Abstract: This invention relates to an adaptive detection system and method for analyzing range-doppler-azimuth data for target detection. The detection system has a threshold calculator for calculating a threshold value that is based on the standard deviation of the range-doppler-azimuth data and a predetermined probability of detection. The detection system also has a detection module in communication with the threshold calculator to receive the threshold value. The detection module calculates an estimated target amplitude and an estimated noise floor amplitude based on the range-doppler data that is located in a detection window. The detection module detects a target when the difference between the estimated target amplitude and the estimated noise floor amplitude is larger than the threshold value.

Abstract: The present invention relates to a method and an arrangement suitable for embedded signal processing, comprising a number of computational units (100), each computational unit comprising a number of processing elements (20) capable of working independently and transmitting data simultaneously. Said computational units are arranged in cluster, work independently, and transmit data simultaneously, and that said processing elements (20) are globally and regularly inter-connected optically in a hypercube topology and transformed into a planar waveguide.

Abstract: A constant false alarm rate (CFAR) detector prevents false radar triggers due to RF interference by proportionally increasing the radar detection threshold as interference increases. The radar operates with a randomized PRF, which randomizes detected RF interference while maintaining echo signal coherence. Post-detection filters provide a signal channel and an interference channel. The interference channel augments the threshold of the signal threshold detector. The interference channel gain can be adjusted to ensure the detection threshold is always higher than noise in the signal channel, thereby eliminating false alarms due to RF interference. Accordingly, the CFAR detector eliminates a major false alarm nuisance, particularly in radar security sensors. Applications for the low-cost system include indoor and outdoor burglar alarms, automotive security alarms, home and industrial automation, robotics, and vehicle proximity sensors.

Abstract: A system and method is disclosed for a radar receiver, such as a wideband crystal video early warning receiver, to automatically detect the noise level of the radar receiver with immunity to high pulse repetition frequencies and high duty cycle signals. The noise riding threshold circuit utilizes high frequency components of the noise and, to the attenuated extent present, high frequency components of the video signal to produce the noise riding threshold voltage. An amplifier gain control permits adjusting the noise-riding threshold to a fixed relative level. In a preferred embodiment, the noise riding threshold control of the present invention utilizes current feedback amplifiers for wide bandwidth, high gain video amplifiers.

Abstract: A range gated microwave motion sensor having adjustable minimum and maximum detection ranges with little response to close-in false alarm nuisances such as insects or vibrating panels. The sensor resolves direction of motion and can respond to target displacement in a selected direction and through a selected distance, in contrast to conventional hair-trigger motion sensors. A constant false alarm rate (CFAR) detector prevents false triggers from fluttering leaves, vibrating machinery, and RF interference. The sensor transmits an RF pulse and, after a modulated delay, mixes echo pulses with a mixer pulse. Thus, the echo pulses are modulated at the mixer output while transmit and mixer pulse artifacts remain unmodulated and easily filtered from the output. Accordingly, the sensor only responds to echoes that fall within its minimum and maximum range-gated region, and not to close-in or far-out objects.

Abstract: A vehicle (160) such as a motor road vehicle is fitted with an electromagnetic sensor system comprising transmitting means (e.g. 4, 1) for transmitting a radio frequency signal, receiving means (e.g. 2, 6) for receiving reflections of said signal from remote objects, sampling means (20, 28) operable to sample the received reflected signal (or a signal derived therefrom), and processing means (e.g. 36) for processing the sampled signal, and operable to detect said reflections in the sampled signal, and to determine information on the presence, position and/or range of said object. The system includes filter means (e.g. 34) for preventing radio signals transmitted by other sources or noise spikes from causing interference which results in spurious detections or indications of range by the processing means.

Abstract: A system and method for enhancing turbulence detection, display and alerting with avionics weather radars which includes automatically making multiple scans, measuring a wind velocity gradient at varying elevations, and comparing the measured gradient to known predetermined wind velocity gradients over known elevation variations, wherein the predetermined gradients have known vertical shear components, and using a vertical shear component information in making determinations regarding the existence of turbulence.

Abstract: The present invention provide a method and system of dynamically estimating a coefficient of variation of the fluctuation of a waveform and an optimal binary detection threshold using the estimated coefficient of variation. The system discriminates between noise signals and signal-plus-noise signals of a digitized signal by comparison with a threshold. The noise and signal-plus-noise signals are further used to determine a mean noise floor level and a standard deviation, respectively. Subsequently, the system determines the coefficient of variation based on the ratio of standard deviation to mean. The optimal binary detection threshold is calculated using the coefficient of variation, presets for cumulative probability of false alarm and collection time.

Abstract: The direct path of a radio signal from transmitter to receiver is frequently interfered with by reflections of the signal from stationary and moving objects. This is called multipath noise. This invention utilizes a new adaptive filter technique to reduce multipath noise. A nonlinear least squares method measures the delay, Doppler shift and amplitude of the multipath due to each object and subtracts a very accurate reconstruction of each multipath signal from the noisy signal. If an object is a target, its range, range rate and magnitude is got from the measured multipath delay, Doppler shift and amplitude. Position and velocity of the target can be obtained by geometric triangulation with multiple transmitters. Target angle can be measured by the relative phase of the corresponding filter coefficients across multiple antennas. The system can be used on a surveillance aircraft to cancel ground reflections and measure targets.

Abstract: A signal processing method is particularly for use in object detection systems which allows a sensed target signal to be “held” once it has raised above a detection-threshold. The method involves reducing the detection-threshold values of the detection-threshold function within the target region. This method is useful for such applications as automotive radar sensors, airbag deployment systems, communication systems demodulation, security sensor systems, sanitary flushing systems and lighting systems.

Abstract: An electronic counter-measure receiver can be colocated with a threat simulator radar, which transmits a radar signal. As a pulsed-Doppler signal, this transmitted radar signal is sampled as a reference signal by the receiver to determine quadrature, coherent matched filter coefficients. A return signal is received and processed with the reference signal as quadrature signal components with the quadrature, coherent matched filter coefficients within a matched filter. The return signal is processed as a first intermediate frequency via a mixer and local oscillator and a second quadrature intermediate frequency via a digital local oscillator and mixer. A fast Fourier transform is performed to determine Doppler information. In a continuous wave transmission for sampling arbitrary but unevenly spaced in time pulses are generated from a pulse generator source internal to the receiver.

Abstract: The invention relates to a radar method for an automatic intelligent traffic control (AICC) in a motor vehicle. The use of a frequency modulation continuous wave method (FM-CM) is suggested in order to securely detect the distance to, relative speed and angle of a preceding motor vehicle. It is furthermore suggested according to the invention that when using an A/D converter 5 with 8-bit resolution, the necessary dynamics are generated by means of a level switchover, that the R, V information is generated in FFTs [Fast Fourier Transformations] 6 with blocked R and V-FFTs, that the useful signals are separated from the noise in a detection device 7 by means of a R-dependent adaptive CFAR threshold, that in a track formation 8, the detection is directly assigned to the tracks and that the association of a detection i to a track j is in the process computed as probability r (i, j).

Abstract: A Radon transform based method that provides for target azimuth aspect estimation and target shape measurement. A Radon transform is applied to a binary (N×N pixels) target chip to extract target features that are then used to measure length, width, and diagonal features of the target. In parallel, these features are used to estimate the azimuth aspect angle, or size, of the target. The method is effective in discriminating targets from clutter. The method is also very time efficient and highly flexible in its operation because the features can automatically account for any target rotation or shift. The present invention also provides for a target acquisition system that employs the Radon transform based method for target azimuth aspect estimation.

Abstract: A Two-Stage Hybrid algorithm offers significant improvement in the false alarm rate and detection performance of Space-Time Adaptive Processing in non-homogeneous environments for both radar and digital communications. The first stage analyzes data from a range cell of interest by direct data domain processing, suppressing discrete interferers within the range cell of interest. The second stage implements a purely statistical STAP algorithm, preferably an enhanced version of the Joint-Domain Localized (“JDL”) statistical algorithm. For radar this second stage estimates the interference within the range cell of interest from the surrounding range cells. For a communications system, the second stage estimates the covariance matrix of the interference from the entire data block. For both radar and communications, an adaptive filter that suppresses the interference is generated from the estimate by second-order statistics.

Abstract: A radar processing system is disclosed with an improved cluster target resolution capability. The invention provides a system and method for processing radar returns and generating first and second contiguous range/doppler cells. Within the cells, first and second dichotomous angle measurements corresponding to radar returns in the first and second contiguous range/doppler cells are derived. An adaptive threshold is then applied to the angle measurements to determine whether the first and second measurements correspond to first and second targets in the first and second range/doppler cells respectively.

Abstract: A search radar including the improvement of apparatus for enhancing the estimation of the target angle within a search scan of the radar is disclosed. More specifically, the improvement apparatus utilizes the generated scan angles and target amplitude measurements correspondingly associated therewith to generate intermediate signals which are representative of the natural logarithm of the target amplitude measurements plus the square of the corresponding scan angle multiplied by a predetermined constant. For each search scan, the apparatus computes separately signals representative of the moments of: the scan angles, the squares of the scan angles, the products of the scan angles and corresponding intermediate signals, and the intermediate signals. In turn, the apparatus operates on the computed moment representative signals in some prespecified mathematical relationship to effect an optimum estimation for the target angle in each search scan of the radar.

Abstract: An improved performance receiver associated with a radar system for detecting targets over a specified range area whereby the receiver, which is responsive to a return signal corresponding to an actual target or a false target, includes: an attenuator for attenuating an amplitude associated with the return signal; sensitivity time control means coupled to the attenuator wherein the attenuation is coordinated to the sensitivity time control means and the attenuation of the return signal is selectively variable such that the amplitude of the return signal is attenuated to a first level at closer ranges of the specified range area and attenuated to a second level at farther ranges of the specified range area, the first level being greater than the second level; a mixer for downconverting the return signal to a signal exhibiting an intermediate frequency; a detector for extracting a target video signal from the downconverted return signal; detection threshold setting means for generating a detection threshold sig

Abstract: A radar signal processing (RSP) chip is used to process massive radar signals. The RSP chip includes a multiply and accumulate (MAC) array and a programmable delayer. The programmable delayer provides a concurrence alignment of the radar signals. The MAC array includes several MAC units. Each MAC unit can be set to either a parallel operation mode or a pipeline operation mode. Moreover, the RSP chip also includes a reference code generator, which further includes a look-up table circuit to store a data table for fast computation uses. A control unit is also included in the RSP chip for producing several control signals to control the operations. The RSP chips can be fabricated using VLSI technology and can be serially coupled one after another.

Abstract: A ranging device is disclosed that monitors for changes in a scene of interest. The ranging device includes a transmitter that sends pulses into the scene, a receiver that generates pulse samples in response to pulse returned from the scene, and a target discriminator that analyzes the pulse samples. The target discriminator detects targets entering the scene, targets leaving the scene, and targets moving in the scene through the use of at least one non-averaging statistical characteristic of the pulse samples. The target discriminator may generate short term and long term high order statistical samples in response to the pulse samples as well as detector samples consisting of the ratio of high order statistical samples. The detector samples are highly indicative of the presence or absence of a target in the scene.

Abstract: The invention relates to a radar device comprising two antennae fed by the same emission means, but serving reception means which are separated at least in part into two channels, followed by exploitation means. It is applied, in particular, when the antennae have substantially the same main lobe, but side lobes or scatters which are at least in part different. The exploitation means are capable of considering as a false alarm any echo received with a level below a selected threshold in one of the reception channels.

Abstract: A false alarm rate is maintained at or below a desired rate over a fluctuating mean noise level for providing additional sensitivity and increased range performance in a constant false alarm rate (CFAR) circuit in a radar system by: utilizing a variable CFAR detection threshold level for distances out to the radar's horizon; and, for distances beyond the radar's horizon, utilizing a relatively low fixed CFAR detection threshold level in place of the variable CFAR detection threshold level when there are no environmental factors present that produce additional radar returns.

Abstract: A radar system and method for operation of the same in a manner in which the false alarm rate is stabilized is provided. The system includes an automatic gain control (AGC) processing function which is utilized to control the pre-processed false alarm rate such that the displayed false alarm rate is substantially intolerant to temperature fluctuations.

Abstract: A single antenna poly-frequency Continuous Wave (CW) Doppler radar system having leakage cancellation. The system provides for transmitting a plurality of carrier frequency signals and receiving the return signals by means of a single antenna coupled to an antenna interface through which a portion of the transmitted signal may leak. The signal appearing on an output port of the antenna interface is then down-converted to an intermediate frequency (IF) signal by a stable mixing signal. The IF signal is coupled to an adder which in turn is coupled to an output. The IF signal is further split into a pair of cancellation loops for each carrier frequency signal.

Abstract: A cell averaging (CA) constant false alarm rate (CFAR) device for use in a radar system which filters noise and clutter from a signal containing a plurality of range cells. A moving window average calculator (MWAC) calculates a moving window average (MWA) for each range cell in a signal. A central processing unit (CPU) estimates a skew factor of a probability density function (PDF) and calculates an offset factor based on information contained in the signal. A multiplying device multiplies the offset factor by the MWA calculated for each range cell and creates a second signal containing a plurality of range cells. A comparator compares each range cell of the second signal to each corresponding range cell of the original signal, selects a the larger value of the two signals, and creates a third signal which is essentially free of noise and clutter.

Abstract: The radar signal processing apparatus according to the present invention comprises a noise distribution measurement system comprising an edge detecting circuit, a noise distribution measuring circuit, a template, and a pattern matching circuit and an adaptive type target detecting circuit.

Abstract: A method and arrangement for generating a clutter threshold by means of a CFAR circuit. In the process the partial registers of the CFAR are subdivided into storage blocks each containing a plurality of cell, and a block sum is formed from the sample values stored in each storage block. To form the clutter threshold for a signal under test, the individual block sums are compared in pairs according to a predetermined scheme, during which the greater block sum is determined. From these resulting greater sums, the smallest block sum (minimum) is selected and, from this, the clutter threshold is determined with a predetermined weighing. According to an alternative method, the block sums are sorted according to an order of precedence. Thereafter, block sum having a predetermined ordered rank is selected from the sorted block sums, and the clutter threshold is determined from this selected sum after a predetermined weighing.

Abstract: This target detection polarimetrical processing circuit comprises, in parallel, a polarimetrical CFAR detector provided with a target detection output, a polarimetrical clutter-rejection filter associated with a CFAR detector provided with a target detection output and a bank of polarimetrical filters associated with CFAR detectors provided with target detection outputs, and an "OR" type logic circuit combining the different target detection outputs and a selection circuit activating the polarimetrical clutter-rejection filter and disabling the bank of polarimetrical filters when the degree of polarization of the clutter exceeds a certain threshold and conversely disabling the polarimetrical clutter-rejection filter and activating the bank of polarimetrical filters when the degree of polarization of the clutter is below said threshold.

Abstract: A radar system for identifying an object of interest. A transmitter produces a first signal and a duplexer receives the first signal from the transmitter. An antenna transmits the first signal into the atmosphere and receives a second signal reflected by objects present in the atmosphere. A receiver samples the second signal and develops a third signal. A clutter filter removes a clutter component from the third signal at all frequencies and develops a fourth signal which is free from clutter. An electromagnetic interference (EMI) detection unit identifies EMI present in the fourth signal produced and develops a fifth signal which is free from EMI. A logic device compares the fourth and fifth signals to produce a sixth signal which is free from both clutter and EMI and represents only objects of interest. A display unit receives and displays the sixth signal to allow an operator to track objects of interest.

Abstract: A method and apparatus estimate the detection range R.sub.1 of a radar in the presence of noise and clutter. The radar return signals from a range cell under test and from a plurality of surrounding range cells on either side of the range cell under test are measured. From the values of the return signals from the surrounding cells, a factor .alpha. is determined. The mean value of those signals is then multiplied to form a threshold value for determining the presence or absence of a target. A desired false alarm rate is maintained, however. A number of radar return signals sufficient substantially to average out local variations in clutter are used to determine a mean clutter value m.sub.c. A value which is a function of .alpha. and m.sub.c is output as the estimate of detection range R.sub.1.

Abstract: A signal processor is described for object detection systems such as radar and sonar systems in which wave energy is transmitted and received as a train of discrete pulses of frequencies stepped in predetermined sequence. The received signal processor comprises a plurality of processing channels of number corresponding to the number of sub-pulses in the transmitted pulse train, each channel including frequency selective means such that signal returns of frequencies corresponding to but one of the transmitted sub-pulses are processed by that channel. Means are provided for simultaneously sampling the signal levels in all channels and indicating that channel in which the signal level is greatest, this sampling process being serially repeated at times related to each of the times of transmission of one sub-pulse of the train.

Abstract: This invention improves the detection performance of doppler radar by censoring clutter at the output of the doppler processor, and it functions in operative association with a range CFAR. By a selective rejection of signals based on doppler characteristics and on signal amplitude, it will reduce the sum of clutter and noise at the input to the CFAR. Thus the CFAR detection threshold level is lowered, which thereby improves the detection performance for moving targets.

Abstract: A process and system for improving the detection of signals in additive correlated non-Gaussian noise using multichannel data. This improves detection performance of receivers through the signal processing architecture when the observation data X(n) is first split into an upper and lower path. In the upper path, the known signal is first subtracted from the data and then passed directly to the prediction error filter. The output of the prediction error filters are then input to the zero-mean non-linear processor and their associated estimated variances are used to determine H.sub.0 and H.sub.1 where H.sub.0 denotes the condition where no signal is present in the data and H.sub.1 denotes the signal present case.

Abstract: An optical chirp processor for the collection and processing clutter samples is presented that allows the simultaneous estimation of both the clutter mean and variance. The estimated clutter mean and variance allow the actual calculation of both clutter model parameters using a power spectrum analyzer, and a CFAR special purpose processor unit. The power spectrum analyzer is composed of: a spatial frequency demultiplexor, and a four element photodetector array. The special purpose processor is composed of: an A/D converter, a square root calculator, an averaging calculator, a combiner unit, a parameter memory unit, and a threshold calculator unit. The components of the CFAR processor may be implemented in a conventional CFAR processor (when modified by the teachings of the present invention) or in individual electronics components.

Abstract: The present invention improves upon conventional windshear data processing techniques in three mutually exclusive aspects. First, the present invention provides an improved method and system for detecting microburst downdraft candidates. The improvement lies in its capability of detecting multiple candidates in range. Because of the added capability to detect multiple candidates in range, the present invention also provides an improved method and system for azimuthal association of the multiple candidates in range to define an accurate locus of headwind and tailwind pairs. Second, the present invention provides an improvement in that it utilizes a non-circularly symmetric spatial model to compute the vertical component of a total hazard factor. Third, the present invention provides an improvement in the accurate detection of small radii microbursts by correcting bias present in the data from which the small radii microbursts may be detected.

Abstract: An artificial intelligence system improves radar signal processor performance by increasing target probability of detection and reducing probability of false alarms in a severe radar clutter environment. This utilizes advances in artificial intelligence and expert systems technology for the development of data analysis and information (signal) processors used in conjunction with conventional (deterministic) data analysis algorithms to combine radar measurement data (including observed target tracks and radar clutter returns from terrain, sea, atmospheric effects, etc.) with topographic data, weather information, and similar information to formulate optimum filter coefficients and threshold tests. Present fielded radar systems use one CFAR algorithm for signal processing over the entire surveillance volume. However, radar experiments have shown that certain CFAR algorithms outperform others in different environments.

Abstract: A method and apparatus for controlling the false alarm rate of a receiver which detects each received signal having a power level greater than a predetermined threshold level which is received within a predetermined detection interval. The receiver is adapted to receive signals in response to source signals having a predetermined transmission period. The signals detected within each transmission period can include an initial signal and a plurality of excess signals received subsequent to the initial signal. The total number of detected signals and the number of excess signals received within the predetermined detection interval are counted and a ratio therebetween is determined. Based upon the ratio of the total number of signals to the number of excess signals, the relationship between the power level of the received signals and the threshold level is adjusted in order to control the false alarm rate of the receiver.

Abstract: The invention improves the radar detection capabilities for moving targets by censoring clutter and noise after it is outputted from a doppler processor. It effects the resulting clutter and noise suppression of doppler radars through use of thresholders that function in operative association, one principally for noise and the other principally for clutter.

Abstract: A radar signal processor for use in a pulse radar system. Reception signals are given from a range divide and output circuit to a plurality of integration point variable coherent integrators, each of which is allocated to a different range domain. The range domain is given to an integration point setting section provided corresponding to each integration point variable coherent integrator. The integration point setting section determines the number of coherent integration points based on the given range domain and sets it in the corresponding integration point variable coherent integrator. The signal resulting from coherent integration by the integration point variable coherent integrator is discriminated to frequencies, then supplied to any square detector for square detection for each frequency component. Square detection output is fed into a CFAR detector, which then makes its false alarm rate constant for a supply to a display, etc.

Abstract: A four-terminal network in tandem with a tunnel diode (TD) threshold receiver currently used in radar or communications improves its sensitivity. Previous inventors have shown that the temperature and sensitivity properties of a conventional TD threshold device used for detecting very short duration bursts of microwave energy would be enhanced by appropriately biasing the TD by a current derived from the thermal noise; the current sets the TD operating point. The magnitude of the current is determined by a constant false alarm rate (CFAR) feedback loop. The subject invention recognizes that a TD changes states (i.e., a detection event) when the area under the current vs. time curve or the charge passing through the device exceeds a prescribed number of picocoulombs. To maximize the charge and improve detection, a form of superheterodyne conversion is introduced to convert the oscillatory short pulse microwave signal received by an antenna to a monopolar baseband signal.

Abstract: This invention makes use of the technique known as CFAR (Constant False Alarm Rate). Its objective is to create a method of adjusting the detection threshold of a radar consisting in:breaking down the area monitored by the radar in one sweep period, into sectors in which clutter can be assumed to be uniform,creating the histogram y(x) of received signal amplitudes in a sub-sample of distance-direction cells in each sector,in each sector, estimating the clutter histogram using a model m(x) defined analytically with coefficients adjusted so as to follow the shape of the recorded histogram y(x) at least in part of its variation interval, andcalculating the value of the detection threshold S in each sector starting from a set value of the false alarm probability Pfa and the model analytical equation using the relation: ##EQU1## where N is the total number of events contained in the modeled histogram. The invention is particularly appropriate for adjustment of the detection threshold of a marine patrol radar.

Abstract: A car security system has a proximity sensor such as a radar sensor with variable sensitivity and capable of producing a detection signal upon detecting motion of a person in a monitoring area. A control circuit is provided controls the sensitivity of said proximity sensor. The system also has a monitoring/alarming control circuit for control of predetermined monitoring and alarming control on the basis of the output from the proximity sensor, and alarming devices such as a headlight flash circuit, buzzer and siren for performing a predetermined alarming operation under the control of the monitoring/alarming control circuit. The sensitivity control circuit operates in response to a predetermined operation such as an arming start operation to vary the sensitivity of the proximity sensor so as to automatically set the sensitivity to a first sensitivity level which is the highest level within a range which does not cause the sensor to produce the detection output.

Abstract: A method of processing IR signals from a repetitively scanned array of photovoltaic cells is shown to consist of the steps of: (a) subtracting IR signals received on successive scans to produce response signals corresponding only to IR signals from moving or scintillating objects; (b) generating inhibiting signals for IR signals from the edges of wind-driven clouds or from scintillating objects; and (c) inhibiting those response signals that are from the edges of moving clouds or scintillating objects.

Abstract: Disclosed is a method for the adjusting of the detection threshold of a radar receiver for a distance zone called a search zone surrounded by distance zones called adjacent zones, fitted out with a module enabling the computation of the mean value as a function of the distance of the ambient noise along an axis starting from the receiver wherein, for each search distance zone, the detection threshold is raised by a zero value when the ambient noise is low and by a value that increases monotonically with the level of the noise measured when the ambient noise is greater than a pre-determined threshold.

Abstract: A video signal processor for a radar system includes A/D converters for receiving radar signals to digitize the signals at a predetermined speed, direct averagers for writing signals included in the predetermined size of azimuth among the digitized radar signals into different memories according to the azimuths and for averaging signals corresponding to the same range gates, cell average processors having a microcomputer and a RAM for cell-averaging the output of the direct averagers with the processing program down-loaded from a main controller, an extractor for extracting only target data from the output of one of the cell average processors, a radar video processor controller for generating various control signals, and a communication processor for performing the data transmission and reception between the main controller and the radar video processor controller of the radar system.

Abstract: A rank cell array for ranking a series of sample values including a number of identical rank cells (RC1, RC2. . . ) permitting ready modification of the sorting window size in an OS CFAR radar application, for example. Each rank cell (RC1, RC2. . . ) includes a multiplexer (49), a D flip-flop (41), first and second comparators (43, 45), and a multiplexer controller (49). Each clock interval, the foregoing circuitry examines the sample value entering the sorting window, the sample value leaving the sorting window, the sample value in the preceding rank cell, and the sample value in the succeeding rank cell to determine the sample value in the rank cell during the next clock interval.

Abstract: A method and apparatus of point target filtering in a weather radar system for eliminating point targets such as airplanes in real time. A one-dimensional filter is used that operates on a single radar dwell of data at a time. The filter searches for point targets in a reflectivity data field by looking for increases and decreases in the magnitude of the radar return. Each sample volume of the radar dwell is compared to adjacent sample volumes and the differences are tested against predetermined point target thresholds. The differences greater than such predetermined thresholds are flagged. After the entire radar dwell is processed, flagged point target data in the sample volumes are replaced with the data from the sample volume just before the point target which is not considered to part of the point target. The point target filter removes the point targets and the performance limiting contamination they represent to automatic weather data processing programs.

Abstract: A constant false alarm rate (CFAR) circuit uses three windows for calculating mean level thresholds. In addition to a lead window and a lag window each separated from a cell of interest by a predetermined number of cells, a straddle window is used which includes the cell of interest. Each of the lead, lag and straddle windows are subjected to editing to remove three adjacent cells including the cell with the highest power level. The remaining cells are used to calculate a mean level threshold for each of the three windows. The largest of the three mean level thresholds is used, unless it is derived from the straddle window and it is significantly larger than the largest of the mean level thresholds derived from the lead and lag windows. In addition, use of the mean level threshold derived from the straddle window may be excluded for range cells associated with one or more range and azimuth.

Abstract: A radar system comprises a radar carrier frequency oscillator for producing a radar carrier signal, a receiver including a mixer for producing Doppler signals, a Doppler filter bank and an alarm circuit, including a series of Doppler bins, having an alarm threshold level. The radar system is provided with a frequency modulator for modulating the radar carrier signal and any interference signal received by the receiver whereby the bandwidth of the frequency modulated interference signal exceeds the bandwidth of a number of Doppler filters in the Doppler filter bank. The alarm circuit may have two threshold levels and may be controlled in dependence upon a predetermined pattern of crossings of the threshold levels.

Abstract: A radar capability display apparatus utilizing radar theory equations which are stored in a computer to relate the measured characteristics of interference signals in radar return echoes to determine the amount of radar performance degradation that the interference signals create. These loss of performance factors which are obtained at each antenna beam angle and range, are displayed on the radar's screen as the radar capability display.

Abstract: Detection and extraction of unknown signal in noise may be important in radar When an unknown signal of a transient nature is received, representation in terms of basis functions, localized in both time and frequency, such as Gabor representation, may be very useful for signal detection. By using time-frequency decomposition, noise energy tends to spread across entire time-frequency domain, while signal energy often concentrates within a small region with a limited time interval and frequency band. Signal recognition in the time-frequency domain becomes easier than that in either time or frequency domain. By setting a CFAR threshold for and examining time-frequency Gabor coefficients which exceed the threshold, presence of a signal may be determined. CFAR time-frequency processing for detection and extraction of signals in noise improves detection and extraction performance for low Signal-to-noise-ratio (SNR) signals.