JPH0339638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for removing multiple echoes mixed in a received signal of a beam scanning radar device.

[Conventional technology]

A conventional device of this type is shown in FIG. In the figure, 1 is an input terminal, 2 is an output terminal, 40 is a transceiver, 50 is a multi-order echo detector composed of a delay circuit A 51, slicers 52 and 53, and a cancellation pulse generation circuit 54; is a multi-order echo canceller.

4 and 5 are explanatory diagrams of the operation of the apparatus shown in FIG. 3, and the operation will be explained using these figures. Normally, beam scanning radar equipment divides the elevation plane into arbitrary elevation steps (in Fig. 4, 5 For each elevation step, the beam is scanned from elevation step numbers 1 to 5 using an arbitrary number of hits (for convenience of explanation, 3 hits), and this is repeated. (The beam scanning order may be from elevation step number 5 to 1.) Furthermore, the transmission repetition period satisfies the required coverage area shown in Figure 4, and the time required for beam scanning is minimized. Therefore, it is common to select a period corresponding to the maximum detection distance corresponding to each elevation angle step. At this time, as shown in Figure 4, if a target larger than the specified radar cross section is located at a distance corresponding to the transmission repetition period,
The coverage area for that target will expand as shown in the figure. This indicates that the target is received at a reception level sufficient for detection, which is shown in Figures 5a and b.
As shown by the relationship between the echoes B _{1 and} B ₂ with respect to the target B, the echoes are mixed into the received signal as multi-order echoes, which are unnecessary for the device and result in erroneous detection. Conventional devices generally use staggered transmission/reception processing as described below as a method for dealing with this problem.

From the above, the transmitter/receiver 40
As shown in Figure b, three hits are transmitted for each elevation step and at a stagger ratio (Rc + △R)/(Rc) from the input terminal 1 to the antenna (not shown). Input the received echo from input terminal 1 and perform low noise amplification, frequency conversion,
It performs reception processing such as video detection, and outputs the result of video integration of three hits as shown in FIG. 5C. For convenience of explanation, as shown in Fig. 5a, there are two targets to be received: target A at a distance R _A , which is received as a primary echo, and target B, which is at a distance B, which is received as a secondary echo. When assuming a seed, it is obvious that the input of the transceiver 40 is obtained as shown in FIG. 5b, and the output of the transceiver 40 is obtained as shown in FIG. 5c. In the multi-order echo detector 50, the output video of the transceiver 40 is delayed by a delay circuit 51 by ΔR corresponding to the periodic change due to the stagger, thereby obtaining the video shown in FIG. 5d. Next, slicer 5
In steps 2 and 53, the output video of the transceiver 40 and the output video of the delay circuit 51 are each quantized by prescribed threshold values, and quantized videos are output. The removal pulse generator 54 performs the AND operation of the output videos of the slicers 52 and 53, and calculates B ₁ and the fifth pulse shown in FIG. 5c.
Elimination pulses are generated at two locations: a time when B ₂ shown in FIG. d coincides with the time, and a time delayed by ΔR from this time. On the other hand, in the multi-order echo canceller 60, the secondary echo B ₁ is extracted from the output video (shown in FIG. 5d) which has been delayed by ΔR in the delay circuit 51 using the cancellation pulse of the output of the multi-order echo detector 50. ,B ₂ is removed and 1
Only the next echo, A, is output from the output terminal 2 as a received signal (shown in FIG. 5e). In this way, multi-order echoes mixed into the received signal are removed.

[Problem that the invention seeks to solve]

Since the conventional device is configured as described above, it has the following problems.

(1) If there are unnecessary echoes from the ground, sea surface, etc. in a short distance area, or unnecessary echoes from rain clouds distributed over a wide area, the primary echo may be removed by mistake.

(2) In the case of a device using the pulse compression method, the transmission pulse time is relatively long, and if either of the secondary echoes B ₁ or B ₂ shown in Figure 5c is superimposed on the transmission time period, the secondary echo Since it becomes impossible to detect this, it becomes impossible to remove it.

This invention has been made to solve the above-mentioned problems, and provides a beam scanning radar device that can stably remove multi-order echoes and keep the error removal rate of primary echoes low. With the goal.

[Means for solving problems]

The beam scanning radar device according to the present invention performs transmission/reception processing for a specific one or a plurality of consecutive humans at a longer cycle than other humans for each elevation angle step, and the extended cycle portion of the output video. The system detects multi-order echoes during the time period and generates a cancellation pulse, and uses this cancellation pulse to remove the multi-order echoes mixed into the video output from the transmitter/receiver.

[Effect]

The beam scanning radar device according to the present invention extends the transmission repetition period only for a specific one or a plurality of consecutive humans at each elevation angle step.
Detection and removal of multi-order echoes by detecting multi-order echoes in a long-distance area where unnecessary echoes are not mixed in, and selecting the final human transmission repetition cycle so that multi-order echoes are not superimposed on the transmission time period. can be performed stably, and the error cancellation rate of the primary echo can be kept low.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is an input terminal, 2 is an output terminal, 10 is a transceiver, 20 is a slicer 21, and 2 is a slicer.
A multi-order echo detector 30 is composed of a cancellation pulse generating circuit 2, and a multi-order echo canceller 30 is composed of a delay circuit 31 and a gate circuit 32.

FIG. 2 is an explanatory diagram of the operation of the apparatus shown in FIG. 1, and the operation will be explained using this diagram. Since the general operation of the beam scanning radar device and the generation of multiple echoes are the same as in the case of FIG. 3, the explanation will be omitted, and only the different parts will be explained. As shown in FIG. 2b, the transceiver 10 transmits three hits for each elevation angle step, and only the last hit (third hit) is transmitted from an antenna (not shown) from the input terminal 1 by extending the transmission repetition period. do. At this time, the period R _D of the third hit shall be set to be equal to or greater than the maximum distance of the target for multi-order echoes, taking into consideration the installation altitude of the device, the upper limit of flight altitude of the aircraft, the system gain of the device, etc. It is. Next, the transceiver 10 inputs the echo received by an antenna (not shown) from the input terminal 1 and performs reception processing such as low-noise amplification, frequency conversion, and video detection, as shown in FIG. 2C. Outputs the result of video integration of 3 people. Here, when assuming the same target as in Fig. 3 (shown in Fig. 2 a), the input of the transceiver 10 is as shown in Fig. 2 b, and the output of the transceiver 10 is as shown in Fig. 2 b. It is obvious that the result shown in FIG. 2c can be obtained.

The multi-order echo detector 20 detects the output video of the transceiver 10 by quantizing it with a predetermined threshold value using the slicer 21 in the time period of the extended period of the video output from the transceiver 10 shown in FIG. 2c. Next, the quantized video output from the slicer 21 is shaped by a removal pulse generation circuit 22 (for example, using a specified signal pulse width, a value twice that value, etc.) to generate a removal pulse.

On the other hand, in the multi-order echo canceller 30, the transmitter/receiver 1
The output video of 0 is delayed by the period R _C (shown in Fig. 2 b and c) in the delay circuit 31, and the gate circuit 3
2, the multi-order echo B ₁ (shown in FIG. 2c) is removed by the cancellation pulse of the multi-order echo detector 22 output to obtain the output shown in FIG. 2d. At this time, the video of the multi-order echo detection section (shown in FIG. 2c) is not used as the radar output video. Here, the delay circuit 31
Since the transmission repetition period differs for each elevation angle step, the delay time must be set to match this. Therefore, as is clear from FIG. 4, in the delay circuit 31, generally, the transmission repetition period at elevation step 5, that is, the lowest elevation beam, is the maximum, so the capacity of the memory used as the delay element is adjusted to this value. It would be a good idea to prepare accordingly. In addition, since the cancellation pulse generation circuit 21 shapes the cancellation pulse in order to reliably remove multi-order echoes, the delay time of the delay circuit 31 is set to be slightly larger than the corresponding transmission repetition period. It is desirable to keep it.

Further, in the above embodiment, for convenience of explanation, the specific hit is the final hit, but it is not necessarily limited to the final hit or the single hit.

In the above embodiments, the transmitter/receiver 10 is not staggered, but if it is staggered, the periodic change due to the stagger is applied to the cancellation pulse generation circuit 22 for a multi-order echo video as shown in FIG. 5c. This can be removed by adding a circuit that can generate a removal pulse in a time period corresponding to minutes.

〔Effect of the invention〕

As described above, according to the present invention, multi-order echoes can be detected in a long-distance area where unnecessary echoes are not mixed in, and the multi-order echoes are configured not to be superimposed on the transmission time period. This has the effect that echoes can be stably removed and the error removal rate of primary echoes can be kept low.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a beam scanning radar device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of FIG. 1, FIG. 3 is a system diagram showing a conventional beam scanning radar device, and FIG. 4 , FIG. 5 is an explanatory diagram of the operation of the conventional beam scanning radar device of FIG. 3. 10... Transmitter/receiver, 20... Multi-order echo detector, 2
DESCRIPTION OF SYMBOLS 1...Slicer, 22...Removal pulse generation circuit, 30
...Multi-order echo remover, 31...Delay circuit, 32...Gate circuit. In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a beam scanning radar device that divides beam scanning in the elevation plane into arbitrary elevation steps and processes transmission/reception with an arbitrary number of hits for each elevation step, a specific one or a plurality of successive hits are transmitted and received for each elevation step. A transmitter/receiver that performs transmission/reception processing with a longer transmission repetition period than other humans, and humans other than the cycle-extended human in the extended period of the period-extended period in the received signal output for each elevation angle step of the transceiver. A slicer that quantizes and detects echoes (so-called multi-order echoes) from a target located at a distance corresponding to the transmission repetition period of a multi-order echo detector constituted by a cancellation pulse generation circuit to be created; , a gate circuit that removes multi-order echoes by gating with a multi-order echo cancellation pulse output from a multi-order echo detector, and a multi-order echo remover that removes multi-order echoes mixed into the received signal. A beam scanning radar device characterized by: