JPH0260272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a direction finding device in which a plurality of element antennas are arranged in a line.

[Conventional technology]

Conventionally, there has been a device of this type as shown in FIG. This device performs a rough square search using a sum beam and a fine square search using an amplitude comparison of two beams.

The n element antennas 1a to 1n are arranged linearly with an interval d from each other to form an antenna aperture, and are divided into two groups, an aperture surface A and an aperture surface B, each having n/2 elements. Ru. Opening planes A and B
The outputs of the element antennas 1a to 1g (g=n/2) and 1h to 1n (h=n/2+1) that constitute the correspond to the respective groups via respective phase shifters 2a to 2g and 2h to 2n. are connected to distributors 3a and 3b. The output of the distributor 3a is connected to the input terminal 6a of the 90° hybrid 6, and the output of the distributor 3b is connected to the input terminal 6a of the 90° hybrid 6.
The output of 90° hybrid 6 is passed through 90° phase shifter 5
is connected to the input terminal 6b of. The output terminals of the 90° hybrid 6 are connected to input terminals 7a and 7b of a signal processor 71.

Next, the operation will be explained.

First, the phase φ _i of the i-th phase shifter 2i (i=1...n) is φ _i =(i-1)2πd/λsinθ(i=1, 2,...n)...
(1). Here λ is the wavelength,
θ is the azimuth angle. When the phase shift amount of the 90° phase shifter 5 is set to 90° and a radio wave arrives from the direction θ, the input terminal 7b receives the output from the distributor 3a and the output via the 90° phase shifter 5. A sum beam is output by combining the output from the distributor 3b, that is, the waves received by the aperture surface A and the aperture surface B in the same phase. This sum beam has a level as shown in FIG. 2 when the azimuth is plotted on the horizontal axis.

Next, the phase shift amount of the 90° phase shifter 5 is set to 0°, and when the relative phase difference between the input terminals 6a and 6b of the 90° hybrid 6 is +90°, the phase shift amount of the 90° phase shifter 5 is set to 0°. When the relative phase difference between input terminals 6a and 6b is -90°, the received waves from aperture surface A and aperture surface B are combined and derived to input terminal 7b. Therefore, the azimuth angles θ a and θ _b of the beam nose as seen from the input terminals 7 a and 7 _b are respectively θ _a = sin ^-1 (sin θ + λ/2nd) ...(2) θ _b = sin ^-1 (sin θ - λ/ 2πd) …(3).

That is, as shown in Figure 2, compared to the direction θ of the sum beam, θ _a is to the left, and θ _b is to the right, |θ _a
The L and R beams are shifted by −θ|, |θ _b −θ|, and the cross point of both beams approximately coincides with the direction θ of the sum beam.

Next, the procedure for detecting the direction will be explained with reference to FIG. First, in order to perform the rough measurement shown in Fig. 3a, the phase shift amount of the 90° phase shifter 5 is set to 90°, and
While changing the phase of ~2n, move the sum beam to the azimuth θ.
Scanning is performed sequentially from the − side to the azimuth θ+ side. During this time, the direction θ _t at which the received power at the input terminal 7b is maximum is known, and this is taken as the approximate direction of the target. i at this time
The phase φ _i of the th phase shifter 2i is φ _i =(i−1)2πd/λsinθ _t (i=1, 2...n)...(
4) It is becoming.

Next, in order to perform the precise measurement shown in Figure 3b, the phase of the 90° phase shifter 5 is set to 0°, and the input terminals 7a and 7b receive the R beam at θ _t and the L beam at θ _t , respectively. The signal processor 71 calculates the true bearing (target bearing) θ _t ' based on the received power difference Δ between both input terminals 7a and 7b.

However, in the direction θ _{t ,} there are not only the sum beam of the azimuth θ _t but also various side lobes of the sum beam between the azimuths θ− and θ+. If the direction of the sum beam of the beam with the highest side lobe among these side lobes is θ _e , and the level difference between the sum beam of θ _t and the sum beam of θ _e is L, then from the direction θ _e If the time fluctuation width of the radio waves arriving from the target is larger than L within the time it takes to scan the beam up to θ _t , it is said that the received power due to the side lobe in the azimuth θ _e is greater than the received power due to the sum beam in the azimuth θ _t . A situation arises that results in a false orientation in the orientation θ _e .

Conventional direction finding devices are configured as described above, so especially when trying to detect the side lobes of a target, there are often situations where the time variation in the arrival level is larger than the side lobe ratio of the array antenna. The disadvantage is that the two-beam precision measurement system has little value because the probability of a false heading occurring during rough measurement is extremely high.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional antennas as described above, and a changeover switch is added between one of the element antennas and the phase shifter and at the output terminal of the hybrid. When performing rough measurement using the sum beam, select the output of one of the element antennas using the switch, and compare the output of this one with the sum beam from the remaining element antennas using a signal processor to detect false signals. It is an object of the present invention to provide a highly accurate direction finding device that can reduce the probability of direction occurrence and fully utilize the usefulness of precise direction finding using two beams.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to the drawings. In FIG. 4, 8 is a changeover switch;
The terminal COM is connected to the element antenna 1a, and the terminal NO
is connected to the phase shifter 2a, and the terminal NC is connected to the terminal NC of the changeover switch 11 via the power supply line 9 and the attenuator 10a. In addition, the terminal of the changeover switch 11
NO is connected to one output terminal of the 90° hybrid 6 via an attenuator 10b, and the terminal COM is connected to the input terminal 7a of the signal processor 7.
Furthermore, an attenuator 1 is connected between the other output terminal of the 90° hybrid 6 and the input terminal 7b of the signal processor 7.
0c is inserted.

Next, the operation will be explained using FIG. 5.

When using the sum beam for coarse measurement, select switch 8.
and 11 terminals COM at the positions shown in the figure.
Turn to NC side. As a result, an element beam generated only by the element antenna 1a appears at the input terminal 7a,
A sum beam of an array pattern of (n-1) elements formed by the element antennas 1b to 1n appears at the other input terminal 7b. The envelope of this sum beam and the envelope of the side lobes have a shape roughly along the element beam. Therefore, as shown in FIG. 5, the level difference δ between the envelope of the element beam and the envelope of the side lobe does not depend much on the orientation and is a substantially constant value. Furthermore, since attenuators 10a, 10b, and 10c are connected to each input terminal 7a and 7b, the level difference δ is between attenuator 10a and attenuator 10c.
By selecting the amount of attenuation, the optimum value can be set.

The signal processor 7 receives the reception level of the element beam of the antenna 1a, that is, the reception level of the input terminal 7a, and the reception level of the sum beam, that is, the reception level of the input terminal 7b.
If the latter is lower than the former, the data is invalid.

In other words, compare the reception levels of both sides, and if the latter is lower than the former, it is a false heading, and the data at this time is discarded as invalid, and the reception level of the sum beam is higher. Continue scanning until the bearing is found. In addition, the input terminal 7b
In this case, the reception level of the sum beam including not only the side lobes of the sum beam but also the main lobe is inputted to the input terminal 7b according to the direction.

The level difference δ between the element beam and the side lobe is always maintained at a constant level difference δ even if the power level arriving from the target varies over time, so the received radio waves due to the side lobe will never become valid data. , are all rejected, eliminating the occurrence of false orientations seen in conventional devices. When the approximate direction is found, both the changeover switches 8 and 11 are switched to the NO side, and precise direction finding is performed as in the conventional case.

Furthermore, as described above, since the level difference δ is a substantially constant value δ even when the azimuth changes, it is easy to set the optimum value, and the configuration of the subsequent signal processor 7 as a sidelobe canceller circuit is easy. Since it is also simple, processing speed can be increased,
A high-performance direction finding device can be realized by combining this method with a precision direction finding system using two beams.

In the above embodiment, the beam of the element antenna 1a is used as a sidelobe canceller, but other element antennas may be used. Also,
As shown in FIG. 6, instead of the changeover switch 8, a directional coupler 12 is connected to the element antenna 1a and the phase shifter 2.
a, and the element beam of the element antenna 1a may be input to a separate input terminal 7c for amplitude comparison. In this case, the coarse square search method is the same as in the above embodiment (of course, there is no switch switching operation in this case), and the fine square search is performed in the same way as in the conventional case. .

[Effects of the Invention] As described above, according to the present invention, the beams of the element antennas constituting the array antenna can be switched and used, and the beam from a specific element antenna and the sum beam from the remaining element antennas can be used. Since the direction finding device was configured for comparison, it is possible to perform coarse direction finding with ease of processing and high accuracy.
This has the effect of providing a high-performance direction finding device that makes the existence of a beam precision direction finding system significant.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional direction finding device, Fig. 2 is a diagram of the sum beam, R beam, and L beam, and Fig. 3 is a diagram explaining the direction finding procedure by the conventional direction finding device.
FIG. 4 is a block diagram of a direction finding device according to an embodiment of the present invention, FIG. 5 is a diagram explaining the direction finding procedure of the direction finding device according to an embodiment of the present invention, and FIG. FIG. 2 is a block diagram of an embodiment. 1a, 1b to 1n...element antenna, 2a, 2
b~2n...phase shifter (first phase shifter), 3a, 3
b...Distributor, 5...90° phase shifter (second phase shifter), 6...90° hybrid, 7... Signal processor, 8, 11... Changeover switch, 10a, 10
b, 10c...attenuator, 12...directional coupler.
In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A plurality of linearly arranged element antennas, a plurality of first phase shifters into which the outputs of the respective element antennas are introduced, and the outputs of the respective phase shifters are divided into two groups. first and second distributors introduced separately;
A second phase shifter that shifts the phase of the output of the first distributor by a predetermined phase, and an output of the second phase shifter and an output of the second distributor are introduced. In a direction finding device that performs a coarse direction search that determines the approximate direction of a received wave using a sum beam and a precise direction search that determines the true direction by comparing the amplitudes of two beams, the coarse direction search described above a first switch that disconnects a specific element antenna among the plurality of element antennas and the first phase shifter corresponding to the specific element antenna when performing the above; When the connection between the specific element antenna and the first phase shifter is disconnected by the switch, the output of the specific element antenna introduced via the first switch and one of the hybrid a second switch that outputs the output of the specific element antenna by switching between the output terminal of the antenna and the output terminal of the antenna;
This second phase shifter is changed while changing the phase of the first phase shifter.
Compare the output of the specific element antenna introduced through the switch with the output of the sum beam from the plurality of element antennas other than the specific element antenna introduced through the other output terminal of the hybrid. If the output of the sum beam is lower than the output of the specific element antenna, it is determined to be a false orientation, and if the output of the sum beam is higher than the output of the specific element antenna, the above outline is determined. After determining the direction and detecting the general direction, the first switch is switched to connect the specific element antenna to the first phase shifter, and the second switch is switched to the hybrid side. A direction finding device comprising: a signal processor that executes the precise direction finding. 2. A plurality of linearly arranged element antennas, a plurality of first phase shifters into which the outputs of each of the above-mentioned element antennas are introduced, and a first phase shifter into which the outputs of each of the above-mentioned phase shifters are divided into two groups and introduced. and a second distributor;
A second phase shifter that shifts the phase of the output of the first distributor by a predetermined phase, and an output of the second phase shifter and an output of the second distributor are introduced. In the direction finding device, which performs a coarse direction finding that determines the approximate direction of a received wave using a sum beam and a precise direction finding that determines the true direction by comparing the amplitudes of two beams, the plurality of element antennas described above. a directional coupler that is provided between a specific element antenna and the first phase shifter corresponding to the specific element antenna, and guides the output of the specific element antenna to the outside during a rough direction search; and the output of the specific element antenna led to the outside of this directional coupler while changing the phase of the first phase shifter, and other than the specific element antenna introduced through the output terminal of the hybrid. The output of the sum beam from the plurality of element antennas is compared, and if the output of the sum beam is lower than the output of the specific element antenna, it is determined to be a false orientation, and the direction of the specific element antenna is determined to be false. When the output of the sum beam is higher than the output, the general direction is determined, and after the general direction is detected, the specified direction is inputted through the directional coupler and the first phase shifter. The output of the first divider containing the output of the element antenna and the output of the second divider which passed through the second phase shifter whose phase was set to 0° were introduced, and the hybrid outputted. The phase difference between the above two groups is ±
A direction finding device characterized by comprising: a signal processor that executes the precise direction finding described above to determine the true direction based on the difference in the amplitude of the composite wave having an angle of 90 degrees.