Trapped image guide leaky-wave antennas for millimeter wave applications

A leaky-wave antenna is developed from a novel dielectric waveguide for millimeter wave applications. Design formulas and data are provided, and measured and computed results are presented for a prototype model.     

An Improvement Method of Matrix Converter Drives Under Input Voltage Disturbances

While the matrix converter has many advantages that include bidirectional power flow, a size reduction, a long lifetime, and sinusoidal input currents, it is vulnerable to the input voltage disturbances, because it directly exchanges the input voltage to the output voltage. The instantaneous effective power control (IEPC) method has been proposed to compensate the input voltage disturbances, in which the instantaneous effective power is kept constant by controlling input current. However, to date, no method has been proposed to maintain the stability of the system with the IEPC. The purpose of this paper is to propose a method to control the stability of the system with IEPC. First, this paper explains the IEPC theoretically. Next, a model of the system with the IEPC is developed, and stability analyses are conducted. Then, based on the results of the analyses, a stability control method for the system with the IEPC is proposed. Furthermore, the validities of the proposed method are demonstrated by simulation and experiments. Finally, a restart performance of the system after momentary power interruption is discussed. Because the IEPC does not need phase-locked-loop to detect the phase angle of the input voltage, fast restart is expected     

Experiments of device failures in a spatial power-combining array

The performance of a spatial power-combining array with device failure is investigated. Experimental results show that the array still combines the power in the broadside direction when the DC open-circuit failure occurs. Analysis of measured radiation patterns indicated that the power radiated from the patch antenna attached to the failed device is much smaller than the power radiated from other patch antennas. The effects of the chip resistor and the RF impedance of failed device are discussed     

Millimeter-wave silicon MMIC interconnect and coupler usingmultilayer polyimide technology

This paper reports our latest progress in developing low-loss and low-crosstalk silicon MMIC interconnects for millimeter-wave applications. The proposed silicon/metal/polyimide (SIMPOL) structure based on multilayer polyimide technology is extremely effective in reducing noise crosstalk, and also provides very low line loss, even at the millimeter-wave regime. The measurement results of the developed SIMPOL structures demonstrate extremely low noise crosstalk (<-40 dB) in the entire frequency range (up to 50 GHz), which is limited by the dynamic range of the measurement equipment, and excellent insertion loss (<-0,25 dB/mm) up to 45 GHz. In addition, the SIMPOL concept is applied for the first time successfully in the design and fabrication of branch-line hybrids at millimeter-wave frequencies, 30 and 37 GHz     

A low-impedance open-bitline array for multigigabit DRAM

The noise-generating mechanisms inherent in the open-bitline DRAM array using the 6F² (F: feature size) memory cells and techniques for reducing the noise are described. The sources of differential noise coupled to the paired bitlines laid out in two arrays are the p-well, cell plate, and the group of nonselected wordlines. It was found, by simulation and by experiment with a 0.13-μm 256-Mb test chip, that the level of noise is dramatically reduced by using a low-impedance array with careful layout featuring low-resistivity materials, tight bridging between pairs of adjacent arrays, and a small array, achieving a comparable level of noise to that seen in the twisted and folded-bitline array. On basis of these results, it turns out that the open-bitline array has a strong chance of revival in the multigigabit generation, as long as these noise reduction techniques are applied     

Coherence-Based 3-D and Spectral Imaging and Laser-Scanning Microscopy

The basics of three-dimensional (3-D) and spectral imaging techniques that are based on the detection of coherence functions and other related techniques are reviewed. The principle of the 3-D source retrieval is based on understanding the propagation law of optical random field through the free space. The 3-D and spectral information are retrieved from the cross-spectral density function of optical random field or numerical calculation of the inverse propagation of the cross-spectral density. We will first introduce the coherence-based spectral tomography techniques with low-coherence light sources. These techniques limit their scheme of coherence detection only along the optical axis and some of them achieve simultaneously the high resolution and high speed of detection taking advantage of an imaging lens. We then provided explanations of the principle of 3-D source retrieval that is based on the propagation law of optical random field through the free space along with the introduction of the numerical holography and computed tomography techniques. We will lastly show 3-D spectral imaging schemes with the concurrent laser-scanning cross-sectioning techniques: one is the confocal laser scanning microscopy and the other is the two-photon laser-scanning fluorescence microscopy.     

Deep-submicrometer BiCMOS circuit technology for sub-10-ns ECL 4-MbDRAM's

A 0.3-μm sub-10-ns ECL 4-Mb BiCMOS DRAM design is described. The results obtained are: (1) a V_cc connection limiter with a BiCMOS output circuit is chosen due to ease of design, excellent device reliability and layout area; (2) a mostly CMOS periphery with a specific bipolar use provides better performances at high speed and low power; (3) the direct sensing scheme of a single-stage MOS preamplifier combined with a bipolar main amplifier offers high speed; and (4) the strict control of MOS transistor parameters has been proven to be more important in obtaining high speed DRAMs, based on the 4-Mb design     

Progress of a tunable active bandpass filter

A review of a tunable active bandpass filter developed in our research group is given here. Presented first is the basic structure of an end-coupled microstrip-line bandpass filter. Next discussed is the concept of using coupled negative resistance to compensate the loss of tank circuit. Then, the method of using varactor diode or mesfet varactor to tune the center frequency of the passband is discussed. The capability of optical-control of mesfet varactor and the concept of using mesfets as three-terminal varactors are also discussed.     

一种计算微波电路的并行算法--FDTD-Diakoptics

ＦＤＴＤ－Ｄｉａｋｏｐｔｉｃｓ将复杂的微波电路分割为若干简单的子电路,使用有限时域差分方法（ＦＤＴＤ）独立求解每个子电路的时域特性,使用并行算法连接各子电路,最终得到整个电路的特性。本方法适用于结构复杂,规模较大的微波电路的分析设计,与整个电路使用ＦＤＴＤ进行设计研究的方法比较,本算法在保证相同数值精度的条件下可以提高计算效率五倍左右,故具有广泛的应用前景。     

Non-leaky coplanar (NLC) waveguides with conductor backing

In this paper, we present a structure called a non-leaky coplanar (NLC) waveguide with conductor backing. It is a multilayered structure with two possible configurations. The spectral domain approach with a complex root searching procedure is used to investigate leakage phenomena. The simulation results confirm that the leakage in conductor-backed coplanar waveguide (CBCPW) occurs in the form of wave in the parallel plate waveguide with infinite width. The results show that the leakage in the multilayered structure can be removed if the geometrical and material parameters of the structure are chosen appropriately. Experiments were carried out to investigate the transmission of these structures. It was found that the resonance in the transmission of finite-width conductor-backed coplanar waveguide (FW-CBCPW) is caused by the energy leakage from the dominant CPW mode. The resonance is eliminated in the NLC waveguides. These NLC waveguides are feasible and practical in the uniplanar MMIC design due to their planar nature