146 results about "Ambiguity function" patented technology

A system for geolocating a radio frequency (RF) transmitter in the presence of multipath interference may include a plurality of RF receivers arranged in spaced relation. The system may also include a controller coupled to the plurality of receivers and configured to generate a plurality of measurements associated with the RF transmitter. The controller may also compute a plurality of ambiguity functions based upon the plurality of measurements and due to the multipath interference, and project the plurality of ambiguity functions onto a common geo-referenced grid. The controller may also detect a peak on the common geo-referenced grid indicative of a geolocation of the RF transmitter.

A method for use in a wireless communication system with a network overlay geolocation system having a sparse deployment network in which base stations of the wireless communication system may or may not have a co-located wireless location sensors (WLS). The method enables detection and measurement of a target mobile's signal independently from a primary WLS located at the base station serving the target mobile, which enable location estimated in previous “no location” areas. The method selects based on predetermined criteria from one or more of several techniques that aid in the detection and determining a location for the target mobile. The method selects from timing advance, power levels, pattern matching, EOTD, speed, and pseudo range measurements to estimate the location of the mobile. The method also uses ambiguity function processing to detect the signal and measure an attribute of the signal.

Systems and method of detection and discrimination of targets in the presence of interference are disclosed. A system transmits a signal and then receives signals including interference and reflections of transmitted signals. The system processes the received signals and transmitted signals to generate a 2D representation of the STAP cube with one of the dimensions collapsed. The system then reduces the interference contributions and identifies angle and Doppler component of potential targets. The system then computes slices, which are one dimensional representation of cross-ambiguity functions of the received and transmitted signals. It reduces the interference contributions in the slices and determines range components of the targets.

Aspects of the present invention relate to methods and systems for high-accuracy differential tracking of global positioning system (GPS) receivers. In one embodiment, a network having multiple receivers is provided. The receivers are configured to communicate with each other. The receivers in the network are configured to measure raw satellite data, and to share the raw satellite data measured by each receiver. Each receiver is configured to process the measured raw satellite data with a Peak Ambiguity Function Value (AFV) Tracking Solution (PATS) to track relative motions of the neighboring receivers so as to derive relative location information for the plurality of receivers.

The invention is a method for improved active sonar using a singular value decomposition filtering and a Volterra-Hermite Basis Expansion to model real active sonar measurements. The fitting model minimizes the sum of the squared errors between a measured channel response, z(t), and model response, y(t), which is a fitted Volterra Series solution. The model requires as input an excitation waveform, x(t), to which is fitted the model response, y(t). A contracted broadband cross-ambiguity function is used to correct the excitation waveform for Doppler and range effects. Once completed, the modeled response can be used to determine the linearity or non-linearity of the channel effects. Appropriate measures can be utilized to reduce these effects on the measured channel response.

A method for obtaining an adaptive angle-Doppler ambiguity function (AF) for a target using multiple-input-multiple-output (MIMO) radar that includes a transmit antenna array having a plurality of antenna elements. The method includes generating transmit signals for transmission by the transmit antenna array, the transmit signals defining at least a first transmit trajectory of a phase center within the transmit antenna array; transmitting the transmit signals using the transmit antenna array and receiving receive signals from the target, the receive signals resulting from the incidence of the transmit signals upon the target; and obtaining at least an angle-Doppler ambiguity function (AF) from the receive signals. The first transmit trajectory is such that, in operation, the phase center undergoes random phase center motion (PCM), such that a phase center position within the transmit antenna array varies randomly with time. A system for obtaining an AF is also disclosed.

The invention relates to a waveform design for a formation flying satellites SAR (synthetic aperture radar), and provides an orthogonal waveform designing method which is used for carrying out phase encoding for linear frequency modulation (LFM) signals. The orthogonal waveform designing method includes generating a linear frequency modulation signal at first, dividing the linear frequency modulation signal into N parts according to equal time intervals to form N sub-pulses, carrying out random phase encoding for each sub-pulse by M times according to the number M of the formation flying satellites, establishing an ambiguity function expression, calculating cluster tolerance xi meeting formation flying satellite synthetic aperture radar Doppler mismatch, finding out a critical N value meeting requirements by the aid of a searching comparison method, finally selecting energy and functions which are in autocorrelation and cross-correlation as cost functions, namely fitness functions in genetic algorithm, searching code values of phase encoding of the various sub-pulses by the aid of the genetic algorithm, and finding out orthogonal waveforms after optimization at last. The waveforms have low autocorrelation side lobes, cross-correlation peak values, bandwidth occupation ratio and Doppler mismatch, and excellently suppress echo signal interferences among different space-borne SARs.

The invention relates to a radar moving target long-time phase-coherent accumulation detecting method based on an RFRAF, and belongs to the technical field of radar signal processing and detection. The method comprises the following steps that (1) radar echo data are demodulated, pulsed and compressed in the distance direction, and pulse accumulation is completed; (2) parameters are initialized; (3) the RFRAT is adopted to compensate distance and Doppler migration, and then long-time interpulse phase-coherent accumulation is completed: (4) the parameters are transversely searched, an RFRAT domain detecting unit map is constructed, and constant false alarm detection is conducted; (5) target moving parameters are estimated, and moving trace points are output. The advantages of the ambiguity function and fractional order Flourier transformation are synthesized, high order phase signals of a target generated in the moving process can be flexibly matched and accumulated, the distance and Doppler migration are compensated, accumulation and gain of a radar to complex moving target signals are improved, the capacity of detecting weak moving targets in strong clutters is possessed, the moving trace points of the target can be acquired, and popularization and application value are achieved.

The invention relates to a time difference, frequency difference and frequency difference change rate joint estimation method which comprises the following steps: (1) two receivers synchronously collect a target radiation source signal, wherein the digital signals collected are respectively s1(n) and s2(n); (2) mesh generation is carried out on the target radiation source signal in the time difference range and in the frequency difference change rate range respectively, a second-order ambiguity function H (Tau, f) is calculated for each mesh point, and the initial estimate (Tau-^, f-.^) of time difference and frequency difference change rate is obtained by searching for the module values of the second-order ambiguity functions H (Tau, f) of the mesh points; (3) compensation is made for frequency difference expansion through a cross ambiguity function CAF (Tau, f) according to the initial estimate f-.^ of frequency difference change rate to get new time difference estimate and frequencydifference estimate; and (4) new frequency difference change rate estimate is obtained through a frequency difference change rate cross correlation function according to the new frequency differenceestimate. The method of the invention is applicable to the passive location of time and frequency difference under high dynamic conditions.

The invention relates to a quick implementation method for passive radar range migration compensation and belongs to the technical field of radar target detection. The method comprises the following steps: (1) a direct wave signal and an echo signal received by a passive radar antenna are segmented and rearranged into two-dimensional matrices; (2) each row of the direct wave and the echo wave is transformed to the frequency domain; (3) the transformed direct wave matrix is multiplied by the conjugate transpose of the transformed echo wave matrix; (4) each row is extracted after being processed by a low-pass filter; (5) each column is subjected to CZT; and (6) each row is transformed to the time domain, and a cross-ambiguity function result subjected to migration compensation is obtained. Compared with a conventional range migration compensation method based on CZT and IFFT to achieve keystone transform, the provided method reduces operation steps and the amount of computation substantially while the gain accumulated is almost the same.

Systems and methods for on-the-fly characterization of an arbitrary array of antenna elements are provided. An array of arbitrary antenna elements and a reference receiver is provided. A location for a target source of signals is provided or assumed. Cross ambiguity functions are computed between the signal received by the reference receiver and the signal received by each antenna element. The cross ambiguity functions are analyzed to determine the phase and amplitude response of the antenna array to signals originating from the location of the target source of signals.

The invention discloses an intelligent selection method of video thumbnails, comprising the following steps: 1) acquiring N numbered thumbnails of a video, wherein N is more than or equal to 2 and less than or equal to 100, and N is a constant; 2) calculating the characteristics of each thumbnail, such as frontal face position and size, profile face position and size, whole body position and size, upper body position and size, lower body position and size, gray level histogram distribution value, gray level histogram variance distribution value, colorful RGB histogram variance distribution value, difference value that a colorful RGB image is changed into a gray level image, the variance value of a gray level image pixel point, the variance value of the colorful RGB image pixel point, the dispersion distance value between the colorful RGB blocks, and the like; 3) calculating the characteristic values of each thumbnail respectively through ambiguity functions; 4) weighting and calculating the characteristic values of each thumbnail to obtain a final fraction; 5) sequencing the N numbered thumbnails according to the fraction of each thumbnail; and 6) selecting the thumbnail with the highest fraction as the thumbnail representing the video.

A cross-ambiguity function generator (“CAF”) uses properties of quantum mechanics for computation purposes. The CAF has advantages over standard analog or digital CAF function generators, such as improved bandwidth. The CAF may be used for traditional geolocation or RADAR applications.

The invention discloses a method for detecting multiple GPS (global positioning system) satellite weak echo signals. The method comprises steps as follows: a modulation parameter and a C/A code disclosed by a GPS are used for performing separation reconstruction on a GPS signal received by a reference channel, and a reference signal is obtained; direct waves and multiple paths of the direct waves are inhibited for the echo signals; circular cross-ambiguity function processing is performed on an echo channel signal and different reference signals respectively, and multiple delay-doppler spectra are obtained; the multiple delay-doppler spectra are subjected to TF-LV coordinate transformation, and multiple detection quantities are obtained and superposed; the best detection threshold is obtained according to probability distribution of the detection quantities and compared with peak values of the detection quantities, so that the multiple GPS satellite weak echo signals are detected. The method can have a good detection property for multiple GPS echo signals in a low signal-to-noise ratio environment.

The invention provides a radar-communication integrated realizing method. According to the radar-communication integrated realizing method, based on analysis on the characteristics of the ambiguity function of transmitted signals of a communication system, communication signals are directly transmitted when the number of transmitted code elements in one transmission period satisfies requirement; the communication code elements pass through a pulse type shaping filter; obtained signals are transmitted out through using a transmitter and by means of an antenna; a receiving end carries out radar detection processing on the signals directly using the communication signals; the receiving end carries out demodulation on the signals through a receiver, so that baseband signals can be obtained; the baseband signals pass through a matched filter, so that an output signal to noise ratio is maximum; if a function which is to be realized by the system is a communication function, sampling judgment is performed on the demodulated baseband signals, so that the communication function can be realized through communication code element information; and if a function which is to be realized by the system is a radar function, a certain code element accumulation is performed on the signals, so that high radar resolution can be obtained, and time delay and Doppler frequency are extracted through using related technologies, and a radar detection function can be finally realized.

The invention relates to an outer transmitter-based radar range migration compensation method based on frequency domain phase correction and belongs to the technical field of radar target acquisition. The method comprises the steps that segment treatment is conducted on echo signals firstly; then echoes are converted to the frequency domain; phase correction is conducted on the echoes in the frequency domain to enable in-phase superposition of the signals to be achieved within the bandwidth and eliminate the influence of range migration; finally, the phase-corrected echoes are converted to the time domain through Fourier inversion, mutual ambiguity function calculation is conducted between the echoes and direct wave signals, and then a mutual ambiguity function diagram is obtained. According to the method, under the condition of a tracking mode (target speed is known) or that rough target speed is known, the accumulation gain of the method is similar to that of Keystone conversion, while the amount of calculation is far smaller.