In this paper, a number of double-layered microwave integrated circuits (MIC) have been designed and analyzed based on a developed finite-difference time-domain (FDTD) solver. The solver was first validated through comparisons of the computed results with those previously published throughout the literature. Subsequently, various double-layered MIC printed on both isotropic and anisotropic substrates and superstrates, which are frequently encountered in printed circuit boards (PCB), have been designed and analyzed. It was found that in addition to protecting circuits, the added superstrate layer can increase freedoms of design and improve circuit performance, and that the FDTD is indeed a robust and versatile tool for multilayer circuit design.

A new type of interaction circuitry for a broadband gyro-TWT is presented in this paper. A method for the analysis of dispersion characteristics of a periodic structure, which is composed of conducting posts in a rectangular waveguide, is presented. This method utilizes a mode matching technique and equivalent circuit model. The calculated and measured results demonstrate that this periodic structure could be utilized for the interaction circuit of a wide band Gyro-TWT.

An analytic design formula is proposed for a TEM mode dielectric bandpass filter with attenuation poles at desired frequencies in the stop band. In order to sustain the constant ripple in the passband due to attenuation poles, the initial resonant frequencies of the various resonators adopted in a filter with attenuation poles are newly calculated. The proposed design theory is verified by designing various bandpass filters with attenuation poles in the stop band.

A balanced single side-band (SSB) mixer employing a sub-harmonic configuration is designed for up and down conversions in K-band. The designed mixer uses anti-parallel diode (APD) pairs to effectively eliminate even harmonics of the local oscillator (LO) spurious signal. To reduce the odd harmonics of LO at the RF port, we employ a balanced configuration for LO. The fabricated chip shows 12$\pm$2dB of conversion loss and image-rejection ratio of about 20dB for down conversion at RF frequencies of 24-27.5GHz. As an up-conversion mode, the designed chip shows 12dB of conversion loss and image-rejection ratio of 20 ～ 25 dB at RF frequencies of 25 to 27GHz. The odd harmonics of the LO are measured below -37dBc.

In this paper, the optimal design of a novel microstrip directional coupler with a grooved housing for high directivity characteristic is presented. It will be shown that the high directivity of the microstrip coupler can be achieved simply by attaching an optimized housing structure. over the microstrip, which is much easier to fabricate than other conventional types. The dimensions of the proposed structure are maximized by using (1+1) evolution strategy (ES) combined with the deterministic algorithm. To improve the effectiveness of the results, efficient optimization procedures suitable for the model are proposed. From these results, it is determined that the proposed structure indicates an improved directivity. The optimized results are verified by full wave analysis at the center frequency of 850MHz.

Since the manufacturing process in the LTCC process does not allow solid ground planes between ceramic layers to isolate the signal lines, the buried ground should be realized as a meshed ground plane. Both characteristic impedances of the signal lines and couplings between different signal layers are influenced by the properties of these meshed planes. In this paper, we propose a new analysis method for coupling behavior between internal transmission lines, which are isolated by the buried meshed-ground planes. The coupling behavior between layers isolated by meshed-ground planes is investigated by the coupled-transmission line model for the isolated layers. The coupling factors between isolated lines with the meshed-ground are extracted by 2-D FEM calculations.

In this paper, a ceramic antenna and diplexer are designed for dual-band handset ap plications. Basically, the antenna is designed by using the meander line configuration. The diplexer presented in this paper is composed of both low- and high-pass filters. We have designed the low- and high-pass filters with attenuation poles to improve the attenuation performances of the diplexer. The attenuation poles are located at each rejection frequency region so as to improve the shrinkage characteristic of the diplexer. In order to accomplish the volume effectiveness, the antenna and the diplexer have been designed and fabricated in a multi-layer structure. The diplexer designed with a multi-layer structure has inductors and capacitors, which are implemented by LTCC (Low Temperature Co-fired Ceramics) process technique. Design of the multi-layer antenna and diplexer has been achieved by employing the full 3-D EM simulation. The designed antenna and diplexer offer excellent return loss and broadband performances with highly isolated rejection performance.

A new design technique of fabricating 40 GHz up-converter modules for digital microwave radios has been developed. The design of the up-converter module is based on unit circuit blocks, which are to be characterized using a special test fixture. The complete module design may be as simple as a cascade layout of these unit circuit blocks. Also, the 40 GHz up-converter module employs a new microstrip-to-waveguide transition and a tapped edge-coupled filter, which are less sensitive to fabrication tolerances.

In this paper, new design equations based on the pole-zero analysis for multi-layered interdigital stripline linear group delay bandpass filter with tap input ports are presented. As a design example, a four-pole group delay filter with center frequency of 2.14GHz, bandwidth of 160MHz, and group delay variation of $\pm$0.1nS for LTCC technology or multilayered PCB technology is designed. In the design process, it is not necessary to simulate the entire structure, as the simulation of half structures is sufficient. Good results can be attained after the optimizing process was performed three times using the proposed equations and a commercial EM simulator.

This paper presents a new active antenna consisting of a microstrip patch for the passive radiator, a mixer for frequency conversion, a voltage controlled oscillator (VCO) and a phase detector for phase control. The microwave signal frequency has been converted into intermediate frequency (IF) on the antenna elements by the mixer. The active antenna consists of two ports, the IF port has a transmitted IF signal via power combined to the baseband and the dc control port is under the control of the phase-detector. The input voltage of the VCO is controlled by the phase detector. The scan range of the array is determined by the phase detector and the VCO and is obtained between 30$^{\circ}$ and - 30$^{\circ}$

Spurred by the constant pressure to achieve miniaturization, researchers have designed many different types of compact antennas. One such type is the slotted patch antenna used for dual band operation. In this paper, we propose a novel method of selecting the feeding point of the antenna, which results in superior antenna performance in terms of return loss. Computer simulations verify the validity of the proposed method.