JPS5940278A - Radar apparatus - Google Patents

Abstract

PURPOSE:To prevent the narrowing of the angle measuring range of an angle of elevation even when a radar has an altitude, by mounting a phase shifter for applying predetermined phase shift to each antenna of an array open sampling system radar. CONSTITUTION:The outputs of antennas of a radar having an array open sampling system arranged at equal intervals (d) are subjected to phase-shifting only by a phase (2pi dHi)/(lambdaR) (wherein Hi is the altitude of the radar, lambda is a transmission wavelength, R is the distance of an object and the radar and i is an antenna number) by a phase shifter 14. By this phase-shifting, a radar beam directed direction is brought to a direction for making the object and an object image due to reflection at a sea level or the like symmetric with respect to said radar directed direction and the radar altitude comes to substantially zero. Therefore, even when the radar has the antenna altitude, the angle measuring range of an angle elevation does not become narrow.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a radar device that tracks targets located at low elevation angles.

First, a conventional tracking radar device will be explained with reference to the drawings. 1st
The figure shows the configuration of a conventional tracking radar device.
11 is a stabilized local oscillator (STALO: 5Table
+21 is a coherent oscillator, (3) is a phase detector, (4) is a gate circuit, (5) is a pulse modulator, (6) is a distributor, (7)
is an amplifier, (8) is a circulator, (9) is a mixer,
α1 is the intermediate frequency (Fr
Equency; Engineering F) Amplifier (hereinafter referred to as NIP amplifier), ■ is a 90° phase shifter, nz is an antenna, 01
is a calculator.

Now, coherent oscillator (OOHO: 0OHeren)
The continuous wave of RF output from the stabilized local oscillator (11)
(Racli.

It is mixed with a continuous wave (Frequency) by a mixer (9).

The output of this mixer (9) is pulse-modulated by a pulse modulator (5) and reaches a 1-distributor (6). At this time, the distributor (
6), it is assumed that N distributions are performed. This distributor (6)
The outputs of each are amplified by an amplifier (7), passed through a circulator (8), and are radiated as radio waves from the antenna 02. The radiated radio waves are reflected by the target, and the antenna port z
reach. At this time, if the target exists at a low elevation angle altitude, as shown in Figure 2, the reflected wave from the target T will be the direct wave W1 that reaches the antenna α2, as well as the reflected wave from the image T', that is, the sea surface or It consists of a reflected wave W2 reflected by the ground, and a so-called multipath effect occurs.

The signal is then input to the mixer (9) via the circulator (8) again. By the way, mixer (9) receives 4
The signals from No. 1 and the stabilizing local excavator (11 are mixed, x
After being converted to p, the signal is input to the amplifier a0. engineering p
The output of the amplifier section is distributed to two phase detectors (3),
In one phase detector, the output is mixed with the output from the coherent oscillator (2), and after passing through the gate circuit (4), the amplitude 1 phase component of the received signal No. 4 from the target is extracted, resulting in a 9 complex signal V1. The actual part work 1 is obtained. In the other phase detector, the output of the coherent oscillator (2) is mixed with the output of the amplifier (I[1) via a 90° phase shifter aυ, and its output is sent from the target via the gate circuit (4). The amplitude 9 phase components of the received signal 4 are extracted and the imaginary part Q1 of the complex signal ■1 is obtained.Similarly, the (N-1)O antenna α
2, the complex signal v9. Real part H-1t Imaginary part QH-1
e At the antenna α2 of N, the real part of the complex signal VN8.
The imaginary part Qy is obtained respectively. Such a complex signal ■1
．． v2. . . , ■ are input into the calculator alpha device. Computer 0 uses these complex signals to perform calculations to estimate the direction of arrival of direct wave W1 from among the waves arriving at antenna III that have undergone multipath effects, and calculates the estimated elevation angle value A of the target.
Output.

By the way, in this calculation, it is assumed that the number n of arrival directions of radio waves to the antenna 12 is known, and the above-mentioned complex signal 7 is
1. V, ..., v+i, and the antenna's y-index cuff 1 obtained when n radio waves arrive at directions virtually
Find the arrival direction of the radio waves that minimizes the difference between #, 72/, , -1, and 7N/. Among these directions of arrival, the direction with the largest elevation angle is estimated to be the direction of arrival of the direct wave.

For convenience of explanation, it is assumed that n = 2 and that there is one image of the target and one image of the target relative to the sea surface or the ground,
The elevation angles of the target and image seen from antenna 02 are α1. If α2 is used, then α1 and α2 must be λ λ 17 stones <α1. α2×11... (1) must be satisfied. Here λ is the transmission wavelength.

α represents the interval between the antennas when the antennas O3 are arranged at equal intervals. If antenna a'a is located at an altitude H relative to the sea surface or the ground, α2 is -12■ α2 ”” tan (u % tanα1), where R is the ground distance from antenna Q2 to the target.
... is given by (2).

Therefore, from equation (2), Iα2 becomes α1, and the range of the measurable elevation angle α1 of the target is determined only by α2 from equation (1). Therefore, the angle measurement range of α1 becomes narrower than when H==Q.

In order to improve this drawback, the present invention inserts a phase shifter between each antenna and the transmitter/receiver, and will be described in detail below with reference to the drawings. FIG. 3 is a configuration diagram of a radar device showing an embodiment of the present invention. The difference from FIG. 2 is that a phase shifter α] is inserted between the distributor (6) and the amplifier (7). . The signal flow is almost the same as in the conventional case shown in FIG. 1, but it is assumed that the phase of the output of each antenna 02 can be changed during reception by a phase shifter na.

For example, when the antennas are arranged at equal intervals, λ is the spacing d9 transmission wavelength between the antennas, H is the radar altitude from the sea surface or ground, and R is the distance from the radar to the target.
The phase given to phase shifter I is based on +1 antenna port z, the phase of the phase shifter connected to +-2 antenna port z is 2πd, and the phase of the phase shifter connected to H/λR1+3 antenna QX5 is 2πd. 4πd, H/λR9+N antenna (the phase of the phase shifter connected to 12 is set to 2π(N-1)dH/
If λR is used, it is equivalent to directing the beam in the direction shown by the single point confusion in FIG.

Therefore, the target and image are located at symmetrical positions with respect to this dot-dashed line, and α
The absolute values of 1 and α2 are equal. Therefore, even if the radar altitude H takes a certain value, the same angle measurement range as when n=Q can be obtained.

As described above, in the radar device according to the present invention, by using the shift phase, even when the altitude of the radar has a certain value, the angle measurement range can be kept constant without narrowing.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional radar device, Fig. 2 is a diagram showing the relationship between the radar, a target, and an image, Fig. 3 is a block diagram of a radar device according to the present invention, and Fig. 4 is a diagram in which the antenna beam direction is tilted. This is a diagram showing this. In the figure, (1) is a female local oscillator, (2) is a coherent oscillator, (3) is a phase detector, (41 is a gate circuit,
(5) is a pulse modulator, (61U distributor, (7) is an amplifier, (8) is a circulator, (9) is a mixer, Q (
I is an intermediate frequency amplifier, wholesale is a 90° phase shifter, O3 is an antenna, and α is a computer. G4 is a phase shifter, T is a target, T' is an image, Wl is a direct wave, w2 is a reflected wave from the sea surface, and A is an estimated angle measurement value. Note that the same or corresponding parts in FIG. 9 are designated by the same reference numerals. Agent Tsutomu Kuzuno - Figure 1'z W2 Z#-/ Qu-r IN (bt 2nd
Figure 3

Claims (1)

[Claims] A radar device using an array open sampling method for determining the angle of a target, which includes a phase shifter between each of the arrayed N antennas and a transmitter/receiver to determine the distance between the target and the radar. is R, the altitude of the radar is ■, the distance between the antennas when the above antennas are arranged at equal intervals is d, and the transmission wavelength is λ.
When. For each of the above N phase shifters, the phase is 2π(lH1/λ
A radar device characterized in that it is configured to give R (1=1.2...,N).