4 results about "Bessel function" patented technology

This invention discloses a method and system for measuring the frequency response of an electro-optic modulator based on a spectral analyzer. The system includes a laser, a 95:5 single-mode fiber splitter, an optical power meter, an electro-optic modulator, a control power supply, an RF signal generator, and a spectral analyzer. The measurement method includes the following steps: calculating a calibration factor to correct optical power drift through optical path splitting, driving the modulator by applying several discrete single-frequency RF points, and measuring the carrier power P0(f) using the spectral analyzer. i ) and the first-order sideband power P1(f i ), and determined by the power ratio R(f) i )=10 (P1‑P0) / 10 Combining the Jacobi–Anger expansion / Bessel function relation, the phase modulation index β(f) is solved by inverse solution. i Then, the phase transfer function H(f) at each frequency point is calculated and fitted. i The continuous frequency response S of the modulator is obtained. 21 This invention simplifies the testing process, reduces reliance on high-speed photodetectors and vector network analyzers, and enables high-precision electro-optic response testing of electro-optic modulators at high frequencies.

The application discloses a non-circular sparse array DOA estimation performance evaluation method based on information theory, which comprises the following steps: firstly, a multi-dimensional probability density function (PDF) of a received signal is constructed, a joint PDF of the received signal and DOA and a DOA posteriori PDF are derived through information theory, and a system DOA information quantity is obtained by simplifying the DOA posteriori PDF with a Bessel function; then, a DOA posteriori PDF of given noise is derived, and a DOA information approximate upper limit is obtained by simplifying the DOA posteriori PDF with a Taylor expansion; finally, a DOA estimation performance index entropy error is obtained by using the posteriori differential entropy; the application builds a non-circular sparse array system DOA information theory framework based on information theory, in actual signal processing, the entropy error of a parameter can be calculated only by estimating the posteriori PDF of the parameter, and a performance limit independent of an algorithm is provided; in addition, it is found through simulation that the DOA information quantity approaches the DOA information upper limit under a high signal-to-noise ratio, and the entropy error approaches the Cramer-Rao limit, thereby verifying the rationality of the index.

This invention discloses a method for spatial domain filtering and spectrum correction of broadband signals in the mode domain of a circular array. The method involves performing a Discrete Fourier Transform (DFT) on the received time-domain data to obtain the array element frequency domain data. The broadband signal frequency band data is then extracted and subjected to a Circular Fourier Transform (CFT) to obtain the sub-band data in the mode domain. The distance between frequency points and the zeros of the Bessel function within the broadband signal frequency band is calculated, and a zero-point correction method is used to replace the frequency points. Sub-band frequency points in the mode domain are selected according to the correction results. The sub-band weighting vectors for mode domain beamforming are obtained according to the minimum variance and distortion-free criterion for data independence, and the beamformer is calculated. The sub-band data in the mode domain are weighted and summed based on the weighting vectors of each sub-band to obtain the beam output frequency domain data. Zeros are padded at all frequency points except for the broadband signal frequency domain data. An Inverse Fourier Transform is then performed on the beam output frequency domain data to obtain the beamforming output data sequence. This invention effectively preserves the original spectral components of the broadband signal while improving the signal-to-noise ratio.

The application provides a kind of GIL loss fast calculation method considering electromagnetic space distribution, relate to high voltage gas insulated transmission technology field, solve the problem that existing GIL loss calculation method is difficult to consider physical rigor and calculation efficiency.The method, the coaxial hollow cylindrical structure electromagnetic field model of GIL is established, and then the diffusion equation of time-harmonic electromagnetic field is constructed and the boundary condition is set;Solving time adopts the linear combination of first kind Bessel function and second kind Bessel function as the general solution form, determines the undetermined coefficient, obtains the magnetic field intensity and electric field intensity distribution expression in the conductor region and shell region;Finally, based on the Poynting theorem, the analytical expression of unit length conductor ohmic loss and shell eddy current loss is calculated and derived, and the conductivity parameter is embedded in the form of explicit function of temperature, that is, the GIL loss calculation is completed.The calculation realized by the application can provide a clear, differentiable and traceable heat source coupling interface for the heat network model.