Monopulse processor digital correction circuit

Claim 2

In a monopulse radar having sum Σ and difference Δchannels for providing angular measurements of a radar target from the radar, said sum channel including a first quadrature detector, said difference channel including a second quadrature detector, each of said first and second detectors having an in-phase I channel and a quadrature Q channel; a method for digital compensation of phase and gain drift in said first and second detectors comprising the steps of: first, injecting a first signal of known amplitude and arbitrary phase into both said first and second detectors; second, measuring the uncorrected voltage outputs of said in-phase I and quadrature Q channels of said first detector and said second detector to provide values V.sub.ΣI (1) from said in-phase channel of said first detector and V.sub.ΣQ (1) from said quadrature channel of said first detector and V.sub.ΔI (1) from said in-phase channel of said second detector and V.sub.ΔQ (1) from said quadrature channel of said second detector; third, inserting a 90° phase shift in said first signal to provide a second signal; fourth, injecting said second signal into both said first and said second detectors; fifth, measuring the uncorrected voltage outputs of said in-phase I and quadrature Q channels of said first and second detectors to provide values V.sub.ΣI (2) from said in-phase channel of said first detector and V.sub.ΣQ (2) from quadrature channel of said first detector and V.sub.ΔI (2) from said in-phase channel of said second detector and V.sub.ΔQ (2) from said quadrature channel of said second detector; sixth, computing directly from said values V.sub.ΣI (1), V.sub.ΣQ (1), V.sub.ΣI (2) and V.sub.ΣQ (2) a first set of four correction coefficients K 1 , K 2 , K 3 and K 4 ; seventh, computing directly from said values V.sub.Δ I (1), V.sub.ΔQ (1), V.sub.ΔI (2) and V.sub.ΔQ (2) a second set of four correction coefficients K 5 , K 6 , K 7 and K 8 ; eighth, removing said first and second signals from both said first and second quadrature detectors; ninth, applying said first set of coefficients to the output signals of said in-phase and quadrature channels of said first detector to provide third and fourth signals having compensation for phase and gain drift; and tenth, applying said second set of coefficients to the output signals of said in-phase and quadrature channels of said second detector to provide fifth and sixth signals having compensation for phase and gain drift.

Claim 3

The method of claim 1 wherein: said sixth step of computing from said values V.sub.ΣI (1), V.sub.ΣQ (1), V 93 I (2) and V.sub.ΣQ (2) a first set of four correction coefficients K 1 , K 2 , K 3 and K 4 includes: computing said first set of coefficients from the relationships: K.sub.1 =A[V.sub.ΣQ (2)/D.sub.Σ ] K.sub.2 =-A[V.sub.ΣI (2)/D.sub.Σ ] K.sub.3 =-A[V.sub.ΣQ (1)/D.sub.Σ ] K.sub.4 =A[V.sub.ΣI (1)/D.sub.Σ ] where: D.sub.Σ =V.sub.ΣI (1)V.sub.ΣQ (2)-V.sub.ΣQ (1)V.sub.ΣI (2); and A equals the desired corrected signal amplitude.

Claim 4

The method of claim 1 wherein: said seventh step of computing from said values V.sub.ΔI (1), V.sub.ΔQ (1), V.sub.ΔI (2) and V.sub.ΔQ (2) a second set of four correction coefficients K 5 , K 6 , K 7 and K 8 includes: computing said second set of coefficients from the relationships: K.sub.5 =A[V.sub.ΔQ (2)/D.sub.Δ ] K.sub.6 =-A[V.sub.ΔI (2)/D.sub.Δ ] K.sub.7 =-A[V.sub.ΔQ (1)/D.sub.Δ ] K.sub.8 =A[V.sub.ΔI (1)/D.sub.Δ ] where: D.sub.Δ =V.sub.ΔI (1)V.sub.ΔQ (2)-V.sub.ΔQ (1)V.sub.ΔI (2); and A equals the desired corrected signal amplitude.

Claim 5

The method of claim 2 wherein: said seventh step of computing from said values V.sub.ΔI (1), V.sub.ΔQ (1), V.sub.ΔI (2) and V.sub.ΔQ (2) a second set of four correction coefficients K 5 , K 6 ,K 7 and K 8 includes: computing said second set of coefficients from the relationships: K.sub.5 =A[V.sub.ΔQ (2)/D.sub.Δ ] K.sub.6 =-A[V.sub.ΔI (2)/D.sub.Δ ] K.sub.7 =-A[V.sub.ΔQ (1)/D.sub.Δ ] K.sub.8 =A[V.sub.ΔI (1)/D.sub.Δ ] where: D 66 =V.sub.ΔI (1)V.sub.ΔQ (2)-VΔQ(1)V.sub.ΔI (2); and A equals the desired corrected signal amplitude.

Claim 6

The method of claim 4 wherein: said ninth step of applying said first set of coefficients to the output signals of said in-phase and quadrature channels of said first detector includes: applying said first set of coefficients according to the relationships: V'.sub.ΣI =K.sub.1 V.sub.ΣI +K.sub.2 V.sub.ΣQ, and V'.sub.ΣQ =K.sub.4 V.sub.ΣQ +K.sub.3 V.sub.ΣI where: V.sub.ΣI and V.sub.ΣQ are the output signals, respectively, of said in-phase and quadrature channels of said first detector; and V'.sub.ΣI and V'.sub.ΣQ are said third and fourth signals, respectively; and wherein: said tenth step of applying said second set of coefficients to the output signals of said in-phase and quadrature channels of said second detector includes: applying said second set of coefficients according to the relationships: V'.sub.ΔI =K.sub.5 V.sub.ΔI +K.sub.6 V.sub.ΔQ, and V'.sub.ΔQ =K.sub.7 V.sub.ΔI +K.sub.8 V.sub.ΔQ where: V.sub.ΔI and V.sub.ΔQ and the output signals, respectively, of said in-phase and quadrature channels of said second detector, and V'.sub.ΔI and V'.sub.ΔQ are said fifth and sixth signals, respectively.

Claim 7

In a monopulse radar having sum Σ and difference Δ channels for providing angular measurements of a radar target from the radar, said sum channel including a first quadrature detector, said difference channel including a second quadrature detector, each of said first and second detectors having an in-phase I channel and a quadrature Q channel; a method for digital compensation of phase and gain drift in said first and second detectors comprising the steps of: first, injecting a first signal of known amplitude and arbitrary phase into both said first and second detectors; second, measuring the uncorrected voltage outputs of said in-phase I and quadrature Q channels of both said first and said second detectors to provide values V.sub.ΣI (1) from said in-phase channel of said first detector and V.sub.ΣQ (1) from said quadrature channel of said first detector and V.sub.ΔI (1) from said in-phase channel of said second detector and V.sub.ΔQ (1) from said quadrature channel of said second detector; third, inserting a 90° phase shift in said first signal to provide a second signal; fourth, injecting said second signal into both said first and said second detectors; fifth, measuring the uncorrected voltage outputs of said in-phase I and quadrature Q channels of both said first and second detectors to provide values V.sub.ΣI (2) and V.sub.ΣQ (2) from said first detector and V.sub.ΔI (2) and V.sub.ΔQ (2) from said second detector; sixth, computing directly from said values V.sub.ΣI (1), V.sub.ΣQ (1), V.sub.ΣI (2) and V.sub.ΣQ (2) a first set of four correction coefficients K 1 , K 2 , K 3 and K 4 ; seventh, computing directly from said values V.sub.ΔI (1), V.sub.ΔQ (1), V.sub.ΔI (2) and V.sub.ΔQ (2) a second set of four correction coefficients K 5 , K 6 , K 7 and K 8 ; eighth, repeating said first, second, third, fourth, fifth, sixth, and seventh steps a plurality of times to provide a plurality of values of said K 1 , K 2 , K 3 and K 4 of said first set of correction coefficients and K 5 , K 6 , K 7 and K 8 of said second set of correction coefficients; ninth, computing from said plurality of values of K 1 , K 2 , K 3 and K 4 a third set of correction coefficients K 1 av., K 2 av., K 3 av. and K 4 av., each of said coefficients of said third set comprising the average value of corresponding coefficients of said plurality of values of said first set; tenth, computing from said plurality of values of K 5 , K 6 , K 7 and K 8 a fourth set of correction coefficients K 5 av., K 6 av., K 7 av. and K 8 av., each of said coefficients of said fourth set comprising the average value of corresponding coefficients of said plurality of values of said second set; eleventh, removing said first and second signals from both said first and said second detectors; twelfth, applying said third set of correction coefficients to the output signals of said in-phase and quadrature channels of said first detector to provide third and fourth signals having compensation for phase gain and drift; and thirteenth, applying said fourth set of correction coefficients to the output signals of said in-phase and quadrature channels of said second detector to provide fifth and sixth signals having compensation for phase gain and drift.

Claim 8

In a monopulse radar having sum Σ and difference Δ channels for providing angular measurements of a radar target from the radar, said sum channel including a first quadrature detector, said difference channel including a second quadrature detector, each of said first and second detectors having an in-phase I channel and a quadrature Q channel; a method for digital compensation of phase and gain drift in said first and second detectors comprising the steps of: first, injecting a first signal of known amplitude and arbitrary phase into both said first and second detectors; second, measuring the uncorrected voltage outputs of said in-phase I and quadrature Q channels of both said first and said second detectors to provide values V.sub.ΣI (1) from said in-phase channel of said first detector and V.sub.ΣQ (1) from said quadrature channel of said first detector and V.sub.ΔI (1) from said in-phase channel of said second detector and V.sub.ΔQ (1) from said quadrature channel of said second detector; third, inserting a 90° phase shift in said first signal to provide a second signal; fourth, injecting said second signal into both said first and said second detectors; fifth, measuring the uncorrected voltage outputs of said in-phase I and quadrature Q channels of both said first and second detectors to provide values V.sub.ΣI (2) and V.sub.ΣQ (2) from said first detector and V.sub.ΔI (2) and V.sub.ΔQ (2) from said second detector; sixth, computing directly from said values V.sub.ΣI (1), V.sub.ΣQ (1), V.sub.ΣI (2) and V.sub.ΣQ (2) a first set of four correction coefficients K 1 , K 2 , K 3 and K 4 ; seventh, computing directly from said values V.sub.ΔI (1), V.sub.ΔQ (1), V.sub.ΔI (2) and V.sub.ΔQ (2) a second set of four correction coefficients K 5 , K 6 , K 7 and K 8 ; eighth, repeating said first, second, third, fourth, fifth, sixth, and seventh steps a plurality of times to provide a plurality of values of said K 1 , K 2 , K 3 and K 4 of said first set of correction coefficients and K 5 , K 6 , K 7 and K 8 of said second set of correction coefficients; ninth, computing from said plurality of values of K 1 , K 2 , K 3 and K 4 a third set of correction coefficients K 1 av., K 2 av., K 3 av. and K 4 av., each of said coefficients of said third set comprising the average value of corresponding coefficients of said plurality of values of said first set; tenth, computing from said plurality of values of K 5 , K 6 , K 7 and K 8 a fourth set of correction coefficients K 5 av., K 6 av., K 7 av. and K 8 av., each of said coefficients of said fourth set comprising the average value of corresponding coefficients of said plurality of values of said second set; eleventh, removing said first and second signals from both said first and said second detectors; twelfth, applying said third set of correction coefficients to the output signals of said in-phase and quadrature channels of said first detector to provide third and fourth signals having compensation for phase gain and drift; and thirteenth, applying said fourth set of correction coefficients to the output signals of said in-phase and quadrature channels of said second detector to provide fifth and sixth signals having compensation for phase gain and drift.

Claim 9

The method as claimed in claim 6 wherein: said sixth step of computing from said values V.sub.ΣI (1), V.sub.ΣQ (1), V.sub.ΣI (2) and V.sub.ΣQ (2) a first set of four correction coefficients K 1 , K 2 , K 3 and K 4 includes: computing said first set of coefficients from the relationships: K.sub.1 =A[V.sub.ΣQ (2)/D.sub.Σ ] K.sub.2 =-A[V.sub.ΣI (2)/D.sub.Σ ] K.sub.3 =-A[V.sub.ΣQ (1)/D.sub.Σ ] K.sub.4 =A[V.sub.ΣI (1)/D.sub.Σ ] where: D.sub.Σ V.sub.ΣI (1)V.sub.ΣQ (2)-V.sub.ΣQ (1)V.sub.ΣI (2); and A equals the desired corrected signal amplitude; and wherein: said seventh step of computing from said values V.sub.ΔI (1), V.sub.ΔQ (1), V.sub.ΔI (2) and V.sub.ΔQ (2) a second set of four correction coefficients K 5 , K 6 , K 7 and K 8 includes: computing said second set of coefficients from the relationships: K.sub.5 =A[V.sub.ΔQ (2)/D.sub.Δ ] K.sub.6 =-A[V.sub.ΔI (2)/D.sub.Δ ] K.sub.7 =-A[V.sub.ΔQ (1)/D.sub.Δ ] K.sub.8 =A[V.sub.ΔI (1)/D.sub.Δ ] wherein: D.sub.Δ =V.sub.ΔI (1)V.sub.ΔQ (2)-V.sub.ΔQ (1)V.sub.ΔI (2); and A equals the desired corrected signal amplitude.

Claim 10

The method of claim 7 wherein: said twelfth step of applying said third set of correction signals to the outputs of said in-phase and quadrature channels of said first detector includes: applying said third set of coefficients according to the relationships: V'.sub.Σ.sub.I =K.sub.1 av.V.sub.ΣI +K.sub.2 av.V.sub.ΣQ, and V'.sub.ΣQ =K.sub.4 av.V.sub.Σ.sub.Q +K.sub.3 av.V.sub.ΣI where: V.sub.ΣI and V.sub.ΣQ are the output signals, respectively, of said in-phase and quadrature channels of said first detector; and V'.sub.ΣI and V'.sub.ΣQ are said third and fourth signals, respectively; and wherein: said thirteenth step of applying said fourth set of correction coefficients to the ptput signals of said in-phase and quadrature channels of said second detector includes: applying said fourth set of coefficients according to the relationships: V'.sub.ΣI =K.sub.5 av.V.sub.ΣI +K.sub.6 av.V.sub.ΣQ, and V'.sub.ΔQ =K.sub.7 av.V.sub.ΔI +K.sub.8 av.V.sub.ΔQ where: V.sub.ΔI and V.sub.ΔQ are the output signals, respectively, of said in-phase and quadrature channels of said second detector, and V'.sub.ΔI and V'.sub.ΔQ are said fifth and sixth signals, respectively.