Shinichi Taira

S-band active phased array antenna with analog phase shifters using double-balanced mixers for mobile SATCOM vehicles

We propose an S-band active phased array antenna (APAA) with analog phase shifters (PSs) that use double-balanced mixers (DBMs). The quadrature phase shift keying modulator integrated circuits (ICs) used as the phase shifters can control both the amplitude and phase of the input signal continuously and independently by using the control voltages. The phase and amplitude errors during phase rotation were 0.5/spl deg/ rms (max=1.7/spl deg/) and 0.3 dB rms (max=0.7 dB), respectively. The range in which the amplitude could be linearly changed was 7 dB. The proposed antenna exhibited sufficient performance for mobile vehicles to handle satellite communications: beam-pointing resolution of 0.04/spl deg/, beam-pointing accuracy in the null pointing of 0.4/spl deg/ rms, and sidelobe suppression with an amplitude taper achieved by setting the amplitude of the PS using two DBMs. Comparison between the analog PS and a reflection-type four-bit digital PS showed that although the analog one is unsuitable for use in a passive PAA, it is suitable for use in an APAA.

Development of the onboard processor for Pi-SAR2

The synthetic aperture radar (SAR) has been utilized for monitoring natural disaster areas because the SAR observation can be performed irrespective of the daylight and weather conditions. To reduce the time from observation to distributing SAR images to the headquarters for disaster control and disaster area, we have developed an onboard processor which is capable of doing a full-spec processing for the airborne SAR called as the polarimetric and interferometric SAR (Pi-SAR2) since 2009. We demonstrated that the developed onboard processor is effective to reduce the time from observation to distribution and the SAR image can be transferred to the ground within 15 min after observation via the communication satellite called as the engineering test satellite VIII (ETS-VIII) in the experiments on March 2011.

Introduction of a terrestrial free-space optical communications network facility: IN-orbit and Networked Optical ground stations experimental Verification Advanced testbed (INNOVA)

A terrestrial free-space optical communications network facility, named IN-orbit and Networked Optical ground stations experimental Verification Advanced testbed (INNOVA) is introduced. Many demonstrations have been conducted to verify the usability of sophisticated optical communications equipment in orbit. However, the influence of terrestrial weather conditions remains as an issue to be solved. One potential solution is site diversity, where several ground stations are used. In such systems, implementing direct high-speed optical communications links for transmission of data from satellites to terrestrial sites requires that links can be established even in the presence of clouds and rain. NICT is developing a terrestrial free-space optical communications network called INNOVA for future airborne and satellitebased optical communications projects. Several ground stations and environmental monitoring stations around Japan are being used to explore the site diversity concept. This paper describes the terrestrial free-space optical communications network facility, the monitoring stations around Japan for free-space laser communications, and potential research at NICT.

Development of Ka-band Aeronautical Earth Station for WINDS

Remoteley sensed images are useful for assessing damage caused by large-scale disasters. However, observation data recorded using aircraft are currently transmitted after the plane has landed using a terrestrial network, as inflight satellite communication links are inadequate. Therefore, the process of obtaining data is time-consuming. In this respect, the National Institute of Information and Communicaitons Technology (NICT) have developed an aeronautical earth station for the Wideband InterNetworking test and Demonstration Satellite (WINDS), wherein the remote sensing data observed from the aircraft can be transmitted via satellite links. NICT established the aeronautical earth station onboard an aircraft (Gulfstream II). A test flight was then conducted tomeasure the antenna teacking performance. Results confirmed that the tracking performance was good and that the interlock function worked when the drive angle was at limited values.

A Study on an Onboard Switch for Mobile Satellite Communications

An onboard switch enables satellite communications systems with a multibeam structure to operate more efficiently. A study of an onboard baseband switch for mobile satellite communication network has been conducted. In this baseband switch, field programmable gate arrays are used for signal processing, and the OpenFlow protocol is applied as the switch control. A breadboard model of an onboard switch has been developed for evaluating its performance. The performance test results for the breadboard model showed that the performance of the onboard switch is sufficient to meet its design. The adoption of field programmable gate arrays and the OpenFlow protocol for the onboard switch make it possible to construct a highly flexible onboard system.

Initial Performance of an Onboard Packet Switch for High-Data-Rate Mobile Satellite Communications

The use of an onboard switch results in a more effective multi-beam satellite communications system. The National Institute of Information and Communications Technology has been studying a mobile satellite communications network, and developing an onboard packet switch. A compact mobile earth station that can be installed in mobile systems or easily carried anywhere has been assumed for this communication system. This system is used to realize mobile satellite communications networks with a signal transmission rate of more than several hundred kilobits per second. The onboard packet switch functions as bridges operating in the data link layer of the open systems interconnect networking model. When the switch is located in a satellite, the satellite can be regarded as the central hub. One beam of the mobile link corresponds to one segment of the network. The bridges’ learning process is carried out between the beams, and the switching system builds and maintains tables with media access control address information. The onboard packet switch was installed in the Engineering Test Satellite Eight, which was launched by the H-IIA rocket in December 2006. An initial test in the geostationary satellite orbit has already been conducted. The results of the test show that the onboard packet switch satisfied system requirements.

A study of an optical profile for the prediction of satellite mobile communication channel to support telemedicine on route

We are aiming to create an optical profile to support mobile e-Health and to confirm the merits of the High inclined Earth Orbiter in the nation wide. This paper deals with actual optical data in the urban and sub-urban area in Japan captured with Fisheye camera, and 6 Hi-vision cameras. Also the data of the receiving power density on S band of the mobile satellite(GEO) obtained, and we show the analysis of the both data(optical and radio), and its models to predict propagation from the land mobile satellite service(LMSS). This optical study was well done. The result of comparing with ITU-R simulation might be acceptable to predict the satellite propagation of the line of sight in urban area. We intend to study more using with ETS-VIII the next generation mobile communications satellite with NICT.

S-BAND MOBILE VEHICULAR ACTIVE PHASED ARRAY ANTENNEA FOR SATELLITE COMMUNICATIONS USING ETS-VIII SATELLITE

This paper describes an S-band active phased array antenna (APAA) for vehicles to handle satellite communications. It was developed for mobile satellite communications experiments using the Japanese engineering test satellite ETS-VIII, which will be launched in 2004. It is a fully electronic beam-scanning antenna whose gain in the scanning range is above 12.3 dBi. It is 440 mm in diameter and 117 mm high. Two-layer self-diplexing antennas used as radiating elements of the array and dense allocation of the radio frequency (RF) devices enable the antenna to have a compact and low-profile body. An endless phase shifter using double balanced mixers (DBM-PS) can precisely control not only the signal’s phase but also its amplitude. The amplitude and phase variance during the phase shift from 0° to 360° in the four phase shifters are -0.6 dB to 0.7 dB and -1.7° to 1.2°, respectively. The dynamic range of the amplitude control in these phase shifters is around 7 dB. The beam controller has two closed-loop tracking methods: using a sum or difference pattern. Antenna using these methods showed similar variances of the receiving signal power of around 1 dB when the antenna was rotated in the azimuth plane at an angular velocity of 30°/s.

Field tests of a spread spectrum land mobile satellite communicationsystem using ETS-V satellite

The performance of a Direct Sequence Spread Spectrum Communication system in actual land mobile satellite channel is evaluated with experiments. Field test results in L-band with the ETS-V satellite are presented, in which the use of a multi-bitquantized Coherent Matched Filter receiver improves the initial acquisition and the bit error rate performances. The BER characteristics in urban and suburban environments are found to agree with that of nonSS BPSK on a non-selective Rician fading channel.