1 Introduction

The Engineering Test Satellite VIII (ETS-VIII) will be equipped with a large deployableantenna (with an effective aperture diameter of13 m) to maintain sufficient antenna gain formobile satellite communication experiments,including voice communications with hand-held terminals and high-speed data communi-cations [1] [2]. The evaluation of ground andin-orbit characteristics of the large deployableantenna is essential to the development of thefuture satellite on-board antennas necessaryfor future satellite communications systems.The results of deployment tests and evalua-tions of electrical characteristics on the groundhave been reported already [3] [4]. On theother hand, the evaluation of the in-orbit char-acteristics of the onboard antennas is sched-uled to begin following the launch of the ETS-VIII.

To evaluate the characteristics of the ETS-VIII onboard antennas, such as in-orbit radia-tion patterns and reflector surface distortion,the CRL has designed experiments to measurethe receiving signal power at multiple-loca-tions in the coverage area of a single satellitebeam. The newly developed portable earth

station discussed herein will be used for meas-uring the receiving signal power.

The portable earth station is also designedas an RF unit, which will enable communica-tion experiments through modem connectionfor IF signal input and output. This paper dis-cusses the configuration and electrical charac-teristics of the developed prototype portableearth station.

2 Configuration of the portableearth station

2.1 Circuit configurationFig.1 shows a block diagram of the

portable earth station. The design specifica-tions of the station include a transmissionEIRP of 20 dBW or greater at an antenna gainof 12 dBi, a G/T of－15 dB/K or greater (atthe output terminal of the low noise amplifier(LNA)), a dynamic range in measurement of30 dB or greater for receiving signal power, atransmission frequency band of 2657.5 ±2.5MHz, and a receiving frequency band of2502.5 MHz ±2.5 MHz.

The portable earth station consists mainlyof the antenna unit, transmission unit, receiv-ing unit, measurement and control unit, and

JANG Jae-Hyeuk et al. 169

4-6 Portable Earth Station4-6-1 RF Unit for Portable Earth StationJANG Jae-Hyeuk, MIURA Amane, and YAMAMOTO Shin-ichi

For the purpose of verifying the in-orbit electrical characteristics of the Engineering TestSatellite VIII (ETS-VIII) on-board antenna, we plan to measure the receiving signal power atmultiple points in the beam area of it. We developed the portable earth station for measur-ing the receiving signal power and measured the electrical performance. The measurementresults show that the expected performance can be achieved for the portable earth station.

Keywords Engineering Test Satellite VIII, On-board antenna, In-orbit electrical characteristics,Portable earth station.

170

frequency conversion unit. The configurationof each of these units is described below.

(1) Antenna unit (Ant. unit)The antenna unit consists of an S-band

stair type array antenna (also used for automo-bile-based mobile stations), in addition to thepower divider and phase shifter required tooperate the antenna. The antenna consists of 4rows of sequentially rotated 1×4 elementarrays, in which the two front rows are used totransmit signals and the two rear rows areused to receive signals. Experimental resultsshow that the antenna gain is 12 dBi or greaterin both transmission and reception. The con-figuration and electrical characteristics of theantenna unit are described in more detail in 4-5, “Land mobile station for ETS-VIII mobilesatellite communications experiments.”

(2) Frequency conversion unit (Up/Down con-verter)The frequency conversion unit will not be

used to measure the onboard antenna charac-teristics but instead will be used solely forcommunication experiments, which will be

performed through a modem connectionenabling input and output of IF signals at 140MHz and －10 dBm. The frequency conver-sion unit consists of an up converter and adown converter.

The up converter is designed to convertinput IF signals at 140 MHz and －10 dBminto output RF signals at a frequency of2657.5 MHz and at power of 0 dBm orgreater. The down converter is designed toconvert input RF signals at 2502.5 MHz and－30 dBm into output IF signals at 140 MHzand power of －10 dBm or greater. Tables 1and 2 show the main specifications of the upand down converter components, respectively.

(3) Transmission unit (Tx unit)As the frequency conversion unit is used

only for communication experiments, anotherCW signal source is required to supply trans-mission signals when measuring the character-istics of the onboard antenna. Thus, a crystaloscillator and a filter featuring performanceequivalent to that of the band-pass filter (BPF)in the up converter are installed in the trans-mission unit to measure these characteristics.

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

Block diagram of the portable earth stationFig.1

The transmission unit consists of a stepattenuator, a solid-state power amplifier(SSPA), a band-pass filter (BBF), a directionalcoupler having a coupling factor of 30 dB, anRF switch, and a coaxial fixed termination,arranged in this order from the input terminal.The circuit is designed to output signals at2657.5 MHz and 40 dBm (10 W) or greater inresponse to input signals from the up convert-er of the frequency conversion unit or fromthe crystal oscillator installed in the transmis-sion unit.

The Switch/Step attenuator driver of thesignal measurement and control unit controlsthe step attenuator and the RF switch, the for-mer adjusts the power level of the transmis-sion signals and the latter switches the trans-mission signals between the fixed termination

and transmission output terminal. The trans-mitted signals are monitored by measuring thecoupled power of the directional coupler usingthe power meter installed in the signal meas-urement and control unit. Table 3 shows themain specifications of the transmission unitcomponents.

(4) Receiving unit (Rx unit)The receiving unit consists of a BPF

(band-pass filter), an LNA (low noise amplifi-er), and an AMP (amplifier), arranged in thisorder from the input terminal. The circuit isdesigned to produce output signals at －30dBm or greater following input of a signal at2502.5 MHz and －100 dBm. Table 4 showsthe main specifications of the receiving unitcomponents.

JANG Jae-Hyeuk et al. 171

Main specifications of the up con-verter components

Table 1 Main specifications of the downconverter components

Table 2

172

(5) Signal measurement and control unitThe signal measurement and control unit

consists of a spectrum analyzer, a power sen-sor, a power meter, a laptop PC, anSwitch/Step attenuator driver, a GPS antennaand receiver, and a 4-way lumped elementpower divider. This unit monitors the trans-

mitted and received signals and controls thesignal measurement equipment.

The spectrum analyzer measures thereceived signal power and the power metermonitors the transmitted signals. TheSwitch/Step attenuator driver controls the stepattenuator and the RF switch within the trans-mission unit. The GPS antenna and receiver isinstalled to supply the reference signal (10MHz) used to synchronize the signal measure-ment equipment and the local oscillator and todetermine time and position data. The refer-ence signal is supplied to the signal measure-ment equipment and other devices through the4-way lumped element power divider. Thelaptop PC is outfitted with a GPIB card and aserial port. A GPIB card is used to control thesignal measurement equipment and to recordmeasurement data. A serial port is used torecord the GPS receiver position and timedata.

(6) Other (data collection system)To evaluate electrical characteristics (such

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

Main specifications of the transmis-sion unit components

Table 3 Main specifications of the receivingunit components

Table 4

as radiation patterns, for example) of the satel-lite onboard antennas, we will build portableearth stations, arrange them discretely withinthe ground area irradiated from a single satel-lite beam, and measure the receiving signalpower. We will prepare a host computer, out-fitted with an ADSL modem, for remote con-trol of the separate portable earth stations andfor the simultaneous collection of dataobtained at each station, and will also preparemobile terminals, such as portable phones andPHS devices, to be installed in the portableearth stations in order to export measurementdata to the host computer. The host computerand the portable earth stations will be linkedvia Internet to form a data-collection systemcapable of managing all portable earth stationsin a unified manner. (See 4-6-4, “Data collec-tion system,” regarding the methods of remotecontrol and data collection.)

2.2 Configuration of the RF unit of theportable earth station prototype

Fig.2 shows the cabinet rack-mountedequipment and configuration diagram of theportable earth station prototype built accord-ing to the configuration shown in Fig.1. Theantenna unit, the receiving unit, and the GPSantenna are not shown in Fig.2, as we are nowconsidering a variable configuration for theinstallation of these components. For exam-ple, they may be installed away from the cabi-net rack for a clearer line of sight or they maybe installed on top of the cabinet rack, depend-ing on the position of the rack and on the spe-cific application.

The cabinet rack is 1100 mm high, 570mm wide, and 750 mm deep. There are 6shelves in the cabinet rack with fans mountedon the back to release heat.

The topmost sub-rack within the cabinetrack contains the components for the transmis-sion unit (except for the SSPA, which is toolarge to install in the sub-rack, as it isequipped with an integrated DC power supplyand a cooling fan; this device is installed onthe second shelf). When the transmission unitis in use, an RF cable connects the RF signal

input/output terminals on the front panel of thetransmission unit sub-rack and those on thefront of the SSPA.

With the exception of the SSPA device, thesecond to the fifth shelves house the signalmeasurement and control unit. The secondshelf holds the GPS receiver and the 4-waylumped element power divider (in front of theoutput terminal of the GPS receiver). Thethird shelf contains the laptop PC, the fourthshelf holds the spectrum analyzer, and theSwitch/Step attenuator driver and the powermeter are installed on the fifth shelf. The lap-top PC on the third shelf is mounted on a slid-ing steel tray that can be pulled out for use andpushed in for storage. The bottom sub-rackcontains the frequency conversion compo-nents for the up and down converters.

3 Electrical characteristics of theportable earth station

3.1 Electrical characteristics of the upconverter

Fig.3 is a diagram of power levels at con-secutive stages of the up converter. This dia-gram tracks the power level to be measuredfor an input IF signal of 140 MHz and －10dBm with an attenuation value for the variableattenuator of 0 dB. The output signal of themeasured up converter is at 2657.5 MHz and13.6 dBm. The maximum gain of the meas-ured up converter is 23.6 dB. The spurious

JANG Jae-Hyeuk et al. 173

Appearance and configuration dia-gram of the portable earth stationprototype((a) photograph of the portable earth sta-tion; (b) configuration diagram)

Fig.2

174

response is －70 dBc or less at 2657.5 ±2MHz, the amplitude-frequency characteristicis 0.41 dBp-p at 2657.5 ±3 MHz, and the vari-able range of the variable attenuator is 27 dB.As the up converter is used in the communica-tion experiment, it is necessary to measure thephase noise of the local oscillator in advance.Fig.4 shows the results of this phase-noisemeasurement.

3.2 Electrical characteristics of thetransmission unit

Fig.5 shows the input/output characteris-tics of the transmission unit. The values in thefigure are measured at the coupled output ter-minal of the directional coupler for a frequen-cy of 2657.5 MHz with the variable attenuatorof the transmission unit set to 0 dB. The sig-nal starts to saturate with input power of 0dBm; the output power here is 41.5 dBm.Gain in the linear region is 41.5 dB.

As described in the discussion of the cir-

cuit configuration of the transmission unit(2.2), the input signal for the transmission unitconsists either of the up converter signal or thetransmission unit’s oscillator signal. Thus,both of these signals are input into the trans-mission unit to measure spurious response andamplitude-frequency characteristics as the out-put power is adjusted to 40 dBm using thevariable attenuator. The resultant spuriousresponse values are －70 dBc or less at 2657.5±2 MHz for both signals. The amplitude-fre-quency characteristics values are 0.6 dBp-p at2657.5 ±3 MHz for the up converter signaland 0.5 dBp-p at 2657.5 ±3 MHz for the oscil-lator signal.

3.3 Electrical characteristics of thereceiving unit

Fig.6 is a diagram of power levels at con-secutive stages of the receiving unit. Themeasured values in the figure correspond to anRF input signal of 2502.5 MHz and－100dBm. The gain of the receiving unit is 84.8dB and the output power is －15.1 dBm. Theamplitude-frequency characteristic is 0.6 dBp-p at 2502.5 ±3 MHz, and the C/N ratio is 32dB or more at 2502.5 ±3 MHz (when theRBW of the spectrum analyzer is 3 kHz). TheC/N value indicates the output dynamic rangeof receiving signal power.

Fig.7 shows the input/output characteris-tics of the LNA in the receiving unit. The gainof the LNA is approximately 50 dB. The fig-ure noise is 0.4 dB. Assuming an antenna gain

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

Phase noise of the local oscillator inthe up converter at 2517.5 MHz

Fig.4

Diagram of power levels at consecu-tive stages of up converter

Fig.3

Input/output characteristics of thetransmission unit at 2657.5 MHz

Fig.5

JANG Jae-Hyeuk et al. 175

of 12 dBi, a feed line loss of 1 dB, antennanoise temperature of 300 K, and environmen-tal temperature of 300 K, G/T is calculated as－14.17 dBK.

3.4 Down converterFig.8 is a diagram of power levels at con-

secutive stages of the down converter. Thevalues in the figure are measured for an RFinput signal of 2502.5 MHz and －30 dBmwith the variable attenuator set to 0 dB. Themeasured output signal of the down converteris 140 MHz and 11.6 dBm, and the maximumgain is 41.6 dB. The spurious response is －30 dBc or less at 140 ±3 MHz, the amplitude-frequency characteristic is 0.6 dBp-p at 140±3 MHz, and the range of the variable attenua-tor is 21 dB.

Fig.9 shows the input/output characteris-

tics of the amplifier in the down converter.The gain in the linear region is 49.3 dB andthe signal starts to saturate with input powerof －22 dBm.

The phase noise of the local oscillator inthe down converter is measured similarly tothat of the local oscillator in the up converter.Fig.10 shows the results.

Diagram of power levels at consecu-tive stages of receiving unit

Fig.6

Input/output characteristics of theLNA at 2502.2 MHz

Fig.7

Diagram of power levels at consecu-tive stages of down converter

Fig.8

Input/output characteristics of amplifi-er in the down converter at 140 MHz

Fig.9

Phase noise of the local oscillator inthe down converter at 2363.5 MHz

Fig.10

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

4 Summary

We have discussed the circuit configura-tion and the electrical characteristics of theprototype portable earth station built to meas-ure the electrical characteristics of the ETS-VIII onboard antennas and to facilitate com-munication experiments. The ETS-VIII isplanned to be launched in the near future, andthe portable earth stations will be used for ini-tial verification of the onboard antennas afterlaunch. The portable earth stations will then

be used in the basic experimental phase inwhich the electrical characteristics of theonboard antennas are evaluated and communi-cation experiments are performed. Weplanned to build five portable earth stations bythe end of 2003. At the same time, we willconduct extensive preparations for post-launchexperimentation, including studies on methodsof evaluation of the onboard antenna, theplacement of the portable earth stations, andcalibration methods for the individual stations.

References1 N. Hamamoto, Y. Hashimoto, M. Sakasai, Y. Tsuchihashi, and M. Yoneda, "An experimental multimedia

mobile satellite communication system using the ETS-VIII satellite", AIAA-98-1301, A collection of technical

papers of the 17th ICSSC, pp. 408-416, Feb. 1998.

2 Y.Kawakami and S.Yoshimoto, "The onboard mission system for satellite mobile communications and

broadcasting in the ETS-VIII", AIAA ICSSC, 2000-1149, 2000.

3 T. Orikasa, K. Uchimaru, A. Tsujihara, and A. Miyasaka, "Development of the Large Deployable Reflector for

ETS-VIII Evaluation of the Electrical Characteristics", Technical Report of IEICE, AP2001-138, 65-72,

Nov.2001. (in Japanese)

4 T. Kuroiwa, Y. Tsutsumi, T. Maruyama, M. Homma, A. Tsujihata, A. Miyasaka, "Deployment testing for large

deployable reflector", 51th IAC, IAF-00-I.1.06, Oct. 2000.

JANG Jae-Hyeuk, Ph. D.

Research Fellow, Mobile SatelliteCommunications Group, WirelessCommunications Division

Antenna, Radio Wave Propagation,Satellite Communications

YAMAMOTO Shin-ichi

Senior Reseacher, Mobile SatelliteCommunications Group, WirelessCommunications Division

Mobile Satellite Communications

MIURA Amane, Ph. D.

Senior Researcher, Mobile SatelliteCommunications Group, WirelessCommunications Division

Antenna, Satellite Communications