Hideyuki Oh-hashi

A broadband three-way tapered-line power divider with several strip resistors

A novel three-way power divider using tapered lines 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 EE/OE/OO-mode analysis based on the fundamental propagation modes in three-conductor coupled lines. The fabricated three-way power divider shows a broadband performance in input return loss which is greater than 20 dB over a 3:1 bandwidth in the C-Ku bands.

Simple design formula for parallel plate mode suppression by ground via-holes

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.

A Ku-band low-loss stripline low-pass filter for LTCC modules with low-impedance lines to obtain plural transmission zeros

A Ku-band low temperature co-fired ceramic (LTCC) multi-layered stripline low-pass filter (LPF) is presented. By employing a low-impedance line as an inductive element in the resonator, plural transmission zeros can be obtained near passband. Therefore, the presented LPF realizes excellent attenuation characteristics despite a small number of resonators. The LPF has extremely low insertion loss and compact dimensions, an especially thin profile, and is suitable for RF-modules. An LPF with dimensions of 0.9 mm/spl times/0.9 mm/spl times/0.4 mm has been fabricated, and measured results show the validity of the proposed structure.

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.

A compact Ku-band power combining network using rectangular coaxial line technology

A compact Ku-band power combining network with a combining loss less than 0.45 dB has been developed using rectangular coaxial line technology. Novel hybrid couplers using impedance-transforming nonuniform coupled transmission-lines are employed as power combiners to reduce the degradation in the combining network performance due to manufacturing inaccuracy.

A displacement-error monitor of a multi-layer LTCC module

A displacement error of each sheet of a multi-layer low temperature co-fired ceramic (LTCC) module is one of the critical issues to obtain high yield production. This paper introduces an embedded passive component that monitors displacement error of a certain layer by measuring its frequency response. Also, the displacement-error monitor (DEM) is so designed that the displacement of a certain direction cause significant change of the response but the opposite direction as well as the perpendicular one does not. Embedding the DEMs in sheets of LTCC, we can monitor the error and can feedback to the process of fabrication to reduce discarded products. Two lots of LTCC modules were fabricated and tested. Displacements were monitored by the DEM and also were inspected directly by cutting off at a certain pattern. The measured results agree well with the displacements inspected at the cross section.

A Realistic Distributed Circuit Model for EBG Structures Based on Physical Implementations

In this paper a new equivalent circuit for the EBG structure which represent the feature of surface-wave suppression is proposed. The equivalent circuit of the EBG unit cell consists of capacitors, inductors and transmission lines of series branches, as well as a capacitor and an inductor of shunt branch. These equivalent circuit parameters are based on physical implementations of EBG structures. Therefore it is easer to extract the parameters than conventional equivalent circuits. Also, the proposed equivalent circuit can calculate a large-scale EBG structure characteristic without a long computation time although the constitution is simple.

A Broadband Traveling-Wave Power Divider/Combiner using Asymmetric Tapered-Line Power Dividers

A compact and broadband traveling-wave power divider/combiner cascading 1:1:2 three-way and 1:1 two-way power dividers is presented. Both tapered-line power dividers have several strip resistors to obtain sufficient output isolations. Additional open stubs applied to the 1:1:2 three-way tapered-line power divider compensate phase velocity difference between asymmetrically coupled tapered lines. The fabricated four-way power divider/combiner shows broadband performances which are a 0.4-dB insertion loss and a 14-dB return loss at all ports over a 3:1 bandwidth in the C-Ku bands.