128 results about "Bistatic radar" patented technology

An improved system and method for monitoring objects, people, animals, or places uses a passive Modulating Reflector (MR) tag where an antenna is alternately short and open circuited according to a time-varying pattern by a modulating network thereby causing the reflective characteristics of the antenna to vary in accordance with the time-varying pattern. When an interrogator transmits an RF waveform that impinges on the antenna, the return signal reflecting off the antenna is modulated in accordance with the time-varying pattern allowing a remote receiver to demodulate information from the modulated return signal. The MR tag can be used with a wide variety of tag-interrogator configurations employing monostatic and/or bistatic radar techniques to allow monitoring, locating, and/or tracking of objects, people, animals, or place with which MR tags are associated.

A bistatic radar system includes a transmitting radar site; a receiving radar site; and an optical fiber RF link system for transmitting RF signals from the receiving site to the transmitting site and for transmitting command and control signals from the transmitting site to the receiving site.

A system for sensing aircraft and other objects uses bistatic radar with spread-spectrum signals transmitted from remotely located sources such as aircraft flying at very high altitudes or from a satellite constellation. A bistatic spread spectrum radar system using a satellite constellation can be integrated with a communications system and/or with a system using long baseline radar interferometry to validate the digital terrain elevation database. The reliability and safety of TCAS and ADS-B are improved by using the signals transmitted from a TCAS or ADS-B unit as a radar transmitter with a receiver used to receive reflections. Aircraft and other objects using spread spectrum radar are detected by using two separate receiving systems. Cross-Correlation between the outputs of the two receiving systems reveals whether a noise signal is produced by the receiving systems themselves or is coming from the outside.

The invention relates to a multi-parameter combined estimation method based on bi-static FDA-MIMO radars. The method comprises the following steps: firstly designing a transmitting signal by utilizing characteristics of FDA and MIMO radars; carrying out matched filtering, vectorization and spatial smooth processing on a receiving signal; then estimating a combined steering vector and estimating a DOA and a speed parameter by utilizing an ESPRIT algorithm, and carrying out decoupling and parameter estimation on the DOD and distance information by combining characteristics of a transmitting waveform; and carrying out ambiguity resolution on a distance result estimated by utilizing an ESPRIT algorithm and combining a distance estimated by virtue of a pulse delay estimation algorithm, and carrying out ambiguity resolution on a speed by virtue of an MUSIC algorithm by combining signal characteristics of a large number of pulses. The method provided by the invention has the advantages that the problem that the distance and speed can not be accurately estimated under the condition of a single PRF can be effectively solved, and the estimation of the three-dimensional position and speed of a target can be realized; and a simulation result shows that the method provided by the invention has good estimation accuracy and stability.

The invention discloses a clutter suppression method based on a bistatic multiple-input and multiple-output radar, which comprises the steps of: (1) separating echo signals; (2) rotating; (3) projecting; (4) estimating a clutter covariance inverse matrix; (5) detecting a weighted vector; and (6) detecting a moving target. The clutter suppression method based on the bistatic multiple-input and multiple-output radar can be suitable for conditions that a transmitter and a receiver of a bistatic radar move, and can eliminate the distance dependence of the bistatic radar. The clutter suppression method based on the bistatic multiple-input and multiple-output radar overcomes the defect of insufficient independent identical distribution training samples for space-time adaptive processing by adopting a rotary projection method for separated coordinates of all echo data, and has the advantages of sufficient independent identical distribution training samples, and capabilities of accurately evaluating clutter characteristics and forming a deep clutter notch in an actual main clutter area through space-time adaptive filtering as well as effectively suppressing clutters.

The invention discloses a method for detecting a moving target on the ground by utilizing a bistatic radar based on MIMO (Multiple Input Multiple Output), mainly solving the problems that the traditional distance dependence compensating method has large calculating amount and the compensation can be carried out by needing knowing some radar parameters. The method comprises the realization steps of: (1) carrying out matched filtering on echo data of the radar by utilizing transmitted waveform; (2) eliminating a distance dependence characteristic of a clutter spectrum by utilizing a projection method; (3) evaluating a clutter wave covariance matrix by utilizing the data of which the distance dependence influence is eliminated; (4) obtaining an optimal weight vector according to a principle of space-time adaptive processing; and (5) weighting the data by utilizing the optimal weight, eliminating the background clutter wave and detecting a target signal. In the invention, the principle issimple; the calculation of eliminating the distance dependence by utilizing the projection method has low complexity; compared with a bistatic radar based on SISO (Single Input Multiple Output), the method disclosed by the invention has better ground moving target detecting performance; and the moving target on the ground can be detected under the condition of not knowing radar parameters.

The invention discloses an improved algorithm based on parameter estimation and compensation of a quadratic phase function, and belongs to the technical field of signal and information processing. Thealgorithm performs range walk correction on slow time-range frequency domain echo signal considering range walk and Doppler diffusion through Keystone transform, and then eliminates a coupling relation between the range frequency f and the slow time tn in a second-order phase item corresponding to the acceleration in a narrow-band condition; meanwhile, a folding factor corresponding to the blindspeed is searched, a folding factor compensation item is constructed to correct the range walk caused by the blind speed; then the target acceleration is estimated by using the quadratic phase function, and a second-order phase item corresponding to the acceleration is constructed to compensate Doppler diffusion of the echo signal; and finally, long-term phase-coherent accumulation is performed soas to realize high-speed weak target detection of bistatic radar. The method disclosed by the invention is high in operation speed, stable in performance and applicable to detection of weak targets with a low signal-to-noise ratio and difficultly estimated target parameters.

The invention discloses a bistatic inverse synthetic aperture radar (ISAR) image fusion method based on sub aperture parameter estimation, which mainly solves the problem of low efficiency of the existing bistatic ISAR image fusion and has a realization process comprising the following steps of: building a bistatic radar turntable model; obtaining the target distance Doppler image of two radars; using the Doppler difference values of isolated strong scattering points at different sub apertures for estimating the target rotating angle speed; then, carrying out orientation calibration accordingto the obtained target rotation angle speed; estimating the half bistatic angle through the conversion relationship between coordinate systems; carrying out distance direction matching filtering and motion compensation on data of the two radars; then, adopting a back propagation (BP) algorithm for carrying out compensation on the echo phase according to the estimated half bistatic angle and the target rotating angle speed; and mapping the data of the radar 1 and the radar 2 after the compensation completion to the same rectangular coordinate system for carrying out coherent fusion. The theoretical analysis and experiment results show that the method of the invention can obtain images with better effects, can obtain more target information and can be used for target identification.

A bistatic radar receiver is centrally located within an array of multiple bistatic transmitters at an airport to precisely determine bird positions and altitudes. Bird target reflections from multiple transmitters are received by the radar receiver. Target location is determined by the transmitter location, receiver location, and measured transmitter-to-target-to-receiver ranges. Target position and altitude accuracy is similar to GPS. The radar receiver antenna is composed of a vertical array of elements and rotated 360 degrees in azimuth. The output of each element is downconverted, digitized, and digitally beamformed to provide multiple simultaneous antenna beams each electronically scanned in elevation. When bistatic transmitters cannot be deployed, a narrow-azimuth wide-elevation transmit antenna beam is overlapped with a wide-azimuth narrow-elevation receive antenna beam electronically scanned in elevation to provide a composite narrow azimuth and elevation beamwidth.

A bistatic radar has a radar transmitter at a first location on a moving platform having a motion and a radar receiver at a second location, remote from the first location. The transmitter illuminates a target along an indirect path with an encoded radar signal. The target reflects the encoded radar signal to the radar receiver. The transmitter concurrently provides the encoded radar signal to the radar receiver along a direct path. The encoded radar signal is radiated at a start time from a central reference point, and contains the first location, the pulse start time, the central reference point and the motion of the moving platform. Bit synchronization codes are also included. The radar receiver receives the encoded radar signal from the radar transmitter along the direct path during a first time interval, and the same encoded radar signal reflected from the target along the indirect path during a second time interval. The radar receiver decodes first information contained in the encoded radar signal from the direct path received during the first time interval to extract direct path information. The radar receiver also decodes second information contained in the encoded radar signal from the indirect path received during the second time interval to extract indirect path information. The radar receiver combines the direct path information and the indirect path information to to generate a target image or perform target detection. Linear Frequency Modulated (LFM) pulse coherency is maintained by extracting from the direct path pulse phase corrections and applying the phase correction to the indirect received LFM pulses.

A multi-radar system is configured such that radars A and B perform synchronization so that their transmission timings and frequency bands are substantially the same. For this reason, in a case where the radars A and B operate as bistatic radars, the radars A and B yield the same detection results from reflected waves from a place on a surface of a target T where the detection object regions of the radars A and B overlap. Therefore, the signal-to-noise ratio can be improved by synthesizing the target detection results obtained by the radars A and B operating as bistatic radars. This results in improved target detection performance.

The invention discloses a method for positioning indoor moving persons by the aid of WIFI (wireless fidelity) reflected signals. The method is implemented by a WIFI transmission source and a passive bistatic radar device, and the WIFI transmission source is used as a non-cooperative irradiation source of the passive bistatic radar device. The method includes comparing and computing direct WIFI signals transmitted by the WIFI transmission source and the reflected WIFI signals reflected from the bodies of the moving persons to obtain Doppler shift of the reflected WIFI signals; computing moving speeds, directions and distances of the moving persons relative to the passive bistatic radar device so as to relatively position the moving persons; enabling the passive bistatic radar device to acquire satellite positioning information of the passive bistatic radar device via a navigation positioning module and a compass of the passive bistatic radar device, and acquiring satellite positioning information of each tested moving person by means of coordinate transformation. The method has the advantages that the indoor moving persons can be identified, positioned and monitored by the method, and equipment implemented in the method is simple and convenient and is easy to use and low in cost.

A system and method for controlling clutter Doppler spread in a bistatic radar system is developed resulting in enhanced detection of low-Doppler targets or improved SAR mode performance. In an illustrative embodiment, a bistatic radar system (10) includes a transmitter (12) for transmitting electromagnetic energy (106) towards a target (16), a receiver (14) adapted to receive the electromagnetic energy (116) reflected from the target (16), and a processor (122) for optimizing a parameter or parameters of the system such that the directional derivative of the bistatic Doppler field along the isorange contour is near a desired value. The parameters to be optimized may include the transmitter velocity vector, the receiver velocity vector, or the receiver azimuth flight direction. The desired value is the minimal absolute value of the directional derivative in order to minimize the clutter Doppler spread, or the maximum absolute value of the directional derivative in order to maximize the clutter Doppler spread.

An improved system and method for monitoring objects, people, animals, or places uses a passive Modulating Reflector (MR) tag where a characteristic of an antenna is modified according to a time-varying pattern by a modulating network thereby causing the reflective characteristics of the antenna to vary in accordance with the time-varying pattern. When an interrogator transmits an RF waveform that impinges on the antenna, the return signal reflecting off the antenna is modulated in accordance with the time-varying pattern allowing a remote receiver to demodulate information from the modulated return signal. The antenna is embedded in a dielectric material. The MR tag can be used with a wide variety of tag-interrogator configurations employing monostatic and/or bistatic radar techniques to allow monitoring, locating, and/or tracking of objects, people, animals, or place with which MR tags are associated.

A bistatic radar system and method. In the illustrative embodiment, a receiver is positioned in a horizontal plane. A transmitter is then positioned in Middle Earth Orbit at a position that is nearly vertical to the plane of the receiver. This configuration provides significant flexibility for the radar system. As such, the radar system may engage in flight patterns, in which the transmitter and receiver have velocity vectors in opposite directions (GMTI mode), the same direction (SAR mode) and variations in between (mixed mode). Lastly, a broad beam is generated from the transmitter and illuminates an area enabling several receivers to simultaneously observe the illuminated area.

The invention relates to a method for synchronizing the time and the frequency of a motor-driven configured bistatic radar. The frequency and the time between a receiving station and a transmitting station of the bistatic radar can be realized by utilizing the characteristics of long-term stability, low phase noise and low stray; when the receiving station and the transmitting station are deployed separately, the real-time statistics of time synchronization errors of the receiving station and the transmitting station are completed on the basis of pulses per second of a navigation satellite; when the time synchronization errors exceed a limit value and the state of the pulses per second of the navigation satellite is normal, time resynchronization between the receiving station and the transmitting station is completed in a navigation satellite time service synchronization mode; the receiving station and the transmitting station enter a timekeeping synchronization state again. The method is applicable to synchronizing the time and the frequency of the motor-driven configured bistatic radar, and has the advantages of short erecting and withdrawing time, high maneuverability, high working stability and the like. Before the receiving station and the transmitting station are deployed separately, the modes of direct time contrast synchronization and long-time autonomous timekeeping maintenance are adopted, and have the advantages of being not limited by the navigation satellite and not impacted by electromagnetic environment in wartime.

The related clutter baseband signal generation method for satellite-carried bistatic radar comprises: setting initial condition, building the clutter equidistance ring model; deciding the clutter unit validation, calculating the clutter unit motion vector led by earth rotation; then, according to satellite position and orbit parameters, calculating satellite velocity vector and the corresponding time frequency and space frequency for clutter unit; summarizing all clutter unit space-time 2D fast-beat to calculate clutter covariance matrix and clutter data for succeeding algorithm processing.

The invention relates to an ultra-wideband radar human-motion-target imaging method based on IBST (Inverse Boundary Scattering Transform). The method comprises the following steps of: establishing an ultra-wideband radar motion target scene model and setting imaging parameters; establishing a target motion speed and angle set; inputting the echo signals of two receiving antennae and carrying out cumulative mean and matched filtering treatment to obtain an output signal with a high SNR (Signal-To-Noise); carrying out fitting interpolation calculation on the output signal by utilizing a cubic spline function and extracting quasi-wavefront; respectively calculating target boundary images of the two receiving antennae under corresponding coordinate systems for elements in the set by utilizing the IBST based on a bistatic radar; carrying out coordinate transformation and finding (vi, theta j) on which twice imaging is matched under a new coordinate system, to be used as the estimated values of target motion speed and motion direction, wherein the corresponding images are target boundary images; and calculating the motion tracks of a target in an orientation direction and a distance direction tracks by using the estimated values and synthesizing a target motion track. The ultra-wideband radar human-motion-target imaging method provided by the invention has low requirements for system hardware, and can be used for imaging the motion target boundary and calculating the motion track.

The invention discloses a bi-static radar eustatic movement target detection method based on a Beidou satellite radiation source. The method comprises the following steps: performing range migration correction on an echo signal under long observation time by adopting symmetric second-order Keystone transform, and performing unified de-sloping processing on the echo signal under the whole observation time, and then performing the framing processing, performing coherent accumulation on an intra-frame signal and performing incoherent accumulation on an inter-frame signal, thereby effectively solving a problem that a Beidou satellite is low in target echo signal-to-noise ratio when being served as an external radiation source. The range motion and the range bending can be simultaneously removed under the condition of unknowing a Doppler parameter by adopting the symmetric second-order Keystone transform, so that the range migration correction can be better realized; since the intra-frame signal only needs to perform the addition computation and the inter-frame signal does not to perform Doppler centroid compensation operation when being in the energy accumulation processing, and the computation burden is greatly reduced.

The invention discloses a passive bistatic radar signal processing method based on dimension reduction constant modulus blind equalization. The passive bistatic radar signal processing method comprises the following steps: S101: restoring direct wave signals in signals received from a reference passage of a passive bistatic radar by using a constant modulus blind equalization method after dimension reduction; S102: according to the signals received from a monitoring passage of the passive bistatic radar, performing multidiameter self-adapting wave filtering processing on the direct wave signals by using a smallest mean square error algorithm; S103: estimating a doppler time delay cross-correlation detection objective of a distance between the signals obtained through the multidiameter self-adapting wave filtering processing and the direct wave signals. The passive bistatic radar signal processing method disclosed by the invention uses the energy sum of weight vectors and percentage as a threshold, omits an undersize weight vector coefficient, and can effectively decrease the number of the weight vectors participating in iteration, so that the calculated amount of the algorithm is reduced.