Centimeter Receiver Design Considerations with a look to the future Steven White National Radio Astronomy Observatory Green Bank, WV.

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  • Slide 1
  • Centimeter Receiver Design Considerations with a look to the future Steven White National Radio Astronomy Observatory Green Bank, WV
  • Slide 2
  • Slide 3
  • Todd. Hunter, Fred. Schwab. GBT High-Frequency Efficiency Improvements, NRAO May 2009 Newsletter
  • Slide 4
  • Performance Limitations Surface (Ruze /16) = 50% 300 meters 63 Ghz Atmosphere e -t t = optical depth Spill Over T s Pointing Receiver Noise Temperature (Amplifier) T R
  • Slide 5
  • Frequency Coverage 300 Mhz to 90 Ghz l: 1 meter to 3 millimeters l < 1/3 meter - Gregorian Focus l > 1/3 meter - Prime Focus
  • Slide 6
  • Gregorian Subreflector
  • Slide 7
  • Reflector Feeds Profile: L (size), S (size), Ka (spacing), KFPA (spacing), Q (spacing) Linear Taper: C, X, Ku, K Design Parameters: Length (Bandwidth), Aperture (Taper, Efficiency) GBT = 15, Focal Length = 15.1 meters, Dimensions = 7.55 x 7.95 meters
  • Slide 8
  • Optimizing G/T
  • Slide 9
  • Prime Focus Feed Cross Dipole 290-395 MHz
  • Slide 10
  • Gregorian Feeds 140 & 300 Hybrid mode prime focus S, Ku (2x), L
  • Slide 11
  • Radio Source Properties Total Power (continuum: cmb, dust) Correlation Radiometer Receivers (Ka Band) Bolometers Receivers (MUSTANG) Frequency Spectrum (spectral line, redshifts, emission, absorption) Hetrodyne Prime 1 & 2, L, S, C, X, Ku, K, Ka, Q Polarization (magnetic fields) Requires OMT Limits Bandwidth Pulse Profiles (Pulsars) Very Long Baseline Interferometry (VLBI) Phase Calibration
  • Slide 12
  • Prime Focus Receivers ReceiverFrequencyT rec T sys Feed PF1.1 0.290 - 0.395 1246 K X Dipole PF1.2 0.385 - 0.520 2243 K X Dipole PF1.3 0.510 - 0.690 1222 K X Dipole PF1.4 0.680 - 0.920 2129 K Linear Taper PF2 0.910 - 1.230 1017 K Linear Taper
  • Slide 13
  • Gregorian Receivers Frequency Band Wave Guide Band Temperature [GHz] [GHz] [ K] T rec T sys 1-2 L OMT (Septum) 620 2-3 S OMT (Septum) 8-1222 4-6 C OMT (Septum) 518 8-10 X OMT (Septum) 1327 12-15 Ku 12.4 -18.0 1430 18-25 K 18.0 - 26.5 2130-40 22-26 K 18.0 - 26.5 2130-40 26-40 Ka 26.5 - 40.0 2035-45 40-52 Q 33 - 50.0 40-7067-134 80-100 W 75 to 110 ~ 3 10^-16 W/Hz
  • Slide 14
  • Receiver Room Turret
  • Slide 15
  • Receiver Room Inside
  • Slide 16
  • Polarization Measurements Linear Ortho Mode Transducer Separates Vertical and Horizontal Circular OMT + Phase Shifter (limits bandwidth) 45 Twist Or 90 Hybrid to generate circular from linear
  • Slide 17
  • Linear Polarization Orthomode Transducer
  • Slide 18
  • Circular Polarization
  • Slide 19
  • A Variety of OMTs
  • Slide 20
  • K band OMT
  • Slide 21
  • Equivalent Noise
  • Slide 22
  • Amplifier Equivalent Noise
  • Slide 23
  • Amplifier Cascade
  • Slide 24
  • Input Losses
  • Slide 25
  • HFET Noise Temperature
  • Slide 26
  • Radiometer
  • Slide 27
  • Correlation Radiometer (Ka/WMAP)
  • Slide 28
  • 1/f Amplifier Noise
  • Slide 29
  • MUSTANG 1/f Noise
  • Slide 30
  • HEMT 1/f Chop Rates Amplifier (band) o [GHz] rf [GHz] f chop ( =.1 ) [Hz] rf ( =.1, f = 5 Hz ) [GHz] L1.50.50.83 C4.0122 X10372 Ka3010800.6 Q45153750.2 W903015000.1 E.J. Wollack. High-electron-mobility-transistor gain stability and its design implications for wide band millimeter wave receivers. Review of Sci. Instrum. 66 (8), August 1995.
  • Slide 31
  • A HFET LNA
  • Slide 32
  • K-band Map Amplifier
  • Slide 33
  • Typical Hetrodyne Receiver
  • Slide 34
  • Frequency Conversion
  • Slide 35
  • Linearity
  • Slide 36
  • Intermodulation
  • Slide 37
  • Some GBT Receivers K bandQ band
  • Slide 38
  • Ka Band
  • Slide 39
  • Receiver Testing Digitial Continuum Receiver Lband XX (2) and YY (4)
  • Slide 40
  • Ku Band Refrigerator Modulation
  • Slide 41
  • Ka Receiver (Correlation) Zpectrometer
  • Slide 42
  • Lab Spectrometer Waterfall Plot
  • Slide 43
  • Slide 44
  • MUSTANG Bolometer
  • Slide 45
  • Focal Plane Array Challenges Data Transmission ( State of the Art) Spectrum Analysis ( State of the Art) Software Pipeline Mechanical and Thermal Design. Packaging Weight Maintenance Cryogenics
  • Slide 46
  • Focal Plane Array Algorithm Construct Science Case/Aims System Analysis, Cost and Realizability Revaluate Science Requirements Compromise Instrument Specifications. Polarization Number of Pixels Bandwidth Resolution
  • Slide 47
  • K band Focal Plane Array Science Driver Map NH 3 Polarized without Rotation Seven Beams Limited by IF system 1.8 GHz BW Limited by IF system 800 MHz BW Limited by Spectrometer
  • Slide 48
  • Focal Plane Coverage simulated beam efficiency vs. offset from center 1.Initial 7 elements above 68% beam efficiency (illumination and spillover) 2.Expandable to as many as 61 elements 3.beam efficiency of outermost elements would drop to ~60%. 4.beam spacing = 3 HPBWs
  • Slide 49
  • Slide 50
  • KBand Focal Plane Array
  • Slide 51
  • K Band Single Pixel Phase Shifter Thermal Transition OMT FeedNoise Module HEMT Isolators Sliding Transition
  • Slide 52
  • Seven Pixel
  • Slide 53
  • Whats next for the GBT? A W band focal plane array Science Case is strong and under development. Surface is improving Precision Telescope Control System program is improving the servo system. Needs. Digital IF system Backend (CICADA) Funding (Collaborators)
  • Slide 54
  • References Jarosik, et al. Design, Implementation and Testing of the MAP Radiometers, N. The Astrophysical Journal Supplement, 2003, 145 E.J. Wollack. High-electron-mobility-transistor gain stability and its design implications for wide band millimeter wave receivers. Review of Sci. Instrum. 66 (8), August 1995. M. W. Pospieszalski, Modeling of Noise Parameters of MESFETs and MODFETs and Their Frequency and Temperature Dependence. IEEE Trans. MW Theory and Tech., Vol 37. No. 9 Norrod and Srikanth, A Summary of GBT Optics Design. GBT Memo 155. Wollack. A Full Waveguide Band Orthomode Junction. NRAO EDIR 303. https://safe.nrao.edu/wiki/bin/view/GB/Knowledge/GBTMemos https://safe.nrao.edu/wiki/bin/view/Kbandfpa/WebHome
  • Slide 55
  • Thank you for you attention! Questions ?

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