JPS604873A - Azimuth detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to detect the azimuth of a radar radio wave with low pulse repeating frequency and to attain to enhance sensitivity without enlarging an apparatus, by operating an approximate azimuth and a detailed azimuth to an arrival radio wave. CONSTITUTION:The antennae of an antenna group 10a corresponding through a receiver 3a are successively connected to the memory circuits of an approximate azimuth operating circuit 11a for definite time while antennae similarily corresponding through a receiver 3b are successively connected to memory circuits for a definite time. In this case, a demodulated level is stored in each memory circuit 5. When the change-over of change-over switches 2a, 4a and 2b, 4b is thoroughly completed, operators 8a, 8b respectively use two high level informations among level informations to calculate an approximate azimuth. In the next step, an operator 6 determines a detailed azimuth on the basis of each approximate azimuth information.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an azimuth detection device that uses a plurality of antennas and detects the direction of arrival of incoming radio waves by utilizing the output level difference from each antenna.

A first example of a conventional direction finding device of this type that uses eight antennas is shown in FIG. In the figure, antennas 1a to 1h have the same characteristics, and are arranged at 45° intervals in the horizontal plane. Reference numeral 2 designates a changeover switch that sequentially changes over the eight antennas 1a to 1h, 3 represents a receiver, and 4 represents a changeover switch that successively changes over the demodulated output from the reception Ia3. 5a
5h is a storage circuit for storing the demodulated signal level from the receiver 3, and 6 is a storage circuit 5a to 5h of the 8 (Ill).
This is a calculation unit that calculates the direction of arrival of incoming radio waves from the level information from. In addition, a computing unit 7 inputs the switching timing of the changeover switch 2.4 and the storage information of the storage circuits 5a to 5h.
It is a command unit that specifies the timing at which a command is received.

Next, the operation will be explained. The changeover switches 2 and 4 are switched in conjunction with each other according to the designation of the command unit 7, and the corresponding antennas and memory circuits are successively connected via the receiver 3 for a certain period of time. That is, each of the antennas 1a to 1h and each of the memory circuits 5a to 5h are sequentially connected via the receiver 3 for a certain period of time. As a result, the signals captured by each of the antennas 1a to 1h are processed by the receiver 3 and stored in the storage circuits 5a to 5h corresponding to each level.

When the changeover switches 2 and 4 have been switched once, the computing unit 6 receives the storage level information of the storage circuits 5a to 5h in response to a command from the command unit 7, and the computing unit 6 determines the direction of arrival from this level information. calculate.

Next, a method of calculating the direction will be explained. Now antenna 1
a to 1h are respectively 0' and 45° in the horizontal plane.

90°, 135', 180', 225', 270", 3
Assume that they are aligned at an angle of 15°. The output level pattern of each antenna at this time is as shown in FIG. However, this diagram uses the basic 0 to avoid complexity.
Only the antenna patterns in the ° and 45° directions are shown as solid lines,
Others are indicated by broken lines.

First, the arithmetic unit 6 determines that the internal output level of the antennas 1a to 1h is 1.
The second and second strongest ones are found from the level information in the memory circuits 5a to 5h, and the approximate direction of arrival is determined. Note that the direction of arrival is the angle between the two antennas found.

Next, the detailed direction of arrival is calculated from the difference between the two levels. The calculation is as follows. Here, since all the antennas have the same characteristics, the pattern of two adjacent antennas is P1 = Acos θ P 2 = Acos” (θ-45°) PL, P2 is the output level (power) from the antenna, θ is the direction of arrival of radio waves (0°≦θ≦45°)
, n are real numbers.

It can be approximated as Determine the detailed direction of arrival between adjacent antennas.

Conventional direction finding devices are configured as described above, so they must search the entire circumference of the antenna group by switching the antennas one after another.For example, they must search the entire circumference of the antenna group. When attempting to detect the arrival direction of radio waves, it is necessary to switch antennas at a time when each antenna can reliably receive at least one pulse.

For example, when trying to detect the arrival direction of radio waves with a pulse repetition frequency of at least 200 Hz (pulse interval 5 m5), it is necessary to stop each antenna for 5 rrls, so with 8 antennas, the switching time is 5 m5 x 8
= 4.0ms or more is required. On the other hand, direction detection is impossible unless the antenna of 8111iI is switched once during the time when the radar radio waves are pointing towards us.

Therefore, in the conventional device described above, if the beam width of the radar is 2 degrees, the direction can be detected only for radar radio waves with a rotation speed of 8.3 rpm or less. In addition, since the conventional device switches the antenna, it has drawbacks such as azimuth detection errors due to input level fluctuations over time.

A second example of a conventional direction finding device using eight antennas is shown in FIG. This conventional device does not switch antennas, and has as many circuits from the antennas to the memory circuits in parallel as there are antennas, so the drawbacks of the first conventional example are completely eliminated.

However, on the other hand, the number of receivers increases and the equipment becomes larger.

In order to avoid this, the receiver is not a tuning type, but a simple wideband direct detection receiver is used to suppress the size of the device. However, since the direct detection receiver has a reception sensitivity that is 10 dB or more lower than that of a tuned receiver, it naturally has the disadvantage that the reception sensitivity of the device is also lower.

This invention has been made to eliminate the above-mentioned drawbacks, and includes a plurality of approximate azimuth calculation circuits that calculate the approximate arrival direction of incoming radio waves, and a plurality of approximate azimuth calculation circuits that calculate the approximate arrival azimuth of incoming radio waves, and both ends of the overlapping angle portion of the approximate azimuth by each of these calculation circuits. By providing a detailed azimuth calculation circuit that calculates the detailed direction of arrival of the incoming radio waves based on the captured signal level of the antenna, it is possible to achieve high sensitivity, a rotation speed of 16 rpm or more, and a pulse repetition frequency of 20, without increasing the size of the device.
It is an object of the present invention to provide a direction detection device that can also detect the direction of radar radio waves of 0 Hz or less.

An embodiment of the present invention will be described below with reference to the drawings. Fourth
In the figure, 1a to 1h are eight antennas with the same characteristics arranged radially on the same plane at intervals of 45 degrees, with angles of 0 degrees and 45 inches, respectively.

90°, 135”, 180°, 225°, 270°31
They are arranged in a 5° direction (see Fig. 5 fal (bl)), and 2a is an antenna la arranged every 90'.

A changeover switch 2b switches between the first antenna group 10a consisting of Ic, Ie, and Ig, and a changeover switch 2b switches between the second antenna group 10b consisting of antennas lb, Id, If, and 1h arranged every 90°. , 3a and 3b are receivers, 4a is a changeover switch for changing over the output of the receiver 3a, and 4b is a changeover switch for changing over the output of the receiver 3b.

5a, 5c, 5e, and 5g are the antennas la.

This is a storage circuit that demodulates the strength of each signal captured by lc, le, and Ig by receiver 3a, and then stores the strength as level information, and similarly, 5b, 5d, 5f, 5
h indicates the antennas 1b and 1a.

This is a storage circuit that stores each signal strength captured by 1f and 1h as level information.

And 8a is the memory circuit 5a, 5c, 5e.

8b is an arithmetic unit that calculates the approximate direction of arrival of an incoming radio wave from the storage level information in 5g; similarly, 8b is a storage circuit 5b, 5d,
This is a calculation unit that calculates the approximate direction of arrival from the storage level information in 5f and 5h, and in this way, the area surrounded by the dashed line in the figure determines which of the antennas in the 1st and 2nd antenna groups 10a and 10b will be captured. The first step is to determine the angle between the antennas that captured the 1st and 2nd highest signal levels as the approximate direction of arrival of the radio waves. A second general azimuth calculation circuit 11a, llb is configured.

Reference numeral 6 denotes a computing unit that precisely determines the direction of arrival of radio waves from the level information from the two computing units 8a and 8b, which is similar to the computing unit 1.6. This is a detailed azimuth calculation circuit that calculates the detailed arrival azimuth using the captured signal levels of the antennas at both ends of the overlapping angle portion of the rough azimuth determined by the second general azimuth calculation circuits 11a and 11b.

In addition, 7 is a changeover switch 'la, 4a and a changeover switch 2
b, 4b switching timing, arithmetic unit 8a is memory circuit 5a
, 5c, 5e, and 5g, the timing at which the arithmetic unit 8b receives level information from the memory circuits 5b, 5d, 5f, and 5h, and the timing at which the arithmetic unit 6 receives level information from the arithmetic units 8a and 8b. It is a command unit that specifies the timing of receiving.

Next, the operation will be explained. First, the switches 2a and 4a are switched in conjunction with each other according to the instruction from the command unit 7, and the receiver 3a
The corresponding antenna and memory circuit (antenna la,
Memory circuits 5a, 5c, 5e, 5 for lc, le, Ig
g corresponds to each. ) are connected sequentially for a certain period of time, and similarly the corresponding antennas and memory circuits (storage circuit 5b for antennas lb, ld, If, lh) are connected via the receiver 3b.
.

5, d, 5f, and 5h correspond to each other. ) are connected sequentially for a certain period of time.

As a result, the signals captured by each of the antennas la, lc, le, and Ig are demodulated by the receiver 3a, and each level is stored in the corresponding storage circuit 5a.

5c, 5e, and 5g. Similarly, antenna Ib,
The captured signals of ld, If, and lh are demodulated by the receiver 3b,
Each level is stored in the memory circuits 5b and 5d.

5f and 5h, respectively.

and switch 'la, 4. When the switching of a, 2b, and 4b completes, the arithmetic unit 8a receives the level information from the memory circuits 5a, 5c, 5e, and 5g according to the instructions of the instruction unit 7.
Arithmetic unit 8b receives level information from storage circuits 5a, 5d, 5f, and 5h, and each of these arithmetic units 8a, 8b determines the general direction using two pieces of level information having higher levels. This allows the direction of arrival to be narrowed down to 1/4 quadrant, that is, 90°.

Figure 5 (al~(di) is a model showing how the approximate direction is determined when the direction of arrival of radio waves is between 0° and 45°; .The approximate azimuth determined by the second approximate azimuth calculation circuits 11a and llb is shown.

Next, the arithmetic unit 6 receives the above-mentioned general azimuth information according to the command from the command unit 7, determines the rough azimuth from these two pieces of general azimuth information, and narrows down the arrival azimuth to 1/8 quadrant, ff1J, 45°. As an example, FIG. 5(e) shows a case where there is an incoming radio wave between 0° and 45°, in which the overlapping angle portion of the above-mentioned general direction is determined to be the rough direction.

Furthermore, based on this rough azimuth data, the antenna la is set.

1, c, 1e, and Ig, and antenna 1b,
From ld, If, and lh, select two mutually adjacent antennas of one fine needle, that is, the antennas located at both ends of the overlapping angle portion (in the example of Fig. 5, select the antennas in the 0° direction and the 45° direction. The antennas Ia, 1b)L are then connected via the command unit 7 to the switch 2a so that the selected antenna 211M and its corresponding memory circuit are always connected.

Command 2b, 4a, 4b.

As a result, the above 1. Second general direction calculation circuit 11a, l
The above selected antennas l'a, l in each of lb
Two series of circuits are formed from b to memory circuits 5a and 5b, and operate in parallel without antenna switching. Also, this selected antenna la.

1b are adjacent to each other, the above-mentioned equation (1) can be applied, and the detailed orientation can be calculated using the equation (11).

In this way, in this embodiment, the receiving system has two systems, so the number of switching contacts in the circuit is 1/1 compared to the first conventional example.
2, the switching time for making one round of antennas can be halved, and the direction of incoming radio waves can be detected even when the number of rotations of the other party's radar is twice as high.

Furthermore, at the stage of detecting the detailed direction of arrival, there is no switching of antennas, and the two receiving systems operate in parallel, so even if the level of arriving radio waves changes over time, there are no errors in direction detection. .

Furthermore, compared to the second conventional example, the number of receivers is reduced to 1/1.
4, the device can be made smaller. Also,
Since the number of receivers is small, even if the receiver is a high-sensitivity tuning type, the size of the device will not be significantly increased, and the device can be made to have high sensitivity at a low cost.

In the above embodiment, the calculation units 8a and 8b each determine the approximate direction, and the calculation unit 6 determines the rough direction. However, the calculation unit 8
Detect the maximum level of each of a and '8 b, and set the coarse direction between the angles facing each antenna captured at the maximum level, and fix the two antennas for detailed direction detection. The same effect can be obtained with an antenna that captures at maximum level.

Furthermore, in the above embodiment, a case was explained in which two series of general direction calculation circuits were provided, but the number of series of the calculation circuits is not limited to this, and may be any number as long as n (≧2), and the more the number of series increases, the more Sensitivity can be improved.

As described above, according to the present invention, the incoming radio wave is determined by the plurality of approximate azimuth calculation circuits that determine the approximate arrival direction of the incoming radio wave, and the captured signal levels of the antennas at both ends of the overlapping angle portion of the approximate azimuth by each of these calculation circuits. A detailed azimuth calculation circuit that calculates the detailed direction of arrival is installed, so the device does not become large.
Even radar radio waves with a high rotational speed and a low pulse repetition frequency can detect their direction, and have the effect of greatly improving sensitivity.

[Brief explanation of the drawing]

1 and 3 are block diagrams of a conventional direction finding device, and FIG. 2 is an antenna pattern diagram for explaining its operation.
FIG. 4 is a block diagram of a direction finding device according to an embodiment of the present invention, and FIG. 5 (al to tel are diagrams for explaining its operation. 1a to 1h...antenna, 3a, 3b... ·Receiving machine,
5a to 5h...memory circuit, 6...detailed direction calculation circuit, 10a, 10b...first. Second antenna group, 11a
. 11b... 1st. Second general direction calculation circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Figure 2 1δO−

Claims (1)

[Claims] (1) A plurality of antennas arranged radially on the same plane at predetermined angular intervals, and among the antennas, antennas are arranged at angular intervals n (≧2) times the predetermined angular interval. One receiver for receiving the captured signal of each antenna of the $n antenna group, and a plurality of storage circuits for storing the captured signal levels of the corresponding antennas in the same number as the antennas of the first to nth antenna groups, and 1 of the captured signal levels
．． The angle between the antennas that captured the second highest one is determined to be the approximate arrival direction of the incoming radio wave.The first to rl$! Detailed azimuth calculation that calculates the detailed arrival azimuth of the incoming radio wave based on the captured signal levels of the antennas at both ends of the overlapping angle portion of the approximate azimuth determined by the I approximate azimuth calculation circuit and the first to n$l II approximate azimuth calculation circuits. A direction finding device characterized by comprising a circuit.