Research On APSK Modulation And LDPC Coding Based On Power Line Communication

High-resolution images have great application significance in space observation and astronomical observation.The comprehensive aperture imaging technology using a certain form of sparse aperture array is an important technology to solve high-resolution and large-aperture imaging.Synthetic aperture imaging technology is to synthesize multiple small-aperture lenses for co-phase imaging,and its resolution is equivalent to the spatial resolution of a large-aperture lens.The three key technologies of the imaging system are: array design and optimization,phase error detection and correction,image reconstruction and restoration.Among them,the synthetic aperture can be used as an equivalent single aperture,and the adjustment error caused by the arrangement among the sub-mirrors must be eliminated.The adjustment error mainly includes the translation error and tilt error between the sub-mirrors.This paper focuses on the detection and correction of phase errors in three key technologies,and proposes a wavefront detection technology based on the phase difference method to detect aberrations caused by system installation errors.The adjustment of the integrated aperture system is usually based on one of the sub-mirrors,and the other sub-mirrors are separately adjusted according to the reference position,so the installation errors of the sub-mirrors can also be corrected separately.In this article,we take the adjustment error compensation of the sub-mirrors as an example,and use the adjustable phase plate developed by the research group to perform phase compensation on the translation error in the adjustment error of the sub-mirrors and the defocus aberration introduced by the lens deviating from the ideal position.Inquired.The main research contents of the paper are as follows:1.It describes the research background and significance of the subject,investigates and compares several wavefront detection techniques commonly used in adaptive optics,and finally determines to use the phase difference algorithm as the wavefront detection method The necessity of the method research briefly introduces the current status of the phase difference method at home and abroad.The principle of optical synthetic aperture imaging and the related theoretical knowledge of detection and adjustment error based on phase difference method are introduced.2.Introduces the principle of optical synthetic aperture imaging,regards the imaging system as an invariant linear system,and describes the imaging characteristics of the system with coherent transfer function(coherent illumination)or optical transfer function(incoherent illumination);The basic theory of wavefront detection related to the difference method is to use the focal plane image and the defocused image to construct the objective function,and optimize the objective function to obtain the maximum likelihood estimate of the distorted wavefront due to the adjustment error.The numerical optimization part uses a genetic algorithm,which increases the versatility and stability of the detection of mounting errors based on the phase difference method,and avoids falling into a local minimum.3.A variety of numerical optimization algorithms are discussed.Due to the good numerical effect and rapid convergence characteristics of genetic algorithm,the genetic algorithm is selected to solve the wavefront aberration coefficient,and the research on the optical synthetic aperture adjustment error compensation technology based on phase difference method4.Using the zernike polynomial,the adjustment error of the optical comprehensive aperture is converted into wave aberration,and the optical system is introduced through the generalized optical aperture function with wave aberration.Based on the optical lens imaging system model,the computer simulation simulates the focal plane image and the defocus plane image,and establishes the objective function.Based on the principle of phase difference method,the distortion wavefront aberration coefficient caused by the adjustment error is solved.For a few percent of the wavelength,the rms error value in the accuracy test simulation verification is0.0514?.5.Using the adjustable phase plate based on the piezoelectric ceramic internal liquid column designed by the research group,an axial lens adjustment error compensation model based on the phase difference method was constructed,and the length of the piezoelectric ceramic liquid column was changed by applying a voltage,ie Change the optical path of the incident light wavefront.Since the phase modulation plate is placed parallel to the optical axis,its horizontal displacement shrinkage mainly affects the translation error in the adjustment error and the defocus aberration introduced by the lens from the ideal position.That is,the Z1 term of piston error and the Z4 term of defocus aberration in the zernike polynomial.The research results show that the accuracy of the model to compensate the piston error and defocus error caused by the installation error is about 92%,and it can be applied to the low-cost compensation of the installation error of the optical comprehensive aperture component.