US 10,320,365 B2 · Filter that minimizes in-band noise and maximizes detection sensitivity of exponentially-modulated signals

Abstract

Frequency domain (FDTF) and time domain (TDTF) trans-filters compress in-band AWGN, demodulate input signals and have no threshold due to applied noise. Two parallel frequency selective networks with opposite amplitude vs frequency slopes are designed to remain 180 degrees out of phase over the signal band in the FDTF whereas two parallel delay networks are used in the TDTF. Output amplitudes are equal at band center and are summed producing a monotonic amplitude vs frequency characteristic going thru zero at center frequency with abrupt phase reversal. This produces the parabolic output noise density and differentiates applied signals. Absence of nonlinear circuit components and product devices prevents generation of noise×noise products, avoiding the threshold phenomenon. Exponentially modulated digital signals produce output impulses due to the slope and abrupt phase reversal. The impulses have strong fundamental frequency components and may be recovered at baseband without frequency conversion. Cascading trans-filters increases noise reduction and impulse amplitude. The trans-filter algorithm may be used separately or in conjunction with one or more hardware trans-filters.

Claims26

Dependent claims

A filter that demodulates an exponentially-modulated signal, having noise in its signal band, and compresses the noise in its signal band, said filter comprising:

a pair of parallel paths having a common input into which is fed the exponentially modulated signal and wherein at least one of said parallel paths comprises a time delay for delaying the exponentially-modulated signal passing therethrough, each of said parallel paths comprising a respective output signal and wherein said respective output signals are delayed in time from each other by a predetermined parameter, said parallel paths and said time delay comprising only linear components, said linear components minimizing a threshold that is normally present in exponentially-modulated signal demodulators that use non-linear components;
a summing network for receiving said respective output signals and summing said respective output signals to generate an output that is a function of a rate change of a carrier frequency of the exponentially-modulated signal, said output comprising impulses for abrupt changes in the carrier frequency corresponding to data transitions that form a baseband of said exponentially-modulated signal;
and
wherein said filter is operative on any modulation format of said exponentially modulated signal and generates said impulses while compressing noise in the signal band.

1 more element

A system, formed of at least two filters, that demodulates an exponentially-modulated signal, having noise in its signal band, and compresses the noise in its signal band, said system comprising:

a first filter comprising:
a first pair of parallel paths having a common input into which is fed the exponentially modulated signal and wherein at least one of said first parallel paths comprises a time delay for delaying the exponentially-modulated signal passing therethrough, each of said first parallel paths comprising a respective output signal and wherein said respective output signals are delayed in time from each other by a predetermined parameter, said parallel paths and said time delay comprising only linear components, said linear components minimizing a threshold that is normally present in exponentially-modulated signal demodulators that use non-linear components;
a first summing network for receiving said respective output signals from said first pair of parallel paths and summing said respective output signals to generate an output that is a function of a rate change of a carrier frequency of said exponentially-modulated signal, said output comprising impulses for abrupt changes in the carrier frequency corresponding to data transitions that form a baseband of said exponentially-modulated signal;
and
wherein said first filter is operative on any modulation format of said exponentially modulated signal and generates said impulses while compressing noise in the signal band;
and
a second filter comprising:
a second pair of parallel paths having a common input into which said impulses are fed and wherein at least one of said second parallel paths comprises a time delay for delaying the impulses passing therethrough, each of said second parallel paths comprising a respective output signal and wherein said respective output signals of said second pair of parallel paths are delayed in time from each other by said predetermined parameter, said second pair of parallel paths and said time delay comprising only linear components, said linear components minimizing the threshold that is normally present in exponentially-modulated signal demodulators that use non-linear components;
and
a second summing network for receiving said respective output signals from said second pair of parallel paths and summing said respective output signals to further increase amplitudes of said impulses for abrupt changes in the carrier frequency corresponding to data transitions that form the baseband of said exponentially-modulated signal while further compressing noise in the signal band.

7 more elements

Dependencies are inferred from the claim text.

Filter that minimizes in-band noise and maximizes detection sensitivity of exponentially-modulated signals

Life of this patent

Filter that minimizes in-band noise and maximizes detection sensitivity of exponentially-modulated signals

Life of this patent

Abstract

Claims26