Patent GB-1065220-A (GB)
Title: Single-channel signal-processing network and monopulse receiver systems embodying the same
IPC: G01S13/44
Filed: 1965-12-23
Abstract: 1,065,220. Electric analogue calculating. COMPAGNIE FRANCAISE THOMSONHOUSTON-HOTCHKISS BRANDT. Dec. 23, 1965 [Dec. 24, 1964], No. 54706/65. Heading G4G. [Also in Division H4] The invention relates generally to a system for deriving, from a plurality of input signals, each of which is a function of the same set of independent variables, a set of output signals each being a function of a respective single one of said variables. In the described application to a monopulse radar, the input signals Vg, Vs and Vo are derived by a known sum and difference network (4), Fig. 1 (not shown), from the outputs of four antennae (A), (B), (C), (D) arranged in an upright square, such that Also, if # and # being said independent variables are the azimuth and elevation angles of the target, respectively, then The system is thus described as producing out- Vg Vs put signals representing - and -, and thus Vo Vo the angular co-ordinates of the target. The three input signals are heterodyned in mixers 18, 20 and 22 respectively with the output of oscillator 24, to produce IF signals Signal S may be then used via line 82 for range determination. Signals Dg and: Ds are modulated in balanced modulators 40 and 42 respectively by the output of a local oscillator 52 at a frequency #m, via phase shifters 48 and 50 respectively, introducing phase shifts of (# - 90 degrees) and # respectively. If # 2 # #m, then the outputs of modulators 40 and 42 are, respectively. The two outputs are added in hybrid junction 56, and the produced sum further added to a signal, produced by 90 degrees phase shifting signal S, is hybrid junction 58, to produce a sum signal, where The term V is removed by limiter 34, and the sum signal is then fed to an angle discriminator or frequency discriminator 36, which, since frequency is the time derivative of phase, produces at its output, the time derivative of Vg V8 #(t), thus, if- = g,- = 8, and (#m<SP>t</SP>+#) Vo Vo = #, then the output is This output is fed to two balanced demodulators 64 and 66 fed with demodulating signals from oscillator 52 via delays 68 and 70, which introduce respective delays of # and (# - 90 degrees). The demodulators 64 and 66 respectively produce outputs It is shown that, A similar expression holds for Ps. The two demodulator outputs are each fed to a low pass filter 74 and 76 having cut-off frequencies less than 2fm. The outputs #g and #s of filters 74 and 76 are given by Since, however, g and s are usually very small, Thus the object is achieved. It has been assumed that the amplifier 34 has a linear phase/frequency characteristic response. If, however, its response is non-linear with a group transfer time of #, then a delay of # can be introduced at 72 to compensate for it. In a briefly described application to four input signals D 1 , D 2 , D 3  and S, where D 1 /S=f(x, y, z), D 2 /S=g(Fx, y, z), D 3 /S=h(x, y, z), output signal #x, #y, #z are produced being functions of the one variable only. For D 1  and D 2  the system is described, whilst for D 3  a separate local oscillator (153), Fig. 3 (not shown) is used generating a different frequency fm 2  to produce frequency diversification for D 3 .