JPS5931013B2 - Receive beamformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receive beamformer that is used in conjunction with nonuniform receiver play and has a broadband and interference wave removal function.

In passive sonar, in order to detect broadband signals, it is desirable to use a receiver array with constant directional gain over a wide band.

An example of a receiver array with such characteristics is a non-uniformly spaced linear array in which the receivers are arranged densely in the center of the array but sparsely arranged at the edges of the array.

Now, FIG. 1 is a block diagram of a conventional receive beamformer that uses an unevenly spaced linear array to generate a receive beam with constant directional gain over a wide band.
is the receiver array, 21, 2□... is the receiver, 3□,
32... are amplifiers, 40, 42... are shading filters, 5□, 52... are delay lines, 6 is an adder, and 7 is an output terminal.

That is, in the receiving beam frame configured in this way, the signals received by the receivers 21, 2, . . . are sent to the amplifiers 31 for each channel.

3□... is amplified to an appropriate level, then passed through shading filters 41, 42..., and propagation delay compensation is performed in delay lines 51, 52..., and then the adder 6 is added for all channels and output to the output terminal 7.

Here, shading filter 4. ．． 42...ha...
In the high frequency range, only the output signals of the receivers arranged in the center of the play are used effectively, and in the low frequency range, the output signals of the receivers of the entire array are used effectively. The amplitude response is determined as follows.

In other words, the shading filters corresponding to the receivers at the ends of the array have low-pass characteristics that have gain only in the low frequency range, and the shading filters corresponding to the receivers located at the center have low-pass characteristics. has the characteristics of a high-pass type with low gain in the low frequency range and high gain in the high frequency range, and the shading filter corresponding to the receiver in the middle has the characteristics of the band-pass type between the above two filters. to have.

However, the phase characteristics are linear phase, and the delays are chosen equally for all channels.

However, a filter with such characteristics can be easily realized using a finite impulse response digital filter.

By this method, the receive beamformer can form a receive beam with constant directional gain over a wide band and can be used to detect wide band directional signals.

However, the conventional receiving beamformer as described above has the disadvantage that when a noise source is near the receiver array 10, interference waves generated from this noise source interfere, reducing the signal detection ability. Ta.

The present invention has been made in view of the above points, and an object of the present invention is to provide a receiving beamformer that has a function of suppressing interference waves while maintaining broadband performance, and is capable of improving signal detection ability.

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

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

In this figure, 111 to 11 are input terminals, 121 to 11 are input terminals, and 121 to 11 are input terminals.
12 is a shading filter with linear phase characteristics to which input terminals 111 to 11k are connected; 13, to 1;
3 is a delay line connected to the output of the shading filters 121 to 12 for propagation delay compensation for interference waves;
4 is an adder for beam formation of interference waves, in which all outputs of delay lines 131 to 13 are connected to inputs; 151 to 1;
5 is a filter whose input is commonly connected to the output of the adder 14.

Further, 16 and 16 are connected to the outputs of the delay lines 131 to 13 and are used to compensate for the amount of delay to the filters 151 to 15, and 171 to 17 are connected to the outputs of the delay lines 161 to 16, respectively. a subtractor, 181-18, with the output and each output of the filter 151-15 connected to two inputs;
are connected to the outputs of the subtractors 171 to 17, and each has a delay time equal to the difference between a fixed delay time and the delay time of the delay lines 13□ to 13, and 191 to 19 are connected to the delay lines 18 , ~18, and is used to compensate for the propagation speed of the signal wave; 20 is the delay line 191~1;
9 is an adder connected to all outputs, and 21 is an output terminal connected to the output of adder 20.

In the receiving beamformer configured in this way,
The received signals of the channels obtained from the receivers in the non-uniformly spaced linear array are input to the input terminals 111 to 11, respectively.
k.

This received signal is then filtered through a shading filter 12.
~12k, then delay line 13. 13k, and then added for all channels by an adder 14, whereby a broadband receiving beam output for interference waves can be obtained in the same manner as in the conventional case shown in FIG.

Next, the output signal of this adder 14 is filtered by filters 151 to 1.
5k is subtracted from the output signals of delay lines 131 to 13 passed to delay lines 161 to 16k using subtracters 17° to 17k. Interfering wave components are removed.

After that, the output signals to the subtracters 17, .about.17 are output to the delay line 1.
8□ to 18k to cancel the influence on delay lines 13□ to 13, pass through delay lines 191 to 19k to compensate for the propagation delay of the signal wave, and further adder 20 for all channels. O is added and output to the output terminal 21. Here, in order to ideally perform interference wave removal, the amplitude characteristics of the filters 15 to 15 are expressed as Hk(f)-Wk(f)/(Wl( f) Ten...
...Wk(f)) (k=1.....,k)
...(1), and its phase characteristics are linear and have equal delays.

However, ■(f), . . . , Wdf) is the amplitude characteristic of the shading filters 121 to 12.

In this way, if it is assumed that each channel contains interference waves of equal amplitude and the propagation delay is completely compensated for by the delay lines 131 to 13k, the output signal of the adder 14 will be The amplitude of the interference wave included is (% (f)) based on the values at input terminals 111 to 11k.
+W2(f)+...''=Wηf)).

On the other hand, the amplitudes of the interference waves included in the output signals from the delay lines 16 and 16 are w, (f),...Wk(
f).

Therefore, if the filters 151 to 15k have the amplitude characteristics expressed by equation (1), the 2
Since the amplitudes of the interference waves at the two inputs are equal and the delays are combined by the delay lines 161 to 16k,
Interference waves are completely removed on the output side of the subtracters 171-17.

On the other hand, for signal components, when the number K of receivers is large, the gain of the filters 15□ to 15 becomes small, so that the path including the filters 151 to 15k can be ignored.

Therefore, a wideband reception beam can be formed for the signal component, almost the same as in the conventional system shown in FIG.

In this way, in the reception beamformer described above, interference waves incident from a specific direction can be removed while forming a broadband reception beam using the shading filters 121 to 12k. It is also possible to generate a receiving beam that can detect broadband signals without the influence of interference waves.

In addition, in the above reception beamformer, the delay line 19
By switching the delay times from □ to 19, the direction of the main beam can be changed.

Also, delay lines 191 to 19k, adder 20, output terminal 2
By having multiple systems consisting of 1 in parallel, multiple standby systems can also generate beams.

Additionally, delay line 13. ~13 and delay line 18, ~1
By changing the delay time of 8 in conjunction, the direction of the interference wave to be removed can also be changed.

Although the delay lines 18□, 191, . . . , 18 and 19k have been explained separately, they can actually be realized as one.

As explained above in the embodiments, the receiving beamformer of the present invention performs propagation delay compensation for interference waves on the output signals of the shading filter group to which the output signals of the non-uniformly spaced linear receiver array are input. means and its output signal, the amplitude characteristic of each shading filter is expressed as Wl(
f),..., When starting with WK(f), Hk(f)=Wk(f)/ (W, (f)+...+
WK(f) ) (k=1.2...,K) The output signals of these and each output signal of the delay compensation means are passed through a filter having an amplitude characteristic of After performing delay compensation for canceling the propagation delay compensation for the interference wave and propagation delay compensation for the signal wave on the output signal of this subtractor group, all Since it generates a wideband receiving beam while removing interference waves, it is possible to detect weak signals in a wideband even in an environment with strong interference waves.

Therefore, if applied to passive sonar, the multi-target characteristics can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional receiving beamformer.
FIG. 2 is a block diagram showing an embodiment of a receive beamformer according to the present invention. 111-11k...input terminal, 12. ~12k...
Shading filter, 13, ~13k...delay line, 14...adder, 15□~15k...filter,
161-16k...delay line, 17□-17k...subtractor, 18□-18k, 191-19k...delay line, 20...adder, 21...output terminal.

Claims (1)

[Claims] 1K receivers are used with non-uniformly spaced linear receiver plays arranged densely in the center and sparsely arranged at the ends, and for the receivers at the ends of the array. This receiver array is combined into a group of shading filters that have the following characteristics: a low-pass type for the receiver in the center, a high-pass type for the receiver in the center, and a band-pass type for the receiver in the middle. a receiving beamformer for passing the output signal of the shading filter group, the receiving beamformer comprising means for performing propagation delay compensation for interference waves on the output signal of the shading filter group, and a means for transmitting the output signal to the amplitude characteristic of each shading filter as Wl(f). ,... When WK(f), Hk(f)=Wk(f)/(Wl(a) 10...+W
K(f)) (k=1.2...,K) The output signals of these and each output signal of the delay compensation means are passed through a filter having an amplitude characteristic of After performing delay compensation for canceling the propagation delay compensation for the interference wave and propagation delay compensation for the signal wave on the output signal of this subtractor group, all and means for adding the output signals of the receiver beamformer.