US 4,537,502 AGranted

Multiple discrete frequency ranging with error detection and correction

AssigneeThe Boeing Company

InventorsDale D. Miller, John N. Polky

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Abstract

A range determination apparatus for determining target range within a range depth of D and within a range bin error of e comprises a carrier frequency transmitter for transmitting a carrier frequency and a generator for generating at least two modulating signals having frequency f.sub.1 and f.sub.2, respectively. A modulation device, operative for at least two discrete frequencies for providing one of simultaneous or sequential modulated signals, is coupled to the carrier frequency transmitter for modulating the carrier. The two modulating frequencies and a common sub-multiple counting frequency are related such that f.sub.o =m.sub.1.sup.' f.sub.1 =m.sub.2.sup.' f.sub.2. A receiver is provided for receiving a reflected signal from the target and for producing a corresponding received electrical signal. A phase detection device is responsive to the modulating signals of the generator and the received signals for detecting the phase difference x.sub.1.sup.' and x.sub.2.sup.', respectively, between the modulating signals of the frequencies and each of the corresponding received signals. A data processor is coupled to receive the detected phase differences for each of the received signals.

Claims9

Dependent claims

Range determination apparatus for determining target range within a range depth of D and within a range bin error of e comprising:

(a) a carrier frequency transmitter for transmitting a carrier frequency,
(b) means for generating at least two modulating signals having frequency f.sub.1 and f.sub.2 respectively,
(c) modulation means coupled to said carrier frequency transmitter for modulating said carrier, said modulation means operative for said at least two discrete frequencies f.sub.1 and f.sub.2 for providing one of simultaneous or sequential modulated signals,
(d) said at least two modulating frequencies and a common sub-multiple counting frequency f.sub.o related such that
f.sub.o m.sub.1 'f.sub.1 =m.sub.2 'f.sub.2
where,
m.sub.1 '=m.sub.1 m.sub.r
m.sub.2 '=m.sub.2 m.sub.r
m.sub.r .gtoreq.4e+1
m.sub.1 m.sub.2 .gtoreq.D/m.sub.r
and where m.sub.1,m.sub.2 and m.sub.r are pairwise relatively prime,
(e) a receiver for receiving a reflected signal from said target and for producing a received electrical signal corresponding thereto,
(g) phase detection means responsive to said modulating signals of said generating means and said received signals for detecting the phase difference x.sub.1 ' and x.sub.2 ' respectively between the modulating signals of frequencies f.sub.1 and f.sub.2 and each of the corresponding received signals,
(h) data processing means coupled to receive said detected phase differences for each of said received signals, said data processing means operative
(1) to calculate ##EQU14## where R(x).sub.m is defined as the residue of x modulo m, (2) to compare R(x.sub.1 ').sub.m.sbsb.r with R(x.sub.2 ').sub.m.sbsb.r
and if unequal to modify at least one of x.sub.1 ' and x.sub.2 ' by adding or subtracting an integer.ltoreq.e to produce modified phase differences x.sub.1 " and x.sub.2 " so that residues
R(x.sub.1 ").sub.m.sbsb.r and R(x.sub.2 ").sub.m.sbsb.r of the modified phase differences are equal, and
(3) to decode one of (1) the residue number triplet [R(x.sub.1 ').sub.m.sbsb.1, R(x.sub.2 ').sub.m.sbsb.2, R(x.sub.1 ').sub.m.sbsb.r ] and the modified residue number triplet [R.sub.1 ").sub.m.sbsb.1, R(x.sub.2 ").sub.m.sbsb.2, R(x.sub.1 ").sub.m.sbsb.r ] relative to the moduli set [m.sub.1,m.sub.2,m.sub.r ] to obtain the target range.

15 more elements

A method for determining the true target range within a range depth D and within a range bin error e from multiple modulated frequencies of radar comprising the steps of:

(a) transmitting a plurality of distinct frequencies f.sub.1, f.sub.2 . . . f.sub.i . . . f.sub.s,
(b) said plurality of frequencies related such that, for i=1, 2, . . . s,
m.sub.1 'f.sub.1 =m.sub.2 'f.sub.2 =m.sub.1 'f.sub.i
where ##EQU15## where the m.sub.i 's are pairwise relatively prime, (c) receiving reflected echo signals from said target for each frequency f.sub.i, i=1,2, . . . s,
(d) detecting the phase difference x.sub.1 ' respectively between the transmitted and received signals for each frequency f.sub.i, i=1,2 . . . s,
(e) calculating in response to each x.sub.1 ', the residues ##EQU16## (f) for each distinct pair of indices i,j where i=1,2 . . . s and j=1,2 . . . s, computing,
d(i,j)=min(R(x.sub.i.sup.r -x.sub.j.sup.r).sub.m.sbsb.r, m.sub.r -R(x.sub.i.sup.r -x.sub.j.sup.r).sub.m.sbsb.r)
and choosing i.sub.o, j.sub.o at which d (i.sub.o,j.sub.o) is maximal,
(g) selecting integer y, o.gtoreq.y<m.sub.r as one of:
y=R(x.sub.j.sbsb.0.sup.r +[R(x.sub.i.sbsb.0.sup.r -x.sub.j.sbsb.0.sup.4).sub.m.sbsb.r /2].sub.m.sbsb.r
if R(x.sub.i.sbsb.0.sup.r -x.sub.j.sbsb.0.sup.r).sub.m.sbsb.r .gtoreq.2e, and
y=R(x.sub.i.sbsb.0.sup.r +[R(x.sub.j.sbsb.0.sup.4 -x.sub.i.sbsb.0.sup.r).sub.m.sbsb.r /2])
if R(x.sub.j.sbsb.0.sup.r -x.sub.i.sbsb.0.sup.r).sub.m.sbsb.r .ltoreq.2e
when [ ] denotes the greatest integer functions,
(h) computing b.sub.i, i=1,2, . . . s such that
b.sub.i =R(x.sub.i.sup.r -y).sub.m.sbsb.r if R(x.sub.i.sup.r -y).sub.m.sbsb.r .ltoreq.e,
and
b.sub.i =R(x.sub.i.sup.r -y).sub.m.sbsb.r -m.sub.r if R(x.sub.i.sup.r -y).sub.m.sbsb.r >e,
(i) subtracting x.sub.i -b.sub.i to form the differences
x.sub.i.sup.* =R(x.sub.i -b.sub.i).sub.m.sbsb.i
i=1,2, . . . S, and
(j) decoding the set (x.sub.1.sup.*, x.sub.2.sup.* . . . x.sub.i.sup.* . . . x.sub.s.sup.*, y)
relative to the moduli set (m.sub.1, m.sub.2 . . . m.sub.i . . . m.sub.s, m.sub.r) to find the true target range.

20 more elements

Dependencies are inferred from the claim text.