SKA TDP Receiver Antenna Interface March 21, 2008 Total system noise contributions Choice of operating temperature Wideband feeds under development Quadridge feed test results LNA status IF/LO development Overall plan

.19.05

SKA Antenna and Receiver Cost for as a Function of LNA Temperature All for Wideband Feeds with Constant A/Tsys at 1.4 GHz

SKA Antenna Concept An antenna in the 6 to 15m diameter range requires receivers for the 0.3 GHz to an upper frequency in the 3 to 25 GHz range. The <3 GHz frequencies will probably utilize a prime-focus uncooled feed and the higher frequencies will probably be with a cooled feed at secondary focus.

SKA Wideband Feed Candidates 1.ATA Log Periodic 2.Kildal Inverted Log Periodic 3.Cortes Quasi Self Complementary. 4.Bradley Sinous. 5.Lindgren Improved Quadridge Further development is planned in 2008 followed by integration tests Important criteria are efficiency and system noise temperature when integrated with LNA’s – Aeff/Tsys – as well as low cost manufacture and maintenance.

Lindgren Quadridge Feeds These are “quadridge/Vivaldi” antennas which operate over wide frequency ranges which can be scaled.. They are manufactured by the ETS-Lindgren company based in Finland. Model , 0.5 to 4 GHz Model , 2 to 14 GHz

Feed Patterns Are Improved by Surrounding Feed with Cylinder or Placing Absorber Near Feed Measured patterns below are for H plane at 2.2, 4, 8.4, 11, 14 and 18 GHz Feed in Absorber-Lined Cylinder Feed with Absorber on Outside Rim Feed in Cylinder Feed Alone

Cryogenic Dewar Design for Lindgren Antenna LNA’s Cryocooler Feed Polyethylene Window 15K Plate

Receiver Noise Measurement on Pad at Goldstone Test Setup with Feed and LNA at 15K Raw Spectrum Analyzer Plots of LNA Outputs with Cold Sky and 300K Absorber

Prototype SKA 2-14 GHz Feed/LNA Package – Measured Noise Lingren Vivaldi/Quadridge Cooled Feed

Lindgren Quadridge 0.5 to 4 GHz Feed Noise Tests at Goldstone Feed Integrated with LNA Cooled at 60K by Long Life Cooler

Measured Noise of 0.5 to 4 GHz Quadridge Feed Integrated with LNA Lower Curve is Noise of LNA + Cable

Drawing of Current Quadridge to LNA Dewar Interface

Feed/LNA Interface Concept for SKA Dual polarization, twin-lead, high-impedance interface to feed designs Large uncooled feed with small LNA dewar cooled by long life 50K cooler Higher frequencies, > 3 GHz, in another package with cooled feed

Scaling of 4-Wire Feed/LNA Interface to Higher Frequencies Dimensions must be scaled to prevent radiation from transmission lines Frequencies above 3 GHz are best met by cooled feed.

Very Low Noise Amplifier Development Status HEMTs - Indium-phosphide (InP) high-electron-mobility transistors (HEMTs) have been implemented in almost all low-noise amplifiers in radio astronomy for the past 10 years with little change in performance. This may change with the introduction of 35nm gate length devices. SiGe BiCMOS - A high-speed, “do all”, semiconductor process is rapidly being developed by several manufacturers (IBM, STM, Jazz, and others). It combines bipolar silicon-germanium (SiGe) transistors, CMOS FET transistors, many passive components, and several layers of interconnection lines. The technology enables “single-chip” receivers and feedback amplifiers with very high gain stability. Feasible LNA noise temperatures in the 1 to 10 GHz range are: – 15K to 40K at 300K – 3K to 15K at 77K – 1K to 5K at 15K

Example of a SiGe BiCMOS 77 GHz Transceiver Designed by Hajimiri Group at Caltech  Process : 0.13µm SiGe BiCMOS process.  Transistor count: 10,000  Complete 77GHz phased array transceiver with on-chip antennas 6.8mm 3.8mm

Noise Temperature for SiGe Transistors vs Frequency and Temperature Based upon model measurements of 2007 IBM 0.12um wafer. To be published in IEEE 2008 MTT Symposium

Measured and Modeled SiGe Cascode LNA at 15K (3K More Noise Expected at 60K)

IF/LO Work for TDP There is considerable cost for the “middle” portion of the SKA system for frequency conversion, filtering, gain adjustment, photonic transmission, and A/D conversion. Downconverter Digital Signal Processor LNA Decade Bandwidth Feed Very Low Noise, Cryogenic or Ambient? Single or Multiple IC Photonic Output Spectrometer, Array Correlelation, Beam Forming, Pulsar processing

Packaging Progression Multi-Function Chip

0.5-20GHz Quadrature Downconverter LO I+ I- Q+ Q- RF 90° HYBRID Q I RF LO

SKA TDP Overall Hardware Plan During 2008 develop both 300K and 50K wideband differential LNA’s at Caltech for the 0.3 to 11 GHz range Work on wideband feeds will occur independently in 2008 at Caltech and other institutions In 2009 integrate the best of the feed designs with LNA’s to perform off-telescope integrated feed/LNA tests. In 2010 integrate feed/LNA’s with SKA reflector antenna. Continue development of 11 to 25 GHz receivers and IF system. In 2011 test the complete system

WBS Quad-Ridge Feeds – During the past 2 years Caltech has tested quad-ridge wideband feeds for use on an educational 34m radio telescope (GAVRT) under contract to the Lewis Center for Educational Research. A complete system covering 0.5 to 14 GHz with 2 feeds will be installed on the telescope in early 2008 and this work strongly leverages the further development of this type of system for the SKA. The design will be investigated in 2008 and 2009 by computer-aided electromagnetic simulators and by fabrication and test of a system with lower system noise temperature than expected with GAVRT. WBS GHz Receiver – A low cost, very low noise receiver covering this frequency range will be developed over a 4-year period utilizing either a quad-ridge feed or other wideband feeds being developed by others. Key elements of the development are a very low noise amplifier operating at a temperature in the 300K range with <12K noise and very low loss connections between the LNA and feed. WBS GHz Receiver - A low cost, very low noise receiver covering this frequency range will be developed over a 4-year period utilizing a selected feed. Key elements of the development are a very low noise amplifier operating at a temperature in the 80K range with <5K noise and very low loss connections between the LNA and feed. The task includes design, packaging, and testing of integrated circuit low-noise amplifiers and integration of the amplifiers with the antenna feed. Caltech SKA TDP Statement of Work

WBS GHz Receiver - A low noise receiver covering this high frequency range will be developed over a 3-year starting in It is not clear at this time whether the receiver can be included as part of the 1-11 GHz system or if the SKA antenna will support higher frequencies/ The funds for this work element may be needed to improve performance at the lower frequencies. Key elements of the development are a very low noise amplifier operating at a temperature in the 60K range with <8K noise and very low loss connections between the LNA and feed. WBS IF/LO Development - Experience with EVLA has shown that a large portion of the receiver cost is in the wide bandwidth frequency conversion, local oscillator distribution, optical fiber transducers, and A/D conversion. The goal of this work element is to drastically reduce the cost of these functions by development of large scale microwave integrated circuits. Caltech SKA TDP Statement of Work, Continued