11 samples the signal in order to avoid increasing sampling distortion. Therefore, it may become impossible to calculate equation (7) for each sample. At this time, the output signal of the A/D converter 11 during the calculation is ignored. As a result, the algorithm of equation (7) may include sampling intervals where the relationship between the sampling interval of the A/D converter 11 and the signal of frequency 1 input to the A/D converter 11 does not satisfy equation (8). The processing is performed under conditions equivalent to processing the obtained antenna reception signal (hereinafter, the relationship in equation (8) will be referred to as the sampling theorem).

L≦l/(2・r) ...(8
)L:'Sampling interval f:A of A/D converter 11
/D converter 11 input signal frequency Therefore, in this case, control using the load value W(n) of the load calculation means 5 no longer serves the original purpose of removing unnecessary waves. FIG. 7 shows the excitation distribution of the antenna when desired waves and unnecessary waves arrive.

FIG. 7(a) shows the excitation distribution in the initial state where no load is applied to each antenna, and FIG. 7(b) shows the excitation distribution while the A/D converter 11 samples the output signal from the bandpass filter 10. The excitation distribution of the antenna when the load calculation means finishes the calculation of equation (7), FIG. 7(C) shows the load calculation means while the A/D converter 11 samples the output signal from the bandpass filter 10. This is the excitation distribution of the antenna when the calculation of equation (7) is not completed. As shown in FIG. 7(C), when load calculation is performed from a signal that does not satisfy the sampling theorem, control cannot be performed because the input signal does not have information for control, and the antenna pattern is disturbed.

[Problem to be solved by the invention]

Since the conventional adaptive antenna device is configured as described above, when the sampling speed of the A/D converter for digitizing is increased when processing high frequency band signals, the load calculation means is A. /The load value cannot be calculated for each sampling of the D converter. For this reason, A/D
This is equivalent to inputting the output of the converter to the load calculation means once every P samples, and the input signal to the load calculation means is a signal at a sampling rate of 1/P of the sampling rate of the A/D converter. Become. As a result, the input signal to the load calculation means no longer satisfies the sampling theorem, and there is a problem that unnecessary wave removal cannot be controlled using the load value W(n) that is the output of the load calculation means.

This invention was made to solve the above problems, and by having the load calculation means process a signal that satisfies the sampling theorem even when processing a high river wave number band,
An object of the present invention is to obtain an adaptive antenna device that can reliably remove unnecessary waves from antenna input and output only communication signals as antenna output.

[°Means to solve the problem]

The adaptive antenna device according to the present invention is provided with a storage device that temporarily stores digital signals outputted at high speed from an A/D converter, inputs the stored signals to the load calculation means at every calculation interval, and calculates the load value. By means of calculating and outputting , unnecessary waves other than the desired communication signal are removed from the antenna input in a high frequency band.

[Effect]

In this invention, a storage device is provided to temporarily store a digital signal that is the output of an A/D converter, and the stored signal is manually input to the load calculation means at each calculation interval to calculate and output a load value. Because of this, even if a signal in a high frequency band is sampled at high speed so as to satisfy the sampling theorem, it is stored and stored in the storage device, so a signal that satisfies the sampling theorem can always be output at each calculation interval of the load calculation means. Thereby, the load calculation means can calculate a load value that reliably removes unnecessary waves without removing the desired communication signal from the antenna input, and only the desired communication signal can be obtained as the antenna output.

〔Example〕

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

FIG. 1 is a block diagram showing the configuration of an adaptive antenna device according to an embodiment of the present invention. In the figure, 8 is M antenna elements that receive incoming signals, and 9 is connected to each antenna element 8. M receivers, 10 M bandpass filters connected to each receiver 9, 11 an A/D converter connected to each bandpass filter 10, 1
2 are M complex multipliers that multiply the output signal of each A/D converter by the load control value obtained by the unnecessary wave removal means 7; 2 is a complex adder that calculates the sum of the outputs of each complex multiplier 1; 7 is an unnecessary wave removing means that obtains the load control value from the output signal of the A/D converter 11.

Further, FIG. 2 is a diagram showing details of the configuration of the unnecessary wave removing means 7 in FIG.
A storage device for temporarily storing the output signal of the D converter 11, 1
Reference numeral 2 denotes M complex multipliers that multiply the output signal of the storage device 6 by the load value determined by the load calculation means 5, 13 a complex adder that calculates the sum of the outputs of each complex multiplier 12, and 4 generates a reference signal. 3 is a complex subtracter for calculating the difference between the output signals of the complex adder 13 and the reference signal generator 4;
is a load calculation means that inputs the output signal of the storage device 6 and the output signal of the complex subtracter 3 to obtain the load control value.

In addition, in FIGS. 1 and 2, 5(t) indicates the desired wave, and J
(t) indicates an unnecessary wave, x, (n), . . .

x, (n) indicate digital signals that are output signals of the A/D converter 11, W, (n), ..., W6 (n) indicate output signals of the A/D converter 11, and “1(n),・
..., x', 4 (n) represents the output signal of the complex multiplier 12, d (n) represents the reference signal that is the output signal of the reference signal generator 4, and ε(n) represents the output signal of the complex subtracter 3. y'(n) indicates the output signal from the complex adder 13, and y(n) indicates the output signal from the complex adder 2. Further, n is a factor indicating the time of the digital signal.

Next, the operation will be explained.

Since the operations other than the operation of the unnecessary wave removing means 7 are the same as those of the conventional device, the operation of the unnecessary wave removing means 7 will be described in detail here.

The operation of the unnecessary wave removing means is performed according to the flowchart shown in FIG. As shown in 14, the outputs x, (n), . . . , x, 4 (n) of each A/D converter 11 are stored in the storage device 6. Then, as shown in 15, the storage device 6 stores b samples to be processed by the load calculation means 5, that is, x
, (n+b),=z Repeat the operations in 14.15 until XM(n+b) is stored. The required number of sample data is stored in the storage device 6 in advance. When the sample data necessary for the load calculation means 5 is stored in the storage device 6, load calculation is performed by the load calculation means 5 as shown at 16-19. First, as shown in 16, each A/D
Sample data input from converter 11 to storage device 6 is interrupted. Thereafter, the load calculation means 5 inputs one sample data from the storage device as shown at 17. Then, as shown in 18, the load value w, (n+i), =, WN (n+
i) is calculated using, for example, (7)2. At this time, the load calculation means 5 uses the output signal ε(n+i) of the complex subtracter 3. The calculated load value w, (n+i), -, W
M (n+ i) is complex multiplier 1 and complex multiplier 1
2 is output. In the complex multiplier 1, the outputs X, (P), ..., x, (P) of the A/D converter and the load value wl(r
l+i), ..., ws (n+i), the complex adder 2 calculates the sum of these, and the antenna output y (n
).

The complex multiplier 12 receives the next output data X from the storage device 6.
I (n+i+1), -, Output to device 3. The complex subtracter 3 subtracts the output d (n+i+1) of the reference signal generator 4 from the input signal y' (n+i+1) from the complex adder 13 . Then, the output ε(n+i+1) is input to the load calculation means 5. These processes 16 to 19 are performed b times and the process returns to process 14 again.

In this way, in this embodiment, A/
A storage device 6 for storing the output signal of the D converter 11 is provided, and a means for calculating the load value separately from the calculation processing of the antenna output is provided. Even if the D converter 11 is used, the load calculation means 5 always processes the input signal that satisfies the sampling theorem, and the unnecessary wave removal means 7 increases the gain in the communication signal direction as shown in FIG. 7(b) and eliminates unnecessary waves. It is possible to output a load value W(n) that controls the excitation distribution so as to suppress .

In addition, in the above embodiment, LMS (Least-Mean-5qu) is used as the calculation algorithm in the load calculation means.
However, by adding the calculation assisting means 20 to the load calculation means 5 in the unnecessary wave removal means 7 as shown in FIG. 4, the R L S ( Recursive-Least-S
quares) algorithm can be used.

ε(n) = d (n) -W(n-1)' -X
(n) −(9)W (n) =W(n-1)+e
(n) ・K (n) =OO)P (n) =λ
・P (n-1) -λ-K (n) ・X (n) ”-P(n-1)
-02) H: Hermitian determinant, P is (MX...,M] matrix, K is (MX 1 ”
) matrix, X is a (MXI) matrix, W is a (MX 1 ) matrix, λ is a constant, and d (n) is a reference signal. The RLS algorithm differs from the LMS algorithm in that the equations θ■, (II), and O'lJ are used instead of the equation (7).

Here, equation (11) is division, equation 02 is (MX...,
M] Since it includes matrix operations, the amount of calculations is larger than that of the LMS algorithm. The calculation assisting means 20 is a means for assisting the above-mentioned division and matrix operations. This calculation auxiliary means 20 can reduce the calculation time that increases when the RLS algorithm is used. From the above, by adding the calculation assisting means 20, it is possible to implement an adaptive antenna device using the RLS algorithm. FIG. 5 shows the effects of the adaptive antenna device using the RLS algorithm.

In the figure, the vertical axis is the root mean square value of the error signal shown in equations (3) and (9), and the horizontal axis is the number of iterations of the algorithm. In the figure, θ is the LMS algorithm, and shi is the RL
This is a change in the mean squared error obtained by substituting the load value W calculated by the S algorithm into equation 03) with respect to the number of algorithm iterations.

E(ε”) −E (d2)+W”・R, W−2・P
”W...θ3) As seen in Figure 5, the mean square error of the RLS algorithm is reduced with fewer iterations than the LMS algorithm. This indicates that the convergence performance of the RLS algorithm is superior to the LMS algorithm. In this way, by adding the calculation assisting means 20, it is possible to realize an adder/bubble antenna device using the RLS algorithm with excellent convergence performance.

〔Effect of the invention〕

As described above, according to the present invention, since the adaptive antenna device is provided with a storage device for storing the output of the A/D converter, the A/D converter has a high sampling speed corresponding to the frequency band of the signal to be processed. Even if it is used, it is effective to remove only unnecessary waves without suppressing communication signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an adaptive antenna device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of unnecessary wave removal means, which is one of the components of the adaptive antenna device shown in FIG. , FIG. 3 is a flowchart showing the control operation of the unnecessary wave removing means, and FIG. 4 is a block diagram showing the configuration of the unnecessary wave removing means, which is one of the components of the adaptive antenna device according to the second embodiment of the present invention. , FIG. 5 is a diagram showing a learning curve comparing the convergence performance of the RLS algorithm and the LMS algorithm, FIG. 6 is a block diagram showing a conventional adaptive antenna device, and FIG. 7 is an excitation distribution diagram of the adaptive antenna device. 1 is a complex multiplier, 2 is a complex adder, 3 is a complex subtracter, 4
is a reference signal generator, 5 is a load calculation means, 6 is a storage device,
7 is an unnecessary wave removal means, 8 is an antenna element, 9 is a receiver,
1o is a band pass filter, 11 is an A/D converter, 12
1 is a complex multiplier, 13 is a complex adder, and 20 is a calculation aid. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) M antenna elements, M receivers connected to each antenna element, M A/D converters connected to each receiver, and digital data of each A/D converter. In an adaptive antenna device that simultaneously receives a signal output and outputs a weight value for removing unnecessary waves other than communication signals from the antenna input, the adaptive antenna device uses the communication signal as an antenna output. The device outputs M×L digital signals x_i(1) to sequentially output from each of the M A/D converters during L samples.
It shall be equipped with a load calculation means that temporarily stores x_i(L) [i: 1, 2, . . . , M], adds this stored signal and a reference signal, and calculates a load value. An adaptive antenna device featuring: