JPH02196982A - Phase-modulated pulse corrector - Google Patents

Abstract

PURPOSE:To perform normal demodulation even if a target received signal has a Doppler phase shift by composing the correlator of 1st and 2nd channels of specific constitution and an adder which calculates the sum of both the channels. CONSTITUTION:Echo pulses which are distributed to the 1st channel 8 and 2nd channel 9 by code sequences are sampled by generating a channel correlation signal and sent to a memory 17 in the channel 9. The memory 17 outputs a sampled value sequence varying with time in a specific range of the channel correlation signal. An adaptive filter 20 calculates a necessary waiting coefficient from sampled values stored in a memory 16 so as to estimate the value (interpolated value) of the channel 8 at the sample time of the channel 9. An interpolator 18 multiplies the output value of the memory by the coefficient to calculate the interpolated value. The channel 9 is provided with a delay circuit for delay of the calculation time of the channel 8. Lastly, the interpolated value and the output of the channel 9 are added together.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] Jin's invention relates to a phase modulated pulse correlator in a coherent pulse compression spread spectrum radar using a complementary code sequence.

[Conventional technology]

FIG. 3 shows a conventional complementary code sequence phase modulation pulse correlator. In FIG. 3, (1) is the antenna, (2) is the receiver front end, (31) is the switch, (4) is the first matched filter of the first complementary code sequence,
(5) is the second matched filter of the second complementary code sequence, (
6) is a delay circuit, (7) is an adder, C81 is a first channel, and (9) is a second channel.

Pulse signals alternately phase-modulated by the first and second complementary code sequences are received by the antenna (11) and sent to the receiver front end (2). ) input signal to (echo bar)
Table bf. The echo pulse modulated by the echo pulse αst-, g1 complementary code sequence is input to the first matched filter (4), and the echo pulse modulated by the second complementary code sequence is input to the second matched filter (5). In order to do this, the switch (3) operates alternately. FIG. 4I represents the input of the first matched filter (4), and αS represents the input of the second matched filter (5). The first matched filter (4) and the second matched filter Jf -+51 take the autocorrelation of each echo pulsed transmission pulse, and the obtained channel correlation signals are added in the adder (7), but the two channel correlation signals are input to the adder (7) at the same time.

The output of the first matched filter (4) is delayed by a period T in a delay circuit (6). Depending on the characteristics of the complementary code sequence, 0
The first channel correlation signal (l [l and the second
When the range side lobes of the channel correlation signal (ID) are added, they cancel each other out, leaving twice the main rope as in the correlation signal α.

[Problem to be solved by the invention]

However, in the conventional phase modulation pulse correlator, when the Doppler effect is added to the echo pulse a3.

An extra range side rope occurs in the correlation signal az.

This range side rope has become a target.

Adversely affecting functionality. This is the channel correlation signal α
When obtaining G, afi, the sub-Hulst transmission sub-pulses within the echo pulse are combined, but if the phase shift of the sub-pulses increases linearly over time, the correlation information will be disturbed and the result of the combination integration will be small. However, it appears as a large range side rope. Therefore, there is a need to eliminate the influence of Doppler phase shift and suppress range side lobes in a coherent V-tont pulse pressure N radar subjected to complementary code sequence phase modulation.

[Means to solve the problem]

In the phase modulation pulse correlator according to the present invention, the echo pulses distributed into the first channel and the second channel according to the code sequence are sampled by receiving the channel correlation signal, and sent to the memory in the second channel. This memory outputs a sequence of sample values over time over a particular range of the channel correlation signal. Second
In order to estimate the value (interpolated value) of the first channel at the sampling time of the channel, necessary weighting coefficients are calculated from all adaptive filters from the sample values stored in the memory. The weighting coefficients are set to give the minimum mean square error. The interpolator multiplies this weighting coefficient by the memory output value to produce an interpolated value.

In the second channel, a delay circuit is provided to delay the calculation time in the first channel.

Finally, this interpolated value and the output from the second channel are added together.

[Effect]

Since the interpolated value from the first channel and the output from the second channel can be combined with the channel correlation value in the same phase, even if the target received signal undergoes a Doppler phase shift, it can be demodulated while suppressing range side lobes. can do.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In this figure, (1) to (9) are the same as in FIG. 3, and QG.

αη is a memory, α8 is an odd-numbered pulse delay circuit and an interbolator, α9 is an even-numbered pulse delay circuit, and ■ is an adaptive filter. Figure 2 is a detailed diagram of an example of the odd pulse delay circuit, the intervolator α, and the even pulse delay circuit (11). ~OrI is a multiplier, and CD is an adder. FIG. 5 shows sample values of the first channel correlation signal and the second channel correlation signal in a specific range.

Next, the operation will be explained. Receiver front end (2
) is shown in FIG. 4, and the echo pulses are alternately modulated by the first complementary code sequence and the second complementary code sequence. The echo pulse signal modulated by the first complementary code sequence is
An echo pulse signal modulated by a complementary code sequence is called an even pulse. Switch (3) switches the odd-numbered pulses to the first
The matched filter (4) is switched to input even pulses to the second matched filter (5) to obtain respective channel correlation signals. The channel correlation signals are sampled and stored in a first memory ae and a second memory respectively.
(17) is input. Input sample values for each channel correlation signal in the first memory 〇〇 and second memory 〇〇,
Outputs sample values for each range sequentially.

The output of the first memory aI1g is sent to the adaptive filter (2), the odd-numbered pulse delay circuit, and the interbolator. Figure 2 shows an 8-stage intervolator as an example, so as shown in Figure 5, the sample value is 51.
i1 ■, 83 Lord, ..., S13 decoy.

The eight values of 5IS (41) are stored as inputs of the multipliers (2) to (to) in FIG. 2, and the weighting coefficients a1 (58) to a are output from the adaptive filter (to).
s(65) are respectively multiplied and added by an adder (to). As a result, an interpolated value S 8' (57) corresponding to time T8 in FIG. 5 is calculated. In order to simultaneously input the pair of sample values S8 (53) and 88' (57) to the adder (71) in FIG. ).The final correlation signal is obtained as the output from the adder (7).

〔Effect of the invention〕

As explained above, in a coherent pulse compression radar, even when a Doppler phase shift is added to a signal that has been polyphase modulated by a complementary code sequence, the present invention provides a Since the phase can be matched, it is possible to suppress the range side lobe of the correlation signal, so if a zero-phase modulation pulse correlator is used, it can be demodulated normally even if the target received signal undergoes a Doppler phase shift. Become.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a detailed block diagram of an example of the odd-numbered pulse delay circuit and interbolator shown in Fig. 1, and Fig. 3 is a conventional phase modulation pulse correlator. FIG. 4 is a waveform diagram at each part of FIG. 1, and FIG. 5 is a diagram showing a sample sequence of a channel correlation signal. In these figures, (1) is the antenna, (2) is the receiver front end, (3) is the swing f, (41ij first W y Tid filter, (5) is the second matte filter (6) is the delay circuit, (7) is an adder, C81 is the first channel, (9) is the second channel, aO is the first channel correlation signal, am) is the second channel correlation signal, and az is the correlation signal. al C Received echo pulse sequence, αa is the input echo pulse sequence to the first matched filter (4), 119 is the input echo pulse sequence to the second matched filter (5), Oe is the first memory, an is the second
Memory, (I is an odd-numbered pulse delay circuit and an interbolator, al is an even-numbered pulse delay circuit, an is an adaptive filter, Q is a SAW delay circuit, and @ is a SAW delay circuit. a multiplier, @ is an adder, rO is a sequence of sample values in a specific range of the first channel correlation signal, 61) is a sequence of sample values in a specific range of the second channel correlation signal, -~(56) is a sequence of sample values in a specific range of the second channel correlation signal, sample value, (57) is the T8 of the first channel correlation signal
The interpolated values (SO) to (65) are weighting coefficients. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In a phase modulation pulse correlator that demodulates pulses phase modulated by a complementary code sequence, a matched filter is used to correlate the received signal and the transmitted signal, and the correlation signal from the matched filter is input and the correlation signal sample for each range is input. The first channel consists of a memory for outputting values, a delay circuit for adjusting the sample value output time between channels, and a matched filter, a memory, a delay circuit, and a correlation signal between the sample values from the memory. a second channel consisting of an adaptive filter for estimating the value, an interbolator in which the output of this adaptive filter is fed forward and multiplied by the output from the delay circuit, and the first channel and the second channel A phase modulation pulse correlator comprising an adder that calculates the sum of signals.