148results about How to "Reduce sidelobe level" patented technology

The invention discloses a characteristic space-based backward and forward adaptive wave beam forming method, and relates to the technical field of medical ultrasonic imaging. The method comprises the following steps of: performing focusing delay processing and backward and forward smoothing on a plurality of paths of sampled signals of a received array to obtain a sample covariance matrix estimate; performing diagonal loading on the sample covariance matrix estimate and then combining with a direction vector to calculate an adaptive wave beam forming weight; performing characteristic decomposition on the backward and forward covariance matrix estimate after the diagonal loading to construct a signal subspace; projecting the adaptive wave beam forming weight into the signal subspace to obtain a new adaptive wave beam forming weight; and finally, performing weighted summation on a plurality of paths of data subjected to the backward and forward smoothing by the new adaptive wave beam forming weight so as to obtain a path of adaptive wave beam signal. By using the method, the problems of improving the image resolution and contrast, being sensitive to the direction error and the like existing in the conventional adaptive wave beam forming algorithm are solved, and the overall quality of the ultrasonic imaging is comprehensively improved.

A phased array radar system comprising a plurality of radiating elements configured in a common array aperture for detecting and tracking targets; and a transmit and receive arrangement responsive to a first control signal for configuring the plurality of radiating elements to define a plurality of sub-apertures from the common array aperture for detecting and tracking short range targets, wherein the plurality of sub-apertures are independently steerable array apertures and include an amplitude taper applied across each of the plurality of sub-apertures to reduce a peak sidelobe level.

Embodiments of the present invention concern locating targets using non-linear radar with a matched filter which uses exponential value of the transmit signal. According to embodiments, a method of non-linear radar target location includes: transmitting a signal of a transmit waveform towards a target; receiving a signal from the target; creating a matched filter by generating an exponential function of the transmit waveform corresponding to a particular harmonic of the interest; and applying the matched filter to the received signal to generate and output a signature waveform for the target of the particular harmonic of interest. In other embodiments, the matched filtering may be combined with sidelobe reduction.

The invention provides a three-frequency-band high-gain omnidirectional dipole antenna comprising a three-frequency oscillator array, balanced feeder lines, a first dielectric plate, a second dielectric plate, and a third dielectric plate. The first dielectric plate, the second dielectric plate, and the third dielectric plate are arranged successively from top to bottom. The balanced feeder lines are arranged at the top surface and the bottom surface of the second dielectric plate and are printed along the axis direction of a three-frequency oscillator unit. The balanced feeder lines are parallel dual-line transmission lines. The three-frequency oscillator units in the three-frequency oscillator array are printed at the first dielectric plate and the third dielectric plate; and feeding points among all three-frequency oscillator units are connected by the balanced feeder lines. The three-frequency oscillator units consist of upper arms and lower arms, wherein the upper arms and the lower arms are arranged in a mirror symmetry mode. The upper arms and the lower arms include first branches, second branches, and third branches, wherein the first, second, and third branches are arranged along parallel axes; the second branches and the third branches are arranged at the two sides of the first branches symmetrically and the bottoms are connected into one by horizontal branches; and balanced feeding points are formed at central protrusions of the upper arm and the lower arm. The three-frequency-band high-gain omnidirectional dipole antenna has advantages of high gain, omnidirectivity, high efficiency, small size, and low cost; and an effective or benefical reference is provided for an optimized design of other multi-frequency or broadband high-gain omnidirectional array antennas.

A broadband low-minor-lobe analog multi-beam array reconnaissance system comprises a broadband active antenna array, a Rotman lens network, a beam selection switch, a broadband digital receiver, a signal processing unit. The broadband active antenna array is connected with an analog multi-beam network. The Rotman lens network is configured to form multiple beams simultaneously in a large instantaneous bandwidth. Further, by assigning corresponding amplitude and phase weights to respective amplitude-phase weighting modules of the antenna array, the beam selection switch performs radio frequencyselection in multiple beams according to a control command and sends a selected signal to the broadband digital receiver. The digital receiver processes the data from multiple beams and frequency bands in parallel, and performs parameter measurement on the data to form a radar pulse descriptor and sends the radar pulse descriptor to the signal processing unit. The signal processing unit processesthe signal to form a radar descriptor. The system achieves high sensitivity, wide frequency-domain coverage, wide airspace coverage, flexible beam scheduling and good complex electromagnetic environment adaptability.

An antenna system for sharing of operation employs contiguous transmit frequencies. Transmit frequencies are separated into non-contiguous sub-groups isolated from one another by filters 158(+) and 160(−) associated with positive and negative polarisation. Received frequencies are filtered and split into five signals for input to base station receive ports. Non-contiguous transmit frequency sub-groups are combined by a quadrature hybrid 110 and pass with 90 degree relative phase shift to mutually orthogonal antenna stack ports P(+) and P(−) associated with orthogonally polarised sets of antenna elements AS(+) and AS(−): the ports P(+) and P(−) are isolated from one another by the hybrid 110. The 90 degree phase shift results in one transmit subgroup being radiated with left hand circular polarisation and the other transmit subgroup being radiated with right hand circular polarisation. Changing the relative phase shift changes the radiated polarisation to linear or elliptical, and signal amplitude weighting provides control of antenna beam polarisation direction.

The invention discloses a method for designing partial-feed paraboloid multi-beam antenna feed array and is applicable to a satellite communication system. A reflection-side multi-beam antenna adopts a primary feed utilizing a feed array as paraboloid. The principle of forming multiple beams includes beams of the paraboloid antenna are deviated by means of transverse focus offset of the feed. According to the structural size of the integral antenna system and design procedure of feed array arrangement, a novel feed array layout is provided. The number of generable spot beams is twice times of practical feed number, all beams are tightly arranged, appointed spatial angle can be uniformly covered, and each spot beam has electrical characteristics of good gain uniformity, low minor lobe level, small beam width, high pointing accuracy and the like. The method for designing partial-feed paraboloid multi-beam antenna feed array is directly used for satellite-borne equipment or ground control communication station and has wide potential application and typical application value in the satellite communication system.

The invention discloses a high-gain low-sidelobe highly directive antenna based on an artificial medium structure, comprising a microstrip antenna array and a radome composed of a plurality of grooved cross metal strip artificial medium structures; the grooved cross metal strip structure is printed on a tellite and is used as the radome of the microstrip antenna array; the structure can be equivalent to a homogeneous medium with plasma frequency by rationally designing the cycle and size of the metal structure; the equivalent index of refraction of the frequency of the electromagnetic wave is similar to zero when the frequency is in a certain frequency band. The energy of the electromagnetic wave radiated by the microstrip antenna array is collected in the normal direction of the radome when the electromagnetic wave passes through the radome to achieve the effect of gathering energy, thus improving the overall directivity and gain of the antenna and reducing the sidelobe of the antenna. The antenna not only has the advantages of high gain, good directivity, low sidelobe and the like, but also has the characteristics of good mechanical performance, convenient fixed mounting, simple processing, low cost, small structure size and the like.

The invention discloses an acoustic vector array wideband direction finding method based on a sparse decomposition theory, and relates to a direction finding technique and implementation method for target broadband continuous spectrum noise in the acoustic vector sensor array detection field. The sparsification idea is introduced to an acoustic vector array direction finding system; a combined sparse constraint is established according to frequency point components in broadband continuous spectrum noise signal bandwidth; and finally, a unified airspace sparse decomposition form is obtained, thereby realizing direction finding of the broadband continuous spectrum noise. According to the method, a relatively-sharp spectrum peak and a low-amplitude noise floor can be formed; when the number of array snapshots is small, the method is stable in performance and can distinguish coherent signal sources; and when the target DOA (direction of arrival) approaches to the array axial direction, the phenomenon of noise floor fluctuations occurring under the condition of low signal-to-noise ratio of a conventional beam forming (CBF) method and a minimum variance distortionless response (MVDR) method does not exist.

The invention provides a thinner, lighter, lower-bypass level plate-type micro band gap array antenna, replacing routine all metal guide face with fine-new artificial high impedance magnetic conduction face as a reflection back plate of the antenna array, able to reduce the space between the back plate and the gap array face from lambda/4 or 3 lambda/4 down to lambda/10 below (the desired space is zero), thus largely reducing the thickness of the antenna. Because foam medium is ordinarily filled between the back plate and the gap array face to support and isolate, the reduction of the space largely reduces the use quantity of the needed foam medium, thus largely reducing the large-scale antenna weight. Simultaneously, because the new magnetic conduction back plate has special electromagnetic band gap property, it can prohibit the propagation of surface wave and parallel plate mode electromagnetic wave, thus effectively reducing the bypass level of the antenna array. The artificial high impedance magnetic conduction face can be applied to various antenna arrays, such as 1x8, 2x8, 4x4, and other arrays.

The Highly Structured Rosette Antenna Array Data Communications System is a high capacity wireless network in which data is communicated from and to remotely located subscribers. The system uses cells that are comprised of a multiplicity of oblong microcells arranged in a circle, giving the cell a rosette-like pattern like frequency channels are assigned to every N′″ microcell, where N is the number of distinctly different frequency channels. The sum of the distinctly different channels is the total bandwidth assigned to the rosette. Typically, if M is equal to the total number of microcells in the rosette, then M/N is equal to the number of like-frequency microcells in the rosette.

The invention relates to a low-sidelobe robust adaptive beamforming method. Firstly, an optimal criterion based on poorest performance is established, and it is ensured by adopting the beamforming method that lower null level can be obtained while low sidelobes are formed when array errors exist after cross coupling correction; then, a new beamforming system is established by combining a robust low-sidelobe theory and can adapt to interference competition and reduction of sidelobe level and achieve wide null. Especially, the system can select reasonable parameters in a self-adaptive mode according to an input signal, so that a beam forming device can obtain unified low sidelobe levels under different receiving signals.

The invention discloses an automobile noise source acoustic imaging method based on array element random uniform distribution spherical array deconvolution beam forming. The method comprises the stepsof 1, generating a complex sound pressure data matrix p by utilizing sound signals; 2, calculating a cross-spectrum matrix C of the spherical array; 3, dividing a sound source into S observation gridpoints; 4, obtaining a spatial spectrum b; 5, generating a transfer matrix G from S observation grid points to the spherical array; 6, generating a central point propagation function vector psfcentre; 7, generating a Gaussian regularization filtering function vector psi; 8, obtaining an optimal solution of the sound source distribution vector q; 9, solving sound source distribution qJ through iteration; and 10, obtaining a sound source distribution image. According to the invention, high-resolution visual imaging is carried out on spatial distribution of main noise sources of an automobile, and positioning information and relative intensity of the main noise source and the secondary noise source can be accurately obtained from an image.

The ferrite-loaded, Fabry-Perot Cavity antenna uses a novel superstrate based beam scanning/shaping mechanism by optimally placing three magnetized ferrite cylinders within the cavity. Beam scan in a certain direction required oppositely located ferrite cylinder to be axially biased using externally controlled DC magnetizing field. The FPC utilizes a composite dielectric superstrate to inversely relate the mainlobe-to-sidelobe ratio with scan-angle, which demonstrates larger reduction in side lobe level with increases angle of beam scan. The designed 10 GHz ferrite-loaded FPC antenna has dimensions of 6.4 cm×2 cm×1.6 cm. It achieves a −10 dB impedance bandwidth of 525 MHz, directivity of 11.04 dB and a broadside beam steering range of ±12° for 200 kA/m (0.25 T) changes in the externally applied axial magnetizing field.

The invention relates an MIMO radar array design method based on non-uniformed subarray partition. The method comprises the steps of firstly, establishing an MIMO radar signal model which comprises an emission array and a receiving array, wherein the emission array comprises M emission array elements and the receiving array comprises N receiving array elements; then partitioning the emission array into K non-uniformed subarrayAj according to non-uniformed partition rule. The non-uniformed subarrayAj comprises mj emission array elements and each non-uniformed subarray bore diameter is different. According to the method, emission array is partitioned into a plurality of non-uniformed subarraies with different bore diameters through non-uniformed subarray partition to achieve a lower subband level and formed by the minimum variance orthoscopic response beam to achieve a deeper nulling, a higher SINR emission and steadier and stronger antijamming capability.

The invention discloses a low-sidelobe circular polarized microstrip array antenna applied to an electronic toll collection (ETC) system, wherein the antenna is has a three-layer structure successively including a metal foil, a dielectric substrate and a metal foil. A microstrip feed network and radiation units are arranged on the metal foil on the top of the structure; the radiation units employs a grouping mode in which n radiation units are arranged transversely and two radiation units are arranged longitudinally. There is a rotation angle difference of 90 degrees anticlockwise between each of the radiation unit above the longitudinal column and each of the radiation unit below the longitudinal column; compared with a feed phase of the radiation unit below the longitudinal column, a feed phase of the radiation unit above the longitudinal column is delayed by 90 degrees; and magnitudes of the feed currents of the radiation units at the same longitudinal column are equal. A feed joint is utilized to realize application of current excitation on a whole microstrip feed network, so that the whole microstrip feed network applies currents on all the radiation units. A simplified dolph-chebyshev distribution is utilized for current magnitude ratios that are needed by the radiation units on a same transverse line; and current phases are equal. According to the invention, the microstrip antenna has advantages of low axial ratio, low sidelobe and high gain; and moreover, the antenna is easy to process and install; therefore, the provided antenna can be widely applied to the electric toll field and other related fields.

The invention relates to a design method for a real beam former. A real number weight vector of the real beam former is designed by utilizing two different orthogonality relations so as to cause the output of the real beam former to appear obvious local maximum along the corresponding signal direction, thus finishing the forming of the real beam with lower side lobe level and higher direction resolution to weak signals and coherent signals. The method comprises the following steps: an array received data is used for determining a sample autocorrelation matrix and an inverse matrix thereof; a unitary transformation matrix corresponding to the searching direction is determined and unitary transformation is carried out, and only the real number part of a unitary transformation result is taken; the weight vector of the real beam former is obtained according to the sum of the column vector of the matrix of the real number part of the unitary transformation result. The weight vector of the real beam former is acted on the real number part of the sample autocorrelation matrix, and the spatial spectrum of the real beam former is determined: the direction estimation of a corresponding signal is obtained by searching the peak position of the spatial spectrum, and the forming of the real beam is finished. The method provides a new method for array signal processing, with remarkable effect and significant meaning.

The invention discloses a frequency agility radar target information reconstruction method based on coherent accumulation. The method comprises the following steps: establishing a target echo signal model of the frequency agile radar based on coherent accumulation, and an optimization model taking a phase error and scene sparseness as optimization targets, and solving the optimization model through phase self-focusing algorithm reconstruction and an alternating direction multiplier method so as to obtain self-adaptive phase difference and speed and distance information of a target, and achieving reconstruction of the target information. According to the method, accurate target echo phase error estimation and observation scene reconstruction can be carried out, the problem that the coherent accumulation performance of the coherent frequency agility radar is reduced due to the phase error is effectively solved, good coherent accumulation performance is provided, and accurate estimation of the distance and the speed of the target is achieved.

The invention discloses a metamaterial satellite antenna which comprises a metamaterial plate and an antenna installing base, wherein the metamaterial plate is arranged on the back of a feed source, the antenna installing base is used for fixing and installing the metamaterial plate on a wall, the metamaterial plate comprises a core layer and a reflecting plate arranged on the rear surface of the core layer, the reflecting plate is in a grid pattern and comprises a plurality of metal sheets with same intervals, the core layer comprises a base plate and a plurality of artificial microstructures attached on the front surface of the base plate, the reflecting plate is attached on the rear surface of the base plate, plane electromagnetic wave generated by the feed source is emitted with an angle with the normal direction of the core layer after the electromagnetic wave penetrated through the metamaterial plate and compared with emitting along the normal direction of the core layer, the minor level of the antenna can be effectively reduced, and a traditional parabolic antenna is replaced by the sheet metamaterial plate, so that manufacture and processing are easier and the cost is lower, the whole thickness of the metamaterial plate is in millimeter level and the metamaterial plate is quite light and thin. The invention further provides a satellite receiving system.

The invention provides an ultra-wideband radar single-channel digital beam forming method based on a space-time coding array, and aims to reduce the sidelobe level of the distance dimension and the angle dimension of a DBF output signal and improve the precision and the angle resolution of a beam pointing angle. The method comprises the following implementation steps of constructing a space-time coding array; obtaining a digital baseband signal based on the space-time coding array; performing pulse compression on the digital baseband signal; performing Fourier transform on the signal obtainedby pulse compression; performing Keystone transform on the frequency domain signal; setting frequency domain equivalent DBF algorithm parameters; and obtaining an ultra-wideband radar digital beam forming result based on a frequency domain equivalent DBF algorithm. According to the ultra-wideband radar single-channel digital beam forming method provided by the invention, the space-time coding array is constructed, and spatial coding is carried out on the array spatial domain signal, so that the sidelobe level of the distance dimension and the angle dimension of the DBF output signal is effectively reduced, the ultra-wideband radar digital beam forming result is obtained based on frequency domain equivalence, and the precision and the angle resolution of the beam pointing angle are effectively improved.

The invention belongs to the technical field of satellite communication antennas, and particularly relates to a method for designing a slow wave structure of a CTS antenna and a VICTS antenna. Firstly, a parallel plate waveguide dispersion equation model based on a uniform rectangular comb tooth slow wave structure is established to establish a parallel-plate waveguide dispersion equation model with a uniform rectangular comb tooth structure based on horizontal radiation branching; according to the two dispersion equation models, obtaining a mapping relationship between an effective dielectricconstant of a horizontal radiation branching unit and rectangular comb tooth structure parameters and the height of a parallel plate waveguide; finally according to the VICTS antenna design requirements, choosing a variation rule, function or curve of the height of the parallel plate waveguide, and according to the obtained mapping relationship, selecting the corresponding rectangular comb toothstructure parameters under different parallel plate waveguide heights. According to the method for designing the slow wave structure of the CTS antenna and the VICTS antenna, by the nonlinear design on rectangular comb teeth which are of the slow wave structure in the VICTS antenna, while array optimization is achieved, it is ensured that parameters such as the gain of the antenna and the standing-wave ratio do not deteriorate or even are improved.

The invention discloses an anti-velocity-deception-jamming adaptive iteration estimation method, relates to the technical field of radar anti-jamming and especially relates to the radar anti-jamming adaptive iteration estimation technology. According to the method, radar emission signals, jamming signals and reception signals are utilized as prior information; for each Doppler unit, latest iterative estimation target and jamming Doppler spectrum are utilized to design optimal linear filters for the target and jamming respectively to enable the output power of each Doppler unit to be minimum, and to achieve an effect that the algorithm can identify the target and jamming simultaneously, and the target can be identified and estimated effectively under high interfering energy.

The invention discloses a substrate integrated ridge waveguide slot array broadband leaky-wave antenna which is of a symmetrical structure about an H surface. The substrate integrated ridge waveguide slot array broadband leaky-wave antenna comprises a substrate integrated waveguide and a ridge metal layer, wherein the substrate integrated waveguide comprises a lower metal layer, a lower dielectric plate, an upper dielectric plate and an upper metal layer; the lower metal layer, the lower dielectric plate, the ridge metal layer, the upper dielectric plate and the upper metal layer are overlapped in sequence; a row of side via holes is formed in each side of the ridge metal layer, and the side via holes pass through the lower metal layer, the lower dielectric plate, the upper dielectric plate and the upper metal layer in sequence; a row of middle via holes is further formed in the center line of the ridge metal layer in the length direction, and the middle via holes pass through the lower metal layer, the lower dielectric plate and the ridge metal layer (3) in sequence; the antenna can realize frequency scanning of 28 degrees to 84 degrees on the H surface, and the impedance bandwidth can reach 38%; and meanwhile, the antenna has the prominent advantages of being high in gain, low in minor lobe level, easy to machine and integrate and the like.