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Performance Evaluation of Radio Telescope Using Quad-ridge Horn Antenna on Geodetic VLBI

This study evaluates the performance of a radio telescope equipped with a quad-ridge horn antenna for geodetic VLBI. The evaluation includes system noise temperature measurement, aperture efficiency measurement, and comparison with ideal performance. The results show the potential of the retrofitted radio telescope for geodetic VLBI applications.

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Performance Evaluation of Radio Telescope Using Quad-ridge Horn Antenna on Geodetic VLBI

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  1. クワッドリッジホーンアンテナ (広帯域フィード) を用いた電波望遠鏡の測地VLBIにおける性能評価Evaluation of a Radio Telescope Using a Quad-ridge Horn Antenna on Geodetic VLBI 石井敦利1,2,3，市川隆一2，瀧口博士2 岳藤一宏2，小山泰弘2，栗原忍1，小門研亮1，谷本大輔3 1国土地理院，2情報通信研究機構　鹿島,3株式会社エイ･イー･エス

  2. A Original Radio Telescope CARAVAN2400

  3. Retrofitted CARAVAN2400 Broad-band Feed (Quad-ridge Horn) Down Converter

  4. Retrofitted CARAVAN2400 (Front-end)

  5. Retrofitted CARAVAN2400 (Block Diagram of the Front-end)

  6. Geodetic VLBI Experiments

  7. Geodetic VLBI Experiments contd.

  8. Why is wide-band feed adopted?

  9. Why is wide-band feed adopted? • We are developing a new small radio telescope for geodetic VLBI. • =MARBLE Compact VLBI System • < One of a development task > • S/X band receiving simultaneously < Requirements of the task > 1) Compact 2) Simple 3) Inexpensive 4) RHCP and LHCP

  10. Quad-ridge Horn Antenna (QRHA) • Advantage • ・Wideband • That cover multi-octave. • 　・Compact and light • 　・Dual liner polarization • Disadvantage • ・Beam width depend on frequency • 　・Phase center depend on frequency • 　・The beam pattern is not symmetry in E-plane and H-plane. 180mm

  11. Evaluation of Retrofitted CARAVAN2400

  12. Performance of Retrofitted CARAVAN • System noise temperature (R-Sky method) R Sky Measured System noise temperature S-band：280 K (EL = 90 deg)，X-band：245 K (EL = 90 deg)

  13. Performance of Retrofitted CARAVAN contd. • Aperture efficiency measurement using the moon The shape factor Loss factor of atmosphere Ideal measured temperature Area of dish Boltzmann’s constant Flux density of moon System noise temperature Measured temperature Power of background noise Receiving Power from moon Aperture efficiency ＝ 6.3 ± 1.0 % (X-band)

  14. Calculated by reflector antenna analysis program GRASP8 Performance of Retrofitted CARAVAN contd. Aperture efficiency 37.7 dBi (Calculated gain) ‐ 46.5 dBi (Ideal gain) ＝ －8.8 dB ＝13 % (X-band)

  15. Aperture efficiency of Retrofitted CARAVAN (2.4m/2)2π × 6 % ＝ × 50 % (0.83m/2)2π ＝ 2.4m 83cm

  16. Conclusions

  17. Conclusions • ・We designed novel wideband radio telescope. • It adopted wideband feed of simple and compact. • ・This radio telescope was confirmed to be able to apply to geodetic VLBI. But… ・Low Aperture Efficiency ・High Noise Temperature

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

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

  20. Outlook contd. • A Prototype of MARBLE Compact VLBI System

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