In order to improve an oceanic air traffic control system and a navigation system for ships, Electronic Navigation Research Institute (ENRI) has been conducting the navigation experiment using Engineering Test Satellite-V (ETS-V). A transponder called AMEX (Aeronautical Maritime EXperimental transponder) is installed on board the ETS-V. The AMEX consists of a C-band (5/6GHz) section, an L-band (1.5/1.6GHz) section of the transponder and two antennas (C-band and L-band). A C-band frequency is used for the feeder link between the satellite and a ground earth station. An L-band frequency is used for the link between the satellite and mobile stations such as aircraft or ships.

The AMEX has been developed jointly by Ministry of Transport (MOT), Ministry of Posts and Telecommunications (MPT), and NAtional Space Development Agency (NASDA). The development of the AMEX was shared by ENRI of MOT for the C-band section, by Communications Research Laboratry (CRL) of MPT for the L-band section, and by NASDA for the two antennas. The AMEX had been completed by the end of 1985. The ETS-V (with AMEX) was launched by the H-1 rocket on August 27, 1987 and put into the geostationay orbit of 150 degrees East.

This paper describes the circuit configurations and electrical characteristics of each component in the C-band section.

The C-band section was developed in two phases. The first phase is about the engineering model to evaluate electrical characteristics and circuit configurations. And the second phase is about the flight model to test under various environmental conditions which are estimated to be exposed during the launch and space.

The results of these tests showed that the flight model met all requirements, the mechanical configurations, the electrical charactaristics and the various environmental conditions.

The Japanese Engineering Test Satellite V (ETS-V) was launched on 27 August 1987. The ETS-V is the Japanese first domestically developed 3-axis stabilized geostationary satellite of 550 kg class. The main mission on orbit is for mobile satellite communication experiments with aircraft, ships and land mobiles. The communication transponder on the ETS-V is called AMEX (Aeronautical Maritime Experimental Transponder). The AMEX provides links between the fixed earth station and mobile earth stations, and between one mobile station and others. L-band frequencies are used for mobile links and C-band frequencies for the feeder link. The AMEX is developed by the Electronic Navigation Research Institute (ENRI), Ministry of Transport, the Communications Research Laboratory (CRL), Ministry of Posts and Telecommunications and the National Space Development Agency of Japan (NASDA) in cooperation.

This report describes the outline of the AMEX, the characteristics of major components and the results of the checkout after the launch.

The AMEX is a double conversion type transponder between L-band and C-band with the IF frequency of 140 MHz. The AMEX consists of an L-band antenna (1.5m offset parabolic antenna), a C-band antenna (22cm horn antenna), a C-band part, a L-band part and an IF part. The L-band antenna has 2-beam coverages over the northern pacific ocean and the southern pacific ocean.

Class-A GaAs FET high power amplifiers (HPA) are used for L-band and C-band considering the channel operation in SCPC mode. The saturated power per beam is more than 25 W for the L-band HPA and more than 8 W for the C-band HPA. Low noise amplifiers (LNA) of GaAs FET are used for low level signals. Noise figure of the L-band LNA and the C-band LNA is 1.6dB and 2.1dB, respectively.

In order to improve an oceanic air traffic control system and a navigation system for ships, the Electronic Navigation Research Institute (ENRI) is conducting the navigation experiments using the Engineering Test Satellite V (EST-V) from November 1987. The ENRI developed the experimental mobile satellite communication system and ranging system using a mobile antenna with a gain of more than 4 dBi. The data communication with 2.4 kbps information rate, the digital voice communication with 2.4 kbps Linear Predictive Coding (LPC) and the Narrow Band FM (NBFM) with 15 kHz bandwidth are possible in this communication system. The developed ranging system for mobile positioning can measure the range within 0.6 seconds per one mobile with ranging accuracy of one hundred meters.

This report describes the outline and characteristics of the ranging equipment, modems, and data collection and data processing system in the Aeronautical/Coast Earth Station (ACES).

From the test results in the ACES, the ranging accuracy is less than 100m(rms) for C/No of above 41 dBHz. When 8-level soft decision Viterbi decoding and 4.8 kbps BPSK modem are used, BER=10^-5 can be obtained with C/No=39∼40 dBHz. The threshold level of the NBFM is C/No=48∼49 dBHz. Digital voice communication is possible over C/No=39 dBHz with the 2.4 kbps LPC using Forward Error Correction (FEC), and over C/No=47∼48 dBHz with the 4.8 kbps LPC without using FEC. The multipath in the aeconautical mobile satellite link can be measured by using the spread spectrum signal with S/N of more than 10 dB at C/No of 50 dBHz.

As a conclusion, to evaluate the mobile satellite communication system and raging system, our experimental system has adequate performances.

This report describes the configuration and performance of the airborne equipment developed for navigation experiment using Engineering Test Satellite-V(ETS-V). A pair of airborne equipment have been developed and installed on a Beechcraft B99 of the ENRI and a Boeing 747 cargo aircraft of Japan Air Lines. Each of them consists of L-band antennas, a transmitter/receiver, MODEM's and a data processor, etc. It has capabilities to conduct voice/data communications and to return ranging signals in response to interogations from the ground earth station.

Three circular patch antennas (peak gain: 7dBi) are mounted on the B747. One of them is selected with switches to cover the satellite direction on the NOPAC route. The B99 has a 4-element conformal array (peak gain: 10dBi) on each side and a circular patch antenna (peak gain: 7dBi) in the nose radome. One of these antennas giving the most appropriate coverage is selected with switches according to the satellite direction. This configuration gives almost entire coverage over the upper hemisphere of the aircraft except for the backward direction.

The MODEM's of BPSK, A-QPSK and PM, and a SS modulator are installed on board the aircraft for data communications. For digital voice communication, an LPC voice codec is used with the BPSK MODEM. An NBFM MODEM is used for comparison with the digital voice communication.

Both airborne equipment have been tested and confirmed to meet the requirement for electrical performances under environmental conditions specified in RTCA's DO-160A.

This paper describes the principle of the experimental ranging system and the result of the ranging experiment using the ETS-V. The ranging system uses multiplexed burst signals of sinusoidal tone and data with 0.5 sec duration. The distance between the ETS-V and ships is obtained by measuring the phase delay of the sinusoidal tone for fine ranging and the time delay of the data for ambiguity resolution in the ranging equipment.

The ranging experiment was carried out on the South China Sea and the Indian Ocean in 1989. Satellite elevation angles in these areas were 45° and 14°, respectively. The ranging accuracy of less than 50m rms could be obtained for the C/No of more than 42 dBHz and the characteristics of the ranging accuracy showed the degradation of about 2.5 dB in C/No compared with the theoretical value. The signal acquisition time of less than 193.3 msec could be obtained for the C/No of more than 42 dBHz at both elevation angles, but it varied widely for the C/No of less than 44 dBHz due to multipath fading when the elevation angle is 14°.

In order to develop satellite communication and ranging techniques for aircraft and ships in the oceanic area, ENRI started navigation experiment using ETS-V in November 1987. Ship experiments with medium-gain antenna (gain: 12.7dBi) were carried out on the Indian Ocean and with low-gain one (5.8dBi) on the North Pacific. This paper describes the system and the results of the ship experiments using the low-gain antenna.

The low-gain antenna used was a single-element of circular patch one and had a wide beam width. This is considered to cause multipath fading and deteriorate the system performance particularly when the satellite elevation angle (EL) is low. The main purpose of the experiments is to investigate the system performance at the low EL.

The experiment items are as follows: (1) radio propagation (2) data communication and (3) ranging. Propagation experiments showed the fading range was about 3 dB at the EL of 40 degrees and increased rapidly as the EL became low. The performance required for data communication is the bit error rate of 10^-5. This performance was attained at C/N₀=46dBHz even at the low EL, when error correction and bit-interleave techniques were used. Our goal for the ranging experiment is the accuracy of 100 m rms and was reached at C/N₀=43dBHz in the experiment. However the rate of successful ranging was about 50% even at C/N₀=45dBHz. This low rate may have much influence on the system performance.