JPH0410761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a receiving device using an array antenna, in which electric fields in directions other than the desired direction (hereinafter referred to as desired signal waves) are not received based on the received signals of each antenna element. Antenna excitation load (applying arbitrary amplitude and phase changes to each signal received by multiple antenna elements)
This invention concerns an improvement of an adaptive antenna device that automatically determines the

When there is directional noise such as interference waves other than the desired signal wave in the received electric field, in order to receive only the desired signal wave without being affected by these waves, adjust the excitation load of the antenna and remove the interference. It is necessary to reduce the antenna gain in the wave direction to zero.

The adaptive antenna device achieves this function by performing a learning operation and adaptation based on the input signal from each antenna element obtained from each range cell within the pulse repetition period.

A conventional device of this type was constructed as shown in FIG. FIG. 1 shows a two-element adaptive antenna device. In the figure, 1 and 2 are antenna elements, and the signals received by these antennas 1 and 2 are mixed with a sine wave generated by a local oscillator 3 and mixers 4 and 5 to give _an intermediate frequency ( IF) and is further amplified by IF signal amplifiers 6 and 7. Moreover, this
For the IF signal, a sine wave with a frequency ω ₀ lower than ω _IF generated by the local oscillator 8 is mixed by mixers 9 and 10, and the passing frequency ω _IF −ω ₀ is mixed.
After passing through the bandpass filters 11 and 12, IF signals x ₁₀ and x ₂₀ having a center frequency ω _IF −ω ₀ are obtained. x ₁₀ ,
x ₂₀ is the complex envelope value of the signal. (Hereafter, all symbols for IF signals mean complex envelope values.), 1
3 and 14 are mixers that mix the signal x ₁₀ and the load w ₁ and the signal x ₂₀ and the load w ₂ . The two mixed signals pass through an adder 15 and are added, and then pass through a bandpass filter 16 with a passband frequency ω _IF to obtain a signal with a frequency ω _IF .
An IF output signal y is obtained. The IF output signal y is mixed with the signals x ₁₀ and x ₂₀ by mixers 17 and 18 to become signals v ₁ and v ₂ with a center frequency ω _0. After passing through load generators 19 and 20, the loads w ₁ and w ₂ are generated. The mixers 13 and 14 and the adder 15 again generate a weighted sum of the signals to provide feedback of the output signal y. Although the configuration of the load generator 19 or 20 will be described later, control signals S ^* ₁ and S ^* ₂ for forming the main beam having the frequency ω ₀ are also input thereto. signal S ^* ₁ ,
S ^* ₂ is for generating the antenna main beam in the desired direction, and its value is the conjugate complex value of the phase shift S ₁ and S _{2 that occurs in the signals received by antennas 1 and 2} depending on the direction of the desired signal. (* represents a conjugate complex number). Further, 21 is a phase control signal generator attached to the array antenna for generating control signals S ^* ₁ and S ^* ₂ , and in the case of Fig. 1,
When the distance between antennas 1 and 2 is d, the wavelength of the desired radio wave is λ, and the angle of arrival direction of the desired radio wave with respect to the front direction of the antenna is θ, the phase shift instruction signal ₁ is ₁ = 0 ₂ = -2π/λdsinθ. , ₂ . Furthermore, 22 and 23 are phase shifters for the IF signal of frequency ω ₀ and output signals S ^* ₁ and S ^* ₂ with phase changes of ₁ and ₂ , respectively. This signal is input to load generators 19 and 20.

Next, in Fig. 2, the load generator 19 (or 20)
The configuration is shown below. First, 24 is an adder with a center frequency ω ₀ of 2 for the load generator 19 (or 20).
Add two IF signals v ₁ (or v ₂ ) and S ^* ₁ (or S ^* ₂ ). 25, which inputs this output signal, is a narrow band filter that allows only the signal of frequency ω ₀ to pass through. Further, 26 is a band amplifier with a frequency ω ₀ , which generates a load w ₁ (or w ₂ ) with a frequency ω ₀ as its output. The loads w ₁ and w ₂ are fed back through mixers 13 and 14.

In order to analyze the operation of this adaptive antenna device in the IF band, the following vectors w = [w ₁ , w ₂ ] ^T ……(1) x = [x ₁₀ , x ₂₀ ] ^T ……(2) Consider s=[S ₁ , S ₂ ] ^T ...(3). (However, T means vector transposition.) If the time constant of the narrow band filter 25 is τ and the gain of the band amplifier is g, the differential equation regarding w is given as follows.

τdw/dt+w=g(s ^* −x ^* y) ...(4) By the way, since the output signal y is given by y=x ^T w ...(5), equation (4) becomes as follows. τdw/dt+(I+gx ^{* xT} )w=gs ^* ...(6) However, I is a 2×2 unit matrix.

Here, if the input signal is a narrowband signal, x ^* x ^T in equation (6) will be a nearly constant value, and the matrix I + gx ^*
Since x ^T becomes a positive definite Hermitian matrix, the solution to equation (6) converges. The load at that time is given as follows.

w=(I+gR) ^-1・gs ^* ...(7) Therefore, if g is large enough, w=R ^-1 s ^* ...(8). However, R is a correlation matrix of the signal x.

In the above configuration, if the input signal x is a wideband signal, the value of x ^* x ^T will not be constant, and the weight w, which is the solution to equation (6), will not necessarily converge to a constant value, and therefore the output There is a possibility that the interference wave in the signal y cannot be completely removed.

In order to overcome the drawbacks of the above-described adaptive antenna device, the present invention has been improved as follows. That is, for input signals x ₁₀ and x ₂₀ as given in FIG.
7 and 28 to obtain new signals x ₁₁ and x ₂₁ , and the signal
In the same way as the output signal y was generated from x ₁₀ and x ₂₀ , the signal y ₁ is obtained from the signals x ₁₁ and x ₂₁ using mixers 29 and 30, an adder 31, and a bandpass filter 32. . Also, this signal is sent to mixers 33 and 34.
is mixed with the signals x ₁₁ and x ₂₁ through adder 3
5, 36, the load generators 19, 20
Let us generate an input signal to By doing this, the time average of x * x ^T is taken instead of the instantaneous value of signal x ^{* x T} in Fig. 1, and the correlation matrix of signal x is R = E {x ^* x ^T } can be estimated with higher stability, so the weight w can be determined correctly even for a wideband input signal. To state this accurately, it is as follows.
Now, if we consider the vector x ₀ = [x ₁₀ , x ₂₀ ] ^T = x ... (9) x ₁ = [x ₁₁ , x ₂₁ ] ^T ... (10), then in the circuit of Fig. The differential equation regarding the load w is as follows.

τdw/dt+w=g(s ^* −x ^* _{0 y0} −x ^* _{1 y1} )…(11) However, _y0 =y. Furthermore, since the signals y ₀ and y ₁ are as follows: y ₀ =x ^T ₀ w (12) y ₁ =x ^T ₁ w (13), equation (11) becomes as follows.

τdw/dt+{I+g(x ^* _0xT0 +x ^{* 1xT1} )}w=gs ^* ...(14 ⁾ Therefore, as the _estimated value of _the correlation _matrix R of the signal x, R=1/2(x ^* ₀ x ^T ₀ + x ^* ₁ x ^T ₁ )...(15) Since the moving average value can be used, even if the input signal x becomes wideband, the value of the correlation matrix R is low-pass filtered and becomes a constant value. The load w, which is the solution of the differential equation given by equation (14), can stably converge to a constant value as time increases.

The above method can be further expanded by increasing the number of delay stages to N stages (N1) depending on the band of the signal to be processed. That is, the nth stage (n
= 1, 2, ..., N) the output signal of the delay circuit x _o
Then, the differential equation regarding the load w becomes τdw/dt+(I+g _N 〓 ⁿ⁼⁰ x ^* _o x ^T _o ) w=gs ^* (16). If the number of delay stages is increased, the fluctuation of the coefficient in equation (16) will become smaller and stable, but
On the other hand, since the delay in estimating the correlation matrix R due to filtering becomes large, it is necessary to set the number of stages to such an extent that the delay does not become a problem.

As described above, in the adaptive antenna device according to the present invention, it is possible to appropriately adapt the load even to a wideband input signal, and effective cancellation of interference waves can be expected.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional adaptive antenna device, FIG. 2 is a detailed configuration diagram of a load generator used therein, and FIG. 3 is a diagram of a correlation loop for load control of an adaptive antenna device according to the present invention. FIG. In the figure, 1 and 2 are array antenna elements,
3, 8 are local oscillators, 4, 5, 9, 11, 13,
14, 17, 18, 29, 30, 33, 34 are mixers, 6, 7, 26 are IF band amplifiers, 10,
12, 16, 32 are IF band band filters, 1
9, 20 are load generators, 21 are phase control signal generators, 22, 23 are phase shifters, 15, 24, 31, 3
5 and 36 are adders, 25 is a narrow band filter, 2
7 and 28 are delay elements. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1 It has an array antenna, an element that can apply arbitrary changes in amplitude and phase as an excitation load to each signal received by the antenna element, and a correlation loop for controlling the antenna excitation load. , an adaptive antenna that can adaptively control the antenna excitation load so that the influence of electric fields in directions other than the desired direction is canceled out at the output based on the received signal of each antenna element obtained from each range cell within the pulse repetition period. In the device, a signal obtained from a range cell within a pulse repetition period is extracted as a received signal in a correlation loop configuration circuit that controls the antenna excitation load, and a delay element is used to extract a signal obtained from a range cell that is the same as the range cell from which the received signal was extracted. The received signals obtained from other range cells within the pulse repetition period of and further includes a circuit that feeds back a signal obtained by adding this delayed output signal and an output signal which is a weighted sum with respect to the original received signal by an adder as an antenna excitation load value through a correlation loop, It is possible to obtain the correlation matrix for the input signal from the antenna element by low-pass filtering using a moving average using delay, and it is characterized by obtaining a stable antenna excitation load even for wideband input signals. Adaptive antenna device.