Abstract: In a chip radio communication system, a novel technique for increasing the number of transmitters, or users, that can be simultaneously accommodated in the communication system and the data capacity of the system without increasing frequency bandwidth. A system may include plural transmitters, receivers, and a central station for establishing chirp radio communications. Each receiver may discriminate between chirp radio transmitter type based on the differing chirp signal characteristics.

Abstract: A pulse radar system has a high-frequency source, which supplies a continuous high-frequency signal and is connected on the one side to a transmission-side pulse modulator and on the other side to at least one mixer in at least one receive path. A pulse modulator is connected upstream of the mixer with regard to its connection to a receiving antenna. The mixer evaluates a radar pulse reflected by an object together with the signal of the high-frequency source. This system does not require a ZO switch and is insensitive to interference.

Abstract: A radar system has improved range resolution from linear frequency modulated (LFM) first sub-pulse and second sub-pulse, both having linear frequency modulation about different center frequencies. The first transmitted sub-pulse and the second transmitted sub-pulse have chirp slope &ggr;. Sample shifting and phase adjusting is performed for the first radar returns with respect to second radar returns to form a line of frequency modulated chirp slope &ggr; with respect to time, the line connecting the center frequencies of the center frequencies. The first sub-pulse and second-sub pulse can have equal time duration, where the first and second center frequency are equidistant from a reference frequency. The returns are reflected by a target located at a location near a reference point s.

Abstract: A positioning system including a sensor, a drive sequencer and an actuator. The sensor senses the actuator position and provides position signals to drive the sequencer which responsively computes and drives the actuator in open loop moves containing dwell intervals of position. The actuator positions a mirror or other load means to reflect an optical beam as desired. Either preprogrammed or non-repeating sequences of actuator stopping positions can be synchronized with a laser. During dwell times, mirror position accuracy better than 10 microradians is suitable for tuning CO2 pulse burst or CW lasers.

Abstract: In a method for the determination of the unambiguous range for the measurement of the IF deviation in a frequency-regulated radar system, a frequency adjustment or tuning of the radar system is carried out during the reception of an echo signal by adjustingly setting respectively at least one value for the IF deviation around the value zero in the unambiguous range of the IF deviation as well as in an ambiguous range of the IF deviation. Then, the unambiguous range is recognized as such by comparison of the signal amplitude and/or the number of the detected targets during these adjustment settings, because the unambiguous range exhibits the highest signal amplitude and/or the greatest number of detected targets (i.e. echo signals).

Abstract: A pulse-type beamforming apparatus, such as a radar array system, is used for receiving, detecting, localizing, and/or imaging desired signals. The apparatus is used to receive wideband chirp signals. The apparatus contains a receive aperture that is partitioned into multiple channels. The received signal at each channel is mixed with a replica chirp. The replica chirp is effectively delayed in a way that partially removes range-dependent distortion of desired signals. The mixer outputs are then sampled and filtered. The filters on each channel incorporate a time delay that completely removes the remaining range-dependent distortion for all signals in a desired direction. Signals are also compressed and integrated by a digital beamformer.

Abstract: The present invention relates to a radar system having means (12) for producing a code, means (18) for modulating a transmission signal in a transmit branch, using the code, means (32) for delaying the code, means (20) for modulating a signal in a receive branch, using the delayed code, and means (26) for mixing a reference signal with a receiving signal, the modulation of one of the signals being performed by an amplitude modulation (ASK; “amplitude shift keying”) and the modulation of the other signal by a phase modulation (PSK; “phase shift keying”). Furthermore, a radar system is proposed in which blanking of phase transitions is provided. The present invention also relates to methods which may advantageously be carried out, using the radar systems according to the present invention.

Abstract: A pulse radar device includes a transmitting unit, a receiving unit, a first integrating unit for sampling a reception signal at predetermined time intervals from transmission and integrating results of a predetermined number of times of the sampling at each sampling timing, a differential operating unit for, each time a predetermined time period has passed, reading results of the integrating at each sampling timing and differentiating the read results of the integrating in a sampling direction, a second integrating unit for integrating absolute values of a predetermined number of outputs from the differential operating unit at each sampling timing, a peak detecting unit for detecting the peak of an output from the second integrating unit, a distance measuring and detecting unit for calculating a distance to an object and judging presence or absence of an object based on an output from the peak detecting unit and the like.

Abstract: A frequency jitter compensation radar system which frequency modulates a transmitter laser beam with simultaneously generated up- and down-chirped frequency modulated signals. The frequency modulated transmitter beam is used to scan a target and a reflected light beam is received for each pixel location of a radar system. The reflected light beam is heterodyned with a local oscillator laser beam and upon detection two separate electrical signal channels are provided representing tb up- and down-chirped frequency modulated signals. These up- and down-chirped signal channels are compressed and are further processed as the return signals of a radar system as by averaging the peak detection measurement from the two channels for each pixel to provide frequency jitter compensation commonly resulting from speckle from a target. Electro-optic or acoustic-optic arrangements may be used to frequency modulate the transmitter laser beam.

Abstract: A sensor front end for an electronic radar sensor is disclosed that provides for a lower parts count while providing technical functionality by using multifunction parts, i.e., parts that are used both in transmitting and receiving. The sensor front end includes a continuous wave signal source that functions as a signal source when the front end is transmitting a signal and as a local oscillator when the front end is receiving a signal. The sensor front end also includes a tri-mode mixer that functions as a phase-modulator and transmit switch when the front end is transmitting a signal and as a mixer/down-converter when the front end is receiving a signal. The sensor front end further includes a common aperture antenna that acts as both a transmitting antenna for transmitting a sensor signal and for receiving a reflected signal from a object.

Abstract: A wideband adaptive digital beamforming technique for maintaining a high range resolution profile of a target in motion in the presence of jamming utilizes a sequence of adaptively calculated narrowband jamming cancellation weights. The adaptive weights are calculated such that the desired frequency dependent gain is maintained toward the target center. These adaptive weights tend to preserve the range profile quality and low range sidelobes. This technique also tends to eliminate signal cancellation problems as well as adaptive weight modulation effects.

Abstract: Radar apparatus in which output RF signals are modulated on an optical signal prior to transmission. Incoming optical echo signals are converted into RF signals using a detector. The original functionality of the radar apparatus is to a large extend retained, including the Doppler processing. The target radar cross section is determined by the wavelength of the optical signal.

Abstract: The present invention relates to a CW radar method for measuring distances between and relative speeds of a vehicle and one or more obstacles. The present invention further provides that the transmission (s(t)) can be composed of at least four consecutive chirps (A, B, C, D), each having different slopes. The intersection points of all lines in the distance-relative speed diagram from two chirps (A, B) can be calculated from all the ascertained frequency positions K1,n and K2,p. To validate those intersection points, one may observe whether a peak exists in the Fourier spectrum of a third chirp C at a frequency position K3,q, whose assigned line intersects a surrounding area of the intersection point in the distance-relative speed diagram.

Abstract: This invention concerns a procedure for the elimination of interferences, such as pulses and linear chirps, in a radar unit of the FMCW type According to the procedure, the useable signal in the form of a beat signal, is subjected to time-frequency division of the type STFT for division of the signal into narrow-band frequency bands. Interference is detected and eliminated in each frequency band, after which the time signal freed from interference and its Discrete Fourier Transform, DFT, are calculated from the time-frequency division in narrow-band frequency bands.

Abstract: A radar system employing Doppler tolerant radar pulses such as linear FM or hyperbolic FM chirps includes a pulse compressor configured as a digital finite impulse response filter. In one embodiment, the radar returns are split into in-phase and quadrature phase components for manipulation in complex form within the filter.

Abstract: A pulse radar system includes a frequency-agile magnetron comprising an input for giving a feeding voltage of a magnetron tuner. A modulator connected to said magnetron forms pulses of a feeding voltage for the magnetron. A low power signal source also connected to said magnetron generates microwave frequency signals which are given to the magnetron in pauses between pulses. These signals have the frequencies differing from the frequencies of the signals generated by the magnetron and fixed during each period of magnetron pulse repetition. This radar system also includes a signal converter receiving the low power signals reflected by the magnetron. These signals are converted into the signals connected in time to the moments, when the frequencies of the low power source and the frequencies of the magnetron oscillating system coincide with each other. Further, said signals are used for triggering the modulator connected to said converter.

Abstract: Microwave radar: an additional modulation of the microwave signal (s (t)) provided for the emission or of the reception signal (e (t)) makes it possible to separate the payload signal from the noise signal parts in a following demodulation and filter unit (HP, MI2, TP). To this end, a modulation unit (MO, RG) for suitably modulating the signal to be emitted is provided preceding the antenna (A). The undesired noise signals produced by the components of the radar sensor itself are not modulated and can therefore be separated from the payload signal by filtering. This separation ensues after a raw measured signal (mess' (t)) has been generated by mixing transmission and reception signal (MI). A renewed demodulation with the modulation signal (r t)) of the modulation unit supplies the final measured signal (mess2 (t)) determinant for the determination of the distance, whereby the noise signals are previously removed by high-pass filtering and/or are subsequently removed by low-pass filtering.

Abstract: A generalized frequency modulation (FM) based method for converting an analog signal to a digital signal. An analog input signal is sampled at the Nyquist rate. Each sample is converted to a corresponding modulated chirped FM signal. The digital signal is generated by sampling each modulated chirped FM signal at a rate which depends upon the bits per sample of the analog-to-digital (A/D) converter.

Abstract: A system and a method for position determination by impulse radio using a first transceiver having a first clock providing a first reference signal and a second transceiver placed spaced from the first transceiver. The system determines the position of the second transceiver. The second transceiver has a second clock that provides a second reference signal. A first sequence of pulses are transmitted from the first transceiver. The first sequence of pulses are then received at the second transceiver and the second transceiver is then synchronized with the first sequence of pulses. A second sequence of pulses are transmitted from the second transceiver. The first transceiver receives the second sequence of pulses and the first transceiver is synchronized with the second sequence of pulses. A delayed first reference signal is generated in response to the synchronization with the second sequence of pulses.

Abstract: A method provides for contactless measurement of the range between a transceiver unit for microwaves in the frequency band from 1 to 100 GHz and an object to be investigated using a pulse principle. The microwaves are focused onto the surface by an antenna to detect the contour of the object. In particular, the surface of a bolt produced using a spray compacting method can be detected.

Abstract: A source for a linear homodyne transceiver that generates repeated linear chirps. A YIG oscillator with a main coil and an FM coil receives a basic linear current ramp at the main coil to generate a chirp. The FM coil is coupled to receive a PLL error signal. The PLL receives a sample of the output signal from the YIG oscillator at one input and a linear chirp reference signal at the other input generated by a DDS chirp generator. Any variation between the linear chirp frequency at any instant and the actual frequency output by the YIG is corrected by an error signal to the FM coil to correct for nonlinearities of the YIG caused by variations in the chirp rate, the rate of change of frequency per second per chirp, temperature variations and microphonics.

Abstract: The present invention relates to radars and sonars, and more particularly to a synthetic-band technique of pulse compression making it possible to reach a very high distance resolution. Synthetic band consists in transmitting a waveform pattern consisting of a string of N coherent elementary pulses, linearly frequency-modulated, following one another at a recurrence frequency F.sub.r, of rectangular frequency spectra of elementary band B and of stepped carrier frequencies such that their frequency spectra will link up exactly one ahead of another to form a global spectrum of width N.times.B. On reception, the frequency spectra of the signals received in return for the N elementary pulses of a pattern are extracted by calculation, translated and juxtaposed so as to reconstruct a global frequency spectrum of width N.times.B and then compressed. Pulse compression is thus obtained which is equivalent to that which would result from the transmission of a waveform having a single pulse of frequency band N.times.

Abstract: An apparatus and method for accurately determining a target distance in adverse weather conditions utilizing both LASER and RADAR is disclosed. The radar signals are used to determine an approximate range which is then used as a gating window for the determination of which laser reflection is from the actual target as opposed to a reflection from the atmospheric interference. The method basically comprises the steps of initiating a radar pulse in the direction of a target and receiving a reflection, transmitting a laser signal and receiving a plurality of reflections, determining an approximate range based on the radar signals, and using this approximate range to ascertain which of the laser reflections is from the target. This determination is preferably made by generating a gating signal and gate width from the radar signals and passing the set of laser range signals through the gate to eliminate the false signals and select the signal that survives the gate as the accurate target range.

Abstract: In an FMCW distance measurement process, a wave train of carrier frequency f.sub.0 is modulated with a time function f(t) and subdivided into a transmission signal and into a reference signal in deterministic phase relationship with the transmission signal; the transmission signal is sent on a transmission section to be measured and the reference signal is supplied to a phase difference-forming arrangement; the signal reflected in the transmission section with a delay that corresponds to propagation time .tau. is also supplied as a reception signal to the phase difference-forming arrangement that forms the time difference function .theta.(t) between the phases of reference and reception signals; the phase difference function .theta.(t) is separately evaluated in a continuous fraction .theta..sub.= that corresponds to the carrier frequency f.sub.0 and in an alternating fraction .theta..sub.- (t) that corresponds to the modulation time function f(t); and the propagation time .tau.

Abstract: A bi-static spread spectrum digital radar including a transmitting antenna and a receiving antenna array separate from and positioned at a distance from the transmitting antenna. The transmitting antenna transmits a pseudo random digital signal as produced by a pseudo random digital signal generator. The receiving antenna array receives signals simultaneously and parallely as reflected from a target by the transmitting antenna. A plurality of analog-to-digital converters are connected respectively to each element of the receiving antenna array so as to convert the received analog signal into a digital signal. Digital beams are produced and directed to a set of digital receivers. A processor is provided so as to produce a digital output from the set of digital receivers.

Abstract: The present invention provides a method and a system for proximate field orientation of an autonomous device and utilizes a transmitted wave having a first frequency of slow propagation, whereby reflections from obstacles within a proximate area are detected. According to the present invention receivers are arranged in a slanted plane or preferably along a curved base-line to, in a simple way, obtain a three-dimensional direction to an obstacle reflecting the frequency of slow propagation. Additionally, an absorber or a screen or a combination thereof is arranged above at least one receiver to act as an "eyebrow" attenuating undesired reflections which at the receiver come from overhead.

Abstract: A method of defocusing range ambiguities in a pulse radar, in particular of the SAR type, the method comprising the following steps:radar pulses are spread on transmission by using a plurality of "chirp" rules for varying the frequency of the transmitted wave as a function of time;during transmission of successive pulses, chirp rules are alternated between chirps that rise and chirps that fall in the frequency/time plane of the pulse;received echoes are compressed by matched filtering using a correlation operation between the received echo signal and the chirp rule that was applied at the time of transmission of the pulse that gave rise to said echo signal;said method being characterized in that said plurality of rules for varying the frequency of the transmitted wave as a function of time comprise a number M of said rules, with M being an integer greater than or equal to 3.

Abstract: A digital circuit is used to demodulate a linear chirp spread spectrum signal. The digital circuit uses a counter which is clocked so as to count during the time period between the pulses of a chirp signal. The circuitry also uses a digital filter to determine whether the frequencies of the linear chirp signal are within the correct bandwidth. The output of the counter is compared with the previous count to produce a difference count. A processor uses this difference count value to determine the characteristics of a chirp signal being decoded. A difference signal test circuit provides a digital filter for the difference count to eliminate spurious noise conditions.

Abstract: A network of localizers determines relative locations in three-dimensional space to within 1 cm by cooperatively measuring propagation times of pseudorandom sequences of electromagnetic impulses. Ranging transmissions may include encoded digital information to increase accuracy. The propagation time is determined from a correlator circuit which provides an analog pseudo-autocorrelation function sampled at discrete time bins. The correlator has a number of integrators, each integrator providing a signal proportional to the time integral of the product of the expected pulse sequence delayed by one of the discrete time bins, and the non-delayed received antenna signal. With the impulses organized as doublets the sampled correlator output can vary considerably in shape depending on where the autocorrelation function peak falls in relation to the nearest bin. Using pattern recognition the time of arrival of the received signal can be determined to within a time much smaller than the separation between bins.

Abstract: An apparatus for correcting for nonlinearities in modulation systems includes a transmitter (24, 28, 48, 50, 52) for transmitting a time varying modulated radar signal (56). A receiver (58, 62) receives an echo signal (60) resulting from reflection of the transmitted modulated signal (56). A mixer (48) compares the transmitted signal against the echo signal and providing a comparison signal indicative of the comparison. The comparison signal is sampled by an A/D converter (74). The A/D convertor (74) provides a sampled comparison signal to a controller/DSP (22). Controller/DSP (22) resamples the sampled comparison signal at selected resample times and effectively varies the selected resample times to correct for nonlinearities in the comparison signal resulting from nonlinearities of the transmitted time varying modulated signal.

Abstract: An active recognition system comprises a transceiver, tracking electronics, an optical processor, and a data handler. The transceiver transmits chirped pulses and receives a series of reflected ?replicas of the chirped pulse! replica pulses from ?features of! an object ?of interest!. The tracking electronics controls the transceiver to determine object range for gating the optical processor. The optical processor includes a "signal" Bragg cell driven by the reflection signal so that ?a! throughgoing light ?beam! is angularly redistributed as a function of the local spatial frequency of the acoustic waveform within the modulation aperture of the signal Bragg cell. At a first focal plane, the light defines a one-dimensional light distribution that includes moving spots that correspond to respective reflection replicas.

Abstract: Range-Doppler ambiguity is eliminated from an ultra-wideband radar system by transmitting an ultra-wideband chirped pulse towards a moving target, and mixing it with the doppler-shifted chirped pulse which is received as a target echo return signal. Multioctave radar tracing systems can potentiality track stealth aircraft without ambiguity since pulses containing many frequencies can defeat narrow-band radar absorbing material coatings. The unambiguous range-doppler signal processing method mixes the chirped pulse to yield an instantaneous Doppler frequency (which indicates target velocity) and a rate of change in the instantaneous Doppler frequency (which indicates target acceleration).

Abstract: A system and method for determining the range between a receiver of a radio frequency signal and a transmitter of the signal includes transmission of a ranging signal having a grossly timed trigger followed by a chirp waveform. In response to receipt of the leading edge of the grossly timed trigger, the receiver of the ranging signal generates a first reference chirp at about the same time as the expected time of receipt of the chirp waveform, and thereafter compares the two chirps to provide a time correction signal (it being known that when two identical chirp signals, one time delayed from the other, are mixed, the resulting signal will have a frequency proportional to the amount of delay between the two chirp signals.) The time correction signal is used to correct the timing of an outgoing corrected chirp that is to be used to determine range between the transmitter and receiver based on a time of arrival.

Abstract: The present invention pertains to a radar range finder for high-precision, contactless range measurement, which is based on the FMCW principle and operates with digital signal processing at a limited frequency shift. One exemplary embodiment is described.

Abstract: An MTI with no blind speeds which compensates for antenna scan modulation. his design includes circuitry for generating and transmitting consecutive first, second and third doppler-tolerant FM pulses, wherein the first and third FM pulses have a given dispersion characteristic, and the second FM pulse has a dispersion characteristic which is the complex conjugate of the first and third FM pulses. Circuitry is then provided for receiving and compressing the first, second, and third echos from the first, second, and third pulses, respectively. Finally, a processing circuit is used to effectively add the first and third echo pulses and to subtract twice the second echo pulse from this sum to effect the detection of the moving target.

Abstract: A method and apparatus is disclosed for improved out-of-range rejection in pseudo-random noise (PN) coded systems by adjusting the relative phase difference between the two phase states of a bi-phase modulation. The energy in the spectral lines of the bi-phase modulated RF signal to generate a signal to be fedback to a voltage-controlled bi-phase modulator to adjust the relative phase difference between the two phase states. Sampled signals are mixed down to baseband using single sideband suppressed carrier modulation of the center frequency of the transmitted signal and the offset frequency. The offset frequency is chosen to be less than the PN code repetition frequency. The baseband signal is filtered and envelop detected producing a DC voltage proportional to the amplitude of the center line of the PN spectrum which is compared to either a fixed reference or to the amplitude of one or more of the remaining lines in the spectrum.

Abstract: A transmitter (12) broadcasts a PN encoded message (16). A receiver (14) includes a SAW correlator (38) configured to autocorrelate with the PN sequence used in the broadcast signal. A preamble of the message (16) conveys two successive bits (18) that are each encoded with the PN sequence. After the correlator (38) has been preloaded with the PN sequence from the first bit (18), its non-correlation output exhibits reduced amplitude time sidelobes. A timing comparison circuit (60) compares a correlation signal (46) with a timing threshold (72). The timing threshold (72) is established at a very low level to minimize the influence of multipath. False triggering on noise is prevented by disabling the timing comparison circuit (60) until after the first bit (18). At this point in time the correlator (38) has been preloaded with its PN sequence, is again being loaded with its PN sequence, and outputs reduced amplitude time sidelobes.

Abstract: A method and apparatus for identifying a remote target includes a transmitter for transmitting pulses of energy toward the target for generating echo signals, and a receiver for receiving the echo signals, and for generating received signals representing the target, noise and clutter. The received signals are applied through a plurality of cascaded channels, each including a Doppler filter cascaded with a multiplier, each also including range sidelobe suppression, for, in each of the cascaded channels, narrowband filtering the signals passing therethrough about a controllable center frequency, and for, if necessary, converting the signals passing therethrough to baseband, for thereby applying one of a plurality of Doppler filtered baseband signals to the input of each of the range sidelobe suppressors of each of the cascaded channels. The power of the Doppler filtered baseband signals in each range bin is evaluated for determining the frequency at which the spectral density is greatest.

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: An improved MTI radar system including a signal expander/compressor for providing palindromic P2 phase-coded upswept and downswept expanded signals that are alternately transmitted by a radar transmitter. The echos from the upswept and downswept signals are received by a receiver, compressed in the signal expander/compressor and inputted to an MTI subtractor. Since the autocorrelation sidelobes of the palindromic phase coded echos are real, the echos from stationary clutter are completely cancelled so that the system is capable of detecting weak echos from moving targets.

Abstract: An image forming apparatus suitable for use in a laser beam printer includes an image forming unit for forming an image on a photoconductor, and a reproduction unit for reproducing a high density image and a halftone image on the photoconductor. A detector then detects the density of the high density image and the halftone image formed on the photoconductor. A controller controls an image forming condition of the image forming unit based on a detection result by the detector.

Abstract: A bandwidth synthesized radar level measurement system includes a transceiver for generating a transmitted signal and a sweep signal. An antenna coupled to the transceiver sends the transmitted signal toward a level corresponding to a product surface and receives a reflected signal therefrom. A sweep generator generates a chirp slope signal in response to the reflected signal. An intermediate frequency (IF) processor receives the chirp slope signal and a difference signal mixed from the transmitted and reflected signals. The IF processor produces an amplified IF signal and a sweep control receives the amplified IF signal to adaptively control the sweep generator and to produce an output signal including a distance from the antenna to the level corresponding to the product surface.

Abstract: A radar transmits dispersed pulses in which the subpulses are modulated by first and second mutually complementary code sequences, the autocorrelation functions of which are selected so that, in the sum of their autocorrelation functions, the main range lobes add, and the range sidelobes cancel. The received pulses with their Doppler sidebands are applied to a plurality of channels, each of which (except one) contains a mixer-oscillator combination that removes a specific Doppler phase shift along the range dimension at a different channel frequency. One channel has no mixer-oscillator because it is centered at a zero channel frequency. Within each channel, the received signals modulated by the first and second codes are matched-filtered by filters matched to the first and second codes, respectively, to produce first and second time-compressed pulses, each including (a) a main lobe representing the target range, and (b) undesirable range sidelobes.

Abstract: Low time-bandwidth product linear frequency modulated chirp pulses are repetitively generated as contiguous subpulses to form a pulse of extended duration with each subpulse respectively mixed with one of a plurality of stepped intermediated frequencies so that the bandwidth of the contiguous subpulses is increased to the frequency bandwidth of all of the stepped intermediate frequencies such that the contiguous signal formed has a linearly varying frequency over the increased bandwidth and increased pulse duration, providing a large time-bandwidth product linear frequency modulated chirp waveform particularly useful in radar systems.

Abstract: A radar system transmits dispersed pulses, and receives echoes from targets. The echo signals are digitized and applied over a number of signal paths. In each signal path except one, the digitized signal is multiplied by one of a plurality of differential exponential signals, for converting the echo signal of different exponential signals, for converting the echo signal in each path to baseband, with the baseband frequency representing a particular Doppler which depends upon the exponential signal. In the one remaining signal path, no multiplier is used, and the echo signal is deemed to be at baseband. The signals in each path are applied through a cascade of a pulse compressor and a range sidelobe suppressor. Since Doppler filtering has not yet taken place, full compression and range sidelobe reduction is not achieved, because of extraneous pulse-to-pulse phase shifts.

Abstract: A homodyne radar apparatus and method for performing radar cross-section surement by maintaining the linearity and compensating for frequency drift of an FM chirp waveform produced by a YIG tuned oscillator. A digital computer uses a predetermined data look-up table of each YIG oscillator frequency characteristic in conjunction with a digital to analog converter to provide a compensating sweep signal to linearize the frequency output of the oscillator. The computer uses an analog to digital converter in conjunction with a reference circuit output to compare the actual YIG signal nulls resulting from the reference circuit to the nulls in a signal produced by a lab standard oscillator in the reference circuit to adjust start sample delay of the ADC and to correct any frequency drift evidenced by the difference in the null of the signal.

Abstract: A pulse-compression, MTI, doppler-radar system for determining target velty information from a single target-return pulse is improved by the addition of a pulse-compression filter consisting of at least two pulse compressors and by the addition of a phase-comparison processor. The pulse compressors simultaneously pulse-compress separate portions of the single target-return pulse. The phase-comparison processor then determines the phase difference between the compressed pulses to obtain the target velocity information.

Abstract: There is provided a radar apparatus wherein a local signal having a coherent sine wave is modulated to generate a composite signal of two signals modulated by different modulation functions. The composite signal is transmitted as a transmission signal, and a reception signal associated with the transmitted signal is separated into two signal components modulated by the different modulation functions. A difference between the two signal components is found, thereby removing a reflection signal from a static clutter and extracting a signal component which has been frequency-deviated by a moving target. Thus, the moving target is displayed. The transmission frequency can be quickly changed without losing the function of detecting the moving target.

Abstract: A dynamically tunable notch filter is used within a continuously transmitting laser radar system for filtering narcissus signals generated from a continuous linear frequency modulated chirp transmission signal at the transmission aperture antenna with the filter including mixing and band pass filtering at the narcissus dynamic frequency to eliminate the unwanted narcissus signals varying over the dynamic frequency range of the narcissus signals, and to also eliminate unwanted target images, for improved resolution and detection of low level reflected target signals which are often obscured by the presence of the relatively high-level unwanted narcissus signals.

Abstract: Radar apparatus provided with a transmit generator and antenna means for the transmission of comparatively long, linearly frequency-modulated transmitter pulses. Echo signals are received by antenna means and a heterodyne signal is generated in mixer stage. Propagation time differences for different echo pulses are compensated by means of a dispersive delay element incorporated in the radar receiver. Distortion of the echo pulses in the dispersive delay element is corrected on the basis of a Fresnel ripple correction. A Fourier transformation unit transfers the corrected echo pulses to time domain video with low sidelobes.