US 5,861,835 AGranted

Method to improve data obtained by a radar

OwnerHans Hellsteninventor

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Abstract

A method of improving data obtained by radar by interpolation over frequency bands jammed by narrow-band interference, at which the following steps (A)-(J) are carried out. (A) It is determined what frequency values are affected by narrow-band interference. (B) Every radar return which is continuously connected in time and represented by a time-discrete real or complex signal f(t.sub.i), containing N sample, i=1, 2, . . . , N, is Fourier-transformed into a frequency-discrete function F(.omega..sub.i), given by N sample. (C) A series of integers N.sub.1, N.sub.2, . . . , N.sub.M is fixed, such that 1.ltoreq.N.sub.1 <N.sub.2 < . . . <N.sub.M <N. (D) The signal processing device sets F.sub.k (.omega..sub.i)=H.sub.k (.omega..sub.i) within intervals having narrow-band interference. (E) H.sub.1 (.omega..sub.i) is equated to 0 and H.sub.k (.omega..sub.i) for k.gtoreq.2 is constructed according to the following steps (F)-(H). (F) F.sub.k-1 (.omega..sub.i) is inversely Fourier-transformed into a time-discrete function f.sub.k-1 (t.sub.i). (G) The signal processing device sets h.sub.k (t.sub.i)=f.sub.k-1 (t.sub.i) for i=1, 2, . . . , N.sub.k-1, wherein .vertline.f.sub.k-1 (t.sub.i).vertline. constitute the N.sub.k- greatest values of .vertline.f.sub.k-1 (t.sub.i).vertline. and h.sub.k-1 (t.sub.i)=0 for the remaining N-N.sub.k-1 values of the function. (H) h.sub.k-1 (t.sub.i) is Fourier-transformed into a frequency-discrete function H.sub.k (.omega..sub.i). (I) Steps (D)-(H) are repeated M times, wherein 1.ltoreq.k.ltoreq.M. (J) F.sub.NM (.omega..sub.i) is inversely Fourier-transformed to give the finally filtered radar return f.sub.NM (t.sub.i).

Claims6

Dependent claims

A method of Improving data obtained by radar, by interpolation over frequency bands jammed by interference having a smaller bandwidth than the bandwidth of the received radar return, comprising production of a radar signal in a radar transmitter, transmitting of the radar signal via an aerial system, receiving of radar returns via an aerial system in a radar receiver and processing of the radar return in a signal processing device, the method comprising,

(A) monitoring what frequency values are affected by narrow-band interference,
(B) Fourier-transforming every radar return which is continuously connected in time and represented by a time-discrete real or complex signal f(t.sub.i), containing N sample, i-1,2, . . . , N, into a frequency-discrete function F(.omega..sub.i), given by N sample, i=1,2, . . . , N,
(C) fixing a series of integers N.sub.1, N.sub.2, . . . , N.sub.M, such that 1.ltoreq.N.sub.1 <N.sub.2 <
. . . <N.sub.M <N,
(D) modifying F(.omega..sub.i) to a function F.sub.k (.omega..sub.i) by the signal processing device setting F.sub.k (.omega..sub.i)=F(.omega..sub.i) outside narrow-band interference and F.sub.k (.omega..sub.i)=H.sub.k (.omega..sub.i) within intervals having narrow-band interference,
(E) equating H.sub.1 (.omega..sub.i) to 0 and constructing H.sub.k (.omega..sub.i) for k.gtoreq.2 according to the following steps (F)-(H).
(F) inversely Fourier-transforming F.sub.k-1 (.omega..sub.i) into a time-discrete function f.sub.k-1 (t.sub.i),
(G) modifying f.sub.k-1 (t.sub.i) to a function h.sub.k (t.sub.i) by the signal processing device setting h.sub.k (t.sub.i)=f.sub.k-1 (t.sub.i) for i=1,2, . . . , N.sub.k-1, wherein .vertline.f.sub.k-1 (t.sub.i).vertline. constitute the N.sub.k-1 greatest values of .vertline.f.sub.k-1 (t.sub.i).vertline. and h.sub.k (t.sub.i)=0 for the remaining N-N.sub.k-1 values of the function,
(H) Fourier-transforming h.sub.k (t.sub.i) into a frequency-discrete function H.sub.k (.omega..sub.i),
(I) and repeating steps (D)-(H) M times, wherein 1.ltoreq.k.ltoreq.M, and finally
(J) inversely Fourier-transforming F.sub.N.sbsb.M (.omega..sub.i) to give the finally filtered radar return f.sub.N.sbsb.M (t.sub.i).

8 more elements

A method of improving a radar image in a SAR radar by interpolating over frequency bands which are to be found in jammed intervals in the interval .OMEGA..ltoreq..sqroot..omega..sub.i.sup.2 +.mu..sub.j.sup.2 .ltoreq..OMEGA.', comprising production of a radar signal in a radar transmitter, transmitting of the radar signal via an aerial system, receiving of radar returns via an aerial system in a radar receiver and processing of the radar return in a signal processing device, comprising, inter alia, the preparing of a two-dimensional radar image, the method comprising,

(A) monitoring what frequency values are affected by narrow-band interference,
(B) describing the image by a time-discrete real or complex signal f(x.sub.i, y.sub.j), containing N'.times.N" sample, i=1,2, . . . , N', j=1,2, . . . , N", which is a Fourier-transformed into a frequency-discrete function F(.omega..sub.i, .mu..sub.j), given by N'.times.N" sample, i=1,2, . . . , N', j=1,2, . . . , N",
(C) fixing a series of integers N.sub.1, N.sub.2, . . . , N.sub.M, such that 1.ltoreq.N.sub.1 <N.sub.2 <
. . . <N.sub.M <N'.times.N",
(D) modifying F(.omega..sub.i, .mu..sub.j) to a function F.sub.k (.omega..sub.i, .mu..sub.j) by the signal processing device setting F.sub.k (.omega..sub.i, .mu..sub.j)=F(.omega..sub.i, .mu..sub.j) outside narrow-band interference and F.sub.k (.omega..sub.i, .mu..sub.j)==H.sub.k (.omega..sub.i, .mu..sub.j) within intervals having narrow-band interference,
(E) equating H.sub.1 (.omega..sub.i, .mu..sub.j) to 0 and constructing H.sub.k (.omega..sub.i, .mu..sub.j) for k.gtoreq.2 according to the following steps (F)-(H),
(F) inversely Fourier-transforming F.sub.k-1 (.omega..sub.i, .mu..sub.j) into a time-discrete function f.sub.k-1 (x.sub.i, y.sub.j),
(G) modifying f.sub.k-1 (x.sub.i, y.sub.j) to a function h.sub.k (x.sub.i, y.sub.j) by the signal processing device setting h.sub.k (x.sub.i, y.sub.j)=f.sub.k-1 (x.sub.i, y.sub.j) for i=1,2, . . . , N.sub.k-1, wherein .vertline.f.sub.k-1 (x.sub.i, y.sub.j).vertline. constitute the N.sub.k-1 greatest values of .vertline.f.sub.k-1 (x.sub.i, y.sub.j).vertline. and h.sub.k (x.sub.i, y.sub.j)=0 for the remaining N-N.sub.k-1 values of the function,
(H) Fourier-transforming h.sub.k (x.sub.i, y.sub.j) into a frequency-discrete function H.sub.k (.omega..sub.i, .mu..sub.j),
(I) and repeating steps (D)-(H) M times, wherein 1.ltoreq.k.ltoreq.M, and finally
(J) inversely Fourier-transforming F.sub.N.sbsb.M (.omega..sub.i, .mu..sub.j) to give the finally filtered radar image f.sub.N.sbsb.M (x.sub.i, y.sub.j).

8 more elements

Dependencies are inferred from the claim text.