1 / 26

Multi-Pixel Optics of SMA

Multi-Pixel Optics of SMA. Yun- Chih Chou, Chao- Te Li, Ming-Tang Chen Institute of Astronomy and Astrophysics, Academia Sinica. Outline. Current Status of SMA SMA Optics and Multi-Pixel Schemes Solution 1 Solution 2 Solution 3 Conclusion and Future Task. Current Status of SMA.

jonny
Download Presentation

Multi-Pixel Optics of SMA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Multi-Pixel Optics of SMA Yun-Chih Chou, Chao-Te Li, Ming-Tang Chen Institute of Astronomy and Astrophysics, Academia Sinica The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  2. Outline Current Status of SMA SMA Optics and Multi-Pixel Schemes Solution 1 Solution 2 Solution 3 Conclusion and Future Task The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  3. Current Status of SMA The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  4. SMA: Submillimeter Array • Antenna number: 8 • Antenna diameter: 6m • Full operation since 2005. • Location: Mauna Kea, Hawaii (4,045m) • Current operation frequencies: 176-256GHz, 250-350GHz, 330-430GHz. • Dual polarization observation: 345GHz • Field Of View: 14-70 arcsec Introduction of SMA The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  5. Receiver: Wide IF upgrade of 200GHz from 4-8GHz to 4-12GHz. • All 8 antennas have wide IF 200GHz receivers now. • Wide IF upgrade of 300GHz from 4-8GHz to 4-12GHz followed up, and two receivers have been installed. Receiver Update The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  6. SMA Optics and Multi-Pixel Schemes The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  7. Design purpose: Simple frequency-independent optics. • Design techniques: Fresnel imaging techniques, multi-mode Gaussian beam methods. • Frequency-independent illumination on secondary reflector: All bands have common “virtual feed” behind receiver lens. Original SMA Optics The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  8. Beam waveguide: M3 to M6 after Cassegrain reflectors. Ellipsoidal mirrors are M4 and M5. • Incidence angle of M4 and M5 is eliminated to reduce coupling loss on M5 (25 deg). • Advantage: Small coupling loss(M5 0.15% at 400GHz) and cross-polarization(-38dB at 3dB beam). Fresnel Imaging technique SMA Relay Optics The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  9. Wire grid: Added to split RF signals into high and low bands for dual observation (345GHz dual-polarization observation). • LO: Injection before receiver. • Receiver : Scalar horn and lens. • Feed Max gain: Max gain is reached when Bessel field of corrugated feedhorn is 10dB on aperture edge. Optics after RO The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  10. Advantage: Increase FOV and mapping speed. • Max FOV w/o cryostat window limit: • Observation frequency: 345 GHz, key frequency. Purpose of Adopting Multi-feed Arrays The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  11. Array element: 7 (hexagonal). Design goal: • Feature frequency: 345 GHz • Least modification in current optics. • Aperture Plane Array or Focal Plane Array. • Good performance: High beam efficiency, small spillover etc. Multi-pixel Arrays Scheme The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  12. Simple optics of SMA 300 band receiver was built in GRASP10. • Simulation method: Gaussian beam propagation and Physical Optics (PO) calculation. SMA Optics in GRASP10 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  13. Beam efficiency: 81%, integrated to 10dB below peak. • Cross-polarization efficiency: 0.006% Fig. Copolar and Cross-polar El-Az Grid. Original Optics Result The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  14. Solution 1 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  15. Optics: RO unchanged. • Smaller lens due to aperture limit: Diameter reduced from 70mm to 25mm, so all beams are less truncated at cryostat window (diameter 76mm). • Lens radius 12.5mm corresponds to 0.9ω (Gaussian beam radius). • Feed spacing: 25mm. Optics of Solution 1 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  16. Lens truncation reduced beam efficiency greatly. Fig. Far-field cut of off-axis beam Fig. Solution 1 far-field beam grid of 3dB and 6dB. Simulation result The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  17. Solution 2 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  18. Purpose: Reduce beam radius at lens position to eliminate lens truncation. • New RO, Feed and lens: Ellipsoidal mirror M5 is changed to produce more concentrated Gaussian beams. • Lens radius: 12.5mm, 1.25ω. • Feed spacing: 25mm. Optics of Solution 2 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  19. Design method: Fresnel imaging techniques. • New parameter design goal: Similar value to original parameters. Table1. M5 parameters Table2. Feed and lens parameters Parameters of Sol. 2 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  20. Sensitive Feed offset. • Severe spillover at secondary mirror. • In need of new RO design. Fig. Off-axis feed 25mm away from propagation axis. Simulation Result The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  21. Solution 3 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  22. - Optics: RemoveRO. Original 300GHz lens and feed configuration. - Min. feed spacing : 2.44 * f# * λ = 29.7 mm. Optics of Solution 3 The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  23. Off-axis results have similar beam efficiency as on-axis. • This is the best solution of all solutions. Fig. On and off axis Copolar El –Az grid. Simulation Result The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  24. Conclusion and Future Task The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  25. Three solutions of 7-pixel feed arrays of SMA have been designed. Solutions Summary The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

  26. A new FPA solution with simple RO and largest FOV will be proposed. • Possible LO scheme: Change LO injection to waveguide coupling after feedhorn. Fig. All off-axis Gaussian beams distribution on main dish. Future Task The 13th Workshop on Submillimeter-Wave Receiver Technologies in Eastern Asia, Nanjing

More Related