Shigeki Takeda

A siloxane polymer lightwave circuit on ceramic substrate applicable to ultrafast optoelectronic multi-chip-modules

Technique for integrating optical waveguide circuits on electrical circuits is developed toward the application to opto-electronic multi-chip modules (O/E-MCM), which enables one to handle ultrafast lightwave pulses and electrical signals on a common circuit board. We use ceramic material as the substrate of O/E-MCM having a multi-layer structure. A siloxane polymer is utilized to form low loss optical waveguides on ceramic substrates by low temperature processes. The waveguide has shown high transparency around 1310 nm. The group velocity dispersion has been measured and shown to become almost zero at wavelength of 1310 nm and about 0.4 fs/cm nm at 1550 nm. An optical circuit has been formed on simple electrical circuit consisting of a thermometer film resistance layer. A Mach–Zehnder interferometer optical switch exhibiting the waveguide extinction ratio of 30 dB, control power of 5 mW, and switching speed of 6 ms has been demonstrated. Thermal management characteristics also have been demonstrated successfully. This single-mode optical waveguide can thus be formed readily on ceramic substrates involving electrical circuit layers; this result confirms its applicability to O/E-MCM.

A self-equalization band pass filter having arbitrary complex transmission zeros

A self-equalization band pass filter having complex transmission zeros is realized in the form of a Foster type network. Complex transmission zeros enable self-equalization to flatten magnitude and group delay times simultaneously in the same bandwidth while maintaining high selectivity by associated attenuation poles. Only a Foster type network has adequate capability to embody such characteristics involving arbitrary transmission zeros. In addition, the Foster type network has another unique capability to allow a new term by term frequency transform. This frequency transform enables the suppression of an undesired slope in the group delay times. This slope is inevitably produced when the conventional frequency transform is applied. As a design example, a self-equalization band pass filter applied to a 9 th order Bessel filter is shown.

The Foster Type Circuit For The H-matrix And Application to Coupled Line Filter of Even Order

The Foster-type circuit of even order is realized in a simple configuration by use of the H-matrix. The Foster-type circuit has some superior properties to those of the popular ladder networks. Conventionally, the Foster-type circuits are designed by applying the eigen-mode expansion method only to the Z matrix or the Y matrix. This process is well suited for the realization of the circuits of odd order, and hence the axial symmetrical structure is readily realized. However, in this conventional scheme it is difficult to design the Foster type circuit of even order and the axial anti-symmetrical structure, although the theoretical network synthesis itself is possible. This paper shows that the H-matrix and the G-matrix have complementary characteristics to those of the Z-matrix and the Y-matrix for the Foster-type circuit. We show that the circuit of even order and hence the axially anti-symmetrical structure is well realized by the H-matrix. To demonstrate the usage of these properties, an even order band pass filter of the Foster-type circuit is designed based on the H-matrix.

A Low Linear Distortion Filter Configuration for Digital Communication Systems

A low linear distortion filter configuration is proposed. This filter has flat magnitude and flat group delay time in the pass band simultaneously, and has transmission zeros in the stop band. This filter is implemented on the HTS substrate, and is well applicable to software radio base stations.

Small Strip Line Module for Superconducting Filter

We have developed a new strip line filter module with small size and high heat dissipation capacity. The new filter module is composed of substrates for a filter and ground planes, and the size is much smaller than the conventional height of RF housing and has a thickness of the order of a few substrates. For the evaluation of transmission characteristics of the strip line module, simple strip line modules containing no filter and two alumina substrates were used. The minimum insertion loss of the modules is of the order of 0.1dB(input 44dBm) at temperatures of 50K–77K, and their properties are sufficient for actual systems.

High Efficiency Cooling System for High Temperature Superconducting Filters

We developed a high efficiency cooling system for high temperature superconducting (HTS) filters under high power operation over 1W at 2GHz in the front-end for a mobile telecommunication base station. A coaxial cable and a package were designed by optimizing the heat transfer. Then, a cooling system was assembled and its cooling properties were evaluated. Small modules were mounted in it. When the module was cooled to 50K, the system performed a good capability to maintain cooled circumstances in it.

An Extended Four-Port Noise Matching Network

An extended four-port noise matching network is proposed. The use of this four-port noise matching network allows further improvement in the minimal noise figure of linear noisy two-ports by conventional two-port matching networks.