JPS62132186A - Radar signal processor - Google Patents

Abstract

PURPOSE:To detect a moving target alone such as airplane accurately, by employing only one FIR filter using a selected filter coefficient to remove a clutter having a Doppler speed such as rain clutter efficiently. CONSTITUTION:A pulse pair type circuit which comprises a sweep memory 2, a complex type multiplier 3, a bearing average circuit 4 and a tan<-1> table 5 determine a Doppler velocity of rain clutters. A distance averaging circuit 7 averages Doppler velocity distance-wise to ensure that the Doppler velocity of a moving target is not outputted from an output of the circuit 7 even if the Doppler speed of a moving target such as airplane or the like is obtained. A coefficient table 8 contains coefficients that could remove frequency components of rain clutters. Time response is so set that a band reject filter is given in a frequency area, a filter coefficient is selected corresponding to the Doppler velocity of the rain clutters. Thus, sweep memories 9-11, complex multipliers 12-14 and an adder 15 composing an FIR filter acts as filter to remove rain clutters.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a radar that detects moving targets, and in particular, to accurately detect only moving targets such as aircraft from among clutter with Doppler components such as rain clutter. The present invention relates to a radar signal processing device.

(Prior Art and Its Problems) Conventional devices of this kind are configured to select one of the outputs from a plurality of filter punctures using a filter or a filter. However, it had the disadvantage that the circuit scale was enormous.

An object of the present invention is to eliminate the drawbacks of such conventional devices, efficiently remove clutter with Doppler velocity such as rain clutter, and accurately detect only moving targets such as aircraft. An object of the present invention is to provide a radar signal processing device with a small circuit scale.

(Means for solving the problem) The present invention provides F I l using selected filter coefficients.
(By using only one filter to simplify the circuit, and by selecting the coefficients of the f'IIt filter that adapt to the current clutter environment, the circuit configuration can be significantly simplified while maintaining the performance of conventional processing methods.) (Embodiment) Fig. 1 shows an embodiment of the present invention, in which 1 is an input terminal for a complex signal, and 2 is an input terminal for l sweep (the number of data per transmission pulse). Sweep memory that holds data; 3 is a complex multiplier that performs complex multiplication of the input signal from input terminal 10 and the signal delayed by one sweep, which is the output of sweep memory 2; 4 is an azimuth averaging circuit that performs averaging in the azimuth direction; tan contains arctangent data for determining Doppler velocity.
-1f-pull, 6 is the output terminal of Doppler velocity. 7 is a distance averaging circuit that averages the Doppler velocities found in the jan-' table 5 in the distance direction; 8 is a table for extracting the coefficients of the FIR filter corresponding to the Doppler velocities; 9.10
, 11 is a sweep memory that holds data for one sweep, 12.13.14 is a sweep memory 9.10.11
15 is an adder that adds all the results of the complex multiplication, and 16 is an FIR.

This is the output of the filter.

The sweep memory 2, complex multiplier 3, azimuth averaging circuit 4, and jan''-' table 5 are used as a pulse bear circuit (P P P ) in a meteorological Doppler radar, and the sweep memory 9.10゜11, complex multiplier 12, 13, 14, and adder 15 have a circuit configuration of FIR; The sweep memory 2 holds data for one sweep of the transmission period T, and its output is defined as Z2.

The complex multiplier 3 multiplies the complex conjugate signal Z,% of 2I by Z2, and if its output R,tTl is I(('
rl=Z I"・Z2. The azimuth averaging circuit 4 averages the output R (Tl) of the complex multiplier 3, and RtTl=Z
1 Kaoru Z! This is the autocorrelation function of signals separated by one hour. Now ad the Doppler angular velocity of the rain clutter.
・If so, the complex signal 2. ．． 2. is ZI=eJtadt,
Zz=ejωd' (is 10T). Therefore, the complex multiplication is
t, ejωa(t+T)=ejωdT, and if we find the arcta/zent of fT+, then ad
It can be seen that is calculated. This is ad = -L t
a n -' 1 (ITI Tearari, instead of performing this calculation, ad is obtained as data from the jan-' table. The Doppler velocity ωd of the rain clutter is output to the output terminal 6 in real time.

The distance averaging circuit 7 is a circuit for averaging the Doppler velocity ω4 in the distance direction, and its role is that even if the Doppler velocity of a moving target such as an aircraft is determined, the Doppler velocity of the moving target cannot be determined from the output of the distance averaging circuit 7. This is to prevent it from being output. In other words, the distribution of Doppler velocities of moving targets in rain clutter is much smaller than the distribution of rain clutter, and when averaged, most of the output of the distance averaging circuit 7 becomes the Doppler velocity of the rain clutter. It's for a reason. This means that the next stage lj I R filter-I'-rainfall
1. I can't get enough of it.

The coefficient table 8 contains coefficients for removing frequency components of rain clutter, and when the Doppler angular velocity is input, the coefficients of the filter are output.

Sweep memory 9, to, 11, complex multiplier 12.1
3.14 and the adder 15 are circuits forming an FI R filter, and this circuit performs convolution integration. Sweep memory 9, 10, and 11 are the same as sweep memory 2 (memories that hold data for one sweep. There is a time delay of one sweep time T between the input and output of each memory, and the radar data can be transferred to each range bin. This is the same as reading out in the azimuth direction.The input of the sweep memory 90 is xl, and the input of the sweep memo IJ 10 is xl.
, the input of the sweep memory 11 is 'n i, the output of the sweep memory 11 is xn, the input to the complex multiplier 12 of the coefficient table 8 is ω1, and the input to the complex multiplier 13 is ω.
2. If the input to the complex multiplier 14 is ωn, then the complex multipliers 12, 13, and 14 have ω1”, rl, and ωz”xz, respectively.
.

ω.・Perform one-bit complex multiplication. Adder 15 adds all the outputs of complex multipliers 12, 13, and 14, and ω1
'xl+ωz''xt+'°0+ωn'rn, which is ω1゜QJ2+++ω.
If t...x(1 is the input signal sequence, it is nothing but convolution integration.

Since the present invention is configured as described above, if the coefficient table 8 is set as a time response that becomes a band reject filter in the frequency domain, the filter coefficient corresponding to the Doppler velocity of the rain clutter is selected, and the It can be seen that it works as a filter to remove clutter. Even if the signal is a superimposition of rain clutter and a moving target such as an aircraft, if it is separated in the frequency domain, only the rain clutter can be removed by bending the IR filter, making it possible to reliably detect the moving target. At the same time, the current Doppler velocity of rainfall clutter is output in real time.

(Effects of the Invention) As described above, according to the present invention, clutter with a Doppler velocity such as rain clutter can be efficiently removed, and moving targets such as aircraft can be detected even in areas where rain clutter exists. It is.

Therefore, it has the effect of increasing the detection ability of moving targets in aircraft/board-side radars, etc. Furthermore, since the Doppler speed of clutter can be detected simultaneously with the detection of a moving target, atmospheric turbulence near an airport can also be detected, which has a significant effect in contributing to the safe operation of aircraft.

[Brief explanation of drawings]

t=1--The figure is a block circuit diagram showing an embodiment of the present invention. 'ゞ1...
Complex signal input terminal, 2...Sweep memory, 3...
・Complex multiplier, 4...Azimuth average circuit, 5...jan
-'Table, 6... Doppler velocity output terminal, 7...
Distance averaging circuit, 8...Coefficient table, 9-11...
Sweep memory, 12-14... Complex multiplier, 15.
... Adder, 16... Filter output terminal.

Claims (1)

[Claims] A circuit that calculates the Doppler velocity of rain clutter using the pulse pair method used in meteorological Doppler radar, a distance averaging circuit that averages the Doppler velocity signals obtained from the circuit in the distance direction, and removes frequency components of the rain clutter. The present invention is characterized by comprising a circuit for selecting coefficients such as the above, and an FIR filter that operates as a band reject filter according to the coefficients selected by the selection circuit, to remove rain clutter and accurately detect only moving targets. radar signal processing equipment.