A novel diffraction lens quasi-optical monopulse antenna/feed is proposed and analyzed using finite-difference time-domain (FDTD) method. The structure consists of diffraction lenses, a quasi-optical sum- difference network, matching lenses and horns connecting waveguide. This antenna structure is novel, low-loss and compact and may be designed to be polarization-independent. Owing to its low absorptive loss and relative easy for manufacturing, this monopulse antenna/feed structure is suitable for millimeter wave and submillimeter wave application. The parameters of the structure are selected to some extent to get better performance. Calculation results are presented to show its properties.

A design method for diffractive/refractive dielectric lens antennas working at millimeter wave band is presented in this paper. One surface of this kind of lens antenna is refractive and the other is diffractive. The refractive surface is used to control the amplitude distribution of the electromagnetic wave and the diffractive surface is used to adjust the phase distribution of the electromagnetic wave. The side lobe level of this kind of lens antenna is low due to the proper distribution of the field amplitude controlled by the refractive surface, and the thickness of the lens is very thin due to the use of the diffractive surface. Two design examples of the diffractive/refractive lens antenna are given, and their radiation patterns (fed with the corrugated horns) are computed using axially symmetric FDTD algorithm and presented in this paper.

In this article, an improved iterative arithmetic of the symmetric successive over-relaxation preconditioning biconjugate-gradient algorithm (ISSOR-PBCG) is utilized to solve the 3D edge FEM equations derived from the time-harmonic electromagnetic-field boundary value problems. Several typical structures have been analyzed, and the computation time is compared with that of other algorithms such as biconjugate-gradient (BCG) algorithm and the conventional symmetric successive over-relaxation preconditioning biconjugate-gradient algorithm (SSOR-PBCG). The CPU time saved using the ISSOR-PBCG algorithm is nearly 27% and 65.5%, as compared with that using the SSOR-PBCG and the BCG algorithm. It can be seen that the ISSOR-PBCG algorithm is efficient for edge FEM equation sets derived from large-scale time-harmonic electromagnetic-field problems.

A waveguide magic tee at W band is analyzed exactly and developed. The analysis approach is a combination of the mode expansion method and finite element method,whic h is based on the weak form of Helmholtz equation. Mode expansion instead of PML (Perfectly Matched Layers) is used to truncate the computing space of finite element. A magic tee at W band (75∼110 GHz) with the structure,whic h is easy for manufacture,is developed. Calculated results are presented and compared to those in experiments. Agreement has been observed. A sensitivity analysis is carried out, which shows the influence of the tolerance of manufacture on the performance of the magic tee. And the power carrying capacity of the designed magic tee is also evaluated.

In this paper, focal field of reverse-microscope imaging system at millimeter wavelengths is analyzed with ray-tracing method and Stratton-Chu vector diffraction integral formula. Calculations have been compared with experiments and agreement is found. Lens profile is optimized to reduce aberrations and extend field-of-view of the imaging system. The numerical results are presented to show the field distribution of the optimized imaging system.

It is a difficulty problem to measure permittivity of a dielectric material accurately whose permittivity is very close to unit. Open cavity method and interferometer method have been used in the past. In this paper, the sensitivity of these two methods to a small disturbance of permittivity is simulated and compared. Based on the simulation a new approach combining merits of the open cavity method and the interferometer method is proposed, and its advantages are described.

Finite-difference time-domain (FDTD) full-wave analysis of several waveguide junction circulators with full-height ferrite posts of arbitrary shapes is presented. The structures contain T-junction, irregular T-junction, Y-junction, and Y-junction with a bend. Two ferrite shapes of interest are studied, including circular cylinder and triangular post, and the performance of the circulators is presented. Calculation results of the waveguide-junction circulators with circular ferrite post and triangular ferrite post obtained by the present analysis are compared with those from the field-matching and finite-element methods, respectively, as a reference, and better agreement is found in this study.

An electromagnetic beam that is not the solution to the paraxial wave equation but is the solution to Maxwell's equation is simulated directly by the finite-difference time-domain method. Electrical and magnetic field components of the beam are presented graphically. Then the diffraction of the electromagnetic beam pulse by an aperture in a conducting screen is analyzed. The fraction of the beam power through the aperture is defined and calculated. The fields in the time domain near the aperture, which show the diffraction by the aperture, are presented graphically.

Field structures of waveguide Y -junction circulators containing irregular shaped ferrite material,suc h as Y -junction with partial-height cylinder/triangle ferrite posts and metal step impedance transformer, Y -junction with a ferrite sphere, and dual higher order modes circulator,whic h are classified as different junction resonance modes, are depicted to illustrate the circulating process. The analysis method used is a combination of the mode expansion method and finite element method,whic h is based on the weak form of Helmholtz equation. Calculated results (return loss,insertion loss and isolation) of these structures are shown and compared respectively to those in literatures. Consistencies have been observed.

This paper is aimed at analyzing the focal field of some axially-symmetric diffractive lenses with small F-number and electrically large radii which are used in millimeter wave focal imaging, especially for the case of a plane-wave incident onto the lenses obliquely, by using the method of moments (MoM). The analysis of a diffractive lens whose radius is as large as 78.3λ can be performed using appropriate pairs of basis functions and test functions in the MoM, and specific integration methods are adopted to integrate the oscillatory integrals which occurr in the MoM when it is applied on a body of revolution (BOR) for which the rotational symmetry of the BOR has been utilized. Comparison of the simulated results with the experimental data shows that the simulation is valid. An imaging experiment is carried out to show the ability of diffractive lens in a millimeter imaging system.