Kazushi Nishizawa

Electromagnetically coupled coaxial dipole array antenna

A new type of collinear antenna called electromagnetically coupled coaxial dipole array antenna is proposed. The antenna has an advantage of structural simplicity due to a novel use of an electromagnetically coupled feed structure for the radiating element. An analysis of the radiating element is presented and compared with experimental results. Fabrication and measurement of a prototype array antenna are also presented.

Cavity-backed MEMS patch antennas on double-layer silicon wafers

This paper presents cavity-backed patch antennas on a double-layer silicon wafer. The developed antenna has flexibility for obtaining the desired equivalent dielectric constant under the limit of the wafer thickness, because a depth of cavity on each wafer can be adjusted with each other. The wide band characteristic of this antenna has been shown by simulation, and the experimental results at millimeter wave have also been presented

Ultra-Wideband Tapered Slot Antenna Array with Parallel Plate Waveguides

Tapered slot antennas (TSA) are adequately applicable to wideband phased array antennas due to their ultra wide bandwidths. However, a significant degradation of VSWR performance is observed when a smaller aperture is adopted to suppress grating lobes for the phased array. To overcome the difficulty, a new tapered slot antenna is proposed; tapered slot antenna with a parallel plate waveguide (PPTSA). The PPTSA is capable of providing the ultra-wide bandwidth characteristics even when the width of the aperture is less than a half wavelength at the lowest operating frequency. Major performances of a single PPTSA was presented through numerical simulations and experiments in the previous report. In this paper array performances of PPTSA is investigated. A new configuration to suppress ripples from the ground plane is proposed by introducing cut-off waveguides close to the PPTSA. Measured and calculated data for VSWR and radiation pattern are also presented.

Study on circularly polarized cavity antenna fed by L-shaped probes

A circularly polarized cavity antenna that is fed by L-shaped probes is proposed in this paper. This antenna has a simple configuration and good connectivity with a feed circuit. Wideband impedance matching is achieved by using the vertical arm of the L-shaped probe located near the side of the cavity as an impedance transformer, thus eliminating the need for other impedance matching circuits. The effectiveness of the proposed antenna has been confirmed experimentally.

Broadband circularly polarized cavity antenna array fed by L-shaped elements

A circularly polarized cavity antenna that is fed by L-shaped elements has been presented. Wideband impedance matching has been achieved by using the vertical arm of the element as the impedance transformer, and hence, there is no need for other impedance-matching circuits. The effectiveness of the proposed antenna has been confirmed experimentally.

A novel disk type support structure installed in a quadrifilar helical antenna for satellite application

We propose a new type of support structure for helical antennas which are made of rolled cylindrical film resin substrate. The structure is composed of a rod arranged on the cylinder axis and disks fixed to it, which have a function that holds the cylindrical film, at specific intervals. This structure suppresses deterioration in antenna performances under adverse conditions of satellite application with vibrations. The configuration is found to be optimum in which the disks are arranged from the position that fell down from the helical upper end by 0.25 λg along the helical element. Here, λg is guide wavelength along the helical element.

Two resistors loaded ultra-wideband spiral array antennas

In this paper, we propose a new type of a small spiral antenna that has a pair of resistors and verify its ultra- wideband characteristics. Spiral antennas have ultra-wideband characteristics such as a nearly constant input impedance, antenna gain, and low axial ratio. However, when reflectors such as conducting planes or cavities are used, their performances are degraded due to reflections from the end of these spiral arms. In particular, this effect is remarkable at low frequencies where these antennas become small in comparison to their wavelengths. Therefore, new termination technique for small spiral antennas backed by a cavity, their array antenna performances were examined and showed high gain and low axial ratio characteristics.