Abstract: A method of processing radar returns derived from a new radar waveform. The method processes radar returns derived from transmitting the radar waveform to provide simultaneous matched processing and range profiling of different size objects in the presence of clutter. In the present method, radar returns are digitized and processed to produce pulse compressed radar returns having a predetermined (169:1) pulse compression ratio. A pulse to pulse fast Fourier transform on each RF step is performed on the pulse compressed radar returns. The Fourier transformed radar returns are then simultaneously processed by three processing channels, one each for ships, boats and submarines to provide detection of the different size objects. The waveform permits concurrent detection, discrimination, and high resolution range imaging of detected objects within a single dwell, using a single waveform. Thus, a radar search mode using the waveform integrates several search functions without increasing search frame time.

Abstract: A differential gain characteristic can be equivalently improved by providing a compensation circuit. The compensation circuit compensates a differential gain of a voltage-controlled oscillator, of which oscillating frequency is controlled by a control voltage. The compensation circuit comprises a first resistor which is connected to an input side of the voltage-controlled oscillator in series and a series circuit of a second resistor and a first diode, which is connected to the input side of the voltage-controlled oscillator in parallel, and further a first bias electric source for giving a bias voltage to the first diode in a forward direction. It becomes possible to make DG to be less than 5%, even if a modulator having a larger slope of characteristic, such as DG<50%.

Abstract: A switching device is provided which uses an array of high-speed photoconductive semiconductor switches laid out in a stripline configuration to achieve a transmitter-to-receiver isolation sufficient to support a monostatic configuration for a high-power, monostatic impulse radar.

Abstract: A method and apparatus for hybrid analog-digital pulse compression, as well as, a method of use and manufacture includes an analog intermediate frequency filter, a converter, and a digital correlator. The analog intermediate frequency filter filters and weights returned echo signals, and the digital correlator compresses the filtered and weighted echo signals. The frequency or impulse response of the digital correlator is set based on the frequency or impulse response of the analog intermediate frequency filter to obtain a pulse compressor with minimal mismatch loss and improved sidelobe suppression. The invention provides for the lowest possible sampling rate of analog-to-digital convertors used with the apparatus; thus, minimizing the cost of this device and all subsequent digital processing.

Abstract: Apparatus for calibrating a phased array antenna having a plurality of active modules and a test manifold. An RF antenna, which is both a transmitting and receiving antenna is positioned at a far field range from the antenna to be calibrated. A receiver is connected to the output of the far field receiving antenna and the output of the test manifold of the antenna to be calibrated for the transmit calibration and a transmitter is connected to the far field transmitting antenna and the test manifold for a receive calibration, a command phase and amplitude for each steering angle of each module of the antenna being calibrated. The phase and amplitude data from the test manifold is compared with the phase and amplitude data of the far field range to obtain an error signal, and the error signal is combined with the command amplitude and phase iteratively until the error signal is minimized for each module of the antenna.

Abstract: A device which increases the rate of reduction of spurious output signals includes a path capable of carrying a signal from an input to an output. A plurality of storage elements and a plurality of interspaced switches are serially positioned in the path. Isolation elements are positioned in the path between each storage element and each switch. Multiple reflections from the primary signal are capable of reducing in strength when rebounding between the isolation elements and the switches.

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 pulse transmitter for terminating reflected waves is disclosed which utilizes a series switched charged line pulse generator with a shunt element that is switched into the circuit immediately after the pulse is launched into an output line. The shunt element terminates any reflected wave so that it does not go back into the output line. The shunt element is formed by an optically controlled PIN diode coupled in series to a resistor which allows the circuitry to turn on fast and to handle high voltage pulses. The shunt element can be connected to either the input end of the charge line for circuitry embodiments in which the series switch stays closed or the shunt element can be connected at the output side of the series switch for embodiments in which the series switch opens after the pulse is formed such as, for example, where an avalanche switch is used.

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: An MTI radar based on a comparison of the Doppler shifts of the original signal and a phase-reversed signal using pulse compression wherein the received signal is phase detected for in-phase and quadrature components relative to the IF. A Doppler-corrected pulse compressor produces a magnitude signal for the Doppler shift of the received signal from the sequence of in-phase and quadrature components. Another Doppler-corrected pulse compressor produces a magnitude signal for the Doppler shift of the received signal from the conjugates of the sequence of in-phase and quadrature components. The magnitude signal of the same Doppler shift of the two compressors are compared and the difference is the output of the MTI.

Abstract: A radar system simultaneously transmits first and second signals toward a target at higher and lower carrier frequencies, respectively. Each carrier is phase-modulated by a set of pulses. The first set of pulses is dispersed in time, and the second set of pulses is mutually complementary thereto. The transmitted pulses are reflected by the target and received simultaneously. The received signals are processed separately by Doppler filtering. Each Doppler-filtered return is code-matched filtered, and the filtered signals in each Doppler channel are summed with the corresponding Doppler-and-code-matched-filtered signals originating from the other transmitted frequency, to form range signals. Each range signal has its main lobe enhanced and its sidelobes suppressed by the summing of the code-matched-filtered mutually complementary echoes.

Abstract: Received expanded radar pulses pass through a surface acoustic wave (SAW) weighted filter (64) for sidelobe suppression, and then into a SAW tapped delay line (66). The pulses appear at the taps (66a,66b,66c) of the delay line (66) coarsely aligned in time, pass through individual SAW matched filters (68,84,86,88) for compression and envelope detectors (70,90,92,94) for demodulation, and then into a summer (74) for post detection integration. Individual frequency shifters (78,80,82) are provided between the delay line taps (66a,66b,66c) and the matched filters (84,86,88) for shifting the center frequencies of the pulses and thereby the propagation delays through the matched filters (84,86,88) to provide fine alignment of the pulses in time. The delays through the individual delay line taps (66a,66b,66c) and the frequency shifts of the frequency shifters (78,80,82) are adjustable "on the fly" to compensate for variation of pulse repetition rate (PRF) and interpulse jitter.

Abstract: A ranging system such as a radar system transmits signal pulses toward a diffuse target, such as an atmospheric disturbance. The echoes are processed by quantizing and by doppler filtering to produce a plurality of frequency components representing the radial velocities of various parts of the disturbance, which components are expected to be contaminated by an unknown amount of noise. The noise value is established by squaring the echo signals to produce power-representative signals. The signal samples are ranked according to amplitude, and one or more of the largest-value samples are discarded to reduce the order of the sample set. A Kolmogorov-Smirnov test statistic is generated and compared with a threshold established by the desired confidence level. If the test statistic exceeds the threshold, the order of the sample set is again reduced, and the test statistic again compared with the threshold.

Abstract: The maximum amplitude of an input signal (IN) is compressed or reduced to a smaller value suitable for operation on the compressed signal (OUT) by a downstream signal processing stage (16) having insufficient dynamic range, ratio of maximum amplitude to root-mean-square (RMS) noise, to accommodate the original input signal (IN). The input signal (IN) is digitally sampled with coarse resolution to generate a correction signal (44) having a waveform which approximates only the large signal components (24) of the input signal (IN). Where the input signal (IN) consists of recurring received radar pulses, the large signals (24) represent clutter. The amplitude of the correction signal (44) is lower than and increases as a predetermined function of the amplitude of the input signal (IN), and is subtracted from the input signal (IN) so that the large signal components (24) are reduced whereas the small signal components (26), which represent desired target information, retain their original amplitude.

Abstract: A coherent pulse radar system capable of eliminating a signal associated with a multiple time around path or capable of removing range ambiguity of this multiple time around signal. The radar system includes a device for changing phases of transmitted pulses, for phase detecting received radar pulses with respect to transmitted pulses associated with the present and preceding reception period, and for integrating phase detected signals in a coherent manner.

Abstract: A radar receiver and, more particularly, a radar receiver of the type which is utilized in connection with a frequency-modulated, continuous-signal radar apparatus. The radar receiver, in the receiving channel thereof, is provided with a high-pass filter of the second order which is only operated in the linear characteristic curves range, thus acting as an R.sup.4 -filter and which is connected in front of a demodulating rectifier, or in essence, an analog-digital quantitizer.

Abstract: A modulator provides a continuous signal format composed of discrete freqcy steps and is designed to eliminate frequency overlap or smearing normally associated with filter ringing.

Abstract: The invention relates to a method for frequency-shifting the modulus of the transfer function of a transversal filter.In a transversal filter having three delay lines Z1, Z2 and Z3 in series and four multipliers M'0 to M'3, the multiplier coefficients K0 to K3 of which are intended to eliminate the signals at frequencies in the vicinity of zero frequency and integral multiples of the repetition frequency Fr of the samples X.sub.i, the method consists in replacing the multiplier coefficients K0 to K3 by coefficients K'0 to K'3 which are deduced from the first by multiplying them by fixed coefficientse.sup.3jr, e.sup.2jr, e.sup.jr and 1 with r=2.pi.Fd/Fr.The invention is applicable in particular to the elimination of certain undesirable echoes from radar signals.

Abstract: A pulsed radar system has improved signal to noise characteristics obtained by suppressing phase noise. Means are provided to store a copy of the transmitted RF signal pulse, which copy contains any phase noise of the RF carrier that is transmitted. The signal copy is retained and following a delay interval the signal is mixed in a high frequency electronic RF mixer with the received RF pulse signal, the latter of which represents a reduced level signal as reflected by an object back to the system receiver's antenna following the lapse of an interval of time. The RF mixer produces an intermediate frequency signal output in which the phase noise is suppressed thereby enhancing the receiver's signal to noise ratio. A novel pulsed signal delay circuit is employed in the foregoing which retains the copy by continuously recirculating a fraction of that RF input pulse over time until it is needed; as when the pulse is to be applied to the RF mixer.

Abstract: A radar receiver having a clutter-elimination filter in the receiver's intermediate frequency stage. The filter is centered on the intermediate frequency f.sub.i and has a transfer function in which a band-pass characteristic is superimposed on a band-rejection characteristic. The band-pass response has a principal lobe substantially conforming to the function (sin x)/x with x=(w-w.sub.i).pi.T. The band-rejection response presents an attenuation zone centered about f.sub.i ; this zone is wide enough to suppress much of the response from clutter but narrow enough to avoid suppressing much of the energy in the echo from the target. For example, the width of the attenuation zone may be from about f.sub.i -0.2/T to about f.sub.i +0.2/T. The filter provides a maximum response on each side of the attenuation zone, spaced from f.sub.i by about 0.4/T Hz in each direction. Outside the maxima, the response is dominated by the band-pass characteristic and achieves transmission minima at about 1/T Hz above and below f.

Abstract: In a receiving circuit a control circuit and a direction finding circuit generate a digitally encoded "descriptor" which characterizes pulses of r.f. radiation received in a particular azimuthal direction and having a particular carrier frequency. The "descriptor" may be compared with data stored in a processing circuit representing r.f. pulses emitted by sources which have already been detected or which are known to exist. To reduce the workload on processing circuit a number of emulator circuits generate pulse patterns which simulate pulses produced by known sources of little inherent interest. If the received pulses match the simulated pulses a gate inhibits control circuit.

Abstract: A very high voltage stabilized power supply device for a pulse radar system, in particular an airborn radar, which comprises a primary winding connected in a series with an electronic power commutation switch actuated at the recurrence frequency of the pulses produced by the radar, or at a multiple frequency of the recurrence frequency, to the terminals of a rectified and filtered voltage supply source. The primary is wound around an inductive element on which are wound a plurality of secondary windings with a primary-secondary winding transformation ratio equal to unity. Each secondary winding is connected in series to a diode with a filter capacitor in parallel. The outputs of the secondary circuits are connected in series so that their voltages accumulate at the output of the power supply unit. Several modules of this type may be used, with their commutating elements actuated on a staggered basis.

Abstract: The invention relates to a process for adapting the post integration in a switched pulse repetition frequency radar and a circuit implementing this process. For that, the post integration of the detected signals is effected as a function of the signal received from the Doppler filter. For that, switches are used controlled by comparator circuits.The invention is useful in frequency ambiguous coherent Doppler radars using recurrence frequency switching by blocks.

Abstract: Device for eliminating the noise in 1/f from a Doppler radar comprising in the HF emitting system, a phase coder introducing, at frequency PRF/2 a phase shift of 0 and .pi. alternately, and in the receiving system, after the receiver, a decoder, or gain inverter progrmmable between -1 and +1, acting, in the same manner as the coder, upon the receiving signal and comprising a low-pass filter downstream from the decoder for eliminating the noise in 1/f, that appears at PRF/2, the device being applied to a ground surveying radar.