Abstract: An example of an apparatus includes a support member to support equipment above a stage. The apparatus also includes a range sensor rotatably mounted to the support member. The range sensor is to measure a distance to the stage. In addition, the apparatus includes a leveling mechanism to rotate the range sensor to measure the distance along a vertical direction. The apparatus further includes an output device to transmit the distance to a user.

Abstract: Multi-mode multi-input multi-output (MIMO) radar sensors are described herein. An example MIMO radar sensor includes a receiver module including an array of receiver antenna elements to receive radar signals and a transmitter module including an array of transmitter antenna elements. Groups of the transmitter antenna elements form transmitter chains. The example MIMO radar sensor further includes a control system to, in a first mode, activate a first set of the transmitter antenna elements of each of the transmitter chains, and, in a second mode, activate a second set of the transmitter antenna elements of each of the transmitter chains, where the second set is larger than the first set. The transmitter antenna elements are arranged such that distances between phase centers of the transmitter chains in the first mode and the second mode are the same.

Abstract: Methods, devices and systems for increasing wireless communication range are provided. A device includes a reconfigurable antenna system having a plurality of antenna configurations; an antenna logic system configured to select one of the antenna configurations based on signal strength indicators of the plurality of antenna configurations; and a radio frequency (RF) transceiver configured to communicate with a client device using the selected antenna configuration.

Abstract: A phase correcting device includes a local oscillator configured to give a local oscillation signal to a device configured to detect a phase of an inputted signal, a first phase detector configured to detect a phase of the local oscillation signal to output the phase of the local oscillation signal, a reference phase device configured to generate a quasi-reference phase corresponding to a reference phase of the local oscillation signal at a time of an initial setting of the local oscillator to output the quasi-reference phase, based on a reference clock, a second phase detector configured to detect a fluctuation amount of a phase of the local oscillator, based on the phase detected by the first phase detector and the quasi-reference phase, and a correction circuit configured to correct the phase of the inputted signal by using a detection result of the second phase detector.

Abstract: A phase correcting device includes a local oscillator that includes an all digital phase-locked loop configured to output a local oscillation signal, a first phase detector configured to detect a phase of the local oscillation signal to output the phase of the local oscillation signal, a reference phase device configured to generate a quasi-reference phase corresponding to a reference phase of the local oscillation signal to output the quasi-reference phase, based on a reference clock, a second phase detector configured to detect a fluctuation amount of a phase of the local oscillator, based on the phase detected by the first phase detector and the quasi-reference phase, and a correction circuit configured to correct the phase of the inputted signal by using a detection result of the second phase detector.

Abstract: A method of operation for a voice assistant includes detecting the presence of a person and sound in a general location, detecting whether the person is in a specific location of the general location, and if the person is in the specific location, initiating operation of the voice assistant with a predefined specific command other than a global keyword.

Abstract: In accordance with described examples, a method determines if a velocity of an object detected by a radar is greater than a maximum velocity by receiving on a plurality of receivers at least one frame of chirps transmitted by at least two transmitters and reflected off of the object. A velocity induced phase shift (?d) in a virtual array vector S of signals received by each receiver corresponding to a sequence of chirps (frame) transmitted by each transmitter is estimated. Phases of each element of virtual array vector S are corrected using ?d to generate a corrected virtual array vector Sc. A first Fourier transform is performed on the corrected virtual array vector Sc to generate a corrected virtual array spectrum to detect a signature that indicates that the object has an absolute velocity greater than a maximum velocity.

Abstract: An altimeter apparatus for external fuselage mounting for an aircraft includes an altimeter circuit and a chassis. The altimeter circuit is coupled to an antenna system. The altimeter circuit is configured to generate a first signal and transmit the first signal via the antenna system, receive a second signal via the antenna system, wherein the second signal is a reflected version of the first signal, and determine an altitude based on the first and second signals. The chassis is configured to contain the altimeter circuit and the antenna system, wherein the chassis is connected to a fuselage of the aircraft and is located outside of the aircraft.

Abstract: A radar system operates at a carrier frequency near the oxygen absorption line. A selected range bin is monitored to measure the signal-to-noise ratio. The signal-to-noise ratio value is used to adjust the carrier frequency so as to maintain a preselected signal-to-noise ratio.

Abstract: A radio altimeter includes a voltage controlled oscillator outputting a radio frequency signal through a forward path in a direction from the voltage controlled oscillator to a radio frequency antenna, a path extending unit positioned in the forward path to receive the radio frequency signal to delay the radio frequency signal to generate a delayed radio frequency signal. The radio frequency antenna transmits the delayed radio frequency signal to ground and receives the delayed radio frequency signal reflected from the ground. The radio altimeter also includes a mixer that receives the reflected delayed radio frequency signal through a signal reception path from the radio frequency antenna and the radio frequency signal from the voltage controlled oscillator and mixes the radio frequency signal and the reflected delayed radio frequency signal to output a beat frequency signal which is used to calculate altitude with respect to the ground.

Abstract: Distance detection method and device are provided. The distance detection method comprises: providing a directional signal emitting module; providing a directional signal receiving module having a constant bandwidth; providing a distance detection signal to the directional signal emitting module; changing a frequency of the distance detection signal provided to the directional signal emitting module, and judging whether the directional signal receiving module can decode a reflected directional signal into a received signal; and judging a distance between an external object and the directional signal receiving module according to whether the received signal corresponding to the frequency of the distance detection signal can be decoded.

Abstract: A level radar is switchable between pulsed and FMCW radar methods. For example, the radar device may include two separate front ends which can be activated selectively via a logic control system. Upon switching to the respective other measurement principle, the evaluation software is also adapted accordingly. In this way, it is possible to use advantageous properties of both measurement methods in a targeted manner.

Abstract: A device for the optical non-contact vibration measurement of an vibrating object, including a laser Doppler vibrometer that has a laser as the light source for a laser beam, a first beam splitter assembly for splitting the laser beam into a measuring beam and a reference beam, a means for shifting the frequency of the reference beam or of the measuring beam in a defined manner, a second beam splitter assembly by which the measuring beam back-scattered by the oscillating object is merged with the reference beam and superimposed on the same, and a detector for receiving the superimposed measuring and reference beam and for generating a measurement signal. The laser is provided with a polarization filter arranged inside the optical resonator of the laser and the laser is frequency stabilized by regulating to a beat signal of the laser.

Abstract: An avionics system comprises a plurality of avionics components; at least one OFDM transmitter coupled to a respective one or more of the plurality of avionics components and configured to transmit a wireless OFDM signal comprising a plurality of sub-bands; at least one OFDM receiver coupled to a respective one or more of the plurality of avionics components and configured to receive the wireless OFDM signal transmitted by the OFDM transmitter; and a radio altimeter configured to transmit a signal tone that sweeps a frequency spectrum allocated to the radio altimeter at a predefined rate and periodicity. The at least one OFDM transmitter is configured to transmit the wireless OFDM signal in the frequency spectrum allocated to the radio altimeter and to sequentially turn off respective subsets of the plurality of sub-bands in synchronization with the predefined rate and periodicity of the signal tone frequency sweep.

Abstract: A homodyne radar system includes a mixer that outputs a signal having a mixer output frequency that is a frequency difference between two input signals. When the frequency difference is small, low frequency noise may mask the actual signal. A variable phase shifter is added to one of the mixer inputs to change the phase at a predetermined rate of change. The phase shifter shifts the frequency of the input signal so that the mixer output frequency is offset by the predetermined rate. The low frequencies are mapped to frequencies that are above the noise frequencies. The phase shift may be achieved by adding a constant phase at predetermined time intervals. The sampling frequency for the resulting signal may need to be increased to accommodate the higher frequencies.

Abstract: A sensor for detecting a parking space includes a modulating module for supplying a sinusoid wave having a modulation frequency, an active antenna module transmits a FMCW signal based on the modulation frequency and for receiving a reflected FMCW signal, a intermediate-frequency filter for extracting a first demodulating signal having the modulation frequency from the reflected FMCW signal generating modulation signal, a second intermediate-frequency filter for extracting a second demodulating signal having a multiplying frequency of the modulation frequency, an integrator for performing integral operation for the second demodulating signal to generate an integral voltage, a triggering circuit for generating a triggering voltage when the integral voltage is greater than a reference voltage, and a controller for performing operations relating to an existence of a vehicle when receiving the triggering voltage.

Abstract: A system and related method is disclosed for determining a range between a single antenna array and a radio-frequency reflective surface. The system includes a frequency modulated continuous wave (FMCW) signal generator which transmits the FMCW transmission signal through a pair of bias tees and a coupler prior to reaching a circulator. The circulator selectively routes the transmission signal to the single antenna array for transmission. As the transmission signal is reflected from the RF reflective surface, the single antenna array receives the reflected FMCW reception signal. The coupler receives the reception signal and delays and selectively routes the reception signal to a mixer which mixes the reception signal with a transmission signal input to create a low frequency signal. The low frequency signal passes through the pair of bias tees, is converted to digital, and received by a processor which determines the range to the reflective surface.

Abstract: A target object detection apparatus is provided. The apparatus includes a transmitter, a receiver, a threshold determiner, a parameter setter, a parameter selector, and a timing controller. The transmitter repeatedly transmits a transmission pulse at a transmission timing. The receiver receives a reception signal at a reception timing set based on the transmission timing. The threshold determiner determines whether an amplitude value of the reception signal exceeds a predetermined threshold at every sampling point and counts the number of sampling points at which the amplitude value of the reception signal exceeds the threshold. The parameter setter sets a plurality of different parameters for controlling the transmission timing. The parameter selector selects the parameter from the parameter settings, to minimize the number of sampling points counted by the threshold determiner. The timing controller controls the transmission timing, based on the parameter selected by the parameter selector.

Abstract: The present disclosure is directed to low range altimeter (LRA) antenna implementations that are resistant to signal degradation under critical weather conditions. An altimeter may include a first antenna communicatively coupled to a transmitter configured to transmit a ranging signal to a surface. The altimeter may further include a second antenna communicatively coupled to a receiver configured to receive at least a portion of the ranging signal reflected from the surface. Each of the first (transmitting) antenna and the second (receiving) antenna may include a driven element and at least one parasitic director element. In some embodiments, at least a portion of an aircraft surface may function as a parasitic reflector element in accordance with a Yagi-Uda array antenna topology.

Abstract: The present disclosure relates to a radio altimeter including a path extending unit positioned in a signal transmission path or a signal reception path of the radio altimeter, wherein the path extending unit delays a signal received from the outside to reduce a dynamic range of the radio altimeter.

Abstract: One embodiment is directed to a method for operating a radar altimeter. The method includes transmitting a radar signal at a first frequency, ramping the frequency of the radar signal from the first frequency to a second frequency, and transmitting the radar signal at the second frequency. The reflections can be processed by determining an approximate distance to a target based reflections of the frequency ramp and the approximate distance can be refined based on a phase difference between a reflection of the radar signal transmitted at the first frequency and a reflection of the radar signal transmitted at the second frequency.

Abstract: An apparatus for wirelessly connecting a smartphone to a remote FM radio system, for controlling playback of audio content delivered wirelessly to the smartphone via a wide area network, on the remote FM radio system. An apparatus housing receives a DC power signal from a remote DC power source. A control panel has a display and controls for controlling playback of the audio content on the remote FM radio system, at least one of the controls performing a function in common with a playback control appearing on a display of the smartphone. An electronic subsystem communicates with the control panel and wirelessly receives audio content from the smartphone, and communicates the audio content as an FM signal via a user playback command input at the controls of the control panel, to the remote FM radio system.

Abstract: One embodiment is directed towards a FMCW radar having a single antenna. The radar includes a transmit path having a voltage controlled oscillator controlled by a phase-locked loop, and the phase-locked loop includes a fractional-n synthesizer configured to implement a FMCW ramp waveform that ramps from a starting frequency to an ending frequency and upon reaching the ending frequency returns to the starting frequency to ramp again. The radar also includes a delay path coupled between a coupler on the transmit path and a mixer in a receive path. The delay path is configured to delay a local oscillator reference signal from the transmit path such that the propagation time of the local oscillator reference signal from the coupler to the mixer through the delay path is between the propagation time of signal reflected off the antenna and the propagation time of a leakage signal through a circulator.

Abstract: An altimeter system is provided. The altimeter system includes a receiver mixer including an antenna-input and a local-oscillator-input; a transceiver circulator communicatively coupled to an antenna via a transmission line having a selected length and communicatively coupled to the antenna-input of the receiver mixer; and a transmitter configured to output a transmitter signal to the antenna via the transceiver circulator. The transmitter signal is frequency modulated with a linear ramp. The transmitter is communicatively coupled to the receiver mixer to input a local oscillator signal at the local-oscillator-input of the receiver mixer. The receiver mixer is communicatively coupled to input a target-reflected signal from the antenna at the antenna-input of the receiver mixer. The selected length of the transmission line is set so that a composite-leakage signal at the antenna-input of the receiver mixer has a linear phase across a sweep bandwidth.

Abstract: A radar apparatus is provided. An antenna is configured to transmit a frequency-modulated transmission wave toward an object and receive a reception wave from the object. A mixer is configured to mix the transmission wave with the reception wave to generate a beat signal having a first beat interval and a second beat interval. A detecting section is configured to detect a plurality of first peak signals contained in the first beat interval of the beat signal and a plurality of second peak signals contained in the second beat interval. A grouping section is configured to group the second peak signals. A searching section is configured to search a part of the first peak signals corresponding to the grouped second peak signals. A separating section is configured to separate the part of the first peak signals from the other part of the first peak signals.

Abstract: A false lock filter circuit for a pulsed altimeter is provided. The circuit includes a low pass filter having a relatively low bandwidth (LBW LPF), a low pass filter having a relatively high bandwidth (HBW LPF) and a false lock controller. The LBW LPF has an input that is coupled to receive a detector output. The HBW LPF has an input that is coupled to receive the detector output. The false lock controller is coupled to receive outputs from the LBW LPF and HBW LPF. Moreover, the false lock controller is configured to sample an output of the HBW LPF and apply a statistical analysis on the samples to determine if a valid target has been detected.

Abstract: An antenna for a micro air vehicle (MAV) takes the form of a wrap-around antenna (e.g., wrapped around a portion of the MAV) that selectively emits radio signals in different directions depending on a frequency selected by a radio altimeter in the MAV. The radar altimeter may be a pulsed or a frequency modulated continuous wave (FMCW) radar altimeter. The wrap-around antenna includes groups of radiating elements in which at least each group includes an average height that is different from an average height of an adjacent group. Further, the average height of the group determines which group will emit the signals most efficiently so that a desired sector of space may be covered by the signals emitted from the antenna. In one example, the center frequency of the radar altimeter may be controlled in a deterministic manner to cause the radiating elements to successively cover desired sectors of space.

Abstract: A radio altimeter having a high level of integrity is presented. The radio altimeter includes a processing path configured to process a return signal received from a receive antenna using a first modulation technique and a monitoring path configured to process the return signal received from the receive antenna using a second modulation technique.

Abstract: A false lock filter circuit for a pulsed altimeter is provided. The circuit includes a low pass filter having a relatively low bandwidth (LBW LPF), a low pass filter having a relatively high bandwidth (HBW LPF) and a false lock controller. The LBW LPF has an input that is coupled to receive a detector output. The HBW LPF has an input that is coupled to receive the detector output. The false lock controller is coupled to receive outputs from the LBW LPF and HBW LPF. Moreover, the false lock controller is configured to sample an output of the HBW LPF and apply a statistical analysis on the samples to determine if a valid target has been detected.

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 continuous wave ranging system, comprising a modulator 2 for modulating an r.f. carrier wave in accordance with a pseudo random code, a transmitting antenna 5 for radiating the modulated signal towards a target, a receiving antenna 6 and receiver 7 for detecting the signal reflected back from the target, a correlator 8 for correlating the reflected signal with the transmitted code with a selected phase shift corresponding to the current range gate to be tested, whereby the range of the target from the system may be determined, a store 12 containing a plurality of different pseudo random codes, and selector means 13 arranged to supply to the modulator 2 and to the correlator 8 a code from the store 12 which code does not produce a breakthrough sidelobe in at least the next range gate or gates to be tested.

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: 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.

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 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.

Abstract: A receiver for detecting the presence of FM-CW signals emanating from a radio altimeter, and for determining the identity of the source. The received signals are amplified and applied both directly and through a delay circuit to a mixer. The delay is such that the resulting difference signal from the mixer is a low frequency signal in the audio frequency range. This signal is filtered, converted to digital values, and processed by fast Fourier transform techniques. Once processed, the spectral content of the difference signal is analyzed to determine if the signal originated from an airborne altimeter. Characteristics of the original signal modulation are also analyzed to ascertain the identity of the altimeter and its transporting aircraft.

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 method, apparatus and circuit for testing a radio altimeter is disclosed. During the test-mode operation of the altimeter, a signal processor controls a transmitter to generate a radio frequency signal at a first period of time, which is transmitted through an attenuator, transmitted then through a receiver and received by the signal processor at a second period of time for processing of altimeter operational information.

Abstract: To provide a movement-detecting altimeter designed so as to be capable of avoiding excessive accumulation of errors. The movement-detecting altimeter has a movement dependent altitude updating unit which updates an indicated altitude when a moving condition is maintained, and which avoids updating of the indicated altitude when the moving condition is not maintained.

Abstract: This invention relates to a frequency modulation of continuous wave (“FMCW”) radar altimeter capable of controlled linear sweep modes. The FMCW radar altimeter is characterized by the following functions: (1) adopts sweep up frequency and sweep down frequency to solve problems of distance and doppler signal mixture; (2) injects a random generated variable time delay in between sweep intervals to overcome interferences among different altimeters; and (3) switches different sweep frequency bands in accordance with different altitudes.

Abstract: A method for simulating a Doppler signal under stationary conditions is described. The method includes sampling a radar return signal at an integer multiple of the return signal frequency plus a fraction of the return signal period and generating a base band signal from the samples.

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: A method of determining a target location from a vehicle is described. The method includes identifying the target utilizing a video system, determining an angular location vector to the target with respect to the vehicle, determining a position of the vehicle utilizing a digital terrain elevation map and precision radar altimeter, calculating a location where the angular location vector would intersect with the digital terrain elevation map, and generating a target position based on vehicle position and the location of the intersection of the angular location vector and digital terrain elevation map.

Abstract: A method for suppressing ground return radar fading in a radar altimeter is described. The method includes providing a radar gate width which corresponds to an area that is smaller than an antenna illumination area being impinged by transmissions of the radar altimeter, dithering the radar gate viewing area within the antenna illumination area being impinged by transmissions of the radar altimeter, and taking radar return samples with the radar altimeter.

Abstract: An arrangement for the precise measuring of the distance with a FMCW radar device having a frequency-variable digitally-actuated oscillator to generate a transmitting frequency which can be tuned over a predetermined frequency range. The digital actuation involves the use of a digital frequency generator which derives in predetermined frequency steps a references signal from a fixed-frequency oscillator signal. The frequency of the frequency-variable oscillator is adjusted in a phase-locked loop linking it to the references signal.

Abstract: A radio altimeter using a linear oscillator to transmit a saw-toothed signal comprises, in addition to this first oscillator, a second linear oscillator to transmit, in synchronism with the first linear oscillator, another saw-toothed signal with a given saw-tooth duration Td. The plateau of the sawteeth of the two saw-toothed signals are at a distance from each other equal to a value f. The test consists in obtaining a height h′ by beats between the two saw-toothed signals and computing a standard height he=f.c.Td/dF.2 where c is the speed of light and dF the duration of each saw-tooth of the other signal. Application to all FM/CW radio altimeters.

Abstract: A radio altimeter using a linear oscillator to send out a continuous wave that is frequency modulated linearly between two boundary values sends the antenna installation an incident signal, collects the signal reflected by the installation and examines it. This incident signal may be that of the linear oscillator. For the reception antenna installation, this means providing for a rerouting in order to direct a small part of the signal of the oscillator to this installation. In the case of the transmission antenna installation it is enough to provide for a rerouting that injects the signal reflected by this installation into the reception channel. Application to all the FM/CW radio altimeters.

Abstract: A single antenna FM radio altimeter operates in continuous wave (CW) and interrupted continuous wave (ICW) modes to provide an altitude indication. An altimeter transmitter generates a constant FM period CW signal below a critical altitude and a variable FM period ICW signal above the critical altitude. The single antenna, connected to the transmitter and receiver, radiates and receives the CW and the ICW signals. The receiver provides a beat frequency signal. A processor compares the beat frequency signal and the variable FM period signal to critical altitude reference signals and switches the altimeter between the modes accordingly. The processing function provides the transmitter a constant period modulation signal below the critical altitude and a variable FM period signal above the critical altitude. The processing function provides the altitude indication from the beat frequency signal below the critical altitude and from the variable FM period signal above the critical altitude.

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 radar system operates at a carrier frequency near the oxygen absorption line. A selected range bin is monitored to measure the signal-to-noise ratio. The signal-to-noise ratio value is used to adjust the carrier frequency so as to maintain a preselected signal-to-noise ratio.