A new method of S-parameter extraction from the FDTD in analyses of microstrip circuits is proposed. It only uses the Ex-field component parts in three selected transverse cross sections of the transmission line under approach. The reflection coefficient is extracted from a single run of the FDTD. Neither prior knowledge of the line nor any computation of the derivative of the electric and magnetic fields is needed. The proposed new method is directly applicable to analyses of the discontinuities of microwave transmission circuits.

This paper proposes a new way to optically control a millimeter-wave oscillator. In contrast to previously reported optically controlled oscillators, which usually give a negative frequency variance response to the controlling light signals, the method proposed here can produce a positive frequency variance. In our experiments, an increasing optically controlled frequency variance of about 150 MHz has been observed in a Ka-band Gunn oscillator.

A new source which has a bandpass spectrum has been proposed for the FDTD analysis of waveguide discontinuity. Compared with the Gaussian pulse source, a significant computational time saving is achieved by using the new source. The new source can filter out all undesired frequency components. With this excitation scheme, the whole system of investigation can operate under the predesigned frequency band, and stability can be quickly reached in the FDTD calculation. In addition, by using the new source, the FDTD calculation can prevent the effect of unabsorbed frequency components which often requires a sufficiently large computation region. To demonstrate the validity and efficiency of this source scheme, numerical results for a rectangular waveguide containing a dielectric layer are given, compared with the data of Gaussian pulse excitation that have been published.

A simple and effective method is given for the accurate extraction of the reflection coefficient in a discontinuity simulation of the rectangular waveguide by FDTD. It uses only the values of Ex-field on two adjacent cross sections of the waveguide under investigation. Neither a presolution of a related uniform waveguide nor the monomode transmission is needed, and a reflection coefficient is extracted from a single run of FDTD. The reference planes at which the voltage time records of the dominant mode are taken can be chosen very close to the discontinuity. This results in a substantial savings in CPU time and memory storage requirements.

A new kind of waveguide filters is presented in a Ka-band. It is based on the principle of EBG of the single Metal patch and its images on the waveguide walls. The new proposed filter is consisted of two dielectric layers printed single metal patch as shown in fig. l. To prove the validity of the new kind of filters, both results of the FDTD programmed by our self and the software CST are presented and compared. Numerical examples are presented with different sizes of the patch and the permittivity of the dielectric layers in a Ka band rectangular waveguide.

A UWB Antenna with a trapezoid metal Plank and Grounded Metal is presented. It gives a ultra-wide band from 2GHz to 25GHz in which the /sll/is under -10dB.

Some studies of compress of data of FDTD are presented in this papers. It is shown that the artificial attenuation(ART) is effective to improve the calculation efficiency, in the case where the resonate circuits with dielectric layer are included.

A new part time terminated band-pass source scheme is presented for Finite Difference Time Domain (FDTD) calculations in electromagnetic simulations. This source scheme has the band-pass spectrum and the exciting time is much shorter than the ones presented earler[t] and significat CPU time is saved under the new exciting source.

给出了开放微带不连续电路的三端口网络描述。将微带电路向空间的辐射作为一个端口来处理， 成功地消除了由于忽略电路的空间辐射效应引入的电路数字模拟误差。利用时域有限差分法(FDTD)一次运算就可得出三端口网络的S 参数矩阵的各元素， 而无需任何预处理， 大大地节省了CPU时间。实际计算与已发表的数据吻合得很好， 表明文中给出的三端口定义是合理有效的。此三端口微带电路的定义可容易地推广到其他非屏蔽传输线电路的分析， 可广泛用于电磁兼容分析、微带天线及其他开放传输线电路的CAD 技术中。

A Numerical Analysis of the Effects of the Packing of Microstrip Devices with Photonic Bandgap Structure is presented by the Finite Difference Time Domain method in this paper. A microstrip with an asymmetric metal bandgap structure which shows a extra-wide stop band is numerically analysed when its package is changed.