Abstract: [Object] To appropriately evaluate reliability of a reception signal. [Solving Means] A signal processing unit 20 includes a first integration unit 21, a Doppler detection unit 22, and a comparator circuit 28 as a reliability index calculation unit. The first integration unit 21 intermittently integrates a pulse train corresponding to a reception signal by using two systems and obtains two pieces of integrated data. The Doppler detection unit 22 divides each of the two pieces of integrated data into a plurality of range bins in time series, obtains a relationship between a frequency and intensity in each range bin for each of the two pieces of integrated data, and detects a Doppler shift amount from the relationship. The comparator circuit 28 calculates a reliability index of the reception signal by comparing the Doppler shift amounts (wind velocity values) of the two pieces of integrated data.

Abstract: Systems and methods for operating radar systems. The methods comprise, by a processor: receiving point cloud information generated by at least one radar device and a spatial description for an object; generating a plurality of point cloud segments by grouping data points of the point cloud information based on the spatial description; arranging the point cloud segments in a temporal order to define a radar tentative track; performing dealiasing operations using the radar tentative track to generate tracker initialization information; and using the tracker initialization information to generate a track for the object.

Abstract: A radar system includes an antenna. The radar system comprises a processor for providing an error in ground speed estimate based upon Doppler velocity data, and a transmitter. The frequency of radar signals from the transmitter is adjusted according to a velocity of the aircraft calculated using the error in ground speed estimate or using the error in ground speed estimate. The adjusted frequency can allow ground clutter to be removed by high pass filtering in one embodiment.

Abstract: A high fidelity simulation of Doppler that may exactly replicate the phenomenology of the physical world. Compute the linear (Line of sight) kinematics (Slant Range, Radial Velocity, and Radial Acceleration) for each of a multiplicity of emitter-receiver pairs in accordance with exact 3D vector mathematics. Smoothly interpolate the linear kinematic parameters to produce accurate instantaneous values of these parameters at sample rates sufficient to produce negligible error effects in the presence of realistic aircraft maneuvers. Calculate the Doppler frequency, in accordance with well known physics, from the emitter carrier wavelength and a high sample rate. Calculate the Doppler effect as a differential phase (Doppler frequency×sample time) and apply the effect as incremental phase shifts to the carrier signal.

Abstract: Provided is a multi-function radar apparatus capable of measuring both a distance to a target object and a temperature of the target object with high accuracy. A transmission signal produced from a high-frequency signal generating unit (9) is amplified by a transmission signal amplifying unit (12) while intermittently stopped by a transmission intermittent stop switch (11), and is emitted to a target object (13) via a circulator unit (2). A reflected wave from the target object (13) is input as a reception signal to a transmitting and receiving antenna (1) while the transmission signal is emitted, and a radiated wave from the target object (13) is input as the reception signal thereto while the transmission signal is not emitted. The reception signal is amplified by a reception signal amplifying unit (3) via the circulator unit (2), and is mixed by a frequency converting unit (4) with the transmission signal branched by a high-frequency signal branching unit (10) to thereby generate a beat signal.

Abstract: A Mixer structure (210) for Doppler radar applications and a Doppler radar sensor (30) having an oscillator input port (LO) for output signals from an electric oscillator (32), having a radio frequency input port (RF) for output signals from receiving means (34), having an output port (IF) for an overall output intermediate signal produced in the mixer structure (210) and having two mixer branches (12a, 12b) each with a diode (18a, 18b). The mixer branches (12a, 12b) are connected to the oscillator input port (LO) and to the radio frequency input port (RF) in such a manner that intermediate signals (IF1, IF2), which are produced in these mixer branches (12a, 12b) and correspond to a Doppler shift between the oscillator signal and the radio frequency signal, are processed to the overall output signal.

Abstract: The described method characterizes scattering objects in a wireless channel. The present invention determines non-equally spaced path delays and Doppler parameters for a plurality of scattering objects in a wireless channel. More particularly, a frequency-to-time transform applied to a plurality of OFDM pilot samples received over a plurality of OFDM symbol periods generates a set of non-equally spaced path delays and a set of associated complex delay coefficients. Further, a time-to-frequency transform applied to the complex delay coefficients determined for one path delay over multiple OFDM symbol periods generates a set of Doppler parameters comprising a plurality of non-equally spaced Doppler frequencies and their corresponding scattering coefficients for that path delay.

Abstract: A radar device includes: a frequency modulating unit for modulating a frequency of a transmission signal by a triangular wave; a transmitting unit for pulsing the frequency modulated transmission signal to transmit the pulsed transmission signal as a transmission pulse; a receiving unit for generating a beat signal based on a frequency difference between a frequency modulated transmission signal and a reflected received pulse; a range gate setting unit for setting a range gate that determines a sampling timing of the received pulse based on a transmitting timing of the transmission pulse; a sampling unit for sampling the beat signal in each of range gates; a distance and relative velocity calculating unit for calculating a distance to a target and a relative velocity based on the sampled beat signal; and a control unit for controlling a transmission pulse width and a range gate width depending on a subject vehicle velocity.

Abstract: A signal generation system suitable for use in a radar system comprises a local oscillator (LO) and an intermediate frequency (IF) oscillator, wherein the IF oscillator is a Direct Digital Synthesizer (DDS), and the LO is a free running oscillator not itself locked to another oscillator but which acts as a clock reference for the DDS and is the highest frequency oscillator in the system. The LO may also act as a reference for a receive chain digitizer. The invention exploits phase noise advantages of a free running oscillator at some distance from the carrier whilst maintaining coherency with other system components. The system typically finds application in FMCW radars.

Abstract: An ultra-wideband pulse Doppler radar employing a transform domain communication system class of output waveform, a waveform additionally modified for enhanced radar usage. The achieved waveform includes sequential radar output pulse discrimination, improved pulse repetition frequency range ambiguity, phase modulation generating a noise-like output signal appearance and improved resolution characteristics. The invention employs radar waveform shaping in the frequency domain according to a sample of present operating band interference conditions followed by transformation into the time domain for fabricating an output pulse waveform. Mathematical basis for the improved output waveform and correlation comparisons in graphical form are included in the disclosure.

Abstract: Electronically steered radar systems such as frequency scanning radars are particularly suitable for detecting and monitoring slow moving, ground-based targets. So-called crawler radar systems are intended for detection of targets that deliberately attempt to avoid detection by keeping low and by moving slowly. Disclosed is a radar system which includes an electronically steered antenna and a receiver arranged to process signals received from a target located at a distance from the radar system so as to identify a Doppler frequency associated with the target. The antenna stares at, rather than glides past, the target surrounding clutter. This means that the spectral spreading of static ground clutter associated with mechanical radar systems can be eliminated, overcoming one of the shortcomings of mechanical radar systems that would otherwise render a crawler radar system unsuitable for Doppler processing.

Abstract: Systems and methods of improving sampling of WLAN packet information to improve estimates of Doppler frequency of a WLAN positioning device. A device estimates the position of itself. The device includes a WLAN radio module for receiving WLAN signals transmitted by WLAN APs in range of said device, extraction logic for extracting information from said received WLAN signals to identify the WLAN APs, and logic to cooperate with a WLAN-based positioning system to estimate the position of the device based at least in part on the extracted information identifying the WLAN APs in the range of said device. The WLAN radio module includes logic for measuring multiple received signal strength indicator (RSSI) values for sufficiently long WLAN packets to increase the sampled rate of RSSI of WLAN packets from WLAN APs and to thereby improve an estimate of the Doppler frequency of said device.

Abstract: Disclosed is a channel estimator and a method for changing a coefficient of an IIR filter depending on a moving speed of a mobile communication terminal. In the channel estimator, a coefficient changing unit receives I and Q signals from a current base station, and selects a coefficient of the IIR filter optimized depending on the moving speed of the current mobile communication terminal. The coefficient changing unit sets the selected coefficient of the IIR filter to the IIR filter of the channel estimator. Accordingly, it is possible to prevent the performance degradation of the channel estimator caused by the speed of the mobile communication terminal.

Abstract: A radar system and method is provided, in which the radar system includes a first transmitting portion of antenna elements, a second transmitting portion of antenna elements, and a receiving portion of antenna elements, such that the receiving antenna elements form a plurality of subarrays that represent real and synthetic antenna elements. The radar system further includes a transceiving device having a switching matrix. At least first and second switching transmit antenna elements are configured and time-multiplexed, wherein a receive aperture of the receiving antenna elements is increased.

Abstract: A radar system and method is provided, in which the radar system includes a first transmitting portion of antenna elements, a second transmitting portion of antenna elements, and a receiving portion of antenna elements, such that the receiving antenna elements form a plurality of subarrays that represent real and synthetic antenna elements. The radar system further includes a transceiving device having a switching matrix. At least first and second switching transmit antenna elements are configured and time-multiplexed, wherein a receive aperture of the receiving antenna elements is increased.

Abstract: A method and apparatus for detecting emitter movement. The method and apparatus generally include acquiring a measured signal characteristic corresponding to a signal emitted from an emitter, estimating a signal characteristic corresponding to the signal, and comparing the measured and estimated signal characteristics to determine if the emitter is moving. Such a configuration enables a rapid and accurate detection of emitter movement without requiring multiple measurements, complex systems, or time-consuming calculations.

Abstract: In a configuration according to a short-range radar of the present invention and a method of controlling the same, the timing at which a variable-period pulse output from a variable-period pulse generator including a direct digital synthesizer (DDS) has shifted in level first since reception of a search instruction is used as a reference timing, so that a signal that shifts in level at the reference timing or a fixed lapse of time later than the reference timing is generated and output as a transmission trigger signal, and a signal that shifts in level at a timing delayed by half a period of the variable-period pulse or its integral multiple from the timing at which the transmission trigger signal is output is generated and output as a reception trigger signal.

Abstract: A vehicle radar system includes a processing system which operates in one of a plurality of operating modes which are selected based upon an environment (or changes to an environment) surrounding the vehicle radar system. In one exemplary embodiment, the vehicle radar system is provided as a vehicle radar system which operates in one of: a highway traffic mode and a city traffic mode depending upon whether a vehicle in which the vehicle radar system is disposed is traveling along a highway or through a city.

Abstract: A transmitter emits into an intended search space a radar wave having a predetermined frequency pulse-modulated by a trigger pulse of a predetermined width. A receiver receives a reflected wave of the radar wave and outputs a receive signal. A local pulse generator outputs a local pulse signal having the predetermined frequency pulse-modulated by the trigger pulse delayed by the delay unit. A correlation value detector detects a strength correlation value between the receive signal and the local pulse signal. A delay time changing unit changes the delay time sequentially within a range of a predetermined period representing a generation period of the trigger pulse. A correlation value storage unit stores the strength correlation value detected for each delay time changed. A frequency distribution generator generates a frequency distribution of a stored correlation value against the delay time.

Abstract: A tunable high resolution spectral estimator is disclosed as a method and apparatus for encoding and decoding signals, signal analysis and synthesis, and for performing high resolution spectral estimation. The invention is comprised of an encoder coupled with either or both of a signal synthesizer and a spectral analyzer. The encoder processes a frame of a time-based input signal by passing it through a bank of lower order filters and estimating a plurality of lower order covariances from which a plurality of filter parameters may be determined. Coupled to the encoder, through any appropriate data link or interface including telecommunication links, is one or both of a signal synthesizer and a spectral analyzer. The signal synthesizer includes a decocer for processing the covariances and a parameter transformer. The signal synthesizer includes a decoder for processing the covariances and a parameter transformer for determining filter parameters for an ARMA filter.

Abstract: In an FM-CW radar system, a frequency modulating said modulating wave output from said modulating signal generator has a frequency variation skew with respect to a time axis (modulation skew), and the radar system includes a means for varying the modulation skew by controlling the modulation frequency amplitude or modulation period of the modulating signal. The radar system further includes a means for discriminating a signal component varying in response to the variation of the modulation skew, thereby discriminating a signal related to a target object from other signals. In the case of an FM-CW radar system that performs transmission and/or reception by time division ON-OFF control the radar system includes a means for discriminating a signal which, when the frequency used to perform the ON OFF control is varied, varies in response to the variation of the frequency, thereby discriminating a signal related to a target object from other signals.

Abstract: A transmitted signal and a received signal are combined and the combination is expected to determine whether or not a target signal is present. Either the transmitted signal or the received signal is combined with an auxiliary signal containing a range of frequencies corresponding to an anticipated Doppler shift, so that an output of the combined transmitted and received signal will be present only if a target signal exhibiting a Doppler shift within the anticipated range is present. The auxiliary signal preferably comprises finite-duration signal portions of different types so as to provide a substantially uniform frequency response throughout the selected range.

Abstract: In a radio wave radar system using a two-frequency CW modulation method, it is possible to detect a distance between a host vehicle and a forward vehicle and to realize a stable ACC following travel, even in a condition in which the relative speed is 0. By combining the two-frequency CW modulation method with the frequency pulse CW modulation method, that is, by using combination with the two-frequency CW method when the relative speed occurs and the frequency pulse CW method when the relative speed is close to 0, even if the relative speed is 0, the IF signal obtained from the reflected wave from the forward vehicle can be generated to detect the existence of the ACC target vehicle, so that it is possible to realize a stable ACC following travel.

Abstract: The present invention relates to a radar measuring device which, with a simple design, ensures reliable distance determination even when a mixed signal is zero, and a method for operating a radar measuring device. The radar measuring device includes: A high-frequency oscillator (11) which emits two different carrier frequency signals (F1, F2), A first switching device (14) for switching the carrier frequency signals (F1, F2) as a function of first pulse signals (P1) and emitting radar pulse signals (T1, 2), A transmission antenna (16) and a receiving antenna (18), A second switching device (24) for switching the carrier frequency signals as a function of a delayed second pulse signal (P2) and emitting delayed radar pulse signals (S1, 2), A mixing device (21) for mixing received radar signals (R1, 2) with the delayed radar pulse signals (S1, 2) and emitting mixed signals (M1, 2).

Abstract: Disclosed is a transmit-receive FM-CW radar apparatus which switches between transmission and reception by time division control, wherein amplifiers capable of controlling gain are provided in a transmitter signal path and a receiver signal path, respectively, and wherein the gain in the leading edge portion of a receive timing interval or the gain in the trailing edge portion of a transmit timing interval is suppressed by controlling the gain of the amplifier provided in the receiver signal path or the gain of the amplifier provided in the transmitter signal path, respectively.

Abstract: A transmit-receive FM-CW radar apparatus according to one mode of the invention comprises: a mixer for downconverting an IF signal; a switch provided on the input side of the mixer; and a switch controller for controlling the switch on and off in different modes and selecting the IF signal in the different modes for supply to said mixer. A transmit-receive FM-CW radar apparatus according to another mode of the invention comprises: a mixer for downconverting an IF signal; a switch for turning on and off a local signal to be supplied to the mixer; and a switch controller for controlling the switch on and off in different modes and selecting the local signal in the different modes for supply to the mixer.

Abstract: An FM-CW radar apparatus capable of detecting a stationary object, in particular, an overbridge, located above the road ahead in a simple manner uses a traveling wave antenna as a transmitting antenna, and includes a means for varying, in upward and downward directions the projection angle of a combined beam pattern of a transmitted wave radiated from the traveling wave antenna, and an overbridge is detected by varying the projection angle of the combined beam pattern in the upward direction using the varying means. Further, a phase shifter for varying the projection angle of the beam pattern in upward/downward directions by controlling the phase of the radio wave to be transmitted or received is provided on either a transmitting antenna or a receiving antenna or on a transmitting/receiving antenna, and an overbridge is detected by controlling the phase shifter and varying the projection angle of the beam pattern in the upward direction.

Abstract: A radar system and a characteristic adjustment method for the radar system are provided, in which a control voltage waveform of a voltage controlled oscillator for frequency-modulating a sending signal can be set in a short time without increasing the required amount of memory. In adjusting time-varying characteristics of a voltage signal for frequency modulation on a voltage controlled oscillator determining a sending frequency, the time-varying characteristics of the voltage signal for frequency modulation are adjusted to optimize a form of a protrusion in signal intensity included in a frequency spectrum of a beat signal.

Abstract: In an automotive radio wave radar, a center frequency of a transmitted wave is shifted at a certain cycle, and position information of an obstacle detected at three or more center frequencies is subjected to decision by majority to determine whether detection results of the obstacle are erroneous with the occurrence of jamming. If any of the detection results is determined to be abnormal, the abnormal result is discarded. An automotive radio wave radar is realized which can correctly perform the obstacle detection even in the event of jamming without causing erroneous obstacle detection or omission of the detection.

Abstract: A radar device precisely detects a target in short time intervals by detecting a true peak frequency with high accuracy via a calculation which does not require a large amount of computation. A discrete frequency spectrum of a beat signal multiplied by a window function is determined, and values of signal strength at two discrete frequencies which are, respectively, higher and lower than a peak frequency of the discrete frequency spectrum of the beat signal and which are adjacent to the peak frequency. The frequency difference between the discrete peak frequency of the beat signal and the peak frequency of the window function is then determined from the ratio between the values of signal strength at those two discrete frequencies adjacent to the peak frequency. Thus, the true peak frequency of the beat signal is determined with a high frequency resolution.

Abstract: A radar system includes a transmitting/receiving unit, having a voltage controlled oscillator, for repeatedly transmitting a triangular transmission signal including a frequency-gradually-rising up-modulation interval and a frequency-gradually-dropping down-modulation interval and for receiving a reception signal including a reflected signal from a target, a frequency analysis unit, a data storing unit for storing time-varying characteristics of input values to a D/A converter that monotonically change an oscillation frequency of the voltage controlled oscillator with time, in the form of data concerning an expression representing the time-varying characteristics, and a data processing unit for determining the input values to the D/A converter with reference to the data. At least one of the relative distance to the target and the relative speed of the target is detected based on a beat signal during the up-modulation interval and the beat signal during the down-modulation interval.

Abstract: A radar system and a characteristic adjustment method for the radar system are provided, in which a control voltage waveform of a voltage controlled oscillator for frequency-modulating a sending signal can be set in a short time without increasing the required amount of memory. In adjusting time-varying characteristics of a voltage signal for frequency modulation on a voltage controlled oscillator determining a sending frequency, the time-varying characteristics of the voltage signal for frequency modulation are adjusted to optimize a form of a protrusion in signal intensity included in a frequency spectrum of a beat signal.

Abstract: In an FM-CW radar system, a frequency modulating wave output from said modulating signal generator has a frequency variation skew with respect to a time axis (modulation skew), and the radar system includes a means for varying the modulation skew by controlling the modulation frequency amplitude or modulation period of the modulating signal. The radar system further includes a means for discriminating a signal component varying in response to the variation of the modulation skew, thereby discriminating a signal related to a target object from other signals. In the case of an FM-CW radar system that performs transmission and/or reception by time division ON-OFF control, the radar system includes a means for discriminating a signal which, when the frequency used to perform the ON-OFF control is varied, varies in response to the variation of the frequency, thereby discriminating a signal related to a target object from other signals.

Abstract: A high resolution spectral estimator (HREE) filter coupled to a spectral plotter processes either Doppler frequencies provided from the output of a pulse-Doppler radar or a frequency based output provided by a Fourier transformer coupled to a sensing device to allow the spectral plotter to determine the power frequency spectrum of either the pulse-Doppler radar output or sensing device output. The HREE filter preferably comprises a bank of first order filters tuned to a pre-selected frequency, a covariance estimator coupled to the filter bank for estimating filter covariances, and a decoder coupled to the covariance estimator for producing a plurality of filter parameters. Further, it is preferable that the filters comprising the filter bank be adjustable to permit their being tuned to a desired frequency based on a priori information.

Abstract: A system (10) for determining the range between a missile (14) and a target (18) adapted for use with a semi-active missile system. The system (10) includes a first circuit (12) for generating a periodic signal (24) that is periodically frequency modulated. A second circuit (16) determines a closing rate at which the missile 14 is approaching the target 18 via the periodic signal 24. A third circuit (16) determines a value containing information corresponding to the range and the closing rate via the periodic signal. A fourth circuit (16) determines the range from the closing rate and the value. In a specific embodiment, the first circuit (12) includes an illumination system (12). The illumination system (12) includes a periodically modulated carrier signal generator (32) that generates the periodic signal (24). The periodically modulated carrier signal generator (32) includes a frequency source, a frequency modulator, and an illumination system computer.

Abstract: An FM-CW radar apparatus is provided which may be employed in automotive anti-collision or radar cruise control systems. The radar apparatus transmits as a radar wave a high-frequency signal which is so modulated in frequency with a modulating signal as to vary with time in the form of a triangular wave and mixes a received signal with a local signal that is part of the transmitted signal to produce a beat signal consisting of a fundamental frequency component as a function of the distance to and relative speed of a target object. The radar apparatus also includes an amplitude modulator which modulates the amplitude of at least one of the transmitted signal, the received signal, and the local signal in accordance with the modulating signal so that the modulation index falls within a range of zero (0) to one (1). This allows harmonic components with an improved SN ratio to be extracted from the beat signal which may be used in calculating the fundamental frequency component of the beat signal.

Abstract: An anticipatory object detection system includes a transducer device for transmitting a modulated carrier signal and receiving the reflected modulated carrier signal from an object; a detection device for detecting a plurality of Doppler shifted harmonic components from the reflected modulated carrier signal; a range determining device responsive to the amplitude of at least two of the harmonic components for determining the instantaneous range of the object; a velocity measurement device, responsive to the frequency of at least one of the harmonic components, for determining the relative, instantaneous velocity of the object.

Abstract: A radar system for detecting hazardous objects has a transceiver including a transmitting antenna for transmitting microwave power. For a side detection system, power transmission is available when the vehicle is moving forward. A signal processor receives a pulsed vehicle speed signal and a reverse signal and is programmed to terminate transmission when no speed pulse is received for a preset time or when the reverse signal is present. The transmission is terminated by removing power from the transceiver or by rerouting the microwave power from the antenna to an internal calibration circuit. Radar transmission is re-enabled when the vehicle begins to move forward again. For a rear detection system, radar transmissions are enabled when the reverse signal is present.

Abstract: A radar system (30) for determining the range at a future time of a target moving relative to the radar system. The system comprises an R.F. source (56) for providing a signal at a frequency which increases over time from a base frequency f (Hz) at a rate r (Hz/s) for a sweep duration d (s). This signal is transmitted and a signal reflected by the target is mixed (38) with a portion of the transmitted signal to give a signal having a frequency proportional to the range of the target. The R.F. source is arranged to have a sweep rate r equal to the base frequency f divided by a time t (s) which time is the delay until the target will be at the measured range. A predicted range may thus be derived without complex compensation for relative velocity. The system may further provide velocity feedback without requiring extra circuitry.

Abstract: The pulsed Doppler weather radar system reduces ambiguities in measured parameters by staggering at least one pulse of each frame of n pulses transmitted by the radar system. The staggered pulse creates an isolated pulse doublet pair to provide three or more independent and auxiliary Doppler parameter estimates. The parameter estimates are combined optimally in a neuromorphic processor matched to the phenomena of interest, particularly capitalizing on multiparameter volumetric correlations to improve data quality.

Abstract: A radar system having a phased array antenna for transmission and a digital beam forming antenna for reception for observing a plurality of targets by transmitting transmission pulses to the respective targets comprises a subtraction control circuit, a transmission timing control circuit and a transmission beam direction control circuit. The substraction control circuit calculates a required number of transmission pulses (beams) to be transmitted for each of transmission cycles in accordance with detected Doppler frequencies of the targets, so as not to cause ambiguity on the detected Doppler frequencies, and determines a beam direction for each of transmission beams. The timing control circuit and beam direction control circuit control transmission timing and direction of the beams.

Abstract: A transceiver system of a frequency-agile Doppler radar comprises a transmission-side and a reception-side oscillator circuit both connected to a frequency-agility controller for concurrently varying their operating frequencies. Each of these oscillator circuits includes a high-frequency generator coupled via a frequency divider and a frequency multiplier to a pair of auxiliary mixers in a control loop of an associated microwave generator, the loop further including another frequency divider between the two mixers. The step-down ratios of the two frequency dividers of each oscillator circuit is adjustable by the frequency-agility controller. The microwave generator of the transmission-side oscillator circuit emits an outgoing signal to a duplexer connected to the radar antenna while incoming echoes are fed by the duplexer to a first principal mixer receiving a heterodyning signal from the microwave generator of the reception-side oscillator circuit.

Abstract: A vehicle near-obstacle detector in the form of a diplex Doppler radar system provides range information between a vehicle and an object based on the phase shift between a pair of Doppler signals derived from two transmitted radar signals at slightly different frequencies. A speed dependent error introduced by the time constant of a filter circuit converting duty cycle range information based on the phase shift to an analog signal is compensated by introducing a small time shift in the signal path of one of the Doppler signals to effect a shift in the duty cycle range information.

Abstract: An optical gauge measures the shape of a target object by scanning a laser beam over it, (and/or measures the radial velocity of the target), by measuring the Doppler frequency shift of the reflected wave. The Doppler-shifted frequency is demodulated by a phase locked loop, which has a limited hold-in frequency range within which it is capable of staying locked on. With this invention, if the reflected wave's frequency gets close to exceeding the hold-in range of the phase locked loop, the gauge adjusts the drive frequency of an acoustooptical modulator that modulates the outbound target beam. This offsets the frequency of the target beam and keeps the return signal within the hold-in range of the phase locked loop.

Abstract: A laser distance gauge measures the distance and shape of a target by alternately performing (a) a Doppler shift measurement during optical scanning of the target's surface and/or motion of the target and (b) a chirp measurement with a chirp frequency laser signal. To ascertain changes in radial distance from the gauge to the target, the Doppler shift information is integrated and the result is combined with absolute distance measurements made in the chirp mode. A single CW laser, which operates single frequency, serves for both types of measurement. A computer changes the gauge from Doppler mode to chirp mode when the Doppler shift reaches a predetermined amount. When a chirp measurement of absolute distance is completed it reverts to Doppler mode.

Abstract: A coded pulse Doppler radar having apparatus for determining the separation between the frequency spectrum returned from clutter and the frequency spectrum returned from a desired target, and circuitry responsive to the apparatus for adjusting the code to maintain the separation at least at a predetermined minimum value.

Abstract: A radar gauge adapted to sense fluid level in a tank and including a radar gauge circuit in which radar transmission and level sampling are controlled by a transmit frequency and a sample frequency respectively. A first frequency separation between first and second frequencies is controlled by a control input. The first and second frequencies can be divided to generate the transmit and sample frequencies, separated by a second frequency separation. At least one frequency difference is evaluated and the evaluation used to generate the control input, stabilizing the first frequency difference, and to correct the gauge output.