Yoshihiko Konishi

Dual-band-rejection filter for distortion reduction in RF transmitters

A novel concept of dual-band-rejection filter (DBRF) is proposed with its circuit synthesis procedure and examples of its realization with dielectric resonators and microstrip resonators. A DBRF can make two closely spaced rejection bands and a passband between them, with lower loss than a bandpass filter having the same number of resonators and the same frequency selectivity just around the passband. The DBRF can be synthesized by applying novel frequency-variable transformations to a prototype LPF, and its physical size can be smaller than a simple cascade of two conventional band-rejection filters with different rejection bands. The DBRF can be especially applicable to distortion reduction filter in RF transmitters.

Fast Measurement Technique for Phased Array Calibration

A novel measurement method is proposed in order to measure the active electric fields of the individual antenna elements in a phased array antenna. Fast and accurate measurements can be realized by the proposed method because the electric fields of multiple elements can be obtained simultaneously and no phase measurements are required. Hence, it can be easily applied to the on-board diagnostics and re-calibration in the operating phased array antenna systems. In the first step with this method, the phases of multiple antenna elements are successively shifted with the specified phase intervals while the array power variations are measured. Next, the measured power variation is expanded into a Fourier series and the terms are rearranged to put them into the form of the rotating element electric field vector (REV) method. Finally, the REV solution is used to identify the electric fields of the individual elements. Additionally, a theoretical study is carried out on the accuracy of the proposed measurement method. Simple, closed-form equations have been successfully derived for the measurement errors and the calibration accuracy is theoretically estimated. The proposed measurement method is validated with experimental results and the measurement accuracy is compared with the theoretical prediction.

ULTRA-LOW PROFILE AIRBORNE REFLECTOR ANTENNA SUBSYSTEM FOR BROADBAND SATELLITE COMMUNICATIONS

An ultra-low profile airborne reflector antenna with an arbitrary polarization feed system and a wide-range scanning faculty has been proposed for the broadband satellite communication use. We have chosen a shaped elliptical dual reflector antenna with reflector shaping technique to realize both the ultra-low profile and high electric performances. A novel thin-type broadband OMT with pyramid-loaded waveguide turnstile junction has been presented to obtain the arbitrary polarization thin feed system.

Payload Configuration Study for Quasi Zenith Satellite System

Quasi-Zenith Satellite System (QZSS) has been studied in Japan. In this system, it has been planned to provide broadcasting, communication, and global positioning system (GPS) services simultaneously [1]. In order to realize this mission requirement, a lot of payload equipments for the different frequency bands have to be integrated in a satellite. In this paper, we present a conceptual study of the payload configuration for Quasi-Zenith Satellite.

Radar Cross Section Analysis Considering Multi-Reflection inside a Radome Based on SBR Method

The authors propose the simple and efficient method based on the shooting and bouncing rays (SBR) method in order to evaluate multi-reflection effects inside a radome. In this paper, we show the analysis procedure of the proposed method. Next. we compare calculated data with some measured data in order to verify the proposed method. We confirmed that the proposed method is effective for the objects with radome except the areas where strong edge diffraction appears.

Convergence property of IDR variant methods implemented with method of moments

In this study, we investigate the performance of the variants of the induced dimension reduction (IDR) in large-scale electromagnetic scattering problems. Comparative numerical experiments, using IDR(s), GIDR(s, L), and ML(s)BiCGSTAB reveal that GIDR(s, L) shows the fastest convergence property among the three IDR variants. In a numerical experiment with a practical radiation problem, GIDR(s, L) with an s value of around 15 shows the best performance with respect to the balance between the convergence property and the tolerance to the spurious convergence.

Mobile/transportable terminal antennas for L-band mobile satellite communication systems

This paper presents mobile/transportable terminal antennas for L-band mobile satellite communication systems using Mobile Satellite (MSAT). Five types of antennas have been investigated for mobile terminal antennas, which are called a Dome Antenna, a Transportation Antenna, a Disk Antenna and two types of Mast Antennas. Also, another three types of antennas have been developed for transportable terminals. Authors discuss configurations and performances of these antennas. The Dome Antenna, the Transportation Antenna and the Disk Antenna can rotate mechanically in azimuth direction and have broad radiation pattern in elevation direction in order to track the satellite. These antennas achieve gains more than 8dBi, lldBi and 9dBi in elevation coverage range, respectively. The Mast Antennas radiate conical beam and consequently have an advantage that any tracking mechanisms are unnecessary for Copyright c 1997 by the American Institute of Aeronautics, Inc. All rights reserved. them. The Mast Antenna Type-1 reduces beam separation between the transmit and receive frequency band by using a linear array of bifilar helical elements and obtains peak gain more than 8dBi. The Mast Antenna Type-2 is a fan-beam forming bifilar helical antenna for broadening coverage range in elevation direction. Transportable Antennas are planar antennas composed of several patch antennas. The Transportable Antenna Type-1 is a compact size two-element array antenna (287mm X 210mm) and its peak gain is more than 10.5dBi. The Transportable Antenna Type-2 uses a self-diplexing antenna structure having an advantage that it does not need diplexers for isolating transmit and receive ports. It obtains peak gain more than 9dBi. The Transportable Antenna Type-3 is a high gain antenna and achieves peak gain more than 14dBi.