Trans-filter/Detectors are extremely sensitive circuits that recover exponentially modulated signals buried in noise. They can be used wherever Matched Filter/Coherent Detectors are used and operate at negative input signal-to-noise ratios to recover RADAR, SONAR, communications, or data signals, as well as reduce phase noise of precision oscillators. Input signal and noise is split into two paths where complementary derivatives are extracted. Outputs of the two paths are equal in amplitude and 180 degrees relative to each other at the band center frequency. The outputs are summed, causing stationary in-band noise to be reduced by cancellation while exponentially modulated signals are undiminished. Trans-filters are Linear Time Invariant circuits, have no noise x noise threshold and can be cascaded, increasing output signal-to-noise ratio prior to detection. Trans-filters are most sensitive to all types of digital modulation, producing easily detected polarized pulses synchronous with data transitions. Trans-filters do not require coherent conversion oscillators and complex synchronizing circuits.

Trans-filter/Detectors are extremely sensitive circuits that recover exponentially modulated signals buried in noise. They can be used wherever Matched Filter/Coherent Detectors are used and operate at negative input signal-to-noise ratios to recover RADAR, SONAR, communications, or data signals, as well as reduce phase noise of precision oscillators. Input signal and noise is split into two paths where complementary derivatives are extracted. Outputs of the two paths are equal in amplitude and 180 degrees relative to each other at the band center frequency. The outputs are summed, causing stationary in-band noise to be reduced by cancellation while exponentially modulated signals are undiminished. Trans-filters are Linear Time Invariant circuits, have no noise x noise threshold and can be cascaded, increasing output signal-to-noise ratio prior to detection. Trans-filters are most sensitive to all types of digital modulation, producing easily detected polarized pulses synchronous with data transitions. Trans-filters do not require coherent conversion oscillators and complex synchronizing circuits.

The invention relates to a method for simplifying a sampled signal digital filter, the method including at least one step for: in order to obtain a first intermediate filter, gathering channels including discrete nonstationary operations relating to the same signal, the first channels including the nonstationary operations relating to a first signal and the second channels including the nonstationary operations relating to a second signal, in order to obtain a second intermediate filter, on each of the first channels and second channels, commutative stationary operations with the nonstationary operations, in order to eliminate the redundant nonstationary operations, and building the filter corresponding to the last obtained intermediate filter.

The invention relates to a method for filtering a numerical input signal sampled at a sampling frequency in order to obtain a filtered signal, the method including at least one step for: obtaining a first (respectively second) output signal by carrying out first (respectively second) operations on the first (respectively second) processing channel, the first (respectively second) operations including at least the application of a discrete Fourier transform to M/2.sup.p points on a signal coming from the input signal, the integer p being greater than or equal to 1, applying an inverse discrete Fourier transform to M/2.sup.p points on the first signal in order to obtain M points of the spectrum of the first signal, M being an integer strictly greater than 2, the application step being carried out by the addition of the results of two processing channels.

Trans-filter/Detectors are extremely sensitive circuits that recover exponentially modulated signals buried in noise. They can be used wherever Matched Filter/Coherent Detectors are used and operate at negative input signal-to-noise ratios to recover RADAR, SONAR, communications, or data signals, as well as reduce phase noise of precision oscillators. Input signal and noise is split into two paths where complementary derivatives are extracted. Outputs of the two paths are equal in amplitude and 180 degrees relative to each other at the band center frequency. The outputs are summed, causing stationary in-band noise to be reduced by cancellation while exponentially modulated signals are undiminished. Trans-filters are Linear Time Invariant circuits, have no noise×noise threshold and can be cascaded, increasing output signal-to-noise ratio prior to detection. Trans-filters are most sensitive to all types of digital modulation, producing easily detected polarized pulses synchronous with data transitions. Trans-filters do not require coherent conversion oscillators and complex synchronizing circuits.

Trans-filter/Detectors are extremely sensitive circuits that recover exponentially modulated signals buried in noise. They can be used wherever Matched Filter/Coherent Detectors are used and operate at negative input signal-to-noise ratios to recover RADAR, SONAR, communications or data signals. Input signal and noise is split into two paths where complementary derivatives are extracted. Outputs of the two paths are equal in amplitude and 180 degrees relative to each other at the band center frequency. The outputs are summed, causing stationary in-band noise to be reduced by cancellation while exponentially modulated signals are increased by addition. Trans-filters are Linear Time Invariant circuits, have no noise×noise threshold and can be cascaded, increasing in-band signal-to-noise ratio prior to detection. Trans-filters are most sensitive to all types of digital modulation, producing easily detected polarized pulses synchronous with data transitions. Trans-filters do not require coherent conversion oscillators and complex synchronizing circuits.

The invention relates to a method for filtering a numerical input signal sampled at a sampling frequency in order to obtain a filtered signal, the method including at least one step for: obtaining a first (respectively second) output signal by carrying out first (respectively second) operations on the first (respectively second) processing channel, the first (respectively second) operations including at least the application of a discrete Fourier transform to M/2.sup.p points on a signal coming from the input signal, the integer p being greater than or equal to 1, applying an inverse discrete Fourier transform to M/2.sup.p points on the first signal in order to obtain M points of the spectrum of the first signal, M being an integer strictly greater than 2, the application step being carried out by the addition of the results of two processing channels.

The invention relates to a method for simplifying a sampled signal digital filter, the method including at least one step for: in order to obtain a first intermediate filter, gathering channels including discrete nonstationary operations relating to the same signal, the first channels including the nonstationary operations relating to a first signal and the second channels including the nonstationary operations relating to a second signal, in order to obtain a second intermediate filter, on each of the first channels and second channels, commutative stationary operations with the nonstationary operations, in order to eliminate the redundant nonstationary operations, and building the filter corresponding to the last obtained intermediate filter.

The invention relates to a method for filtering a numerical input signal sampled at a sampling frequency in order to obtain a filtered signal, the method including at least one step for: obtaining a first (respectively second) output signal by carrying out first (respectively second) operations on the first (respectively second) processing channel, the first (respectively second) operations including at least the application of a discrete Fourier transform to M/2 points on a signal coming from the input signal, applying an inverse discrete Fourier transform to M/2 points on the first signal in order to obtain M points of the spectrum of the first signal, M being an integer strictly greater than 2, the application step being carried out by the addition of the results of two processing channels.

Trans-filter/Detectors are extremely sensitive circuits that recover exponentially modulated signals buried in noise. They can be used wherever Matched Filter/Coherent Detectors are used and operate at negative input signal-to-noise ratios to recover RADAR, SONAR, communications or data signals. Input signal and noise is split into two paths where complementary derivatives are extracted. Outputs of the two paths are equal in amplitude and 180 degrees relative to each other at the band center frequency. The outputs are summed, causing stationary in-band noise to be reduced by cancellation while exponentially modulated signals are increased by addition. Trans-filters are Linear Time Invariant circuits, have no noise x noise threshold and can be cascaded, increasing in-band signal-to-noise ratio prior to detection. Trans-filters are most sensitive to all types of digital modulation, producing easily detected polarized pulses synchronous with data transitions. Trans-filters do not require coherent conversion oscillators and complex synchronizing circuits.