Tsuneo Tokumitsu

Broad-band monolithic microwave active inductor and its application to miniaturized wide-band amplifiers

A broadband monolithic microwave active inductor composed of two FETs and a resistor is proposed. The most significant innovation of the active inductor is considered to be a novel circuit structure which suppresses stray capacitance to yield a much higher-frequency operating range than a spiral inductor. The inductor is small and independent of the inductance value. The FET-oriented configuration allows a denser chip circuitry packing. A 0.1-10-GHz miniaturized wideband amplifier realized using the active inductors is described. >

Lossless broad-band monolithic microwave active inductors

Lossless, broadband microwave active inductors are proposed for general-purpose use in microwave circuits. These active inductors operate in a wide frequency range with very low series resistance. They are composed of a common-source cascode FET and a feedback FET which is a common-gate FET or a common-gate cascode FET. The loss can be less than 1/8 the loss of the previously proposed active inductor. The inductance value can be controlled by the external control voltage. The configuration and performance of these devices are described. >

Novel unilateral circuits for MMIC circulators

A circuit which is equivalent to a four-port circulator with one port terminated, called a quasi-circulator, is proposed. The quasi-circulator can replace a conventional circulator even though it is not a complete circulator. Examples of novel three-port unilateral circuit modules, called quasi-circulator modules, which are the main part of the quasi-circulator are presented to realize very wide band circulators in monolithic microwave integrated circuit (MMIC) form without using ferrite materials and external magnets. The proposed modules are composed of an active out-of-phase divider and an active in-phase combiner or an active in-phase divider and an active out-of-phase combiner. The modules have many variations. All are very small and operate over a very wide frequency range. Two types of quasi-circulator modules that have very broadband operation up to X or Ku band are demonstrated. A quasi-circulator is also demonstrated. It is shown how an active circulator is realized by quasi-circulator modules. >

Analysis of high speed p-i-n photodiode S-parameters by a novel small-signal equivalent circuit model

A novel small-signal radio frequency (RF) equivalent-circuit of the side-illuminated input tapered waveguide-integrated p-i-n photodiodes (WG PIN PD) is proposed. The proposed RF equivalent-circuit involves both the carrier-transit effect and the external resistance-capacitance (RC) time constant limitation on the frequency response of the p-i-n PD. The carrier-transit effect is realized by adding an RC circuit to an ideal voltage-controlled current source as the input opto-RF equivalent circuit. The carrier transit-time effect is equivalently represented by the time-constant of this input RC circuit. This new equivalent circuit model fits well with both the measured reflection and optoelectronic conversion parameters of the WG PIN PD in a broad frequency range from 45 MHz to 50 GHz.

Divider and combiner line-unified FET's as basic circuit function modules. II

For pt.I see ibid., vol.38, no.9, p.1210-17 (1990). Applications of line-unified FETs (LUFETs) to RF signal processing elements such as multiport combiner/dividers, mixers, balanced modulators, signal path switches, and circulators are proposed and demonstrated. A 2*1 combiner monolithic microwave integrated circuit (MMIC) using an in-phase combiner LUFET and an N*N combiner/divider based on the 2*1 combiner topology are presented. A single-end mixer and a balanced mixer implemented by combining divider and combiner LUFETs are presented, and a balanced mixer LUFET is proposed. A balanced modulator which is realized by slightly changing the phase inverter LUFET configuration is presented. This modulator is also a LUFET. A signal path switch with a configuration of symmetrically combined magic T LUFETs is presented. A circulator which is a combination of in-phase and out-of-phase divider and combiner LUFETs is presented. The areas of the fabricated LUFETs and LUFET MMICs are between 0.1 and 1.5 mm/sup 2/, the average being about 0.5 mm/sup 2/. >

Very small ultra-wide-band MMIC magic T and applications to combiners and dividers

An FET-sized 1-18-GHz monolithic active magic T (180 degrees hybrid) is proposed. It unifies two different dividers, electrically isolated from each other, in a GaAs FET electrode configuration; this is the line unified FET (LUFET) concept. Its characteristics and experimental results are presented. Applications of the magic T to miniature wideband RF signal processing modules such as dividers, combiners, and switches are described. >

A time-delay equivalent-circuit model of ultrafast p-i-n photodiodes

A time-delay equivalent-circuit model of ultrafast p-i-n photodiodes (PDs) is proposed to describe the operation at high-input power levels. This model includes both the carrier transit-induced time-delay effect and stored charge effect of p-i-n PDs in high-power operation. These effects were represented as a linear RC circuit and capacitance, respectively, both combined in parallel to a voltage-controlled current source. The validity of this model was confirmed with good curve fitting to the measured optical-frequency responses of an ultrafast side-illuminated p-i-n PD.

A Monolithic, Port-Interchanged Rat-Race Hybrid using a Thin Film Microstrip Line Crossover

A very small, port-interchanged MMIC rat-race hybrid using a crossover structure of multilayer thin film microstrip lines is proposed for highly flexible and miniaturized function blocks such as balanced mixers, frequency doublers and modulators. A 20-GHz-band rat-race hybrid with output ports on the other side of the hybrid from the input ports is designed and fabricated in a 0.7mm×0.7mm chip. This new circuit configuration will drastically improve the design flexibility and performance of MMICs.

K-band and millimeter-wave MMICs for emerging commercial wireless applications

The state-of-the-art K-band PA, LNA, and multiplier MMICs that meet the LMDS and Point-to-Point systems with an international wide spectrum allocation are presented. Novel flip-chip and three-dimensional MMIC technologies for potential low-cost millimeter-wave MMICs are also discussed. Through these, trend of the design and fabrication methodologies for the K-band and millimeter-wave devices are described.

Very Small and Wide Band MMIC Magic-T using Microstrip Lines on a Thin Dielectric Film

This paper describes newly developed MMIC magic-Ts (180° hybrid circuits) using microstrip lines on a thin Silicon-Oxynitride (SiON) dielectric film. The thickness of the thin film is several micrometers. The quarter-wavelength microstrip line area is effectively minimized using meander-like configurations. The fabricated chip area of the thin film MMIC magic-T with a center frequency of 12 GHz is about 1/10 the size of conventional magic-Ts.