150 results about "Radar altimeter" patented technology

An altitude measuring system is described that includes a radar altimeter configured to measure altitude and a digital terrain map database. The database includes data relating to terrain elevation and at least one data parameter relating to an accuracy of the terrain elevation data and the altitude measured by the radar altimeter. The system is configured to weigh an altitude derived from the terrain elevation data and the radar altimeter measurements according to the at least one data parameter.

Methods and apparatus for detecting obstacles in the flight path of an air vehicle are described. The air vehicle utilizes a radar altimeter incorporating a forward looking antenna and an electronic digital elevation map to provide precision terrain aided navigation. The method comprises determining a position of the air vehicle on the digital elevation map, selecting an area of the digital elevation map in the flight path of the air vehicle, based at least in part on the determined air vehicle position, and scanning the terrain representing the selected map area with the forward looking antenna. The method also comprises combining the digital elevation map data for the selected map area with radar return data for the scanned, selected area and displaying the combined data to provide a representation of the terrain and obstacles in the forward flight path of the air vehicle.

According to one aspect of the present invention, there is provided a radar altimeter which utilizes a downward looking MIMO phased array to form multiple beams, covering a relatively wide sector, e.g., +/−60 degrees or thereabouts. The distance to the ground is then measured in each beam allowing the ground profile to be formed. The beams may be tilted forward to cover from about +90 degrees forward (horizontal) to about 30 degrees behind nadir. The provision of such a forward tilt gives a greater degree of coverage in the direction of approach vector to the ground. This additional cover enables the altimeter to more accurately detect other vehicles in the proximity to the current approach vector of the vehicle to the desired landing zone.

A navigation system is described which includes a navigation processor, an inertial navigation unit configured to provide a position solution to the navigation processor, and a digital elevation map. The described navigation system also includes a radar altimeter having a terrain correlation processor configured to receive map data from the digital elevation map and provide a position solution based on radar return data to the navigation processor. A map quality processor within the navigation system is configured to receive map data from the digital elevation map and provide a map quality factor to the navigation processor which weights the position solution from the terrain correlation processor according to the map quality factor and determines a position solution from the weighted terrain correlation processor position solution and the position solution from the inertial navigation unit.

The present invention provides a radar altimeter system with a closed loop modulation for generating more accurate radar altimeter values. The system includes an antenna, a circulator, a receiver, and a transmitter. The circulator receives or sends a radar signal from/to the antenna. The receiver receives the received radar signal via the circulator. The transmitter generates a radar signal and includes a phase-locked loop circuit for generating the radar signal based on a pre-defined phase signal. The transmitter includes a direct digital synthesizer that generates the phase signal based on a pre-defined clock signal and a control signal. The system includes a digital signal processor and a tail strike warning processor that determine position of a tail of the aircraft relative to ground and present an alert if a warning condition exists based on the determined position of the tail of the aircraft and a predefined threshold.

A radar altimeter is provided that includes a transmitter operable to generate a radio signal at a modulation frequency, and transmit the radio signal toward a ground surface for reflection therefrom to thereby propagate a reflected radio signal. The radar altimeter also includes a receiver operable to receive the reflected radio signal, and determine the altitude of the aircraft based on the modulation frequency of the radio signal and a difference frequency derived from the radio signal and the reflected radio signal. The receiver is also operable to control the transmitter so as to vary the modulation frequency of the radio signal based on the altitude of the aircraft. Preferably, the modulation frequency of the radio signal is greater at lower altitudes than at higher altitudes.

The terrain referenced navigation system uses data from a global positioning system (GPS) to determine a vehicles position, velocity and height above ground. The system uses input data from an altimeter device, a digital terrain elevation data, and a GPS position, velocity and time data. The system applies a GPS error process model in addition to a TRN measurement model, to obtain a state vector which includes estimates of current errors in the GPS data. The PVT data input from a GPS receiver is used to determine a current vehicle position and height in geographic axis. Using specifically constructed Kalman filter states, a geographical position and height of the vehicle is reference to the digital terrain elevation data, and an estimated ground clearance at the vehicle position is determined. The ground clearance is differenced with a radar altimeter output, and the residual is processed by Kalman filter to determine a new state vector, including estimates of current errors in the GPS data. The output can be configured to be either referenced to navigation axis, or to the digital terrain database for use by other digital terrain system functions.

A method of compensating for component errors within a radar altimeter is described. The method includes periodically switching transmit pulses from a transmit antenna to a programmable delay device, calculating an altitude based on a transmit pulse received from the programmable delay device, comparing the calculated altitude to an expected altitude, the expected altitude based on a pre-set delay through the programmable delay device, and compensating an altitude measured by the radar altimeter, based on transmit pulses output through the transmit antenna, by an error correction amount based on a difference between the calculated altitude and expected altitudes.

The invention relates to a semi-autonomous imitation terrain flight system of an unmanned aerial vehicle. The semi-autonomous imitation terrain flight system comprises a GPS (global positioning system) positioning module, an inertia measurement module, a barometer module, a radar height meter, a motor driver, a paddle power structure and a flight controller, and is characterized in that the flight controller obtains data of the GPS positioning module, the inertia measurement module and the radar height meter to perform fusion algorithm calculation; position, posture and height data of the unmanned aerial vehicle is obtained, so that the motor driver is controlled, and accordingly the unmanned aerial vehicle can perform imitation terrain flight along a flight course in a semi-autonomous mode.

Systems and methods for performing self calibration of a radar altimeter. An example system includes a first component that generates a simulated return signal based on one or more range values. A transmitter generates a transmission radar signal and a receiver processes the simulated return signal based on the transmission radar signal. A second component determines one or more calibration factors based on the processed simulated return signal and ideal return signal characteristics. The transmission radar signal is a fixed frequency signal and the first component includes a programmable frequency divider that creates at least on sideband of a known signal. A third component determines if the radar system is in at least one of a calibration mode or normal mode of operation. If the radar system is determined to be in a normal mode of operation, a fourth component applies the determined calibration factors to actual radar return signals.

The subaperture radar altimeter includes a timer unit, a frequency modulated signal unit, an up conversion amplifier unit, a power amplifier unit, an antenna, a low frequency amplifier unit, a down conversion amplifier unit, a phase detection unit, a digital processing unit, an echo tracking unit, a first mixer, a second mixer and a local oscillator. The digital processing unit completes the Fourier conversion of signal, fine range regulation, compression, coarse range correction and echo processing to obtain the echo waveform; and the echo tracking unit completes the estimation and calculation on altitude, echo strength and roughness parameters and the control on the other units based on the estimated result. Compared with delay Doppler altimeter, the present invention has improved azimuth compressing accuracy, raised emitting power utilizing efficiency, improved echo averaging effectiveness, and raised altitude measuring precision.

A method for determining a mechanical angle to a radar target utilizing a multiple antenna radar altimeter is described. The method comprises receiving radar return signals at the multiple antennas, populating an ambiguity resolution matrix with the electrical phase angle computations, selecting a mechanical angle from the ambiguity resolution matrix that results in a least amount of variance from the electrical phase angle computations, and using at least one other variance calculation to determine a quality associated with the selected mechanical angle.

The invention provides a ground verification instrument of a satellite-based marine radar height gauge, which is used for performing absolute calibration, performance examination and function test on the satellite-based marine radar height gauge in a laboratory. The ground verification instrument of the satellite-based marine radar height gauge comprises a time service unit, a transceiving control unit, a transmitting unit, a receiving unit, a frequency heald unit and a numerical control unit. The frequency heald unit utilizes an ultra-stable crystal oscillator signal provided by a radar height gauge to be verified as a clock. The time service unit takes charge of providing accurate synchronous time service for the numerical control unit and the radar height gauge. The transceiving control unit takes charge of respectively and simultaneously sending signals transmitted by the transmitting unit to the receiving unit and the radar height gauge and also controlling the receiving unit to receive the signals transmitted by the radar height gauge or the signals transmitted by the transmitting unit. The numerical control unit takes charge of eliminating channel influences of a verification instrument system, generating calibration signals, simulating echo signals of various target scenes and controlling the transceiving control unit, the receiving unit, the transmitting unit and the frequency heald unit.