Abstract: A method and apparatus that compensate radar channel length variation are provided. The method includes transmitting a signal from the transmitter, determining a response of each of the receivers to the transmitted signal, and storing the determined responses; for each stored response of the stored responses, calculating a path length of the transmitted signal; for each of the transmitters, determining and storing a median receive path difference in the path length between a transmitter and each receiver; for each receiver of the receivers, determining and storing a median receive path difference in the path length between a receiver and each transmitter; and compensating for the median receive path difference and the median transmit path difference by performing a frequency shift on or time delaying a signal to be transmitted by a transmitter or received by a receiver.

Abstract: A radar device is mounted on a vehicle, which is a moving object, and includes a doppler correction phase-rotation controller and a phase rotator. Based on the speed of the vehicle, the doppler correction phase-rotation controller calculates a Doppler correction phase-rotation amount for correcting a Doppler frequency due to movement of the vehicle. By using the Doppler correction phase-rotation amount, the phase rotator pre-corrects Doppler frequency components with respect to a radar transmission signal in each transmission interval of the radar transmission signal.

Abstract: A node unit of distributed antenna system, the node unit comprises a delay measuring part configured to transmit a first test signal for delay measurement to an upper adjacent node unit and detect the first test signal looped back via the upper adjacent node unit and measure a round trip delay between the node unit and the upper adjacent node unit, and a delay providing part disposed on a signal transmission path through which a second test signal for delay measurement, to be transmitted from a lower adjacent node unit, is to be looped back to the lower adjacent node unit, and configured to provide a delay corresponding to the round trip delay.

Abstract: An electronic circuit includes adjustment units configured to receive a same oscillating signal having a predetermined frequency and to adjust a phase and an amplitude of the oscillating signal to produce output oscillating signals, coupling points configured to supply the output oscillating signals produced by the adjustment units to antennas, couplers provided in one-to-one correspondence with outputs of the adjustment units, equal-length lines sharing the same length and extending from the couplers, respectively, mixer circuits coupled to the equal-length lines, respectively, each of the mixer circuits being configured to receive a same reference oscillating signal having the predetermined frequency and a corresponding one of the output oscillating signals, and a control circuit configured to cause the adjustment units to adjust at least one of the phase and the amplitude in response to direct-current components in outputs of the mixer circuits.

Abstract: A radar apparatus includes a correlator which, in operation, calculates a correlation value between the digital transmission pulse signals and the digital reception pulse signals, an error estimator which, in operation, estimates, on the basis of the correlation value, an I component error and a Q component error included in the digital reception pulse signals, a correction parameter calculator which, in operation, calculates a correction parameter for correcting the I component error and the Q component error, and an error corrector which, in operation, corrects, on the basis of the correction parameter, the I component error and the Q component error included in at least one of the digital transmission pulse signals and the digital reception pulse signals.

Abstract: A pulsed radar level gauge for determining the filling level of a product contained in a tank, comprising a frequency generator for generating a Tx frequency signal and a Rx frequency signal. The frequency generator includes one single oscillating crystal for providing an oscillator frequency fosc and frequency modifying circuitry. The frequency modifying circuitry comprises a path including a PLL configured to receive said oscillator frequency fosc as input frequency and deliver a regulated output frequency being equal to the oscillator frequency fosc multiplied M/N, and a frequency divider connected to receive the regulated output frequency and deliver an output frequency equal to the regulated output frequency divided by an integer factor P. A PLL combined with an integer frequency divider is used to generate at least one of the Tx and Rx frequencies based on an oscillator frequency provided by one single oscillator.

Abstract: Methods and systems for suppressing clutter, for example, ground clutter, in radar systems are provided. The methods and systems can be employed in radar systems having an antenna system and at least two receive beams, for example, a main beam and an auxiliary beam. The methods include receiving data streams from each of the at least two receive beams, where each data stream is associated with range bins and include data representing clutter, and, before or after Doppler filtering, generating an adaptive weight from summations of the data streams for each of the range bins, and applying the generated weight to at least one of the data streams to provide Doppler filtered and spatially nulled data streams that can be used to more accurately identify targets, such as, aircraft.

Abstract: A method (e.g., a method for measuring a separation distance to a target object) includes transmitting an electromagnetic first transmitted signal from a transmitting antenna toward a target object that is a separated from the transmitting antenna by a separation distance. The first transmitted signal includes a first transmit pattern representative of a first sequence of digital bits. The method also includes receiving a first echo of the first transmitted signal that is reflected off the target object, converting the first echo into a first digitized echo signal, and comparing a first receive pattern representative of a second sequence of digital bits to the first digitized echo signal to determine a time of flight of the first transmitted signal and the echo.

Abstract: A node unit of distributed antenna system, the node unit comprises a delay measuring part configured to transmit a first test signal for delay measurement to an upper adjacent node unit and detect the first test signal looped back via the upper adjacent node unit and measure a round trip delay between the node unit and the upper adjacent node unit, and a delay providing part disposed on a signal transmission path through which a second test signal for delay measurement, to be transmitted from a lower adjacent node unit, is to be looped back to the lower adjacent node unit, and configured to provide a delay corresponding to the round trip delay.

Abstract: A travel distance measurement device includes a transmitting antenna that is disposed in a vehicle and emits a transmission signal, as a radio wave, toward a ground surface, a receiving antenna that is disposed in the vicinity of the transmitting antenna, and receives a radio wave reflected from the ground surface and acquires a reflection signal, and a distance calculator (an IQ demodulator and a phase conversion integrator) that calculates the travel distance of the vehicle on the basis of the phase of the acquired reflection signal.

Abstract: A method and system for reducing clutter in a number of images. Sub-image pixel values are identified for a sub-image at a location in an image in the number of images. A first portion of the sub-image pixel values corresponds to a number of suspected target pixels in the sub-image. A second portion of the sub-image pixel values corresponds to clutter pixels in the sub-image. Modeled pixel values are generated using a clutter model fitted to the second portion of the sub-image pixel values. The modeled pixel values are subtracted from the sub-image pixel values to form new pixel values.

Abstract: A pulse radar receiver includes a power splitter configured to split a transmit (TX) trigger signal for generating a TX pulse, a phase-locked loop (PLL) configured to receive a division ratio and the TX trigger signal split by the power splitter, and generate a sampling frequency, and a sampler configured to sample a reflected wave received through an RX antenna, according to the sampling frequency generated by the PLL. Accordingly, it is possible to provide a high distance resolution by generating a sampling frequency with a difference from a TX pulse to sample a reflected wave received through an RX antenna. Thus, it is possible to overcome a limitation in the distance resolution due to the pulse width and to measure a minute movement at a short distance. Therefore, the pulse radar receiver is applicable to high range resolution radar applications such as a living body measuring radar.

Abstract: A pulse radar range profile motion compensation method (10) comprises: acquiring receiver samples (12); acquiring an estimate of the range rate of a target (14); removing an additional phase acquired by the echo signals; removing a shift in range cells of the receiver samples (18); applying a pulse Doppler filter (22); identifying the peak Doppler frequency and calculating a shift from zero of the peak Doppler frequency (24); calculating a range rate correction (26); adding the range rate correction to the estimate of the range rate and repeating the removal of the additional phase (16) and the shift in range cells (18), and using the new range rate estimate to obtain motion compensated receiver samples (28); and generating an output signal indicative of the motion compensated receiver samples for generating a range profile (30).

Abstract: Phase and gain of a transmit signal are measured at a transmitter by determining a first time delay having a first resolution at a measurement receiver between a reference signal from which the transmit signal is generated and a measured signal derived from the transmit signal by comparing amplitudes of the reference signal and the measured signal. A second time delay having a second resolution finer than the first resolution is determined at the measurement receiver between the reference signal and the measured signal based on the first time delay. The reference signal and the measured signal are time aligned at the measurement receiver based on the second time delay and the phase and gain of the transmit signal are estimated after the reference signal and the measured signal are time aligned.

Abstract: An ultra wide band (UWB) millimeter (mm) wave radar system includes a signal source having a control input, a GHz signal output and a frequency controlled output. A control loop is coupled between the GHz signal output and the control input including a frequency divider and a digitally controlled PLL that provides a locked output coupled to the control input of the signal source to provide frequency locked output signals that are discrete frequency swept or hopped. A frequency multiplier is coupled to the frequency controlled output of the signal source for outputting a plurality of mm-wave frequencies. An antenna transmits the mm-wave frequencies to a surface to be interrogated and receives reflected mm-wave signals therefrom. A mixer mixes the reflected mm-wave signals and mm-wave frequencies and processing circuitry determines at least one parameter relating to the surface from the mixing output.

Abstract: Delay measurement and delay calibration methods and apparatus are described for use within distributed wireless base stations employing a remote radio head topology. The methods and apparatus are usable in any system that requires accurate delay measurement and/or constant delay through an electronic device. The methods and apparatus for measuring delay embody a highly accurate distributed delay measurement architecture that handles multiple delay paths within distributed wireless base stations employing a remote radio head topology. The method and apparatus are amenable to implementation with current integrated circuit technology. The methods and apparatus for calibrating electronic delay within distributed base stations employing a remote radio head topology are useful for implementing distributed wireless base stations where transmit diversity is desired.

Abstract: A feedback loop corrects timing errors by reducing deviations from a constant radar sweep rate. Errors are detected and fed back to a phase corrector in a high gain feedback system. A precision radar rangefinder can be implemented with a direct digital synthesizer (DDS) that includes feedback error correction for reducing range errors by, for example, 100 times, or to 0.1 mm. An error-corrected DDS swept timing system can enable a new generation of highly flexible, repeatable and accurate radar, laser and guided wave rangefinders.

Abstract: An in-vehicle radar device includes: phase storing means 12 that prestores the phase of a received wave incoming secondarily from outside a target; received wave importing means 13 that imports the received wave on the basis of a radio wave reception timing determined by a transmission timing of the radio wave; phase detecting means 14 that determines the phase of the received wave imported by the received wave importing means; phase correction amount extracting means 15 that compares the phase prestored by the phase storing means 12 with the phase detected by the phase detecting means 14 and extracts and stores a phase correction amount of each of element antennas; and phase correcting means 16 that corrects the phase of a received signal of each of the element antennas on the basis of the phase correction amount obtained by the phase correction amount extracting means.

Abstract: A method for the linearization of frequency modulated continuous wave (FMCW) radar devices having non-linear, ramp-shaped, modulated transmitter frequency progression x(t). With this invention, a correction phase term for compensation of the phase error in the reception signal q(t) is calculated on the receiver side in this device.

Abstract: The height of a radar target above a horizontal plane at a location within the horizontal plane is measured using a synthetic aperture radar (SAR). The synthetic aperture radar is mounted on a moving platform. The moving platform moves along a continuous climbing path with respect to the horizontal plane acquiring a plurality of SAR arrays of radar return information. Monopulse , Interferometric SAR (IF-SAR), and shadow length height measurements are fused to refine the target height measurement. Monopulse and IFSAR are combined to resolve target height ambiguities. The SAR arrays are separated vertically, at separate heights with respect to the target, and acquired sequentially in time, as a single pass.

Abstract: A radar system receiver having an antenna system adapted to receive a jammer signal from both a direct path and from an indirect path. The direct and indirect paths have both differential Doppler frequency and differential time delay induced phase shifts. The antenna system includes a plurality of antenna elements. A plurality of radar receiver sections, each one having a clutter filter, is provided. Each one of the receiver sections is fed by a corresponding one of the antenna elements. An adaptive jammer canceler is fed by the plurality of radar receiver sections for providing a beam forming network to suppress both the direct and indirect paths of the jamming signal.

Abstract: A method for processing radar return data to determine a physical angle, in aircraft body coordinates to a target, is disclosed. The radar return data includes a phase difference between radar return data received at an ambiguous radar channel and a left radar channel, a phase difference between radar return data received at a right radar channel and an ambiguous radar channel, and a phase difference between radar return data received at a right radar channel and a left radar channel. The method includes adjusting a phase bias for the three phase differences, resolving phase ambiguities between the three phase differences to provide a signal, and filtering the signal to provide a physical angle to the target in aircraft body coordinates.

Abstract: A method and bistatic synthetic aperture radar (SAR) imaging system generate an image of a target area without knowledge of the position or velocity of the illuminator. The system includes an illuminator to illuminate a target area with a null-monopulse radiation pattern interleaved with a sum radiation pattern. The illuminator adjusts the phase terms of the sum radiation pattern to maintain a static electromagnetic field pattern at the target area. A receiver receives the radiation patterns reflected from the target area and generates phase compensation terms by correlating a measured electromagnetic vector field with the known static electromagnetic vector field. The phase compensation terms are used to generate an image of the target area.

Abstract: A method and bistatic synthetic aperture radar (SAR) imaging system generate an image of a target area without knowledge of the position or velocity of the illuminator. The system includes an illuminator to illuminate a target area with a null-monopulse radiation pattern interleaved with a sum radiation pattern. The illuminator adjusts the phase terms of the sum radiation pattern to maintain a static electromagnetic field pattern at the target area. A receiver receives the radiation patterns reflected from the target area and generates phase compensation terms by correlating a measured electromagnetic vector field with the known static electromagnetic vector field. The phase compensation terms are used to generate an image of the target area.

Abstract: A system and method for efficient phase error correction in range migration algorithm (RMA) for synthetic aperture radar (SAR) systems implemented by making proper shifts for each position dependent phase history so that phase correction can readily be performed using the aligned phase history data during batch processing. In its simplest form, the invention (44) is comprised of two main parts. First (60), alignment of the phase error profile is achieved by proper phase adjustment in the spatial (or image) domain using a quadratic phase function. Second (62), the common phase error can be corrected using autofocus algorithms. Two alternative embodiments of the invention are described. The first embodiment (44a) adds padded zeros to the range compressed data in order to avoid the wrap around effect introduced by the FFT (Fast Fourier Transform). This embodiment requires a third step (64): the target dependent signal support needs to be shifted back to the initial position after phase correction.

Abstract: From a set of possible switching states and responsive to a sequence of measurements, a corresponding sequence of switching states is determined for a system having a plurality of dynamic models, associates each model with a switching state such that a model is selected when its associated switching state is true. A state transition record is determined, based on the measurement sequence. The sequence of switching states is determined by backtracking through the state transition record. Alternatively, the switching state model is decoupled from the dynamic system model. The decoupled switching state model is transformed into a hidden Markov model (HMM) switching state model, while the decoupled dynamic system model is transformed into a time-varying dynamic system model. A solution to the dynamic system model is estimated using a Kalman filter.

Abstract: The present invention relates to a receiving/transmitting apparatus for radiating a predetermined signal and receiving a signal arriving as a response to the radiated signal, and to a radar equipment in which the receiving/transmitting apparatus is installed. In the receiving/transmitting apparatus and the radar equipment according to the present invention, high coherency is reliably achieved without any great enlargement in hardware scale. Therefore, it is possible to realize with high reliability improvement in performance and reliability as well as price reduction, downsizing, and running cost reduction in apparatuses and systems to which the present invention is applied.

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: An electronic circuit for a proximity sensor, which is target-independent and is based on a phase projection transformation, is configured in such a way that the oscillating circuit can be driven by a square-wave voltage. A synchronous demodulator is used for the phase projection transformation. The electronic circuit can be miniaturized and only low requirements are placed on the stability of the feed voltage. A method for operating a proximity sensor is also provided.

Abstract: A radio frequency identification system includes a transponder and a transponder reader. The transponder, responsive to an interrogation signal continuously transmitted by the transponder reader, generates a transponder signal modulated by an identification signal readable by the transponder reader. The identification signal includes a synchronization portion, a data portion, an output format identification portion, and an error detection portion. The output format identification portion is used by the reader to configure itself for communication with an attached controller. In another aspect of the invention, the transponder reader may be configured to read FSK as well as PSK encoded signals from the transponder.

Abstract: Methods that compensate for phase errors caused by path length variations in a radar system, and that compensate for relative phase errors in upconvertor and downconverter references employed in the radar system. One method samples a signal reflected from a duplexer through a receiver during the time the radar pulse is transmitted. The signal reflected from the duplexer is compared to a radar echo pulse on a single pulse basis. The phase of the sampled signal is subtracted from the phase of the received radar echo pulse reflected to determine the phase error. In a second method, multiple samples are collected during the time each radar pulse is transmitted. Samples of the signal reflected from the duplexer and the radar echo pulse are compared on a pulse to pulse basis. The phase differences are averaged across the pulse duration. The averaged phase differences are integrated on a pulse to pulse basis to determine the phase error.

Abstract: A radar transmitter for producing a radar signal in response to a radar trigger signal fed thereto. The transmitter includes a radio frequency oscillator for producing a signal having a radio frequency carrier to be used in each transmitted radar signal. The signal produced by the oscillator is amplified by a radio frequency amplifier. In response to the system trigger signal, the transmitter is configured in a normal operating mode to operate with three noise cancellation loops; i.e., an automatic level control loop (ALC); an amplitude modulation noise cancellation loop (AM noise cancellation loop); and a phase modulation noise (PM noise cancellation loop). In response to the system trigger signal, the normal operating mode is preceded with two calibration modes: an AM noise calibration mode used to determine a nominal operating point for the AM noise calibration mode; and a subsequent phase modulation (PM) noise calibration mode used to establish a nominal operating point for the PM noise calibration mode.

Abstract: Radar apparatus provided with a transmitting unit (1), having a transmit phase shifter for providing each transmitted pulse in a burst with a selected phase shift, and a receiving unit (7), having a receive phase shifter (9) for cancelling the selected phase shift upon reception. This enables unimpeded radar transmissions and causes an operational repeater jammer to be misled.

Abstract: A method of estimating the directions of radiating sources (56, 58, 60) with respect to an array (46) of a number of antenna elements (48), each of which elements has a separate gain/phase control (50). With nominal gain and phase selected a first estimte of the radiating sources directions (.theta.) is accompished by application of the MUSIC algorithm (2). The algorithm is iteratively applied to a microprocessor (54) using updated gain and phase values. Iteration is terminated at that iteration which produces the maximum difference values of the smallest eigenvalue pair of Q.sub.(i).

Abstract: Improvement of radar sign-to-noise ratio and detection sensitivity in radar systems is achieved by methods employing the subtraction of the unwanted radio frequency interference, RFI, or "clone" signals thereof, from the total received signal. The Clone signals are appropriately adjusted in phase and amplitude, and are obtained from an auxilliary broad beam antenna or from a delayed sample from the system's principal antenna. When multiple RFI signals at different frequencies are present, the entire receive band is subdivided into a plurality of frequency sub-ranges.

Abstract: Discernible frequency characteristics regarding BPSK and CW signals are dved from consecutive transform outputs of a dual channel chirp-Z processor. Physically separated antennas direct the signals to the chirp-Z channels and concurrently occurring transforms are directed from those channels to a particular phase detector in accordance with the type of signal to which such transforms relate. The selection of phase detector is made through switches which are controlled by logic circuitry in accordance with the discernible frequency characteristics.

Abstract: The present invention relates to a pulse Doppler radar wherein the phase position of the reflected signals is evaluated as the most important component in addition to the amplitude. Thus a very good resolution results in the range direction and in the velocity direction for the detection of multiple target situations. The invention can be employed particularly for a so-called HPRF radar.

Abstract: An improved local oscillator arrangement for a monopulse receiver in a semiactive missile guidance system is shown. The monopulse receiver includes an improved reference local oscillator wherein a first local oscillator signal and a pair of reference signals required to demodulate the output of the intermediate frequency section of such receiver are derived simultaneously from the output of a single voltage controlled crystal oscillator. The frequencies of the first local oscillator and the pair of reference signals are related to the frequency of the radar modified by any Doppler shift frequency experienced during an intercept.

Abstract: A system for detecting phase and gain imbalance errors in a synchronous detector. The synchronous detector (10) is assumed to have a fist circuit (16) for providing a first signal representing a first sinusoidal term (e.g., a cosine term) and for providing a second signal representing a second sinusoidal term (e.g., a sine term) complementary to the first sinusoidal term, circuitry (12) for mixing an input signal with the first signal and circuitry (14) for mixing the input signal with the second signal. The system (16) for detecting phase and gain imbalance errors of the invention includes an amplitude compensation circuit (24) for detecting and correcting amplitude errors in the first and second signals and a phase compensation circuit (26) for detecting and correcting phase errors in the first and second signals. For amplitude compensation, the outputs of the amplitude and phase compensation circuits are input to first and second amplitude detector circuits (28) and (30).

Abstract: An antenna system determines the true time delay in two or more correlated signals without a priori knowledge of the time relationship between the signals and uses the determined true time relationship to achieve maximum signal combinations of received and/or transmitted signals, increased receive G/T and/or transmit EIRP. The antenna system can provide adaptive beam steering with optimal time delays for each antenna element of a phased array and can combine distinct antenna apertures to create a larger effective antenna aperture.