Hideyuki Oh-Hashi

Fourier Transform Optical Beamformer Employing Spatial Light Modulator

Optically controlled beam forming techniques are effective for phased-array antenna control. We have developed the Fourier transform optical beamformer (FT-OBF). The antenna radiation pattern inputted into an amplitude spatial light modulator (A-SLM) is optically Fourier transformed to a specific phase-front light beam equivalent to an antenna excitation in the FT-OBF. Optical signal processing, used the Fourier transform optics, is effective to large-scale, two-dimensional, and high-speed signal processing. To implement a flexible and finer antenna beam pattern control, we use an A-SLM as input image formation of the FT optics. And, to realize a small-size FT-OBF, we use symmetric triplet lenses with convex, concave and convex lens. The total optical system becomes below 1/5 length compared with the length using single lens. Finally, we evaluated the developed FT-OBF with the generated amplitude and phase distributions, which excitation signal of an array antenna. We measured an antenna radiation beam pattern, beam steering and beam width control, in the C-band. Measurement results agreed with theoretical calculated results. These results show the feasibility of the spatial light modulator based FT-OBF.

90 Degree Tandem Hybrid with Tolerance to Displacement Error and Thickness Variation in Multi-layered Substrate

90 degree coupled-line hybrid that is tolerant to manufacturing errors in a multi-layered substrate has been developed. The tolerance to displacement error and thickness variation in the multi-layered substrate can be achieved by using diagonally shifted coupled lines with adjacent ground walls. It has been demonstrated that the coupling characteristics of the hybrids fabricated in LTCC agree well with designed ones and their deviation is very small

A 12GHz lumped-element hybrid fabricated on a micromachined dielectric-air-metal (DAM) cavity

A novel lumped-element hybrid is presented. The hybrid is disposed on a newly developed dielectric-air-metal (DAM) cavity, which consists of an SiN membrane above a metallized 30-um-deep cavity made by a micromachining process. This process enables to make every component be worked from one-side of a silicon (Si) substrate, and to leave back-side as a part of a package. This is indispensable to realize a very thin MEMS-packaged-device consisting of two wafers bonded. Also, patterned metal grounds can provide all kinds of lumped elements. Among those, series inductors are investigated in detail. A hybrid with series inductors and shunt capacitors is fabricated. Good agreement between the measured and simulated results was obtained to validate this structure for fabrication of micro-size microwave components on an Si substrate.

A hollow-GCPW (HGCPW) as low-loss and wafer-conductivity-free structure on a single silicon wafer

A low-loss hollow grounded co-planar Waveguide (HGCPW) suitable for a transmission line on a low-resistivity silicon wafer is presented. The HGCPW is disposed in a newly developed dielectric-air-metal (DAM) cavity. which consists of an SiN membrane above a fully metallized cavity made by a micromachining process. Low-loss property is achieved by removing substrate between a signal line and grounds. Existence of a bottom ground metal realizes wafer-conducthity-free structure on a low-resistivity silicon wafer by isolating the line from the substrate completely. Also, the bottom ground enables the impedance to be 50 ohm with narrow line width. HGCPWs on the 6-¿m and 30-¿m DAM cavities were fabricated and tested. The measured losses were about 0.3 dB/mm and 0.1 dB/mm respectively at 12 GHz.

A Broadband Asymmetric Tapered-Line Power Divider with Several Strip Resistors

A novel asymmetric tapered-line power divider is presented. It has several strip resistors which are formed like a ladder between the tapered-line conductors to achieve a good output isolation. The equivalent circuits are derived with the even/oddmode analysis. The fabricated asymmetric power divider with 1:2 power dividing ratio shows broadband performances in return loss and isolation which are greater than 20 dB over a 3:l bandwidth in the C-K bands.

A Novel Three-Port Power Divider with Compensation Networks for Non-Ideal Isolation Resistor

This paper describes a three-port power divider with compensation networks for non-ideal isolation resistor. The compensation networks consist of two additional lines and cancel out the parasitic reactance of the non-ideal isolation resistor. The design method to provide perfect return loss and isolation at the center frequency are presented. The availability of the proposed power divider has been verified by the comparison between calculated and experimental results in the Ku-band.

Broadband directional coupler using dielectric loaded slit

A broadband 40-dB directional coupler using coupling slits opened in common ground conductors between parallel coaxial lines has been fabricated. Dielectric plates are loaded in the slits to compensate for the directivity degradation due to ground conductor discontinuities at the slit ends. The directivity is greater than 24 dB.<<ETX>>

A Low-Loss Serial Power Combiner Using Novel Suspended Stripline Couplers

This paper describes a serial power combiner which consists of novel suspended stripline couplers. The suspended stripline couplers have additional parallel capacitances to improve their directivities. The fabricated three-way power combiner has realized a good performance in insertion loss which is less than 0.23 dB over a bandwidth of 10% in the S-band.

Simple Design Formula for Parallel Plate Mode Suppression by Ground Via-Holes in Multi-Layered Packages

In a multi-layered RF circuit, it is important to avoid unexpected coupling caused by a parallel plate mode excited between different ground layers. Ground via-holes that short-circuit different ground layers are used for suppressing this mode. Quantitative evaluation of relations between suppression effect and ground via-hole disposition is required for optimal design. In this paper, a simple design formula that describes the suppression ratio is derived by mode-matching technique. The results of comparison with an FEM simulation validate our proposing formula. It is shown that the technique is indispensable for designing optimal disposition of via-holes to minimize the area of the ground via-holes for desired performance.

Surface mount shunt capacitor filters using bilateral magnetic coupling

This paper proposes shunt capacitor filters using magnetic coupling which improves the filter performance. The proposed filter structure is designed to place input/output paths parallel to shunt path from a power supply line to a ground plane. And magnetic couplings between the input/output paths and shunt path are utilized to reduce parasitic inductance of the shunt path. The proposed filter provides higher performance with almost same area compare with conventional filters. Measurement and EM simulation are used to evaluate the filter performance. As a result, the proposed filters improved the performance by 8 dB at 20 MHz compared with filters without the couplings.