N path filter having two input and n output paths

Claim 2

An N path filter comprising: two orthogonal input paths receiving in parallel, the input signal to be filtered; N equiphase output paths obtained by combining both input paths; and a final summation device carrying out the sum of N output paths and providing the filter output signal; each input path comprises: an input modulator the modulation signal of which is sinusoidal, the modulation signals of both input modulators being in quadrature, and a low pass filter; each output path includes: a summation device supplying the sum of the signals supplied by both input paths provided with weighting factors, and an output modulator, the modulation signal of which is sinusoidal, and has the same frequency as the modulation signals of the input modulators, the modulation signals of the various output modulators being phase shifted by an equal value.

Claim 3

An N path filter of claim 1, wherein the weighting factor of the signals supplied by an input path and enabling to obtain a certain output path represents the projection of the modulation signal of this output path with respect to the modulation signal of this input path.

Claim 4

An N path filter of claim 2, wherein the modulation signals of the input modulators are approximated by an alternating succession of positive and negative pulses of a duration of one quarter of the period of the sinusoidal modulation signals they approach and separated by a quarter of the period of the sinusoidal modulation signals they approach, the alternating successions of positive and negative pulses of the two input paths being in quadrature; and wherein each input modulator includes a first and a second input switching device, the outputs of which are connected in parallel to the low pass filter of the corresponding input path, the first input switching device receiving the input signal to be filtered and the second input switching device receiving the reciprocal of the input signal to be filtered, the positive and negative pulses controlling the closing of the first and second switching devices respectively.

Claim 5

An N path filter of claim 3 characterized in that it includes an input inverter receiving the input signal to be filtered, and the output of which is connected in parallel to the second input switching devices of the first and second input paths.

Claim 6

An N path filter of anyone of claim 1, wherein the modulation signals of the oUtput modulators are approximated by an alternating succession of positive and negative pulses of a duration of 1/2N peroids of the sinusoidal modulation signals and separated by N-1/2N periods of the sinusoidal modulation signal, the alternating successions of positive and negative pulses of the various output paths being phase shifted of an equal value, and in that each output modulator includes a first and a second output switching device, the outputs of which are interconnected, the output of the first output switching device being directly connected to the final summing device and the reversed output of the second output switching device being connected to the final summing device, the positive and negative pulses controlling the closing of the first and second switching devices respectively.

Claim 7

An N path filter of claim 4, wherein the filter also includes an output inverter receiving, in parallel, the outputs of the second output switching devices of N output paths, the output of which is directly connected to the final summing device.

Claim 8

An N path filter comprising: means (7, 9, 11, 13, 15, 17) for generating a pair of time varying orthogonal signals f1(t) and f2(t) responsive to the application of a continuous time varying signal f(t) said means include: means (7, 9) for modulating the applied signal f(t) with a carrier of frequency Omega radians per second in quadrature, thereby yielding the signals f(t)cos( Omega t) and f(t)sin( Omega t); and Filter means (11, 13) having a time domain impulse response h(t) convolvable with the quadrature signals in order to obtain the orthogonal signals f1(t) and f2(t) wherein f1(t) (f(t)cos( Omega t))xh(t) f2(t) (f(t)cos( Omega t))x h(t); x being the convolution operator; N equiphase paths (19, 25; 21, 27; 23, 29), each path being responsive to the pair of orthogonal signals and having means (21, 27) for forming an output signal element gi(t) according to the relation: gi(t) (aif1(t)+bif2(t))cos( Omega t+i2 pi /N); ai and bi being constant phase elements such that ai cos (i2 pi /N) and bi -sin(i2 pi /N), which relation gi(t) upon substitution thereinto reduces to: gi(t) (f(t)cos( Omega t+i2 pi /N) xh(t))cos( Omega t+i2 pi /N); and means (31) for forming the filter output signal g(t) by algebraically combining the elemental output signals gi (t) such that

Claim 9

An N path filter comprising: means (7, 9, 11, 13, 15, 17) for generating a pair of time varying orthogonal signals f1(t) and f2(t) responsive to the application of a continuous time varying signal f(t) said means include: means (7, 9) for modulating the applied signal f(t) with a carrier of frequency Omega radians per second in quadrature, thereby yielding the signals f(t)cos( Omega t) and f(t)sin( Omega t); and Filter means (11, 13) having a time domain impulse response h(t) convolvable with the quadrature signals in order to obtain the orthogonal signals f1(t) and f2(t) wherein f1(t) (f(t)cos( Omega t))xh(t) f2(t) (f(t)cos( Omega t))x h(t); x being the convolution operator; N equiphase paths (19, 25; 21, 27; 23, 29), each path being responsive to the pair of orthogonal signals and having means (21, 27) for forming an output signal element gi(t) according to the relation: gi(t) (aif1(t)+bif2(t))cos( Omega t+i2 pi /N); ai and bi being constant phase elements such that ai cos (i2 pi /N) and bi -sin(i2 pi /N), which relation gi(t) upon substitution thereinto reduces to: gi(t) (f(t)cos( Omega t+i2 pi /N) xh(t))cos( Omega t+i2 pi /N); and means (31) for forming the filter output signal g(t) by algebraically combining the elemental output signals gi (t) such that

Claim 10

An N path filter according to claim 7, wherein: h(t) is the filter impulse response of the form h(t) Ae t sin ( Omega t) in which A is the relative magnitude, Alpha is the inverse filter time constant.

Claim 11

An N path filter according to claim 7 wherein the means for generating a pair of orthogonal signals includes means for approximating the f(t) cos ( Omega t) and f(t) sin ( Omega t) terms by the respective multiplication of f(t) by a predetermined number of uniform pulses in fixed phase and time relation.