Abstract: A method of processing altitude measurements for an aircraft is disclosed. The method involves filtering raw altimeter data within an altimeter to substantially limit random variations in the altitude measurements for one or more altimeter measurement profiles.

Abstract: An electronic circuit comprises a randomizing bit generator configured to generate a randomizing bit sequence based on a sequence selection input signal. The randomizing bit generator includes a counter operable to provide an individual starting count for the randomizing bit sequence and a parity generator responsive to an output of the counter. The circuit further comprises a pseudo-random number generator responsive to the randomizing bit generator. The pseudo-random number generator is operable to provide at least one pulsed signal based at least in part on the random bit sequence. The electronic circuit is operable to substantially eliminate interference in a series of pulsed signal transmissions comprising the at least one pulsed signal from each of two or more navigation devices, where each of the pulsed signals from each of the navigation devices is separated by an automatically adjustable time interval.

Abstract: An electronic circuit comprises a randomizing bit generator configured to generate a randomizing bit sequence based on a sequence selection input signal. The randomizing bit generator includes a counter operable to provide an individual starting count for the randomizing bit sequence and a parity generator responsive to an output of the counter. The circuit further comprises a pseudo-random number generator responsive to the randomizing bit generator. The pseudo-random number generator is operable to provide at least one pulsed signal based at least in part on the random bit sequence. The electronic circuit is operable to substantially eliminate interference in a series of pulsed signal transmissions comprising the at least one pulsed signal from each of two or more navigation devices, where each of the pulsed signals from each of the navigation devices is separated by an automatically adjustable time interval.

Abstract: A method of processing altitude measurements for an aircraft is disclosed. The method involves filtering raw altimeter data within an altimeter to substantially limit random variations in the altitude measurements for one or more altimeter measurement profiles.

Abstract: A method for maintaining a position of a hovering vehicle that incorporates a radar altimeter is described. The method includes receiving signals at the radar altimeter based on a change of horizontal direction, operating the radar altimeter to generate a Doppler frequency spectrum based on the received signals, and determining a change in vehicle direction and velocity which will reduce a width of the Doppler frequency spectrum of the received signals. A radar altimeter which generates the Doppler frequency spectrum is also described.

Abstract: An in-phase/quadrature component (IQ) mixer is configured to reject returns from a negative doppler shift swath in order to mitigate corruption of returns of a positive doppler shift swath. The mixer includes a sample delay element which produces a quadrature component from the in-phase component of an input signal. Further included are a plurality of mixer elements, a plurality of low pass filters, a plurality of decimators, and a plurality of all pass filters which act upon both the in-phase and quadrature components of the input signal. Also, a subtraction element is included which is configured to subtract the filtered and down sampled quadrature component from the filtered and down sampled in-phase component.

Abstract: An in-phase/quadrature component (IQ) mixer is configured to reject returns from a negative doppler shift swath in order to mitigate corruption of returns of a positive doppler shift swath. The mixer includes a sample delay element which produces a quadrature component from the in-phase component of an input signal. Further included are a plurality of mixer elements, a plurality of low pass filters, a plurality of decimators, and a plurality of all pass filters which act upon both the in-phase and quadrature components of the input signal. Also, a subtraction element is included which is configured to subtract the filtered and down sampled quadrature component from the filtered and down sampled in-phase component.

Abstract: A filter, includes a first order band pass filter configured to process non-zero amplitude gated radar return samples and process a portion of received zero amplitude return samples. The filter also calculates past filter outputs based on filter outputs generated during previous non-zero gated radar return samples.

Abstract: A filter, includes a first order band pass filter configured to process non-zero amplitude gated radar return samples and process a portion of received zero amplitude return samples. The filter also calculates past filter outputs based on filter outputs generated during previous non-zero gated radar return samples.

Abstract: An in-phase/quadrature component (IQ) mixer is configured to reject returns from a negative doppler shift swath in order to mitigate corruption of returns of a positive doppler shift swath. The mixer includes a sample delay element which produces a quadrature component from the in-phase component of an input signal. Further included are a plurality of mixer elements, a plurality of low pass filters, a plurality of decimators, and a plurality of all pass filters which act upon both the in-phase and quadrature components of the input signal. Also, a subtraction element is included which is configured to subtract the filtered and down sampled quadrature component from the filtered and down sampled in-phase component.

Abstract: A radar altimeter for determining altitude of an air vehicle with respect to ground comprises a digital sequencer for digitally modulating a first signal. A transmitter coupled to the digital sequencer transmits a radar signal including the modulated first signal toward the ground. A receiver receives a reflected radar signal from the ground. The received radar signal includes the modulated first signal. A digitizer coupled to the receiver generates digital samples of the modulated first signal. A digital signal processor coupled to the digitizer receives digital samples of the modulated first signal from the digitizer, demodulates the received digital samples, processes the demodulated digital samples and outputs altitude data based on the demodulated digital samples.

Abstract: A radar altimeter for determining altitude of an air vehicle comprises a transmitter for transmitting radar signals toward the ground. A first and a second antenna receive reflected radar signals from the ground. A signal processor is coupled to the first and the second antennas. The signal processor includes filter means for rejecting signals other than signals reflected from a selected ground swath. The signal processor determines the above ground level altitude of the air vehicle based on the radar signals output from the filter means. A phase ambiguity resolution means resolves phase ambiguities that arise due to multiple wavelength separation of the first and the second antenna. The signal processor also determines the horizontal position of the highest point in the selected ground swath.