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.

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.

In this paper the frequency dependence and focusing performance in focal plane of a diffractive lens is analyzed by FDTD method at millimeter wavelengths. Binary lens and four-level lens are onsidered. The field distribution on the focal plane of the diffractive lens for the incident wave at different frequency is presented, which shows the frequency dependence and focusing performance of the lens.

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.