Frequency discriminator using digital non-recursive filters

Claim 2

In a discriminator for detecting sinusoidal frequencies omega 1 and omega 2, the discriminator being operative along a lInear portion of a relative magnitude-frequency characteristic E( omega )/F( omega ) K cos ( omega T/2), E( omega ) and F( omega ) being the output and input frequency functions respectively, T being both the discriminator time delay and a null of the characteristic, and omega lying within the range omega 1 < OR = omega < OR = omega 2, the combination comprising: means (FIG. 4-2; FIG. 5-2, 56) for sampling successive magnitudes of the applied frequencies and for digitally encoding such sampled magnitudes in two''s complement form; a T second multitap delay element (23, 29) to which said digitally encoded samples are applied; first filter means (21, 70, 31, 33, 25, 28, 35, 35a, 37, 41) including the sampling means and the delay element for forming the relative magnitude-frequency characteristic: E1 ( omega )/F( omega ) a1e j T/2 + a2 + a3e j T/2 1ej T/2 + 2 + 1e j T/2, a1, a2, and a3 being coefficients; second filter means (21, 70, 31, 33, 25, 28, 35, 35b, 39, 43) also including the sampling means and the delay element for forming another relative magnitude-frequency characteristic E2 ( omega )/F( omega ) -a13 j T/2 + a2 - a3e j T/2 -1e j T/2 + 2 - le j T/2; and means (45) for forming a combined characteristic such that E( omega )/F( omega ) E1 ( omega )/F( omega ) - E2 ( omega )/F( omega ) K cos ( omega T/2).

Claim 3

In a discriminator for detecting sinusoidal frequencies omega 1 and omega 2, the discriminator being operative along a linear portion of a relative magnitude-frequency characteristic E( omega )/F( omega ) K cos omega T/2, E( omega ) and F( omega ) being the output and input frequency functions respectively, T being both the discriminator time delay and a null of the characteristic, and omega lying within the range omega 1 < or = omega < or = omega 2, the combination comprising: shift register means (23, 29) of delay T; means (FIG. 4-2; FIG. 5-2, 56) for sampling successive magnitudes of the applied frequencies and for digitally encoding such sampled magnitudes in two''s complement form and for serially applying the encoded samples to the shift register means; first means (21, 70, 31, 33) for forming a signal f(t- T/2) + f(t+ T/2) from the shift register input (21) and output (70), f(t) being a generalized function of time; second means (25, 28, 35) for forming a signal 2f(t) from the shift register stage (23) located T/2 delay units from the register input; third means (33, 35a, 37, 41) for algebraically combining the outputs from the first and second means to yield +f(t-T/2)+2f(t)+f(t+ T/2); fourth means (33, 35b, 39, 43) for algebraically combining the outputs from the first and second means to yield -f(t-T/2)+2f(t)-f(t- I/2); and fifth means (45) for algebraically combining the outputs from the third and fourth means such that f(t- T/2)+2f(t)+f(t+ T/2)+f(t- T/2)-2f(t)+f(t+ T/2) 2f(t- T/2)+2f(t+ T/2), the Fourier Transform of which E( omega )/F( omega ) 2e j T/2 + 2e j T/2 4((ej T/2 + e j T/2)/2) K cos omega T/2.

Claim 4

In a discriminator for detecting sinusoidal frequencies omega 1 and omega 2, the discriminator being operative along a linear portion of a relative magnitude-frequency characteristic E( omega )/F( omega ) K cos omega T/2, E( omega ) and F( omega ) being the output and input frequency functions respectively, T being both the discriminator time delay and a null of the characteristic, and omega lying within the range omega 1 < or = omega < or = omega 2, the combination comprising: shift register means (23, 29) of delay T; means (FIG. 4-2; FIG. 5-2, 56) for sampling successive magnitudes of the applied frequencies and for digitally encoding such sampled magnitudes in two''s complement form and for serially applying the encoded samples to the shift register means; first means (21, 70, 31, 33) for forming a signal f(t- T/2) + f(t+ T/2) from the shift register input (21) and output (70), f(t) being a generalized function of time; second means (25, 28, 35) for forming a signal 2f(t) from the shift register stage (23) located T/2 delay units from the register input; third means (33, 35a, 37, 41) for algebraically combining the outputs from the first and second means to yield +f(t-T/2)+2f(t)+f(t+ T/2); fourth means (33, 35b, 39, 43) for algebraically combining the outputs from the first and second means to yield -f(t-T/2)+2f(t)-f(t- I/2); and fifth means (45) for algebraically combining the outputs from the third and fourth means such that f(t- T/2)+2f(t)+f(t+ T/2)+f(t- T/2)-2f(t)+f(t+ T/2) 2f(t- T/2)+2f(t+ T/2), the Fourier Transform of which E( omega )/F( omega ) 2e j T/2 + 2e j T/2 4((ej T/2 + e j T/2)/2) K cos omega T/2.