2009/02/18 IVS TDC Symposiumクワッドリッジホーンアンテナ クワッドリッジホーンアンテナ (( 広帯域フィ広帯域フィードード ) ) をを用いた電波望遠鏡の測地用いた電波望遠鏡の測地 VLBIVLBI における性能における性能評価評価Evaluation of a Radio Telescope Using a Quad-Evaluation of a Radio Telescope Using a Quad-

ridge Horn Antenna on Geodetic VLBIridge Horn Antenna on Geodetic VLBI

石井敦利石井敦利 1,2,31,2,3 ，市川隆一，市川隆一 22 ，瀧口博士，瀧口博士 22 岳藤一宏岳藤一宏 22 ，小山泰弘，小山泰弘 22 ，栗原忍，栗原忍 11 ，小門研亮，小門研亮 11 ，谷本大輔，谷本大輔

33

11 国土地理院，国土地理院， 22 情報通信研究機構　鹿島情報通信研究機構　鹿島 ,, 　　 33 株式会社エイ･イー･エ株式会社エイ･イー･エスス

2009/02/18 IVS TDC Symposium

Diameter of Diameter of AntennaAntenna

2.42.4 ｍｍAntenna TypeAntenna Type CassegrainCassegrainFrequencyFrequency 8180‐8600 MHz8180‐8600 MHzPolarizationPolarization RHCPRHCPNoise Noise TemperatureTemperature

System System ：： 127 K127 KReceiverReceiver ：： 116 K116 K

Aperture Aperture EfficiencyEfficiency

42%42%

Driving SpeedDriving Speed 1°1° ／／ secsec

A Original Radio TelescopeA Original Radio Telescope 　　CARAVAN2400CARAVAN2400

2009/02/18 IVS TDC Symposium

Retrofitted CARAVAN2400Retrofitted CARAVAN2400 　　Diameter of Diameter of AntennaAntenna

2.42.4 ｍｍAntenna TypeAntenna Type Front-fed Front-fed

ParaboloidParaboloidReceiving Receiving FrequencyFrequency

S-bandS-bandX-bandX-band

PolarizationPolarization RHCP RHCP or or LHCPLHCP

Receiver Noise Receiver Noise TemperatureTemperature

S-band S-band ： ： 86K86KX-band X-band ：：170K170K

Driving SpeedDriving Speed 1°1° ／／ secsec

Broad-band FeedBroad-band Feed

(Quad-ridge Horn)(Quad-ridge Horn)

Down ConverterDown Converter

2009/02/18 IVS TDC Symposium

Retrofitted CARAVAN2400 (Front-end)Retrofitted CARAVAN2400 (Front-end)

2009/02/18 IVS TDC Symposium

Retrofitted CARAVAN2400Retrofitted CARAVAN2400(Block Diagram of the Front-(Block Diagram of the Front-

end)end)

2009/02/18 IVS TDC Symposium

Geodetic VLBI ExperimentsGeodetic VLBI Experiments 　　

Experiment NameCA6264 CA7032 CA8175 CA8184

Date 2006 / 9 / 21 2007 / 2 / 1 2008 / 6 / 23 2008 / 7 / 2Station CARAVAN2400

Tsukuba 32mRetrofitted CARAVAN

Tsukuba 32mFrequency X-band 8 ch X-band 10ch, S-band 6chSampling parameter 16 MHz / ch, 1-bit sampling (Using K5)Number of observations

275 375 220 188

Actual duration 24.0 h 24.2 h 24.0 h 24.0 h

2009/02/18 IVS TDC Symposium

Geodetic VLBI Experiments contd.Geodetic VLBI Experiments contd. 　　

2009/02/18 IVS TDC Symposium

Why is wide-band feed Why is wide-band feed adopted?adopted? 　　　　

2009/02/18 IVS TDC Symposium

Why is wide-band feed Why is wide-band feed adopted?adopted? 　　　　　　

We are developing a new small radio telescope for geoWe are developing a new small radio telescope for geodetic VLBI.detic VLBI.

== 　　 MARBLE Compact VLBI SystemMARBLE Compact VLBI System 　　　　 < One of a d< One of a development task >evelopment task >　　　　 S/X band receiving simultaneouslyS/X band receiving simultaneously

< Requirements of the task >< Requirements of the task >　　 1) Compact1) Compact　　 2) Simple2) Simple　　 3) Inexpensive3) Inexpensive　　 4) RHCP and LHCP 4) RHCP and LHCP

2009/02/18 IVS TDC Symposium

Quad-ridge Horn Antenna (QRHA)Quad-ridge Horn Antenna (QRHA) 　　　　AdvantageAdvantage　　・・ WidebandWideband 　　　　　　　　 That cover multi-octave.That cover multi-octave.　・　・ Compact and lightCompact and light　・　・ Dual liner polarizationDual liner polarizationDisadvantageDisadvantage　・・ Beam width depend on frequencyBeam width depend on frequency　・　・ Phase center depend on frequencyPhase center depend on frequency　・　・ The beam pattern is not symmetry in E-plane and The beam pattern is not symmetry in E-plane and

H-plane.H-plane.

180mm180mm

2009/02/18 IVS TDC Symposium

Evaluation of Retrofitted Evaluation of Retrofitted CARAVAN2400CARAVAN2400 　　　　

2009/02/18 IVS TDC Symposium

Performance of Retrofitted CARAVANPerformance of Retrofitted CARAVAN System noise temperature (R-Sky method)System noise temperature (R-Sky method)

RR SkySkyMeasured System noise temperatureMeasured System noise temperature S-bandS-band ：： 280 K280 K (EL = 90 deg) (EL = 90 deg) ，， X-bandX-band ：： 245 K245 K (EL = 90 (EL = 90

deg)deg)

2009/02/18 IVS TDC Symposium

Performance of Retrofitted CARAVAN Performance of Retrofitted CARAVAN contd.contd. 　　　　

Aperture efficiency measurement using the moonAperture efficiency measurement using the moon

maidea LLkSAT 2/1_Ideal measured Ideal measured

temperaturetemperature　　 Area of dishArea of dish

Flux density of moonFlux density of moon

Boltzmann’s constantBoltzmann’s constant

Loss factor of Loss factor of atmosphereatmosphere

The shape The shape factorfactor

Measured temperatureMeasured temperature sysoffonmeasa TPPT _

Receiving Power from moonReceiving Power from moon Power of Power of background noisebackground noise

System noise System noise temperaturetemperature

Aperture Aperture efficiencyefficiency　　

ideameasa TT __＝ ＝ 6.3 ± 1.0 % (X-band)6.3 ± 1.0 % (X-band)

2009/02/18 IVS TDC Symposium

Performance of Retrofitted CARAVAN contd.Performance of Retrofitted CARAVAN contd.Calculated by reflector antenna analysis program Calculated by reflector antenna analysis program GRASP8GRASP8

37.7 dBi (Calculated gain) ‐ 46.5 dBi (Ideal gain) 37.7 dBi (Calculated gain) ‐ 46.5 dBi (Ideal gain) ＝ ＝ －－ 8.8 dB 8.8 dB ＝＝ 13 % (X-band)13 % (X-band)

Aperture Aperture efficiencyefficiency 　　

2009/02/18 IVS TDC Symposium

Aperture efficiency of Retrofitted Aperture efficiency of Retrofitted CARAVANCARAVAN 　　　　

((2.4m2.4m/2)/2)22π × π × 6 % 6 % ＝ ＝ × × 50 %50 %

2.4m2.4m ＝＝83cm83cm

((0.83m0.83m/2)/2)22ππ

2009/02/18 IVS TDC Symposium

ConclusionsConclusions 　　　　

2009/02/18 IVS TDC Symposium

ConclusionsConclusions

・・ We designed novel wideband radio telescope.We designed novel wideband radio telescope.　　 It adopted wideband feed of simple and compact. It adopted wideband feed of simple and compact. ・・ This radio telescope was confirmed to be able to This radio telescope was confirmed to be able to apply to geodetic VLBI. apply to geodetic VLBI.

But…But…・・ Low Aperture EfficiencyLow Aperture Efficiency・・ High Noise Temperature High Noise Temperature

2009/02/18 IVS TDC Symposium

OutlookOutlookA Prototype of MARBLE Compact VLBI System A Prototype of MARBLE Compact VLBI System 1) Using a optimum designed dish 1) Using a optimum designed dish 　　　　　　 Aperture efficiency Aperture efficiency ～～ 40% (X-band40% (X-band ，， Predicted)Predicted) 　　　　　　　　 (2.4m/2)(2.4m/2)22π x π x 6% 6% ＜＜ (1.65m/2)(1.65m/2)22π x π x 40%40%

2009/02/18 IVS TDC Symposium

Outlook contd.Outlook contd.A Prototype of MARBLE Compact VLBI System A Prototype of MARBLE Compact VLBI System 　　 2) Using a wideband low noise amplifier2) Using a wideband low noise amplifier 　　 S-band TrS-band Tr ｘ ： ｘ ： 86K86K 　　　　→→ 65K 65K 　　 X-band Trx X-band Trx ： ： 170K 170K →→ 65K 65K

2009/02/18 IVS TDC Symposium

Outlook contd.Outlook contd.A Prototype of MARBLE Compact VLBI SystemA Prototype of MARBLE Compact VLBI System