JPS6196482A - Radar system - Google Patents

Abstract

PURPOSE:To prevent plural radar systems in adjacent areas from the generation of mutual interference even if carriers in the same frequency band are used for the plural radar systems by applying 'complete complementary sequence system' constituted of N<2> 'multiple difference self-orthogonal sequences consisting of N digits'. CONSTITUTION:The plural radar systems P, Q executing transmission/reception by using carriers consisting of encoded pulses in the same frequency band outputs different encoded pulses each other. When matching filters 12, 13 and 16, 17 input plural encoded pulses outputted from themselves, these filters output plural self-correlation function signals corresponding to the inputs. Receiving plural encoded pulses outputted from other systems, the filters 12, 13 and 16, 17 output plural mutual correlation function signals corresponding to these inputs. When the outputs of the filters 12, 13 and 16, 17 are added by adders 14, 18, compressed pulses having no side lobe are outputted in case of the self- correlation function signals or '0' is outputted in case of the mutual correlation function signals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a plurality of radar systems capable of transmitting and receiving in the same frequency band.

[Technical background of the invention and its problems]

Conventionally, multiple adjacent radar systems installed in a narrow area had to use carrier waves in different frequency bands. The reason is that if the same frequency band is allocated to these radar systems, each radar system will cause mutual interference. It was necessary to prepare a carrier wave for the frequency band.

[Purpose of the invention]

The present invention improves the drawbacks of the prior art described above, and aims to provide a plurality of radar systems that do not interfere with each other even when the same frequency band is used in adjacent areas.

[Summary of the invention]

The present invention provides a plurality of radar systems that perform transmission and reception using a carrier wave consisting of coded pulses in the same frequency band, in which each radar system is assigned a different coded pulse and a number of coded pulses equal to the total number of radar systems. It outputs pulses, and if it inputs multiple encoded pulses output by itself, it outputs multiple autocorrelation function signals corresponding to these, and outputs multiple encoded pulses output from other radar systems. When a pulse is input, a plurality of matched filters each output a plurality of corresponding cross-correlation function signals, and by summing the outputs of the plurality of matched filters, the output becomes an autocorrelation function signal. In the case of a signal, the output is a compressed pulse without side lobes, and in the case of a cross-correlation function signal, the output is a zero output.

[Effects of the invention-]

According to the present invention, even if carrier waves of the same frequency band are used in each radar system, mutual interference does not occur, so the practical advantage thereof is enormous.

[Embodiments of the invention]

In the present invention, a complete complementary sequence system composed of N2 "multiple difference self-orthogonal sequences of order N" is applied to a radar system. First, the complementary sequence system will be explained at length. When there is a sequence of L, and its autocorrelation function becomes Oζ with a multiple shift of N excluding the 0 shift, this sequence is called a multiple difference self-orthogonal sequence of 1st order N.

for example, 81: (1, 1, 1, -1) The autocorrelation function of (-7・0・i・1・i・0・−1) Therefore, Sl is a multiple difference self-orthogonal sequence of order 2.

If there are two sequences of length L, and the cross-correlation function between them becomes 0 when shifted by a multiple of N, then these sequences are
It is assumed that the sequence is a multiple difference mutually orthogonal sequence of the first order N of the pair.

for example.

8s=(1,1,1,-1) TI=(1,1,-1,1) Then, the cross-correlation function between them is (-, O-,
0-, O, -7) 4 '4 ゝ4 Therefore, Sl and Ts are a pair of multiple difference mutually orthogonal sequences of order 2. There are M sequences of length L, and among these, any 2
When M is a pair of multiple difference mutually orthogonal sequences of order N, these M sequences are said to be a set of multiple difference mutually orthogonal sequences of order N.

When there is a set of M sequences and the sum of these autocorrelation functions is 0 for all shifts other than the 0 shift, the set of these sequences is called a self-complementary sequence system of order M. If there are two sets of self-complementary sequence systems of order M, and the sum of the cross-correlation functions of the corresponding sequences is O for all shifts, then these two sets of self-complementary sequence systems are one set of order M. When a sequence is called a mutually complementary sequence system, this self-complementary sequence system of MM is called a first complementary sequence system of order M.

Now, consider a complementary series system of order N (input j; 1≦i≦N, 1≦j≦N). For any i, (]: song +' l e ■also supervised 2. ..., R
'N) is a self-complementary series system.

Now, there are N filters, each Rix.

Ri2. ..., RiNK matching is assumed. These matched filters output an autocorrelation function signal of the input signal when applied with a matching signal. When matching signals are applied to these N filters, N
The sum of these outputs is the sum of the autocorrelation functions of the self-complementary sequence system, resulting in a complete compressed pulse with no side lobes.

These N filters (Rij, j=1.2...
・Rkj < t=x for each of
, 2. ...N) is applied, the output of each filter becomes a cross-correlation function of Rij and Rkj, and the sum of these outputs becomes a completely zero output.

As an example, a self-complementary sequence system of order 2 length 6402 sets (
Pl, P2 ) and (Ql, Q2) indicate the complementary series system.
＋＋−−−＋−＋＋−＋＋＋＋−＋＋＋ −−−−＋
−−+ −−−+−+++ −−−+−++−+++ −+ −−−++++−++−+++ )Ql = (+
＋＋−＋＋−＋＋＋＋ −−−＋ −＋＋＋−＋＋−＋
−−−＋＋＋−+ −−−+ −−+ −−−−＋＋＋−＋＋＋＋−＋＋−
＋ −−−＋＋＋−＋ )Q2 : (＋−＋＋＋ −
−−＋−＋＋−＋＋＋＋−＋＋＋ −−−−+ −−＋
---Using the completely complementary sequence system of this example, two radar systems P without interference while using the same frequency band,
The design method for Q will be described.

The cross-correlation function of carrier waves (pulse trains) Pl and Ql output by radar systems P and Q is Pu:lJ*.

If we write the autocorrelation function as Pl*Pi*etc, then K as mentioned earlier, this complete complementary sequence system has the following properties O Qt*Q1*+ Q2*Q2*= (0... 010・
...O) Next, two radar systems P and Q, which are embodiments of the present invention, will be explained with reference to the drawings.System P
, Q are each equipped with a pulse compression device as shown in FIG.
, 15, matched filters 12 , 13 , 16 , 17
, adders 14 and 18. Also, system P, Q
are the modulated pulses (
carrier wave) Pl, P2. Ql, Q2 are output at the same period, and these modulation pulses are Pl, P2, Q2.
Both L and Q2 are coded pulses that are different from each other.7 In other words, different coded pulses are assigned to each radar system. Furthermore, in this embodiment, since there are two radar systems, each system outputs two modulated pulses (if there are three radar systems, it outputs three modulated pulses). Next, the modulated pulse P1 output from the system P is reflected from the target and received by the system PK again, and this received pulse P1 is stored for a time T in the delay circuit 11. Then, after T time, the modulated pulse P2 output from the system P is received again by the system P, but at this time, the modulated pulse P1 is inputted to the matched filter 12, and the modulated pulse P2 is inputted to the matched filter 13. When the autocorrelation function signals of PI and P2 outputted from the matched filters 12 and 13 are added by an adder 14, a complete compressed pulse without side lobes is obtained. This is likely to be the case when modulated pulses Ql and Q2 are received in system Q, as shown in Figure 3(a).
Shown in d).

Further, when the modulated pulses Ql and Q2 output from the system Q are received by the system P, the received pulse Ql.

Q2 is input to matched filters 12 and 13, respectively,
These matched filters 12 and 13 are PI and P2, respectively.
Otherwise, it will not be consistent. Therefore, matched filter 1
When the cross-correlation function signals of Ql and Q2 output from 2゜13 are added by adder 14, the output obtained is P1*Q
1*+P2*Q2*, resulting in a complete O output. The same thing holds true even if the positions of P and Q are exchanged. This situation is shown in Figure 3(b) (C
). In this way, in radar systems P and Q,
A complete compressed pulse is obtained only when inputting the modulated pulse output by the system itself, and a complete 0 output is obtained even when inputting the modulated pulse output from another system, so these systems use carrier waves in the same frequency band. is practically irreplaceable.

Incidentally, in order for the relationship shown in FIG. 3 to be established, it is necessary that system P and system Q be synchronized. In order to achieve synchronization, for example, it is possible to equip the system P with a filter that matches the signal Q1 and measure the time interval at which the O shift value is obtained.

Incidentally, such a relationship can be extended to cases where it is desired to use three or more radar systems in the same band. In this case, the order N
A completely complementary sequence system (N=3.4, 5, . . . ) is used. N radar systems as P, Q, and R.

..., then the pulse compression device of system P is Pl.

P2. ..., N fills matching PN, and T,
ff.

..., includes a delay circuit corresponding to (N-1)T. System P is PI, P2. ..., N coded pulses modulated by PN are transmitted at T intervals, especially when N is 2
When it is a power of It is.

Furthermore, a system in which the output is obtained as a pulse train will be described. Obtaining the output as a pulse train rather than a single pulse is a practical method for improving the signal-to-noise ratio.To this end, the pulse compression device shown in FIG. 5 is replaced with the pulse compression device shown in FIG. If the pulses shown in FIGS. 4A and 4H are used instead of the transmission pulses shown in FIGS. 4A and 4B, a pulse train is obtained as the output. In this case too, there is no interference from other systems.

For practical design of a radar system, matched filters for modulated pulses Pl, P2, Qt, Q2 consisting of 64 codes are shown in FIGS. 6(a), (b), (C), and (d). When these matched filters are used, even if a coded pulse consisting of 64 elements is input, its autocorrelation function,
This is useful in practice because it provides a cross-correlation function.

[Brief explanation of drawings]

FIG. 1 is an internal configuration diagram of a radar system according to the present invention, FIG. 2 is a diagram showing pulses output from the radar system, and FIG.
The figure shows how modulated pulses are input to the matched filter, Figure 4 shows the pulse train output by the radar system, Figure 5 shows the internal configuration of the radar system that outputs the Norculus train, and Figure 6 shows the internal configuration of the radar system that outputs the Norculus train. The figure is an internal configuration diagram of a matched filter for actual design of a radar system. 11, 15...Delay circuit. 12, 13, 16, 17... matched filter, 1
4, 18... Adder 0 Agent Patent attorney Rule Kensuke Chika (and 1 other person) Figure 1 Figure 2 d U Figure 4 -T-T T T- 7--T-17 T- Ward Mouth figure 5 school

Claims (1)

[Claims] In a multiple radar system that performs transmission and reception using a carrier liquid consisting of encoded pulses in the same frequency band, each radar system outputs different encoded pulses, and the multiple encoded pulses output by itself When pulses are input, multiple autocorrelation function signals corresponding to these are output, and when multiple encoded pulses output from other radar systems are input, multiple cross-correlation function signals corresponding to these are output. By summing the outputs of a plurality of matched filters that output function signals and the outputs of the plurality of matched filters, if the output is an autocorrelation function signal, the output becomes a compressed pulse without side lobes, and the output becomes a cross-correlation function signal. A radar system characterized by comprising: an adding means that outputs 0 in the case of .