Eiji Takagi

High-efficiency monolithic GaAs power MESFET amplifier operating with a single low voltage supply for 1.9-GHz digital mobile communication applications

A monolithic GaAs power amplifier IC using refractory WN/sub xW self-aligned gate power MESFETs has been developed for 1.9-GHz digital mobile communication systems, such as the Japanese personal handy phone system. The power amplifier operates with high efficiency and low distortion with a single low voltage supply of 2.7-3.0 V, by virtue of small drain knee voltage, high transconductance and sufficient breakdown voltage of the power MESFET. An output power of 23.7 dBm and a high power-added efficiency of 24.2% were attained at 3 V for 1.9-GHz /spl pi4-shifted QPSK (quadrature phase shift keying) modulated input when adjacent channel leakage power was -58 dBc at 600 kHz apart.<<ETX>>

MCM-D/L using copper/photosensitive-BCB multilayer for upper microwave band systems

This paper describes an MCM-D/L technology for upper microwave band systems. The substrate of this MCM is constructed of copper/photosensitive-benzocyclobutene (P-BCB) multilayer formatted onto a print wiring board (PWB). Features of the developed MCM are (1) a novel microstrip structure for improvement of high-frequency characteristics and (2) a low-cost simple copper/P-BCB process using polishing technology. As BCB has good thermal and electric characteristics compared with polyimide or epoxy, BCB is expected to be applied to high frequency systems. We have developed a low-cost copper/P-BCB multilayer process with a new microstrip structure, and measured the high-frequency characteristics (10 GHz/spl sim/40 GHz). In the process technology, we took note of the adhesion of the metal film/BCB interface. As a result of a study of the adhesive metal and chemical/thermal treatment before and after fabrication of the film, we found that the necessary adhesion force was obtained by N/sub 2/ plasma treatment of the BCB surface before metal evaporation and annealing (250/spl deg/C:BCB cure temperature) after evaporation. Also, Cr was found to be the best material for adhesion. The high-frequency characteristics (10 GHz/spl sim/40 GHz) were estimated by a ring resonator and microstrip transmission line of copper/P-BCB multilayer fabricated on a PWB. Also, the S-parameters showed good characteristics. The developed MCM-D/L substrate has been proved to be suitable for high-frequency systems.

Frequency dependence of Bloch impedance in a periodic transmission line structure

Frequency dependence of Bloch impedance in a periodic structure was calculated by using simple F-matrix formula. Also, relationship between band-gap on-set frequency and reactance factor was evaluated. Finally, formula was checked by the experiment.