1 Introduction

The ETS-VIII (Engineering Test Satellite-VIII) is equipped with phased array antennasthat use large deployable reflectors as primarymirrors. Setup commands must be executedfor the controller (BFC) of the beam-formingnetwork (BFN1; for related details, see an arti-cle “3-6-3 Beam-forming network” of thisspecial issue.) used. Setup of the BFCinvolves a variety of data, including phase andamplitude parameters required for beam for-mation, necessitating the execution of a largenumber of commands. To render BFN opera-tion more efficient and to save labor in thesetup process, a fixed BFN operating system(BFNOS) has been established. The BFNOSmanages, in a unified manner, the variousparameters required to run the BFN1. TheBFNOS controls the BFN1, constructs arrayweight tables, and displays beam pattern simu-lations. Together these functions combine toyield greater operational efficiency.

2 System configuration

The hardware for the BFNOS consists of acommercially available personal computerrunning under a JAVA-based software devel-opment environment.

The BFNOS is a dedicated element for anexperimental telemetry and command system(T&C system, see an article “4-3 Telemetryand command processing system for experi-ments” of this special issue.) and is connectedvia LAN to the T&C system through a TCP/IPnetwork adapter. RAID-based network stor-age within the T&C system ensures the coor-dination of data between the BFNOS and theT&C system, incorporating the commandsgenerated from within the BFNOS and thetelemetry data transmitted from the satellite.

3 Main functions

Numerous parameters must be set toenable operation of the BFN1, including thephase and amplitude parameters required forbeam formation, BFN1 error correction data,reflector data, and antenna coordinate data.The BFNOS manages these various types ofdata via personal computer, generates the nec-essary command streams, and transmits thecommands through the T&C system. TheBFNOS also displays the telemetry data forthe BFN1 and the BFC, calculates arrayweight, and simulates beam patterns. In short,the BFNOS controls nearly all of the datarequired for operation of the phased arrayantennas of the ETS-VIII. However, BFNOS

IDE Toshiyuki and OKUMURA Minoru 155

4-4 BFN Operating System

IDE Toshiyuki and OKUMURA Minoru

Numerous parameters are required for the setup of Beam-Forming Networks used inphased-array antenna systems. For this reason, a fixed BFN operating system was estab-lished with the aim of increasing efficiency and saving labor. This system manages the vari-ous parameters required for the employment of a BFN unitary, resulting in the more efficientuse of BFN.

Keywords Beam-forming network, Command, Telemetry, Operation

156

manages only a packet command. The poweron/ off operations for the BFN1 and BFC areexecuted by the T&C system.

The BFNOS has five main functions asfollows. The parameter input and settings ofeach function are input via a graphical userinterface (GUI) for a simplification over tradi-tional command-line input troublesome.

3.1 Command generationThis function involves the generation of

commands required to transmit data to the

satellite. Data to be transmitted include set-tings for the operation mode of the antennafeed system, various operational parameters,the array weight table, and the on-board soft-ware. Table 1 lists the various BFC com-mands.

In the MMIC used to set array weight—the main circuit component of the BFN1—there are numerous semiconductor switches tocontrol phase and set amplitude. Accuratesetup of the BFN1 requires advance recording,in the BFN error correction table, of phase and

Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003

List of BFC parameter setup commandsTable 1

amplitude errors attributable to these switches.This data must be transmitted prior to opera-tion of the BFN1, with the initial transfer char-acteristics as the initial setting parameters.Thus, the command for each parameter settingis generated in advance using the GUI com-mand generation and edit function and storedin the hard disk as a command file. Fig.1shows a screen shot of the MMIC error cor-rection table of an example command genera-tion and edit screen. It is also possible to gen-erate array weight setup commands for beam-pattern formation and to verify this patternusing the antenna beam simulation functiondescribed below.

Other command files are also created forother commands in addition to those for theMMIC settings. Fig.2 shows the antenna sys-tem coordinate setup screen.

3.2 Command transmissionThe command transmitting function stores

the generated command and antenna beampattern information to the RAID disk of theT&C system, and transmits a commandthrough the T&C system.

This function enables transmission of thecommand files described in the previous sub-section, including those for the initial settingparameters and the MMIC setting parameters.It also allows for the transmission of com-mands for any array weight table setting gen-erated using the beam forming functiondescribed in the next subsection. This func-tion thus facilitates modification of arrayweight.

3.3 Antenna beam formation The antenna beam formation function cal-

culates the array weight of the antenna feedsystem using the set parameters (includingsatellite position, central coordinates of theantenna beam, and specifications of the feedsystem and the reflector) and generates thecorresponding array weight table. When cal-culating array weight, the gain constraintpoints must be specified in order to secure therequired service area and to provide isolationbetween adjacent beams. Specifying a givencenter of beam directivity on the map indicat-ed in Fig.3 automatically sets 13 constraintpoints in accordance with the ETS-VIII mis-sion specifications. Although operation issimplified in this manner, it is also possible toedit constraint point data using the edit screenshown in Fig.4. Further, this antenna beamformation function can generate the arrayweight for any given beam pattern. Fig.5shows an example of the array weight tableedit screen.

IDE Toshiyuki and OKUMURA Minoru 157

MMIC error correction table setupscreen

Fig.1

Antenna-satellite system coordinatesetup screen

Fig.2

158

3.4 Antenna beam simulationThe antenna beam pattern is simulated

using the set parameters (including arrayweight and reflector specifications) and gener-ates a contour map. Fig.6 shows an exampleof the displayed map. Using this function, thebeam pattern constructed based on the arrayweight generated in the previous subsectioncan be verified on the map. As shown inFig.7, two beam patterns can be displayed onthe same screen, enabling evaluation of beamisolation and other characteristics.

The antenna beam pattern diagram dis-played here can be transmitted to networkstorage within the T & C system and displayedsimilarly on a T & C system screen.

3.5 Telemetry display The telemetry display function calls up

data from the T&C system and provides BFCtelemetry display. Table 2 provides a list ofBFC telemetry data. Both the real-timeprocess screen and the history display screenwill display BFC setting status. The contentsdisplayed based on this function are the sameas the contents displayed using the telemetrydisplay function within the T & C system.

4 Summary

A BFNOS has been established for theunified management of the parametersrequired for operation of phased array anten-nas. This BFNOS enables the efficient per-formance of transmission experiments usingthe large deployable antennas of the ETS-VIII,including the initial setup of the BFN1 andBFC elements, generation of array weightparameters, and antenna pattern simulations.At the time of writing of this article, satelliteproto-flight test was underway, along withconcurrent improvements to system software.By the time of initial satellite operation, thesystem will have undergone even furtherimprovements to operability, including opti-mized parameter settings based on the resultsof final electrical performance tests.

Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003

Beam center specification screenFig.3

Gain constraint point edit screenFig.4

Example array weight table editscreen

Fig.5

IDE Toshiyuki and OKUMURA Minoru 159

Example contour mapFig.6

Example contour map with two beamsFig.7

160 Journal of the National Institute of Information and Communications Technology Vol.50 Nos.3/4 2003

List of BFC telemetry dataTable 2

IDE Toshiyuki

Senior Researcher, Mobile SatelliteCommunications Group, WirelessCommunications Division

Wireless Communications

OKUMURA Minoru

Antenna and Passive EquipmentGroup, Space Subsystem and Equip-ment Division, NEC TOSHIBA SpaceSystems, Ltd.

Satellite Onboard Antenna and RemoteSensing Equipment