Tatsuo Itoh

Broadband power amplifier integrated with slot antenna and novel harmonic tuning structure

A high efficiency class-AB GaAs FET power amplifier integrated with a slot antenna has been designed and fabricated. Broadband second harmonic tuning was achieved using a microstrip line with a periodically etched ground plane. Power-added efficiency greater than 50% was achieved in the 3.7-4.0 GHz bandwidth.

Design of photonic band-gap substrates for surface waves suppression

Suppression of unwanted surface waves supported by a grounded dielectric slab can be achieved by periodically loading the substrates to create a forbidden frequency band for propagation. Approximate formulas for designing such loading are given and verified by means of a numerical full-wave analysis.

A novel high-Q image guide resonator using band-gap structures

This paper presents a novel high-Q resonator using photonic band-gap structures in an image guide. Our initial measurement with an X-band prototype demonstrates a Q-factor of 697, which is limited by the dielectric material (Duroid) used for experiment. A new planar integration technique for image guides using Yagi-Uda slot array is also developed. This resonator structure is potentially useful for millimeter-wave integrated circuits.

All-optically controlled beam-scanning array for antenna remoting applications

In this work, a beam-scanning array for antenna remoting via an optical link is presented. Optical control over the main beam is accomplished through the use of a photosensitive resonator. Experimental data shows a total scan angle up to 36/spl deg/ can be achieved with this optical technique.

A novel 2-D multi-mode parallel time domain diakoptics and its application in filter analysis and design

A novel two-dimensional multi-mode parallel time domain diakoptics based on FDTD is proposed. The discrete time domain Greens function is employed to analyze complicated circuits entirely in time domain with greatly improved efficiency. A part of the results is combined with frequency-domain synthesis method to design a band-pass filter. Excellent agreement with mode-matching and measured results is obtained.

A Novel Microstrip to Coplanar Waveguide Transition for Flip-Chip Interconnection using Electromagnetic Coupling

A novel compact microstrip to coplanar waveguide (CPW) transition is proposed for flip-chip interconnection. Broadband performance of the transition is simulated and agrees well with measured results. A good interconnection between microstrip line on a motherboard to CPW on a flip-chip is accomplished without any vias. For 10dB return loss, the microstrip-to-CPW transition and the microstrip-to-flip-chip interconnection present 170% and 140% bandwidth, respectively.

Resonant coupling type microstrip line interconnect using a bonding ribbon and dielectric pad

Resonant coupling type microstrip line interconnects using a bonding ribbon and dielectric pad have been designed and fabricated. The basic concept of this interconnect is the LC serial resonance of the pad capacitor and ribbon inductor. Both numerical simulation and experiment reveal low return loss and high efficiency connection at the predicted resonant frequency region, which can be readily shifted to higher frequencies by tuning the structural parameters. Furthermore, improvement in bandwidth of the interconnect is demonstrated by using a pad with higher dielectric constant.

Dielectric slab based spatial power combiners

Spatial power combiners have the potential for realization of moderate power sources at millimeter wavelengths by summing the output signals of large numbers of solid-state devices. Most previous work has focused on three-dimensional approaches, such as the wave beam type, grid type, microstrip coupling type, and lens type. A quasi-optical structure based on the dielectric slab-beam waveguide (DSBW) is two-dimensional and therefore more amenable to planar fabrication technologies. An oscillator and several amplifiers based on the DSBW have been reported. These structures excited an electric field parallel to the slab ground plane. Such a mode has very low loss but is difficult to excite cleanly with no perturbation or scattering loss. Dielectric lenses were used to focus and constrain the guided waves. Both the TM and TE surface wave combiners described herein use microstrip delay lines to focus the guided waves in a manner similar to that reported by Schoenberg, Bundy and Popovic (see IEEE Trans. on Micowave Theory and Techniques, vol.MTT-42, p.2480-5, 1994). The delay line length is analogous to the thickness of a conventional dielectric lens. Commercial gain blocks are used to amplify the RF signals. Yagi-Uda slot antenna arrays, fed by microstrip lines, were used to efficiently excite the dominant TM surface wave mode with the electric field normal to the slab ground plane. A microstrip to parallel strip balun was used to feed a dipole antenna and launch TE surface wave in a homogeneous slab. TE and TM surface wave power combiners with net system gain and reasonable bandwidth have been demonstrated.

A Quasi-Optical Sub-Harmonic Self-Oscillating Mixer

A sub-harmonic self-oscillating mixer (S-SOM) integrated with an inset-fed microstrip patch antenna is developed for receiver front-end applications. The circuit is designed as a sub-harmonic mixer in order to facilitate scaling to millimeter wave frequencies. A prototype design at C-Band was measured to have isotropic conversion loss of 10.25 dB for the second harmonic mixing product.

Tapered slot antenna integrated with velocity-matched distributed photodetector

We propose and demonstrate the integration of tapered slot antenna (TSA) and velocity-matched distributed photodetector (VMDP) which is potentially useful for millimeter-wave power combining and phased arrays, as well as RF front-ends for analog fiber optic links. The concept is confirmed by photomixing and antenna measurement with an X-band prototype, and is readily scalable to higher frequencies where the inherent tremendous bandwidth of optics can be fully employed.