Shigeru Makino

Bandpass Directional Couplers with Electromagnetically-Coupled Resonators

Compact 90- and 180-degree directional couplers incorporating bandpass characteristics are presented. They can integrate a bandpass filter and a power-divider/combiner in an RF transceiver, resulting in its miniaturization. The bandpass directional coupler can be represented as a coupled-resonator network, and its coupling coefficients and external-Q can be determined from a desired coupling ratio and operational bandwidth of the bandpass coupler. Measured results are also presented on a Ku-band bandpass 180-degree directional coupler with TE 01delta-mode dielectric resonators

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.

Front fed offset cassegrain type multibeam antenna

Introduction Large high capacity communication satellites with multibeam antennas are being developed in Japan(l), Ilnited States(2) and so on. The merits of multibeam antenna are ( 1 ) high EW, (2) reuse of frequencies. But in the design of multibeam antenna, one of the most difficult problems to be solved is to obtain the high beam-to-beam isolation. In conventional antennas, for instance Offset Gregorian, the increase of scan angle causes the increase of sidelobe level and scan loss on account of aberration and increase of cross polarization level, so beam-to-beam isolation becomes lower.

A widely-tunable balanced bandstop filter with low reflections and separate stop-bands

A frequency-tunable bandstop filter (BSF) with low reflections, separate stop-bands, and more than one-octave tunable frequency range is proposed. The BSF consists of a pair of frequency-tunable shunt resonant circuits in a balanced configuration, which enables the low-reflection characteristics and a great deal of degree of freedom in its design, such as the separate stop-bands. An X- to Ku-band tunable BSF has been fabricated with a ceramic substrate and commercially-available varactor diodes, and its measured characteristics are presented in this paper.

A millimeter-wave cassegrain antenna using shaped beam waveguide feed

As a way to increase the efficiency of the focused beam-fed Cassegrain antenna with a large aperture for use at millimeter-wave frequencies, a method is proposed for shaping the surface of two focusing reflectors in the focused beam waveguide feed. The reflector surface shaping method is presented. Since the reflector is used at millimeter-wave frequencies, it is necessary to take into account the effect of the aberration caused by the deformation of the reflector surface on the radiation characteristics. Both the sub- and main reflectors have quadratic surfaces. The aberration in the main reflector due to self weight deformation can be corrected with the deformation of the subreflector in the homologic design. Hence, in order to validate the present beam shaping method, it is necessary to evaluate the effects of the aberration caused by the alignment error of each focusing reflector on the radiation characteristics. In this paper, a method of shaping the two focusing reflectors is applied to the new 10-m antennas for the millimeter-wave interferometer of Nobeyama National Observatory (model No. 6). The alignment errors in the parallel shift in three axis directions and the rotating motion about the axes are assumed, and the aberration and the gain degradation are quantitatively investigated when each focusing reflector is deformed. It is shown that the grain degradation is small in the range of realizable alignment errors and that the method of shaping the surfaces of two focusing reflectors is effective as a reflector shaping method for a millimeter-wave large-aperture antenna.

An analysis of multimode conical horn antennas with flare-angle changes by using generalized telegraphist's equation

A multimode conical horn antenna can realize a rotationally symmetric radiation pattern with a low cross polarization level by exciting a dominant mode and higher-order modes with appropriate composition ratios. One of the mechanisms to generate the higher-order modes is a flare type in which the flare angle of the horn is varied. This structure is simple and can be made only with a conductor. In this paper, an analysis of a flared multimode conical horn antenna using a generalized telegraphists equation is described. In the present method, many higher-order modes are considered in the telegraphists equation; the results are confirmed to agree well with the measured results and thus the validity of the method is proven. A design method based on the presented analysis procedure is also described. It is confirmed that sufficient accuracy can be obtained in this design.

Super lightweight planar array antenna with stretched structure for satellite communication systems

A novel planar antenna employing a stretched structure and meshed material is proposed in order to reduce the weight drastically and experimental results in S-band are described. As a result, the developed planar array antenna has a weight of 300 g/m/sup 2/, one third that of a conventional one, and has good RF performance.

A patterning method of polarization grids on a reflector using reflector surface developing technique

This article proposes a patterning method of polarization grids on a reflector using reflector surface developing technique for gridded reflector antennas. Gridded reflector antennas have excellent cross-polarization suppression characteristics caused by their polarization grids on a reflector. The proposed grid patterning method is simple to transcribe a plane grid pattern onto a curved reflector surface, being different from conventional complicated methods such as a direct photoetching method by N/C-driven laser system. A key technology for plane pattern design to obtain a desired pattern on a curved reflector surface is described. The method is evaluated through appropriate models and is verified by a measured radiation pattern.

Near-field to far-field transformation for RCS measurement including ground bounce

The authors propose a novel near-field to far-field radar cross-section RCS transformation method that is suitable for an outdoor RCS measurement. The validity of the proposed method is investigated by the simulation and measurement results.

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.