JPH0259432B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides an electronically scanned array radar that uses multiple STC (Sensitivity Time Control)
The present invention relates to a radar device that switches characteristics in accordance with beam scanning and enables dynamic range processing of received power from each beam.

FIG. 1 shows the configuration of a conventional general radar device, and FIG. 2a shows a two-dimensional radar coverage diagram. Normally, in this type of radar, the received power is controlled using STC characteristics as shown in Figure 3, so that the received power from the level flight target is at a nearly uniform level from long distance to short distance. ing.

In FIG. 1, the first intermediate frequency transmission type signal and the first local oscillation frequency generated by the reference signal generation circuit 7 are frequency-mixed by the transmitter 6, become a transmission signal, and pass through the transmission/reception switch 8 to the primary radiation. The light is radiated into space from the reflecting mirror 17 via the vessel 16.

In this way, a portion of the transmitted signal radiated in a predetermined direction is reflected by the target, and is input to the receiver system via the reflector 17, the primary radiator 16, and the transmitter/receiver switch 8, respectively. Become.

First, the high frequency amplifier circuit 9 amplifies the first signal with low noise.
After being mixed with the first local oscillation frequency from the reference signal generation circuit 7 in the mixing circuit 10 and converted into a first intermediate frequency signal, the second local oscillation frequency also from the reference signal generation circuit 7 is mixed in the second mixing circuit 11. The signal is mixed with the intermediate frequency signal and converted into a second intermediate frequency signal, which is input to the intermediate frequency amplification circuit 12. The intermediate frequency signal amplified by the intermediate frequency amplification circuit 12 is sent to the reference signal generation circuit 7.
Gain control is performed using the STC signal generated by the STC generation circuit A 13 by a trigger from , and target information is detected and sent to the signal processing circuit 14 and displayed on the display circuit 15 .

In conventional two-dimensional radar equipment, as shown in Figure 2a, the required coverage area is simultaneously covered by the fan beam, so that at a certain distance, regardless of whether the target is at high altitude or low altitude, As shown in Fig. 3, only one type of STC attenuation can be applied, and therefore, when trying to match the receiving dynamic range and low altitude target received power, there was a drawback that the high altitude target received power was overkilled.

That is, the above will be explained in more detail with reference to FIG. 2b. FIG. 2b shows equal reception power lines superimposed on the vertical in-plane coverage area. In other words, in conventional two-dimensional radar equipment, the fan and the
It forms a beam (cosec ² θ characteristics, etc.). This means that the distribution of the minimum received power (S ₀ ) for detecting a target is designed to be outside the coverage boundary so that there is not much margin.

When entering inside from the equal signal power boundary of this received power (=S ₀ ), the received power intensity increases in proportion to the distance R ⁴ .

The equal received power lines of such increasing powers S ₁ , S ₂ . . . , S ₆ have a similar relationship to the equal received power lines of the received power (=S ₀ ).

When considering a high altitude (H _h ) target and a low altitude (Hl) target, changes in received power intensity occur as shown in FIG. 2b as the distance changes. Considering the reception dynamic range as shown in Figure 2b, STC attenuation = α ₁ (dB) at distance R ₁ for a low altitude target
It turns out that is required.

However, since this type of STC attenuation is commonly applied to high-altitude targets, there has been a problem in the past in that unnecessary attenuation (over-attenuation) is applied.

The above drawbacks are unavoidable in a two-dimensional radar system that uses a fan beam, but the present invention provides an electronically scanned array radar that electronically scans a beam within a required coverage area. By sequentially switching multiple STC characteristics using sequential beam scanning, it is possible to match the received power with the receiving dynamic range from both low-altitude and high-altitude targets. The purpose of the present invention is to provide a radar device that can improve the detection rate.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram showing an embodiment of the present invention.

The difference between FIG. 4 and FIG. 1 is that the two-dimensional antenna consists of a reflecting mirror 17 and a primary radiator 16, a primary radiator 1, a phase shifter 2, a distribution circuit 3, a phase shifter driving circuit 4, and a beam control system. The change to a phased array antenna consisting of circuit 5 and the conventional STC
STC generation circuit A, 1 that generated one characteristic
Instead of 3, it has multiple STC characteristics with different characteristics, and can be switched according to the beam scanning angle to obtain the desired
The point is that the STC generation circuit B, 18 that generates the STC characteristics is used. In this STC generation circuit B, 18,
It is equipped with multiple STC circuits with different characteristics, and has built-in switching means for switching these STC circuits according to the beam scanning angle. In other words, conventionally 1
This differs from the conventional one in that a plurality of STC circuits with different characteristics are provided, and the STC circuits are switched by a switching means in accordance with the beam scanning angle, instead of using one STC generating circuit A, 13.

Next, the operation of the electronically scanned array radar device to which the STC generation circuit B, 18 having built-in switching means for switching between a plurality of (two) STC circuits having different characteristics in accordance with the beam scanning angle will be explained. The first intermediate frequency transmission signal and the first local oscillation frequency generated by the reference signal generation circuit 7 are frequency-mixed by the transmitter 6 to become a transmission signal, which is divided into n by the distribution circuit 3 via the transmission/reception switching device 8. , given a predetermined phase shift amount in the phase shifter 2, and is radiated into space from the primary radiator 1.

The phase shift setting amount of the above-mentioned phase shifter 2 is determined based on the beam scanning angle command and timing from the reference signal generation circuit 7, and the beam control circuit 5 sets each phase shifter 21...
2n and is given via the drive circuit 4.

The transmission signal thus radiated in a predetermined direction is partially reflected by the target and passes through the primary radiator 1, phase shifter 2, distribution circuit 3, and transmission/reception switch 8 to the receiver system. It becomes input.

Thereafter, the received signal is transmitted to the high frequency amplification circuit 9, the first mixing circuit 10, as in the conventional case shown in FIG.
Intermediate frequency amplification circuit 1 via second mixing circuit 11
2 is input. The intermediate frequency signal amplified by the intermediate frequency amplification circuit 12 is gain controlled by the STC signal selected by the STC generation circuit B, 18 by a trigger from the reference signal generation circuit 7, and is sent to the signal processing circuit 14. Target detection is performed and displayed on the display circuit 15.

Here, Fig. 5 is an explanatory diagram illustrating a situation in which an electronically scanned array radar is scanning in a vertical plane, and Fig. 6 shows two types of STC characteristics,
FIG. 2 is an explanatory diagram showing a case in which the method is switched and applied in a time-division manner.

That is, it is applied to STC: #1 beam to #(j-1) beam and STC: #j beam to #n beam.

In Figure 5, the target is low altitude (Hl) and high altitude (Hh).
The purpose of STC operation will be explained using an example of a case in which:

Figure 7 shows that the received power from a high altitude (Hh) target is measured in a relatively high elevation beam, and Figure 8 shows that the received power from a low altitude (Hl) target is measured in a relatively low elevation beam. It shows that it will be done.

Furthermore, when comparing the reception level at a short distance (for example, R=R ₁ in the figure), the level is higher in the low elevation angle beam in FIG. 8, and this tendency is also seen when R<R ₁ . In this case, the amount of attenuation required to keep the received power within the receive dynamic range
STC must be larger in the case of Figure 8 for the same distance. FIGS. 7 and 8 show a state in which the received power of each beam is approximately adjusted to the upper limit of the receiving dynamic range by applying the STC characteristics, respectively.

The above will be explained in more detail with reference to FIG. FIG. 9 shows a beam array superimposed on the coverage area in the vertical plane, and each beam shape shows an equal reception power line with the minimum reception power S ₀ so that the required coverage area can be detected.
Once inside this boundary, the received power intensity increases in proportion to the distance ^R4 . For example, assume that the distance that a low-altitude target passes through the beam nose elevation angle of lowest beam #1 is "γl,1".

The received power strength at this point is expressed as S= _S0 ·(Rmax, 1/γl, 1) ⁴ .

In Fig. 9, the received power intensities from low-altitude targets and high-altitude targets at distance R ₁ are expressed as Sl, respectively.
4, Sh, _o-3 .

Here, at distance R ₁ , the low altitude target is near the beam nose of #4 beam, and the high altitude target is # _o-3
By being located near the beam nose of the beam, the above-mentioned subscript is attached.

Sl, 4, Sh, _o-3 are respectively Sl, 4=S ₀・(Rmax, 4/R ₁ ) ⁴ Sh, _o-3 = S ₀・(Rmax, n-3/R ₁ ) ⁴ , Rmax, 4>Rmax, n-3, the relationship Sl, 4>Sh, n-3 holds true.

If, as shown in Figure 9, Sl, 4, Sh, and n-3 all have the reception dynamic range upper limit value Smax
For beam #4 when exceeding [αl, 1],
(dB) #n-3 beam [αh, 1]
(dB) may be applied as the STC attenuation strength.
αl,1 and αh,1 are as shown in FIG.

here, αl, 1 = 10log (Sl, 4/Smax) [dB] αh, 1 = 10log (Sh, n-3/Smax) [dB] αl, 1 > αh, 1 It is.

As described above, when the beam is sequentially scanned electronically in the elevation direction within the required coverage area, the beam pattern differs depending on the elevation angle, so the received power intensity is adjusted to the reception dynamics for the target at the same distance.
In order to match the range, it is necessary to change the STC attenuation intensity in accordance with the beam or beam group that captures the target, and for this purpose, multiple STC characteristics (STC,) with different characteristics are provided, and the beam scanning The STC characteristics are sequentially switched in response to the

The above describes the case where two stages are applied as the STC characteristic, but it is clear that multiple stages can generally be applied finely. In addition to scanning array radar,
It is clear that the present invention can be applied to all other electronically scanned array radars such as frequency scanned array radars and phase/frequency composite array radars.

As described above, according to the present invention, an electronically scanned array radar is provided with a plurality of STC characteristics, and these are sequentially switched in response to beam scanning in the vertical plane (not necessarily for each beam, but for some STC characteristics). (including switching for each beam group), the received power from the target within the desired coverage area is matched to the receiving dynamic range without over-attenuation, making it possible to improve the detection rate.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a conventional radar using a fan beam, Fig. 2a is a coverage diagram showing the vertical plane coverage area by the configuration of Fig.
Figure b is an explanatory diagram in which equal reception power lines are superimposed on the vertical coverage area in the configuration of Figure 1, Figure 3 is an explanatory diagram showing an example of the STC characteristics in the configuration of Figure 1, and Figure 4 is A block diagram showing the configuration of an electronically scanned array radar to which the present invention is applied, FIG. An explanatory diagram showing an example of the STC characteristics of multiple (in this case two) STCs of the present invention applied in the configuration of
Hh) Received power from target and STC in Figure 6
Figure 8 is a received power characteristic diagram showing an example of the received level when "" is applied, at low altitude (H = Hl)
The received power from the target and the STC in Figure 6
FIG. 9 is an explanatory diagram in which equal received power lines are superimposed on the coverage area in the vertical plane according to the configuration of FIG. 4. DESCRIPTION OF SYMBOLS 1... Primary radiator, 2... Phase shifter, 3... Distribution circuit, 4... Phase shifter drive circuit, 5... Beam control circuit, 6... Transmitter, 7... Reference signal generation circuit,
8... Transmission switching device, 9... High frequency amplifier circuit, 10
...First mixing circuit, 11...Second mixing circuit, 12
... intermediate frequency amplification circuit, 14 ... signal processing circuit,
15...Display circuit, 18...STC generation circuit B.
Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An electronically scanned array radar device that electronically scans a required vertical coverage area with a beam, comprising a plurality of STC circuits with different characteristics and a switching means for switching the STC circuits according to the beam scanning angle,
The output of the STC circuit switched by the switching means controls the received signal strength so that the received power from the target within the required coverage area is matched to the receiving dynamic range without over-attenuation. radar equipment.