Yoshio Inasawa

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.

Design Method for a Low-Profile Dual-Shaped Reflector Antenna with an Elliptical Aperture by the Suppression of Undesired Scattering

A design method is proposed for a low-profile dual-shaped reflector antenna for the mobile satellite communications. The antenna is required to be low-profile because of mount restrictions. However, reduction of its height generally causes degradation of antenna performance. Firstly, an initial low-profile reflector antenna with an elliptical aperture is designed by using Geometrical Optics (GO) shaping. Then a Physical Optics (PO) shaping technique is applied to optimize the gain and sidelobes including mitigation of undesired scattering. The developed design method provides highly accurate design procedure for electrically small reflector antennas. Fabrication and measurement of a prototype antenna support the theory.

Tradeoff study on array-fed reflector antennas for 100-beam-class multibeam communications satellite

Mobile satellite communications systems using 100-beam-class multibeam on-board antenna have been proposed and some of them are already in operation [1–3]. Such systems can concentrate the resource, such as bandwidth, power, etc, on a specific beam. Therefore, these are effective for emergency operation under natural disaster. For such kind of the on-board antennas, size and power consumption are important to install the antenna in the satellite. We studied a tradeoff on the on-board antenna from the view point of size and power consumption. For that purpose, the size is evaluated by the element number of the feed-array. The power consumption is evaluated by that of High Power Amplifiers (HPAs) connected with the elements, because the power consumption of HPAs dominates that of the satellite payload. On our study, we assume S-band system using cellular-phone-size terminals and 30 m-diameter on-board antenna which is an array-fed offset paraboloidal reflector antenna.

One-dimensional beam scanning reflector antenna for small satellite applications

We propose a new compact center-fed reflector antenna with one-dimensional beam scanning function for small satellite application. The proposed antenna has different curves in orthogonal two cross sections. The beam scanning cross section is an imaging reflector form. The non-beam scanning cross section is an axial symmetry Cassegrain form. In this paper, we describe the design method of the proposed antenna based on a doubly curved reflector. The measurement of a prototype antenna demonstrates the validity of the proposed antenna.

Near-Field to Far-Field Transformation for an Outdoor RCS Range

This paper presents the near-field to far-field transformation for an outdoor radar cross section (RCS) range. Direct measurement of the large actual target requires quite a long measurement range. The near-field to far-field RCS transformation method achieves the reduction of measurement range. However the non-uniformity of the incident electric field distribution on the target causes some errors in RCS prediction. We propose a novel near-field to far-field RCS transformation method that can be applied to an outdoor RCS measurement. The non-uniformity of the incident electric field distribution is successfully resolved by introducing the correction term of the ground bounce. We investigate the validity of the proposed method by the simulation and measurement.

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.

A study on characteristic basis function method using combined IP-CBF

We proposed an improved technique of the analysis accuracy for the characteristic basis function method (CBFM) using the multilevel approach. In this technique, improved primary CBFs (IP-CBFs) are used for taking into account multiple scattering between each block. The radar cross section (RCS) of a perfect electric conductor cube was analyzed by using the proposed technique. It was found that analysis accuracy is improved compared by the results of the conventional method.

Calculation accuracy and time of outdoor propagation estimation using vertical plane launch

In the design of radio placement on the large outdoor environments, the huge calculation time of radio propagation estimation is critical matter. In order to shorten the calculation time, we are developing a simulator using vertical plane launch (VPL) technique which is known as speedy ray searching method. In this paper, we evaluate the calculation accuracy and the calculation time of the VPL. First, we describe the calculation procedure of VPL. Next, we describe the measurement of propagation characteristics in an outdoor environment which size is 200 m × 200 m. We put base station on a roof top, and measure the propagation characteristics along some routes on the ground. We compare the measurements with the estimation result of developed, imaging, and ray-launching methods, and then show that the calculation error of the each method is around 5dB. However, the calculation time of developed method is 1/150 of imaging method and 1/7 of ray-launching method. Therefore capability of radio propagation estimation in extremely short time is realized.

Verification of characteristic basis function method using fast far-field approximation

In this paper, we evaluate the fast far-field approximation (FaFFA) for the characteristic basis function method (CBFM). By adopting the FaFFA to the CBFM, impedance matrix calculation time can be accelerated. We calculate the radar cross section of the conductor plate with the use of FaFFA-CBFM, and compare the results with ordinary-CBFM. Both results are in good agreement, and FaFFA-CBFM is faster than the conventional method.

Trade-off of multibeam reflector antenna configuration for satellite onboard application

Recently, demands on high throughput communication for airplanes and ships by high throughput satellite using Ka-band have been increased. Frequency and polarization reuse method with covering service area by multiple spot beams is widely adopted to increase frequency band efficiency. A configuration of reflector and multiple primary feeds is widely used for multi-beam antenna because of its high gain property and simple configuration. In this paper, two configurations, single feed per beam and multiple feed per beam, are compared by Ka-band 16 multibeam scenario.