JPS60238774A - Angle measuring system - Google Patents

Abstract

PURPOSE:To eliminate an error by providing an angle measuring means for obtaining angle information while correcting an angle measuring error based on a multi-path effect which a pencil beam receives through the ground surface, by a correcting data set in advance based on a radar operating condition. CONSTITUTION:A received wave of a target received by pencil beams (a), (b) is received and processed by receivers 1, 2, respectively, and amplitude level data A, B are obtained, and inputted to a subtracter 5 through logarithmic amplifiers 3, 4. Also, in case the beam (b) does not receive a multi-path effect, a multiplier 6 receives an antenna constant K from a correcting data memory 8, and a wave angle phialpha shown by an expression I is outputted. Also, in case a scanning angle data inputted through an input line 1001 is in a multi-path generating angle range, a multi-path correcting operator 7 receives multi-path effect correcting constants K', C corresponding to a target wave angle and high level information from an output line 802, executes the operation of an expression II, and outputs the wave angle phialpha which has eliminated the multi-path effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an angle measurement method, and in particular to a method for receiving received signals of at least one set of pencil beams formed by forming a plurality of adjacent pencil beams having substantially equal characteristics. This invention relates to an angle measurement method that aims to correct the influence of angle measurement errors based on multipath effects caused by ground surface reflections on a radar that has the function of obtaining angle information about a target by comparing amplitudes.

[Prior art]

A plurality of sets of pencil beams having substantially the same characteristics and formed adjacent to each other are provided, and angular information regarding the target is obtained by comparing the received amplitudes of at least one set of pencil beams obtained mainly for a moving target such as an aircraft. Radar angle measurement methods are well known.

However, this type of conventional pencil beam amplitude comparison angle measurement method has the disadvantage that errors occur in the angle measurement data due to the influence of multipath reflection of the beam from the ground surface.

Figure 1 is an explanatory diagram of the pencil beam angle measurement method (A) to explain the basic contents of the pencil beam amplitude comparison angle measurement method.
, and a pencil beam angle measurement method multipath effect explanatory diagram (average) for explaining the basic contents of the pencil beam angle measurement method multipath error.

As shown in Fig. 1 (5), the target reception signal is transmitted via a plurality of (for example, two) adjoining pencil beams a and b, which have almost the same characteristics such as transmission and reception sensitivities and directivity characteristics, using the primary radar system. Let's consider the case where we obtain Figure 1 (5
) is the transmitting and receiving point of the radar device, and O
Ll indicates the maximum transmitting and receiving sensitivity direction of pencil beam a, the so-called nose direction, OLl indicates the nose direction of pencil beam b, OLo indicates the equal transmitting and receiving sensitivity direction of the two pencil beams a and b, so-called crossover direction, and 0! is the target acquisition direction and therefore the target is O! Suppose it is on the twill line.

Now, when LLoQ,4 = ψα, ψα is expressed by the following equation (1), as is well known.

ψα=K(LoiA-Lojil-B) ・・・・・・
・・・・・・・・・・・・(1) In equation (1), A and B are the target received power by pencil beams a and b, respectively, and are the amounts corresponding to the received signal amplitudes by the two pencil beams. It is. Further, K is an antenna constant determined in advance according to the characteristics of the pencil beam. The amplitude comparison angle measurement method using a pencil beam is a method in which ψα determined by equation (1) is calculated from the two received signal amplitudes, and since the OLo direction is known as an operating condition of the radar device, this ψα is used as angle information about the target. It can be used as

However, equation (1) only holds true when the two pencil beams have approximately the same characteristics.
If there is a ground surface that can cause multipath generation in the coverage area measured by the pencil beam, the received signal input through this multipath propagation will affect the characteristics of the pencil beam to be equivalently deformed. This causes angle measurement errors.

FIG. 2 is a diagram of pencil beam reception characteristics including the influence of multipath effects.

As shown in Figure 2, this type of multipath effect caused by the ground surface is mainly caused by the downward pencil beam b.
This affects the vibration level of the signal received by the lc, making it appear as if the pencil beam b had been transformed into b'. In normal reception processing, the average value of such fluctuating bumps is treated as the reception amplitude shown by the dotted line. Furthermore, in the operating specifications of pencil beams generally used for this type of purpose, the significant influence of such multipath effects is mostly limited to pencil beam b.

The dotted line f in FIG. 1(B) is an equivalent beam pattern corresponding to pattern smoothing by the above-mentioned amplitude level averaging process in received signal processing by a downward pencil beam affected by multipath propagation waves, This corresponds to the pattern indicated by the dotted line in Fig. 2, and clearly the pencil beam l)-1): The nose direction shifts upward under the influence of the ma/l/chip path, but this is not the case in the present invention. is equivalently treated as an expansion of the beam width. In Fig. 1 (at the same time), the elevation angle of the target input from the target in the 02 direction as in Fig. 1 (A) is received under the influence of the downward pencil beam, which is treated as equivalently expanded, and the correct elevation angle ψα is as follows. As shown in equation (2), it is obtained by applying correction to equation (1) corresponding to the expansion of the equivalent beam width.

epa = ni' (LopA-,8offB-
C) −= ・= ・= −(2) In equation (2), ′ is the antenna constant based on the pointing width of the pencil beam when receiving the equivalent beam width expansion due to the multipath effect,
C is the amplitude level correction amount for the received signal obtained by the pencil beam that has undergone beam width expansion.

When affected by multipath propagation, the disadvantage is that such errors enter the angle measurement data.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a means for correcting the multipath effect of a pencil beam that is affected by -C due to ground surface reflection, etc. in an angle measurement method that uses a radar to obtain angle information by comparing pencil beam amplitudes. The object of the present invention is to provide a highly accurate angle measurement method that basically eliminates angle measurement errors by obtaining angle information in advance.

[Structure of the invention]

The method of the present invention is a radar that obtains target angle information by comparing the received amplitude of the target by at least one set of pencil beams that are formed adjacently and have substantially equal characteristics and are acquired through a plurality of sets of pencil beams. The angle measurement method includes angle measurement means for obtaining angle information while correcting angle measurement errors due to multipath effects that the pencil beam receives through the ground surface using correction data set in advance based on radar operating conditions. Prepared and configured.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention.

The embodiment shown in FIG. 3 includes receivers 1 and 2, logarithmic amplifiers 3 and 4, each having substantially the same performance, as well as a subtracter 5, a multiplier 6, a multipath correction calculator 7, a correction data memory 8, etc. It is composed of:

To compensate for the effect of multipath propagation waves when comparing the amplitudes of the two received signals of the target obtained by a set of upper and lower pencil beams to obtain angle information, the beam slam or equivalent It is sufficient to approximate the amount of deformation of the downward pencil beam that is deformed as an expansion of the beam width, prepare in advance a correction amount corresponding to this expansion, and then adjust the elevation angle.

This basically corresponds to Kr shown in (2) 2 above.

It is sufficient to prepare C in advance and use this to correct the measured values obtained by the pencil beam, which is subject to multipath effects.

When processing the downward pencil beam as being equivalently enlarged and deformed due to the effect of multi-helix propagation, in order to correct the error in the received amplitude due to this deformation, it is necessary to change the conventional amplitude used for amplitude comparison between pencil beams a and b. The following equation (3) obtained by modifying the comparison interpolation calculation equation is used.

ψ equal to K. B is the power half width of the upper pencil beam. The dimension H is the analog-to-digital conversion constant of the target received signal acquired by the upper and lower pencil beams. Furthermore, α=ψOB/ψB, which is the upper pencil beam power half width/lower pencil beam power half width, ψa is the measurement elevation angle including multipath effects, and ψq is the upper, lower 1
The scanning step angle A in the vertical scanning of the set of pencil beams is the radar signal processing output, which corresponds to the output after analog/digital conversion in the radar device.

Equation (3) above applies when the target is at the vertical angle ψa in the rectangular coordinates determined by the azimuth scanning angle and the vertical scanning angle of the pencil beam.

For example, the radar signal processing output regarding the output voltage x1 at point A, where the vertical scanning angle is +ψq, and the output voltage x2 at point B, whose vertical scanning angle is shifted by -ψq, usually 4o7xx-Jofxz after analog/digital conversion.
It is a trap to calculate. Note that these output voltages x1 and x2 are calculated by the following equations (4) and (5), respectively.
It is shown by the formula.

xs=Goe-b:'ψa-ψq)296110110
00.10. , (4) 8□=Gte-bF(ψa+ψq
)2...... (5) In (4) and (5) 2, bO is the same as above, bl is abo, G1 = Goβ, and Go is the antenna power gain. ,β
is a constant determined by the pencil beam pattern shape, b
o and bl are vertical antenna beam shape constants.

By substituting values based on the actual operating conditions of the radar into the left side of equation (3) and finding the relationship between ψa and A, we can see that the crossover point of the two upper and lower pencil beams is the origin, and ψa
In the normal operating angle range of about 1 degree in the vertical direction, the ψa versus confrontation characteristic is approximately the linear function of ψa mψ3+f
It can be approximated by i. These m and n are constants that can be determined based on the target altitude, and therefore, the values of m and n are determined based on equation (3) for each altitude set in advance over the pencil and one-meter scanning angle ranges that are affected by multipath. By calculating , the true value of the elevation angle ψa affected by multipath can be accurately determined.

Returning again to the embodiment shown in FIG. 3, the explanation will be given again. It is assumed that of the two upper and lower pencil beams, pencil beams a and b, b is subject to a multipath effect.

The target received wave received by the pencil beam a is subjected to reception processing such as predetermined level amplification by the receiver 1, and then is supplied to the logarithmic amplifier 3 as amplitude level data A.

In the same way, the received wave captured by the pencil beam b is supplied from the receiver 2 to the logarithmic amplifier 4 as amplitude level data B, but this amplitude level data B is expressed as shown in Figs. As explained above, it is affected by the multipath effect.

Logarithmic amplifiers 3 and 4 each have amplitude level data A
and B are logarithmically amplified and then digitally converted using a predetermined number of bits.
ffB is supplied to the subtracter 5 as a logarithmically amplified output.

The subtracter 5 performs the following processing, which differs depending on whether the multipath effect is not affected or not, based on the pencil beam scanning angle information received from the radar device main body (not shown) via the input line 1001. .

That is, the pencil beam scanning angle information received via the input line 1001 provides azimuth and vertical angle information of the pencil beam, but multipath effects generated through reflections from the ground surface etc. affect radar operation. It is clear that the signal occurs within the corresponding angle range, and while the subtractor 5 receives the scan angle information, it directly uses J3o for the target signal captured in the scan angle range where the multipath effect does not occur.
A computation of %A-poffB is performed. In this case J3o
When fB is greater than 101A, the polarity sign is changed and subtraction is performed. Thus obtained −(1?oj
iLA-, , go54B are supplied to the multiplier 6 via an output line 501 as radar signal processing outputs.

The multiplier 6 receives the correction data from the correction data memory 8 via the output line 801 and multiplies the input by a constant as shown in equation (1) to obtain K (-1liloyA-JoPB), that is, the elevation angle ψa.
get. As mentioned above, this constant is the antenna constant for transmitting and receiving with a pencil beam, and is stored in the correction data memory in advance. The value of K is read out and used as a multiplier.

Next, a radar signal output Ao fA-A is generated based on the received wave input when the scanning angle data input via the input line 1001 is clearly within the multipath occurrence angle range.
Since o fB includes the shadow of the multipath effect, this must be corrected to obtain the correct elevation angle ψa.

In addition to the aforementioned scan angle data, target altitude data is also supplied to the data input via the input line 1001.

The correction data memory 8 stores the multipath effect correction normal numbers for the elevation angle when a target is captured in the azimuth and vertical angle ranges subject to the multipath effect, that is, ' and C shown in equation (2), as described in (3) above. Based on the calculation basis explained by the formula, when a multipath effect occurs, the amount of correction obtained corresponding to the target elevation angle, altitude, etc. obtained from the pre-calculated load is calculated in advance as the multipath effect correction normal number ', C. Stored.

Multipath correction calculator 7 is 13of A-430FB
Target elevation angle provided from output line 802 relative to the target elevation angle.

/ to the multipath effect correction normal number corresponding to the altitude information.

The calculation shown in equation (2) is performed while receiving C, and the elevation angle ψa from which the multipath effect has been removed is obtained and output.

In this way, it is possible to easily correct multipath angle measurement errors in pencil beam amplitude comparison height measurement processing that include multipath effects caused by reflections from the ground surface, etc.

It is clear that each of the configurations in the embodiment shown in FIG. 1 may be configured in any combination.

〔Effect of the invention〕

As explained above, according to the present invention, in a radar angle measurement method that obtains target angle information by comparing the received amplitude of a pencil beam, the amount of beam deformation based on the multipath effect caused by reflection from the ground surface, etc. is expanded by expanding the beam width. By performing angle measurement processing with a means of correcting angle measurement errors due to multipath effects while using elevation angle correction data that can be calculated and stored in advance based on radar operating conditions, multipath effects can be effectively approximated. This has the effect of realizing an angle measurement method that can extremely easily and efficiently carry out angle measurement processing that basically eliminates the above.

[Brief explanation of the drawing]

Figure 1 shows the pencil beam amplitude comparison angle measurement method.
) and a diagram illustrating the multipath effect of the pencil beam angle measurement method (Figure 2 is a pencil beam reception characteristic diagram including the multipath effect, and Figure 3 is a block diagram showing an embodiment of the present invention. 1.2 ...Receiver, 3.4...Logarithmic amplifier, 5...Subtractor, 6... Multiplier,
7... Multi-factor correction calculator, 8...
・Correction data memory. Agent Patent Attorney Susumu Uchihara 64) Graduated 1 (branch) Y 2 times

Claims (1)

[Claims] A radar angle measurement method that obtains angle information about a target by comparing the received amplitude of the target by at least one set of pencil beams obtained through a plurality of sets of pencil beams that have approximately equal characteristics and are formed adjacent to each other. The apparatus further comprises an angle measurement means for obtaining angle information while correcting angle measurement errors due to multipath effects that the pencil beam receives via the ground surface using correction data set in advance based on radar operation φ. An angle measurement method with the characteristic Φ.