Millimeter-wave Techniques: Theory, Algorithms and Methods

Abstract

The goal of book is to present the theory, algorithms and methods to design the millimeter-wave Gyrotron beam-shaping antenna system (of good metal conductor, e.g., of aluminum or copper) to shape four roughly Gaussian beams of different frequencies into one specified high-quality Gaussian beam at the output of the mirror system. The input beams are from a quasi-optical launcher which converts each of the following mode/frequency pairs into a roughly Gaussian form: TE21,6 (107.5 GHz), TE22,6 (110.0 GHz), TE24,7 (124.5 GHz) and TE25,7 (127.5 GHz). Each of the output beams from the launcher is to be converted into a Gaussian beam with specified waist radius and with as high a coupling coefficient as possible to an ideal Gaussian beam. A design optimization procedure for the mirror system is developed and applied to the case of the four mode/frequency pairs above. The frequencies are specified because they are of interest to General Atomics. The 127.5 GHz frequency is the ITER start-up frequency. In addition, the design obtained is tested by simulation for two other mode/frequency pairs, TE23,6 (112.9 GHz) and TE23,7 (121.5 GHz). The theory, algorithms and methods required in such multi-mode beam-shaping mirror system designs are investigated. These include (1) the iterative phase retrieval technique for phase retrieval from measured magnitude-only data; (2) a theoretical formula developed to evaluate the validity of the image theorem approximation in the cylindrical geometry used during the mirror system design; (3) the Taylor-FFT algorithm developed in this research work for fast computation of the electromagnetic wave propagation and scattering; (4) the newly developed phase gradient phase correction method for mirror surface correction; and (5) the least mean square optimization method, proposed for multi-mode mirror design. Based on our theory, algorithms and methods, a coupling coefficient to the target Gaussian beam greater than 99.99% is achieved for the single-mode designs and an average coupling coefficient up to 99.50% within the window aperture of 88 mm diameter for the multi-mode design. The design has been successfully verified the Method of Moments software Surf3D.

Computational Electromagnetics for Efficient Control Design of Massive MIMO and Beyond

“…For continuous MIMO antenna arrays of infinitesimal small unit cell, the dyadic function L reduces to the dyadic Green's function G e given as follows [21],…”

“…( 5) is that, it requires the inverse of the dyadic function L, which means N 3 computation effort. However, due to the spatial translation invariant of the convolution, FFT and Inverse FFT (IFFT) can be used to accelerate the computation as follow [21], [22] J…”