58results about How to "Suppression of side lobes" patented technology

The invention relates to a low-sidelobe emission directional diagram design method improving DOA estimated performance of a MIMO radar. The method comprises the following steps: setting an interesting area; ensuring column vectors of a beam space weighting matrix to satisfy pairing characteristics; ensuring signals at a receiving end to satisfy rotation invariance; constructing an optimized model of a beam space weighting matrix with directional diagram coupling characteristics, rotation invariance of the signals and equality of various array element emission powers as constraint conditions; introducing an auxiliary variable and relaxing a rank-1 constraint to be a positive semidefinite constraint through utilization of the semidefinite relaxing technology; and through utilization of an interior point method, obtaining an optimal solution of the relaxing problem; through a Gaussian randomization method, the beam space weighting matrix is solved; and DOA estimation is carried out on a target at the receiving end through the ESPRIT algorithm. The MIMO radar waveform design technology which is good in performance in the invention can raise the signal to noise ratio at the receiving end, provide an important theoretical basis and a specific realization method for raising the precision of MIMO radar angle estimation.

The invention discloses a method for sparse synthetic aperture radar (SAR) imaging on basis of echo simulation operators and relates to the technology of the synthetic aperture radars. By utilizing SAR echo characters and sparsity of an observed scene, a sparse regularization model based on an SAR echo simulation operator is established. By coalesce of a threshold value iterative algorithm of the echo simulation operator, radar imaging on a target scene in the observed area is realized. Compared with an existing sparse SAR image method based on two-dimensional observation models, the method can improve operating efficiency and lowering operating cost, and compared with a matched filtering imaging method, under a controlled condition, the method is capable of realizing imaging on the condition of being lower than nyquist rate sample, restraining sidelobe and obtaining clearer SAR images.

The invention provides an antenna device. The antenna device comprises a millimeter wave microstrip antenna, wherein the millimeter wave microstrip antenna is assembled on a shell of electronic equipment, the electronic equipment comprises a main antenna, the main antenna is arranged in the shell, an antenna gap is formed in the shell and is used for radiation/receiving of a radio frequency signal by the main antenna, the millimeter wave microstrip antenna comprises a plurality of unit antennas, the plurality of the unit antennas are arranged at intervals, and the plurality of the unit antennas and the shell are arranged at an interval and are arranged in the antenna gap in an array way. Compared with prior art, the antenna device provided by the invention has the advantages that the millimeter wave microstrip antenna is arranged in the antenna gap for radiation/receiving of the radio frequency by the main antenna, so that independent gap opening on the millimeter wave microstrip antenna is prevented, the same antenna clearance region can be shared with the main antenna, the design space of the millimeter wave microstrip antenna is saved, and the space utilization ratio is improved; and meanwhile, the radiation bandwidths of the unit antennas can also be effectively expanded, the gain is improved, the side lobe is suppressed, and the radiation efficiency of the antenna device is further improved.

The invention discloses a forward-looking radar imaging sea-surface target key point detection and recognition method. The method includes the steps that radar echo data are quantized into a gray scale image; a region of interest is extracted from the gray scale image, partition is performed, and a target region partition image is obtained; the radar echo data and the region of interest of the image are used, and a target region peak point information matrix is obtained; information merging is conducted on the target region partition image and the target region peak point information matrix, the number K of peak points in a target region in a merging result is obtained through counting, the previous K peak points are selected and serve as target effective peak points and form a target effective peak point image in a binaryzation mode, target axial features are extracted, and a target position is determined; the center of gravity of target energy is calculated and serves as the target key point. According to forward-looking radar target features, multiple mode identification methods are used comprehensively, the inherent features of a target can be reserved, meanwhile interference factors such as artifacts and side lobes can be restrained, and the recognition accuracy and the positioning precision of radar imaging sea surface target key points are improved.

The invention provides a metal plate micro-defect detection method based on nonlinear Lamb waves. The metal plate micro-defect detection method comprises the following steps of: S1, acquiring a phasevelocity frequency dispersion curve and a group velocity frequency dispersion curve of a metal plate; S2, acquiring an excitation frequency, Lamb waves of a specific mode and an incident angle of theLamb waves of the specific mode as model parameters according to the phase velocity frequency dispersion curve and the group velocity frequency dispersion curve; S3, deriving a relative nonlinear coefficient beta' according to the Lamb waves of the specific mode in the S2, wherein the relative nonlinear coefficient beta' is used for representing the depth of a defect; S4, establishing a nonlinearultrasonic test system according to the model parameters; and S5, testing the metal plate according to the nonlinear ultrasonic test system established in the step S4, judging whether the relative nonlinear coefficient beta' is reliable or not, and if so, representing the defects of the tested metal plate by utilizing the relative nonlinear coefficient beta'. According to the metal plate micro-defect detection method, the relative nonlinear coefficient beta' represents the defects of the tested metal plate, the defects of the metal plate can be effectively represented, and the detection precision is improved.

The invention discloses a broadband polarization and phase control array based on a birefringent super-surface structure. The broadband polarization and phase control array comprises a substrate, a metal reflection film, a medium layer, a cross sub-wavelength optical antenna unit, a birefringent phase control super-surface structure unit and a birefringent phase control super-surface structure array. According to a reasonable design, the birefringent phase control super-surface structure unit has a birefringent effect and a phase control function, and under incident conditions of circularly polarized light, the reflected light further has polarization control and phase control functions of space sub-wavelength resolution; and with respect to the circularly polarized incident light, the birefringent phase control super-surface structure units are arranged to form a birefringent phase control super-surface structure array according to the needed space polarization and phase distributionin order to obtain a special optical field with any polarization and phase distribution. Moreover, the birefringent phase control super-surface structure unit and the birefringent phase control super-surface structure array have wide operating wavelength ranges.

The invention discloses a liquid metal spiral antenna. The liquid metal spiral antenna is characterized by comprising a medium support body, a spiral radiation body, a feed matching body, a grounded panel and a radio frequency coaxial connector, wherein the medium support body is of a conical frustum structure arranged on the grounded panel, the feed matching body is attached to the lower portion of the outer wall of the medium support body, the radio frequency coaxial connector comprises an outer conductor and an inner conductor, the outer conductor and the inner conductor are arranged coaxially, the outer conductor is connected with the grounded panel, the inner conductor is connected with the feed matching body, the spiral radiation body comprises a lead-angle-variable spiral tube and liquid metal contained in the spiral tube, and the initial end of the spiral tube is attached to the feed matching body and wound spirally along the outer wall of the medium support body to form a cone. The spiral antenna is made reconfigurable, and the bandwidth of the liquid metal spiral antenna is larger than that of a solid metal antenna of the same structure and size.

The key point of the ultrasonic phased array technique is the control of phase difference (time delay); all multi-phased control effects are based on phased time delay such as dynamic focusing and deflection of acoustic beams, forming of digital acoustic beams and the like, which depend on the realization of phased time delay; the precision of the phased time delay directly affects the whole performance of an ultrasonic phased system; the invention provides a novel method used for phase fine regulation; the method sufficiently utilizes the advantage of waveform motivation type, and adopts the method of digital waveform phase difference to realize fine delaying of phased emission, thus improving the phased emission delaying resolution. The digital waveform phase difference is the phase difference of digital waveforms of the same frequency memorized in waveform SRAM of different passages; and the digital waveform data is changed into analog excitation signal after D/A conversion and the digital waveform phase difference is converted into the phase difference of the analog excitation signal.

Provided is a method for suppressing SAR image sidelobe based on wavelet space apodization. The method includes the steps of two-dimensional wavelet decomposing in real and imaginary parts for complex image imaged, space apodization suppressing for each sub-channel obtained by decomposing the two-dimensional wavelet, the data in the real and imaginary parts are acquired by wavelet reconstructing for the sub-channels data after sidelobe suppression, the space apodization sidelobe suppressing for the real and imaginary parts separately, and eventually the complex image based on the wavelet space apodization sidelobe suppression is synthesized.

The invention discloses an SAR image minor lobe suppression method based on module value constraint. The method mainly solves the problem that strong target points in an SAR image shelter weak target points adjacent to the strong target points. The method comprises the implementation steps of 1, inputting the SAR image and acquiring a real part image I and an imaginary part image Q; 2, calculating the azimuth weight of the real part image I and acquiring an azimuth real part image I1; 3, calculating the distance weight of the azimuth real part image I1 and acquiring a distance real part image Ic; 4, calculating the azimuth weight of the imaginary part image Q and acquiring an azimuth imaginary part image Q1; 5, calculating the distance weight of the azimuth imaginary part image Q1 and acquiring a distance imaginary part image Qc; 6, synthesizing the distance real part image Ic and the distance imaginary part image Qc into the final SAR image. According to the method, minor lobes of the SAR image can be better suppressed, the width of a main lobe is decreased, and the capacity of detecting the weak target points in the SAR image is improved. The method can be applied to target recognition.

The invention belongs to the technical field of lasers and discloses a spatially insensitive focusing alignment method and system for dual-beam pumping-detection. A transmissive positive-cone lens system is adopted in combination with a beam reducing system for performing beam shaping on one path of pumping light separately; by designing parameters of a beam shaping system, a central light spot ofa specific size and a Bessel beam with extended depth of focus are obtained; a polarization beam splitting prism and a lambda/4 wave plate are used for detecting feedback signals for one path of detection light; by inserting a 45-degree dichroic mirror, the detection light and the pumping light are coaxially coupled into a focus lens to achieve spatial overlapping of focal areas. The cross sections of Gauss-Bessel beams obtained by means of beam shaping can be kept unchanged, and the depth of focus can be extended to a long range from 100 micrometers to 100 millimeters, so that the strict adjustment requirement for focus alignment on a sample surface in the pumping-detection is greatly lowered.

The invention discloses a microwave photon radio frequency phase shifter based on spectrum processing and a phase shifting method thereof. The phase shifter comprises a laser source, an optical modulator, an optical fiber amplifier, a spectrum processing system, a photoelectric detector and an optical coupler. The optical amplification signal of the optical fiber amplifier is incident on the diffraction grating and is separated into a plurality of reflected light rays. Different spectral components in the plurality of reflected light rays are projected on different pixel points of each row, and the same spectral components are projected on different pixel points of each column. The laser processor modulates the amplitude and phase of the spectral component and forms a plurality of beat frequency light waves. Each optical coupler synthesizes an optical carrier wave and a first-order modulation sideband in a spectrum manner to generate an optical single sideband modulation signal. The optical single sideband modulation signal is subjected to beat frequency in a photoelectric detector to generate a radio frequency signal. The phase noise of the photon radio frequency phase shifter iseffectively restrained, the photon radio frequency phase shifting function is achieved, scanning at any angle can be achieved, flexibility is high, reconfiguration is achieved, and the phase shifter is suitable for large-scale phased array radar.

The invention provides a high-resolution low-sidelobe deconvolution spectrum estimation method based on space-time processing, and belongs to the field of signal processing. The method is suitable forthe high-resolution power spectrum estimation of a received array signal at frequency and azimuth under the condition that the data sample is limited. According to the invention, a deconvolution algorithm is used for the multi-dimensional deconvolution operation of an array signal power spectrum with the limited length and a multi-dimensional window function power spectrum, so the method can completely eliminate the impact caused by a window function under the ideal conditions, and obtains a real power spectrum of a signal. Based on the conventional convolution technology, the method can greatly improve the frequency resolution and angle resolution of a power spectrum estimation result, can greatly inhibit the sidelobe caused by the limited length of data, provides an additional signal tonoise ratio, and provides a new idea for the multi-target detection and recognition and weak signal extraction in the array signal processing. In addition, the method is high in operability, is moderate in calculation burden, is stable in calculation result, and is very wide in application range.

The invention discloses a coding-enhanced focused ultrasound bone tissue microstructure detection method in a bone ultrasound system. The method includes the following steps: 1, adopting an ultrasound back scattering detection method, and enabling detection of a bone tissue microstructure to be equivalent to measuring of average scatterer interval according to a Faran cylinder model; 2, adopting a high-frequency single-array-element focused transducer, utilizing a complementary Golay sequence pair to excite an ultrasound transducer to emit time width signals, taking the emitted signals as a matched filtering function perform decoded compression on echo signals, and utilizing decoded compression back scattering signals to estimate the average scatterer interval, wherein the Golay sequence pair is adjustable in length. By the method, during measuring of the bone tissue microstructure MSS by utilizing ultrasound back scattering technology, ultrasound resolution ratio is increased, and influence, of sound attenuation, on measuring results is reduced. The coding-enhanced focused ultrasound bone tissue microstructure detection method is applied to the field of biomedical detection and tissue characterization.

The invention provides a center-symmetric acoustic vector circular array fast spatial spectral compression super-resolution orientation estimation method. The method comprises the steps that sensors on the upper and lower half rings of an acoustic vector circular array are arranged in a specific order respectively, and acoustic signals are collected to construct a satisfactory steering vector; then based on the average sound intensity anti-noise principle of acoustic vector sensors, a covariance matrix is constructed by using the method of combined processing of sound pressure and vibration velocity, which reduces the dimension of a vector matrix steering vector matrix and improves the anti-noise ability; a new spatial spectrum function is constructed from the spatial spectrum of a real source and a virtual source 180-degree away from the real source to carry out half-spectral search to compress the spatial spectrum of the acoustic vector circular array; and finally, through the discriminant constructed in the invention, the true sound source orientation is quickly determined. According to the invention, the spatial spectrum of the vector circular array is compressed for the firsttime, which greatly improves the operation efficiency while ensuring high resolution; and fast and efficient super-resolution orientation estimation of the acoustic vector circular array is realized.

The invention discloses a multi-phase center distribution design method and a multi-phase center distribution design device for a circular scanning ground-based SAR (Synthetic Aperture Radar). The method comprises the following steps: acquiring a bandwidth frequency ratio parameter and a phase center quantity parameter of a circular scanning ground-based SAR; determining the lowest sidelobe data of a point spread function of the circular scanning ground-based SAR according to the bandwidth frequency ratio parameter, the phase center number parameter and a pre-established phase change diagram,the phase change diagram being pre-established according to the point spread function of the circular scanning ground-based SAR and a grid space parameter; according to the lowest sidelobe data of thepoint spread function, determining spectrum distribution data of the circular scanning ground-based SAR; and designing multi-phase center distribution of the circular scanning ground-based SAR according to the spectrum distribution data and the observation geometry. According to the invention, the problem of high sidelobe in imaging is effectively solved, and the imaging quality is ensured.

The invention relates to a signal amplitude and phase measurement method based on three DFT plural spectral lines and belongs to the signal parameter measurement technology field. The method is characterized by comprising the steps of carrying out the windowing treatment on a sampling signal and then carrying out the DFI conversion; searching three nearby plural spectral lines corresponding to the frequency of a signal to be measured; based on the plural value of the three spectral lines, through a directly derived formula or an approximate polynomial formula, calculating an intermediate parameter, wherein a final amplitude measurement result is equal to a mould of the intermediate parameter and a final phase measurement result is equal to the sum of the argument of the intermediate parameter and one half of Pi. By adopting the method in the invention, the calculation is performed directly based on a spectral-line complex number. Meanwhile, the mould of each spectral line is not needed, so that the calculated quantity is reduced. Moreover, the calculation process can offset the sidelobe interference of another frequency signal, so that the measurement precision is increased.

The invention relates to an amplitude modulation type radial polarization illumination confocal microimaging method and device. The device comprises a laser, a collimation and beam expansion system, apolarization state conversion system, an amplitude type spatial light modulator, a first beam splitter, a scanning galvanometer system, a high-numerical-value aperture objective lens, a sample, a white light source, a three-dimensional displacement table, a second beam splitter, a CCD camera, a cylinder lens, a size-variable confocal pinhole and a photomultiplier. Apodization of the sidelobe is performed by changing the size of the confocal pinhole to solve a problem of a large sidelobe; and the pinhole size is optimized according to the actual focusing spot size, so that noise is suppressed.With the method, the confocal microscopic imaging resolution can be effectively improved. Moreover, the system structure is simple, and no binary optical device needs to be introduced.

The invention discloses an LTCC filtering dielectric resonant antenna, and the antenna comprises a low-temperature co-fired ceramic substrate and a dielectric resonator; the low-temperature co-fired ceramic substrate adopts three layers of substrates, and an integrated waveguide resonant cavity power divider based on an LTCC substrate is located at the bottommost layer; the dielectric resonator isa 2*2 array antenna, and the dielectric resonator is fixedly arranged at the top of the low-temperature co-fired ceramic substrate; the epsilon r of the low-temperature co-fired ceramic substrate is5.9, and the loss tangent is 0.0023; the thicknesses of the three layers of cavities of the low-temperature co-fired ceramic substrate are sequentially as follows from bottom to top: h1 = 0.58 mm, h2= 0.19 mm and h3 = 0.38 mm, and the thickness of the metal layer of the low-temperature co-fired ceramic substrate is 10 [mu]m. According to the filtering medium resonant antenna, the LTCC three-dimensional integration technology is fully utilized, the size is effectively reduced, the overall size is 12mm, 12mm and 2.4 mm, and the filtering medium resonant antenna is suitable for being applied toa 5G wireless communication system and a feed source of a transmission and reflection antenna array.

The invention provides an intelligent monitoring method for leakage of a natural gas pipeline. The method comprises the following steps: collecting an audio signal during operation of the natural gas pipeline by using a sound array; performing imaging positioning on the audio signal by using a beam forming algorithm based on symbol coherence and feature space decomposition; obtaining an audio frequency spectrum in the direction of direction of arrival through a linear constraint minimum variance algorithm; and carrying out standardization processing by taking the frequency spectrum formed by the beam as a characteristic, and inputting the characteristic into a pre-trained natural gas leakage diagnosis model to obtain a pipeline condition. According to the intelligent monitoring method for leakage of the natural gas pipeline, a beam forming algorithm based on symbol coherence and feature space decomposition is used, side lobes are better restrained, the acoustic imaging resolution is better improved, high-contrast and high-resolution acoustic imaging and accurate positioning can be carried out on a leakage source on an on-site image, the accuracy of natural gas leakage diagnosis is effectively improved, and meanwhile, the workload and troubleshooting difficulty of operators on duty are greatly reduced.

The invention discloses an outer radiation source radar direction-finding method and system. The direction-finding method comprises: obtaining a locus function of rotation around a rotation center bya receiver, wherein the receiver rotates around the rotation center in a spiral manner; determining a slope distance process function of a to-be-detected target according to the locus function, wherein the slope distance process function is a process function of an outer radiation source signal reaching the receiver through the to-be-detected target; determining an echo signal according to the slope distance process; constructing a signal identification matrix of a to-be-detected target identification area; and obtaining an azimuth angle of the to-be-detected target according to the echo signal and the signal identification matrix. By employing the direction-finding method and system, the side lobe can be suppressed, the direction-finding effect is improved, the 3dB width can be reduced, and the direction-finding performance is enhanced.