Abstract: Systems and methods are disclosed that include fault monitoring for a radar altitude device. Fault monitoring is performed by receiving first altitude data from the radar altitude device, receiving second altitude data from a second altitude measuring device, receiving terrain data from a terrain database, determining a fault condition threshold adaptively based on the terrain data, determining whether the radar altitude device is exhibiting a fault condition based on the first and second altitude data and the fault condition threshold, and outputting an indication of the fault condition based on the determination of whether the radar altitude device is exhibiting the fault condition.

Abstract: A simulator is provided for dynamically testing and evaluating an electromagnetic radiation in real-time. The performance of radiation from a system-under-test is evaluated as it interacts with a moving target in an ever-changing simulated environment. The simulator includes a computer for synchronized control of a PNT database and of an environmental database. In detail, the PNT database contains Position, Navigation and Timing (PNT) information of the target, and the environmental database contains information pertaining to meteorological conditions and topographical characteristics in the simulated environment. In combination, the computer evaluates a synchronized interaction of the electromagnetic radiation with the PNT information from the PNT database, under conditions set by the environmental database. A response record for evaluating a performance of the system-under-test is thereby created.

Abstract: A method for adjusting the timing of beam projections in a beam detector. The method includes projecting a beam for the purpose of detecting obscuration of the beam and, if a level of signal of the beam detected is less than a threshold for each of a number of consecutive projections or for each consecutive projection over a pre-determined time period, initiating a warning, signalling an alarm or otherwise reacting. The method further includes adjusting the timing of projecting the beam from a nominal transmit interval ‘T’ to be within a window time-period ‘W’ extending from an amount before to an amount after the nominal transmit interval ‘T’.

Abstract: A method of determining an angle within the beam to a target using an airborne radar includes receiving first data associated with first returns associated with a first portion of an antenna. The method further includes receiving second data associated with second returns associated with a second portion of an antenna, wherein the first portion is not identical to the second portion. The method further includes determining the angle within the beam to the target using the first and second data.

Abstract: Present novel and non-trivial systems and methods for generating aircraft height data are disclosed. A processor is configured to receive both first data comprised of radar-based reflection data of a stationary reference point based upon a horizontal distance between the geographic position of an aircraft and the geographic position of the stationary reference point (e.g., landing threshold point) and second data comprised of internally sourced vertical travel data more frequently than the first data. From the first data and second data, an instant vertical distance above the stationary reference point is determined by updating the first data with the second data. Then, instant height data representative of the instant vertical distance above the stationary reference point is generated. Provided with the instant height data, a presentation system comprised of display unit, aural alert unit and/or a tactile alert unit may present the instant vertical distance to the pilot.

Abstract: A weather radar system improves electronics for receiving radar returns. The weather radar system determines an altitude above ground level using return data derived from the weather radar returns. The weather radar system can utilize movement data related to movement of the aircraft to calculate the altitude. In addition, the weather radar system can utilize previous calculations of the altitude to determine the current altitude underneath the aircraft. The weather radar system can reduce the need for a radio altimeter.

Abstract: A method of determining an angle within the beam to a target using an airborne radar includes receiving first data associated with first returns associated with a first portion of an antenna. The method further includes receiving second data associated with second returns associated with a second portion of an antenna, wherein the first portion is not identical to the second portion. The method further includes determining the angle within the beam to the target using the first and second data.

Abstract: A navigation system includes a pressure sensor, a calibration module in communication with the pressure sensor, and an altitude module in communication with the calibration module. The calibration module is configured to determine a dynamic pressure proportionality coefficient based at least in part on a static pressure proportionality coefficient, a measured pressure value from the pressure sensor, and a velocity value. The altitude module is configured to calculate a sensor-based altitude value based at least in part on the determined dynamic pressure proportionality coefficient.

Abstract: Disclosed is a method and device, which provide an enhanced ability to monitor the navigation of an aircraft during a phase of flight in which the aircraft is close to the ground in which the aircraft uses positional information supplied by a satellite positioning system for the navigation. A display screen is used to display a first characteristic sign representing a selected setpoint value for a height parameter of the aircraft. The display screen also displays a second characteristic sign representing a current auxiliary value expressed in the form of an achievable height parameter. An alert is emitted when the second characteristic sign is determined to be within a predetermined height value of the first characteristic sign, and the alert is shown in visual format on the display screen. An alarm is also emitted following a predetermined time after the alert is emitted, if the setpoint value is not replaced by a new setpoint value.

Abstract: Methods and systems for reducing a leakage component of a received-signal are disclosed. A transmit antenna of a radar system transmits a transmit-signal including a transmit component. A receive antenna of the radar system receives a received-signal including a leakage component and a target component. The received-signal corresponds to the transmit-signal. An overlap determination is made to determine whether the target component overlaps the leakage component and/or is received during a time when the leakage component is expected to be received. If overlap exists, a reduction leakage component (e.g., a previously determined reduction leakage component) is subtracted from the received-signal so as to produce a modified received-signal, the modified received-signal including the target component and substantially excluding the leakage component.

Abstract: Ground clutter is effectively separated from true signals echoed by a cable in the flight path of an aircraft, by encoding a transmitted pulse wave in a radar system with at least one transmit (TX) coding sequence, so that received signals echoed by the cable on which the pulse is incident and associated ground clutter are orthogonal or separable from one another. The TX coding sequence is altered into two receive (RX) coding sequences one of which corresponds to the cable and the other to the ground clutter. The two RX coding sequences are then correlated with the received signals, thereby separating the true signals echoed by the cable from the associated ground clutter.

Abstract: A method and processor for resolving a processing radar return data to determine a mechanical angle to a target relative to a radar array having a right antenna, an ambiguous antenna, and a left antenna. An LA linear relationship determining, based upon a characteristic number of LA wraps relative to the mechanical angle. Likewise, determining a RA linear relationship determines a characteristic number of RA wraps and a RL linear relationship determines a characteristic number of RL wraps relative to the mechanical angle. All permutations of LA wraps, RA wraps, and RL wraps are listed, and for each permutation, a truth relationship is determined. A look up table is populated with permutations where the truth relationship is true.

Abstract: A terrain awareness and warning system includes electronics for receiving radar returns and providing terrain and/or obstacle alerts or warnings in response to the radar returns. The electronics receives information from a database and the information is utilized to suppress false alerts or warnings.

Abstract: An aircraft electronics system is provided that includes a radar system, a display, an embedded global positioning/inertial navigation system (EGI) and a processor. The radar system is configured to generate aircraft operational data. The display is configured to display the aircraft operational data. The EGI is configured to generate aircraft behavior components and the processor configured to override the aircraft operation data displayed on the display when at least one of the aircraft behavior components is beyond a defined limit, wherein potentially incorrect aircraft operational data affected by at least one of the aircraft behavior component is not displayed.

Abstract: A method for calibrating an altimeter is disclosed. The method comprises monitoring signal strength of one or more altitude measurements. Based on the signal strength, the method applies piecewise linear altitude correction to the one or more altitude measurements to generate altitude correction data. The method further determines a goodness-of-fit for the altitude correction data. The altitude correction data maintains a correct altitude measurement in the presence of variable signal strength.

Abstract: 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.

Abstract: Systems and methods for terrain contour matching navigation are provided. In one embodiment, a method for terrain contour matching navigation comprises: receiving at least one sample point representing the position of an aircraft, the at least one sample point including a horizontal position and an altitude sample; correlating a first sample point of the at least one sample point across a reference basket array having a plurality of elements; determining a correlation quality; when the correlation quality does not achieve a pre-determined quality threshold, performing at least one additional correlation of an additional sample point of the at least one sample point across the reference basket array; and when the correlation quality does achieve a pre-determined quality threshold, calculating a position error based on the correlating of the first sample point and any additional correlations of any additional sample points.

Abstract: A method to control a track gate and a level gate in an altimeter tracking an altitude of an airborne vehicle comprising emitting signals, directed toward a terrain, from the airborne vehicle, receiving terrain echo signals, positioning the track gate to a selected reference amplitude on the rising edge of the terrain echo signals, positioning the level gate to within a selected range of the peak amplitude level of the terrain echo signals, measuring a change in a location of the peak amplitude between sequentially received terrain echo signals, and varying a separation between the track gate and the level gate based on the measured change in the location of the peak amplitude. The terrain echo signals comprise reflections of the emitted signals from the terrain, and each terrain echo signal has a rising edge and a peak amplitude.

Abstract: 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.

Abstract: Systems and methods for testing a signal generated by a Direct Digital Synthesizer (DDS) in a radar altimeter. In an embodiment of the method, a voltage signal derived by comparing a fixed reference frequency to a ramped frequency signal generated by the DDS based on a clock-based reference signal is generated. The generated voltage signal is integrated over a predefined range of clock signals. The integration is sampled at a previously defined clock tick. The sample is compared to a desired value and an indication that the radar altimeter is malfunctioning is provided if the comparison exceeds a predefined threshold value. The radar altimeter system is deactivated if an indication that the radar altimeter is malfunctioning has been provided.

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: This invention is directed to a 3-dimensional imaging lidar, which utilizes modest power kHz rate lasers, array detectors, photon-counting multi-channel timing receivers, and dual wedge optical scanners with transmitter point-ahead correction to provide contiguous high spatial resolution mapping of surface features including ground, water, man-made objects, vegetation and submerged surfaces from an aircraft or a spacecraft.

Abstract: A radar altimeter system with a closed-loop modulation for generating more accurate radar altimeter values. The present invention combines flight safety critical sensors into a common platform to permit autonomous or semi-autonomous landing, enroute navigation and complex precision approaches in all weather conditions. An Inertial Navigation System (INS) circuit board, a radar altimeter circuit board and a Global Navigation Satellite System (GNSS) circuit board are housed in a single chassis. VHF (Very High Frequency) Omni-directional Radio (VOR), Marker Beacon (MB), and VDB (VHF Data Broadcast) receiver circuit boards may also be implemented on circuit boards in the chassis.

Abstract: A method for operating a radar altimeter to perform a zero altitude calibration is described. The method includes determining a difference between an altitude measured by the radar altimeter and a desired altitude indication and upon receiving a zero calibration command, subtracting the difference from an altitude output by the radar altimeter.

Abstract: Embodiments of the invention provide a method and apparatus for indicating aircraft height relative to an obstruction in a terrain awareness warning system. The method includes receiving data indicative of geographic features of an obstruction, lateral distance of the geographic feature from an aircraft, height and flight path of the aircraft, calculating a projected height of the aircraft at the location of the obstruction using the data, generating a result signal, and displaying a colored indication on a display screen based on the result signal. The apparatus includes inputs for signals from instruments measuring height, flight path, and location of an aircraft, as well as an input for an instrument providing information about geographic features of terrain surrounding the aircraft. The apparatus includes a means for employing the signals to calculate an effective height of the aircraft relative to the terrain, and a screen display for graphically displaying the results of the calculation.

Abstract: A transponder having a subsystem for providing an altitude alert function signifying a deviation from a set altitude is described. The subsystem includes an input for receiving an altitude deviation limit associated with the set altitude, a CPU receiving updated altitude and determining a difference between the updated altitude and the set altitude associated with the altitude deviation limit, and a transponder subsystem output device for providing the difference between the updated altitude and the set altitude to a user.

Abstract: 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.

Abstract: A method for incorporating a forward ranging feature into a radar altimeter is described. The method comprises positioning an antenna of the altimeter such that a side lobe of a radar signal radiates from the antenna in a forward direction and processing a radar return from the side lobe to determine a range to a forward object.

Abstract: A portable, handheld electronic navigation device includes an altimeter and a GPS unit. An internal memory stores cartographic data, for displaying the cartographic data on a display of the navigation device. Accordingly, the device is capable of displaying cartographic data surrounding a location of the unit as determined by GPS and altitude information as determined by the barometric altimeter and GPS. The device provides an enhancement of the calibration and hence the accuracy of barometric altimeter measurements with the aid of derived altitudes from a GPS. The device is able to determine the need for calibration and perform the subsequent computations necessary to facilitate the calibration. Furthermore, the device is able to determine a correction quantity that should be applied to barometric altitude readings, thereby allowing the device to be calibrated while in motion. Both of these features ultimately result in a more accurate determination of altitude.

Abstract: Multiple radar altimeters on a constellation of individual satellites in the same orbit plane relate an advanced ocean altimetry system. Earth rotation separates the respective measurement tracks of each satellite on the ocean surface. Each satellite can host a monostatic radar altimeter, which may contain a co-located transmitter and receiver that generates one surface track of ocean height measurements at nadir. Further, each satellite payload can include a bistatic radar altimeter, comprising a transmitter and a receiver located respectively on neighboring satellites. The bistatic altimeter comprises a virtual nadir altimeter that generates an additional surface track of ocean height measurements along the locus of midpoints on the surface between the satellites' nadir points.

Abstract: A radar altimeter is described which includes a transmitter for transmitting a radar signal, a receiver for receiving the reflected radar signal, and at least one antenna coupled to one or both of the transmitter and receiver. The altimeter also includes a forward facing millimeter wave (MMW) antenna configured to move in a scanning motion and a frequency up/down converter coupled to the MMW antenna, the transmitter, and the receiver, and a radar signal processor. The converter up converts a frequency received from the transmitter to a MMW frequency for transmission through the MMW antenna, and down converts frequencies received to a radar frequency which are output to the receiver. The radar signal processor controls scanning motion of the MMW antenna, processes signals received at the antenna for a portion of the scanning motion, and processes signals received at the MMW antenna for other portions of the scanning motion.

Abstract: An apparatus for calibrating a radar altimeter is described. The altimeter provides an angle to a target based on radar energy received at right, left, and ambiguous antennas. The apparatus comprises a turntable on which the radar is mounted, a turntable controller which controls positioning of the radar altimeter, a radar energy source receiving transmit signals from the radar altimeter, a reflector, and a calibration unit. The reflector reflects and collimates radar energy from the radar source towards the radar altimeter. The calibration unit receives an angle from the controller indicative of a position of the radar altimeter with respect to the collimated radar energy and a measured angle from the radar altimeter. The calibration unit calculates a correction based on differences between the angle received from the turntable and the measured angle received from the altimeter and provides the calibration correction to the altimeter.

Abstract: A surface imaging radar system for an airborne platform, the system comprises a transmitter for generating a radar signal. The system also comprises an antenna configured to transmit a radar signal generated by the transmitter and receive radar return information from one or more directions directly below the airborne platform to an angular direction of approximately 30 degrees greater than straight down. The system also includes a processor configured to generate surface information based on the received radar return information and an image processor for generating an image based on the surface information.

Abstract: A system and method for identifying the position of an airborne platform on a flight path includes at least three radar transceivers that are directed along respective beam paths to generate return signals. Each of the return signals respectively indicate a speed and a direction of the platform relative to points on the surface of the earth. A computer uses the return signal to establish a ground speed, an altitude and a direction of flight for the platform. This information is then used to identify the position of the platform on its flight path. Additionally, the system can include a last known position, or a site-specific radar clutter model, to establish a start point for the platform. The computer can then calculate the position of the platform relative to the start point.

Abstract: A system and method for identifying the position of an airborne platform on a flight path includes at least three radar transceivers that are directed along respective beam paths to generate return signals. Each of the return signals respectively indicate a speed and a direction of the platform relative to points on the surface of the earth. A computer uses the return signal to establish a ground speed, an altitude and a direction of flight for the platform. This information is then used to identify the position of the platform on its flight path. Additionally, the system can include a last known position, or a site-specific radar clutter model, to establish a start point for the platform. The computer can then calculate the position of the platform relative to the start point.

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.

Abstract: A combined altitude and height-above-ground indicator for an aircraft includes a first sensor and a second sensor which respectively sense altitude and height-above-ground, a processor for processing the information supplied by the first and second sensors, and a display for displaying the altitude and height-above-ground information, showing the two items of information against each other, on the same scale against at least one pointer.

Abstract: An altimetric type measurement method for use on a satellite transmits a pulse towards the surface of the sea and carries out frequency transformation on the return signal resulting from the reflection of this pulse at the surface of the sea. This produces a spectral signal of samples successively comprising:(a)--a first zone with a low amplitude level,(b)--a second zone with a sharply increasing slope ending at a peak, and(c)--a third zone of decreasing slope.Samples of the spectral signal are selected within a selection zone that corresponds to the first and second zones for a predetermined maximal level of the height of the waves at the surface of the sea and maximum likelihood processing is applied only to the selected samples.

Abstract: A delay compensated Doppler radar altimeter which eliminates the relative delay curvature associated with the energy reflected by a scatterer located in the along-track direction of an aerial platform for which a most accurate estimation of scatterer elevation is desired. By Doppler shifting each return, the range indicated for each scatterer over its illumination history is equal to the minimum range x.sub.h experienced when the relative velocity between the aerial radar and the ground is effectively zero. Compensating each signal so that its entire along-track history can be used for elevation estimation leads to an advantage of more than 10 dB in gain improvement over existing systems, and less degradation from surface topography.

Abstract: A radar altimeter system uses a microprocessor-based subsystem to process radar signals in software. The subsystem includes a track loop and a verify loop for digital signal processing of the radar signals. The track loop generates a gate pulse and integrates a radar return signal over the time window defined by the gate pulse in order to determine the leading edge of the return pulse. The verify loop positions the gate pulse for maximum overlap with the return pulse and integrates the return pulse over the gate pulse to determine the maximum signal strength of the radar return signal.

Abstract: A terrain clearance signal generator particularly usable with ground proximity warning systems provides a signal representative of terrain clearance when the radio altimeter signal is unreliable, such as in the case of excessive pitch or roll, out of track or other conditions resulting in invalid readings. The system monitors such conditions and takes a sample of the last valid radio altitude reading prior to sensing an invalid condition and, upon sensing an invalid condition, updates the sample utilizing barometric altitude signals or integrated barometric altitude rate or inertially-derived Z-velocity signals.

Abstract: A primary flight display having a vertically oriented linear scale format altimeter therein which includes a non-numbered coarse tape-like image area, for displaying markings relating to altitude and a fine scale tape-like image area juxtaposed with said coarse tape-like image area said fine scale image area for displaying numerals in vertical translational movement and a central current altimeter reading with at least part of the reading disposed about said coarse scale image area.

Abstract: A method for preventing errors in the Doppler radar measurement of velocity in aircraft that result from the radar receiver being locked to backscatter from side lobes of a plurality of main lobes radiated in a fixed radiation geometry. The inertial vertical velocity component (V.sub.IZ) obtained by a baro-inertial control loop is compared with the vertical velocity component (V.sub.DZ) determined from the Doppler frequencies to derive an error detection signal. When the error signal occurs, the inertial vertical velocity component replaces the corresponding velocity component supplied from the Doppler system while the horizontal velocity components are determined, for example, from the last calculated wind and the corresponding airspeed components, for the duration of the error signal.

Abstract: An aircraft radar altimeter includes a programmed microcontroller which permits effective simultaneous tracking of at least two targets such that, for example, both ground and obstacles on the ground can be simultaneously tracked, thus avoiding crashes when the aircraft is operating at very low altitudes. The microcontroller is operatively coupled to the radar transmitter and to the receiver so that information relating to a first target can be stored away while a search and track operation is run on a second target. The information concerning a detected second target is likewise stored away and the microcontroller permits alternate tracking of the two targets with the stored information being used as the basis for establishing an initial position for a target when tracking of that target is resumed.

Abstract: An aircraft microwave altimeter system has a threshold detector with two parallel channels that provide two sets of output signals at two different levels of sensitivity. The signals at the higher sensitivity are supplied to a display whereas those at the lower sensitivity are supplied to a navigation system. A comparator indicates a fault in the system if the two sets of output signals differ by more than a predetermined amount.

Abstract: Systems and methods for testing a signal generated by a Direct Digital Synthesizer (DDS) in a radar altimeter. In an embodiment of the method, a voltage signal derived by comparing a fixed reference frequency to a ramped frequency signal generated by the DDS based on a clock-based reference signal is generated. The generated voltage signal is integrated over a predefined range of clock signals. The integration is sampled at a previously defined clock tick. The sample is compared to a desired value and an indication that the radar altimeter is malfunctioning is provided if the comparison exceeds a predefined threshold value. The radar altimeter system is deactivated if an indication that the radar altimeter is malfunctioning has been provided.