Abstract: A digital polarimeter employs a signal time stretching technique to apply polarization phase shift characteristics to digitally generated polarization agile signal components. An RF signal to be transmitted is down-converted to an intermediate frequency and digitally sampled at a rate feasible with currently-available analog-to-digital converters. Horizontal and vertical signal components of the sampled IF signal are generated by processing the digital signal samples. Each digital signal sample is “time stretched” by storing each sample in M memory locations, such that N samples occupy M×N memory locations. Because each sample is stored in M memory locations, each incremental phase shift from one memory location to the next corresponds to 1/Mth of the actual sampling interval. The stretching process effectively increases the digital sampling frequency, yielding sufficient phase resolution.

Abstract: A pulse radar device, which includes a timing control unit that controls a transmit interval of a pulse signal, a transmitting unit that transmits the pulse signal, a receiving unit that receives a receive signal including a reflection signal component from a target object and a noise component, a receive signal change detecting unit that detects a change in the assembly of the receive signals of the assembly of the pulse signals which are transmitted during a first transmit interval and the assembly of the pulse signals which are transmitted during a second transmit interval, a reflection signal rising detecting unit that detects a rising time point of the reflection signal component, and a ranging/detecting unit that obtains a distance value on the basis of the rising time point of the reflection signal and judges the presence of the target object.

Abstract: A method and apparatus for transponding pulsed RF signals is provided. The method comprises receiving, with a receiver, pulsed RF signals having a plurality of PRIs. Further the method includes generating, with a PRI tracker, control signals from the received pulsed RF signals. The method then filters the received pulsed RF signals with the control signals to thereby obtain enable signals, which in turn control a transmitter permitting retransmission without clock jitter.

Abstract: A method for operating a radar system includes the steps of overlapping mainlobe clutter interference and feedthrough interference in a Doppler output signal of a coherent pulse Doppler radar including the step of phase modulating each pulse of a transmit signal wherein the selected phase modulation is derived from a linear phase ramp required to shift the mainlobe clutter interference into alignment with the feedthrough interference while being held constant over the duration of a pulse. With such an arrangement, the constant phase shift across each pulse has no effect on the performance of intrapulse compression modulation and results in pulse to pulse phase shifts easily being accomplished with existing phase shifters.

Abstract: A downlink telemetry system providing improved apparatus and methods for communicating instructions via pressure pulses from surface equipment to a downhole assembly. The apparatus comprises a surface transmitter for generating pressure pulses, a control system, and a downhole receiver for receiving and decoding pulses.

Abstract: In a homodyne-receiver radar system used for ranging and/or target detection, the frequency-modulated (FM) transmit phase are removed from the received signal. Removal of the known FM transmit phase from the received signal reduces the bandwidth of the received signal to half that of a system that does not remove the transmit phase. This allows the sampling rate, and thus the processor throughput, to be cut in half. With the FM transmit phase removed, the phase sequence of the processed signal is akin to a delayed version of the transmit signal phase history. This allows the range processing to use segments of a single phase sequence for processing all range gates, resulting in a large reduction in the amount of coefficient storage used for the matched-phase sequences required to process the set of range gates.

Abstract: A frequency modulated continuous wave (FMCW) radar system having a voltage controlled oscillator (VCO) for transmitting a RF signal and a linearizer for linearizing the VCO. The FMCW receives the transmitted RF signal as an input and outputs a signal to a modulator, which successively sweeps the VCO frequency over a defined range. The receiver mixes a return signal with a sample of the transmitted RF signal to derive an IF signal. An adaptive frequency sample clock drives an analog to digital converter to sample and digitize the IF signal, with the clock being derived from the transmitted RF signal.

Abstract: An arrangement for controlling radar transmissions for a system of antennas disposed on a moving platform. The radar transmissions are allocated to an antenna face for a future transmission. To effect an adequate allocation, a prediction arrangement is provided to predict the angular position of the moving platform and the antenna faces. Preferably an antenna is assigned that realizes the smallest off-broadside angle of the radar transmission.

Abstract: A signalling system in time-frequency space for detecting targets in the presence of clutter and for penetrating media, includes a transmitter antenna system, receiver and processor system. The transmitter antenna system generates and launches into a medium containing the targets an energy pulse (wave packet) having a predetermined duration and frequency characteristic, and which energy pulse matches at least one of the following: 1) the time-frequency reflection characteristics of the target(s) but not the clutter, or 2) the penetration time-frequency dielectric window of the medium, or 3) the time-frequency characteristics of the window of the receiver. Preferably, the time-frequency wave packet is the complex conjugate of the impulse response of the combined medium and target.

Abstract: A bank of matched filters are employed to impose on a transmitted pulse, as well as the optimum matched filter receiver response, exact amplitude and phase modulations necessary to maximize the likelihood of accurate target identification. This is accomplished by subjecting the output of each matched filter (corresponding to a target signature) to a threshold level detector to eliminate identification outputs caused solely by noise. The outputs from the threshold device represents the target identification from each matched filter. Since each matched filter corresponds to a particular target, the highest output identification signal will indicate the presence of a corresponding target.

Abstract: An interference avoidance system used in conjunction with a vehicular target detection system. The microwave transceiver section of the vehicular target detection system, in which the present invention is incorporated, transmits and receives time-multiplexed microwave signals having at least two channels (frequencies) spaced about 250 kHz apart. The time-multiplexed transmit signal is transmitted and strikes objects (targets) in the environment, and a portion of the transmit signal is reflected back the antenna. A difference signal having a frequency equal to the difference between the frequency of the transmit and the received signal is generated, digitized, and a Fast Fourier Transform (FFT) is performed on the digitized difference signal. A microcontroller analyzes the energy spectrum to determine whether there is interference present. If such interference is present, the microcontroller causes the transmit frequency to change until a frequency is found which is relatively free of the interference.

Abstract: An apparatus and a method for enhancing the radar cross section of a target. The present invention is an impulse radar system that implements a method that comprises the following steps. A pilot impulse radar pulse is transmitted at a target. The pilot pulse comprises a plurality of individual pulses having respective distinct frequencies generated by the impulse radar system. A return pulse from the target is received by the impulse radar system and provides information indicative of target scattering centers. The return pulse is used as a calibration signal for generating a phase conjugated pulse. The phase conjugated pulse is then transmitted at the target. Processing a target return signal derived from the transmitted phase conjugated pulse enhances the radar cross section of the target because the waveform of the transmitted phase conjugated pulse is matched to the characteristics of the target.

Abstract: A circuit for generating an output signal having an output frequency that varies linearly with time, and to an FM CW radar system utilizing such a circuit. The circuit includes a voltage controlled oscillator that produces an output signal at its output terminal at an output frequency that corresponds to the voltage of an input tuning signal. A comparison signal circuit receives the output signal and produces a periodic comparison signal such that when the output frequency varies by .DELTA.f, the comparison signal frequency varies by .DELTA.f/N where N is a positive integer. An update counter periodically causes the value of N to change by a predetermined integer amount. A phase detector compares the comparison signal to a periodic reference signal, and produces a correction signal that is filtered to provide the tuning signal for the VCO. The value of N is preferably changed at an update frequency that is equal to the frequency of the reference signal times an integer.

Abstract: A radar system having improved interference resistance. A transmitting section includes an oscillator capable of switching the oscillation frequency, and a transmitting antenna connected to said oscillator and capable of transmitting electric waves having specified transmitting frequencies transmitted in different directions in a specified order to enable a desired range to be scanned. The oscillator and the transmitting antenna are designed to operate so that every time one scanning is completed or every time the transmitting direction is changed during each scanning period, the transmitting frequency may be changed. The receiver can simultaneously form a plurality of beams in the scanning range, convert the received signals to digital signals, and output signals indicating the frequencies and arrival directions of the received signals. The operating mode of the transmitting section may be altered in accordance with the frequency and arrival direction of the received waves.

Abstract: A frequency input for receiving a frequency signal and digital storing for storing the received frequency signal. A controller has a first and second input and an output. The first input is connected to the digital storage for providing a reference signal and the output provides a frequency control signal. The second input is connected to circuitry for changing the operation mode of the controller to either an amplifier or an integratory. As an amplifier, a digitally set offset and gain is applied to the amplifier for providing an output generating approximately the frequency of a prior signal. A switch connects the frequency output to the second input when operating in the integrating mode to control the output for generating a desired frequency.

Abstract: A radar equipment comprising a display unit (FIG. 1) and a scanning unit (FIG. 2) linked together by electrical conductors (94,72,106,26) for the transmission of information and/or control signals between the units, and circuitry (90,98; 66,69; 102,108; and 25,162, respectively) for superimposing on an individual conductor more than one of the signals.

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 circuit and method for generating an output signal having an output frequency that varies linearly with time, and an FM CW radar system utilizing such a circuit. The circuit includes a VCO, a rate detector, a phase detector, a filter and an integrator. The VCO produces an output signal at its output terminal at an output frequency that corresponds to the voltage of a tuning signal applied to the VCO input terminal. The rate detector receives the output signal and produces a rate signal having a rate frequency that corresponds to the rate of change of the output frequency. The phase detector compares the rate signal to a reference signal having a fixed frequency, and produces a correction signal corresponding to the phase difference between the rate and reference signals. The filter filters the correction signal to produce a first current signal, and the integrator integrates the first current signal to produce the tuning signal.