Method for instantaneous processing of the glint noise and tracking monopulse radar receiver carrying out this method

• US 5,049,888 A
• Filed: 12/15/1983
• Issued: 09/17/1991
• Est. Priority Date: 12/30/1982
• Status: Expired due to Fees

• Current Assignee: Thomson-CSF (Thales SA)
• Original Assignee: Thomson-CSF (Thales SA)
• Inventors: Prenat, Michel
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US06/562,186
• Time in Patent Office: 2,833 Days
• Field of Search: 343/16 M, 342/149
• US Class Current: 342/149
• CPC Class Codes: G01S 13/4427 with means for eliminating the target-dependent errors in angle measurements, e.g. glint, scintillation effects
• CPC Class Codes: G01S 13/685 using simultaneous lobing techniques

Abstract

Method and apparatus for instantaneous processing of the glint noise in a monopulse radar. The radar antenna receives a sum signal S and a difference signal Δ whose phases vary as functions of time. Successive derivatives Q.sup.(k) of order k, are calculated as a function of time from k=0 to k=N'"'"'. Also, the scaler product Q=S×Δ of the sum signal and difference signals is calculated. Then, successive derivatives P.sup.(k) of order k are calculated as a function of time from k=0 up to k=N'"'"'. Also, the power P=|S|² of the signal received, which is equal to the square of the modulus of the sum signal S, is calculated. Next, a plurality of derived angle-error measurement operators (ε_k) are calculated such that a ε_k =Q.sup.(k) /P.sup.(k). Finally, a combined angle-error measurement operator ε is calculated such that ##EQU1## The weighting coefficients β.sub.κ are coefficients representing the quality of the associated derived operator ε.sub.κ relative to the angle-error measurement of the barycenter of the target.

Claims

1. A method for processing glint noise in a monopulse radar having an antenna which receives a signal and produces sum signal S and difference signal Δ

whose phases vary as functions of time, comprising the following steps;

calculating successive derivatives Q.sup.(k) of order k, as a function of time, from k=0 up to k=N'"'"' (N'"'"'≧

2), of the scalar product Q=S.Δ

of the sum signal S and difference signal Δ

;

calculating successive derivatives p.sup.(k) of order k, as a function of time, from k=0 up to k=N'"'"', of the power P=|S|² of the signal received, which is equal to the square of the modulus of the sum signal S;

calculating (N'"'"'+1) derived angle-error measurement operators ##EQU28## and calculating a combined angle-error measurement operation ε

such that ##EQU29## in which (N'"'"'+1) weighting coefficients β

.sub.κ

, for k=0 to k=N'"'"', are coefficients depending on the quality, relative to the angle-error measurement of the barycenter of the target, of the derived angle-error measurement operators ε

₇₈ which correspond thereto.

2. A processing method according to claim 1, wherein said step of calculating a combined angle-error measurement operator includes the step of providing quality coefficients β

.sub.κ

which are proportional to the modulus A_k =|P.sup.(k) | of the derivative, with respect to time, of the power P of the signal received.

3. A processing method according to claim 1, wherein said step of calculating a combined angle-error measurement operator includes the step of providing quality coefficient β

_k which are respectively equal to the ratios ##EQU30## where |P.sup.(k) |_f is a filtered value of A_k=|P.sup.(k) |.

4. A processing method according to claim 1, wherein the quality coefficients β

_k are corrected and set equal to zero if A_k =|P.sup.(k) | is less than or equal to a positive threshold p_k.

5. A processing method according to claim 1, wherein said step of calculating a combined angle-error measurement operator includes the step of providing (N'"'"'+1) quality coefficients β

.sub.κ

, with k from 0 to N'"'"', which are respectively equal to

space="preserve" listing-type="equation">β

.sub.κ

=[τ

.sub.κ

.sup.κ

·

P.sup.(k) ].sup.n

where τ

_k is a time constant and n is a positive integer higher than or equal to 2.

6. A monopulse radar receiver associated with a monopulse antenna which receives signals returned by a target and produces sum and difference signals, and which is provided with sampling and coding means which delivers coded sum signals S and coded difference signals Δ

, comprising;

first means for calculating with respect to time successive derivatives P.sup.(k) of order k, k being between 0 and N'"'"'(N'"'"'≧

2), of the power P=|S² of a signal received;

second means for calculating with respect to time successive derivatives Q.sup.(k) of order k, k being between 0 and N'"'"' of the scalar product Q=S·

Δ

of the sum signal S and difference signal Δ

;

third means for calculating each derived angle-error measurement operator ##EQU31## of order k, k being between 0 and N'"'"', which is equal to the ratio of the derivatives of order k of the scalar product Q=S·

Δ and

of the power P=|S|² of the signal received with respect to time;

fourth means for calculating a coefficient β

_k which is associated with each derived angle-error measurement operator ε

_k of order k, of between 0 and N'"'"', and which characterises the quality of the respective operator ε

_k relative to the angle-error measurement of the barycenter of the target; and

fifth means for calculating a combined angle-error measurement operator ε

which is equal to the linear combination of the (N'"'"'+1) derived angle-error measurement operators ε

_k weighted by the associated quality coefficients β

_k.

7. A radar receiver according to claim 6, wherein the first calculating means includes:

a first circuit for calculating the power p.sup.(o) =P=|S|² of the signal received, from the sampled and coded sum signal S, in series with

a plurality N'"'"' of differentiators arranged in series, the differentiator of order k between 1 and N'"'"' calculating the derivative with respect to time of the signal P.sup.(k-1) applied to its input.

8. A radar receiver according to claim 6, wherein the second calculating means includes:

a first circuit for calculating the scalar product Q.sup.(o) =Q=S·

Δ

of the sampled and coded sum signal S and difference signal Δ

, in series with

a plurality N'"'"' of differentiators arranged in series, the differentiator of order k, k being between 1 and N'"'"', calculating the derivative with respect to time of the signal Q.sup.(k-1) applied to its input.

9. A radar receiver according to claim 6, wherein the third calculating means includes a plurality of (N'"'"'+1) dividers each divider, of order k of between O and N'"'"' receiving at a first input the signal P.sup.(k) delivered by the first calculating means and at a second input the signal Q.sup.(k) delivered by the second calculating means, and calculating the ratio ε

_k of the second input signal to the first input signal.

10. A radar receiver according to claim 6, wherein the fourth calculating means includes a plurality of (N'"'"'+1) circuits, each circuit of order k between 0 and N'"'"', comprising:

a first circuit for calculating the modulus A_k of the signal P.sup.(k) delivered by the first calculating means;

a circuit for normalizing the modulus A_k of the signal P.sup.(k) ;

a threshold circuit delivering a pulse signal (Y) whose level is "0" for the values of A_k which are less than or equal to a positive threshold (p_k), and "1" for the values of A_k which are greater than said threshold (p_k); and

a multiplying circuit which receives the normalized modulus A_k delivered by the normalizing circuit and the pulse signal (Y) delivered by the threshold circuit, and delivers the quality coefficient (β

_k).

11. A radar receiver according to claim 6, wherein the fourth calculating means comprises a plurality of (N'"'"'+1) sub-units, each sub-unit of order k from 0 to N'"'"' comprising:

a first calculating circuit for raising to the k-th power a time constant (τ

_k) and delivering an homogenizing coefficient (τ

_k^k) to an input of

a second calculating circuit for multiplying the signal (P.sup.(k) delivered by the first calculating means and the homogenizing coefficient (τ

_k^k) from the first calculating circuit; and

a third calculating circuit for raising to the n-th power, with n being higher than or equal to 2, the product [τ

_k^k ·

P.sup.(k) ]ⁿ supplied by the second calculating circuit and delivering the quality coefficient β

_k =[τ

_k^k ·

P.sup.(k) ]ⁿ to the input of the fifth calculating means.

12. A radar receiver according to claim 6, wherein the fifth calculating means includes:

a plurality of (N'"'"'+1) multiplying circuits each multiplying circuit of order k between O and N'"'"' receiving at a first input the quality coefficient (β

_k) of order k delivered by the fourth calculating means and at a second input the derived angle-error measurement operator (ε

_k) of order k delivered by the third calculating means and delivering the product (β

_k.ε

_k) of its two input signals;

a first adding circuit which has (N'"'"'+1) inputs fed respectively with the output signals (β

_k.ε

_k) from the (N'"'"'+1) multiplying circuits and delivers a signal ##EQU32## equal to the algebraic sum of the input signals;

a second adding circuit which has (N'"'"'+1) inputs fed respectively with the quality coefficients (β

_k) calculated by the fourth calculating means and delivers a signal ##EQU33## equal to the algebraic sum of the input signals; and

a dividing circuit receiving at a first input the output signal ##EQU34## from the first adding circuit and at a second input the output signal ##EQU35## from the second adding circuit and delivering the combined angle-error measurement signal ε

which is equal to the ratio of the first input signal to the second input signal.