Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array Integrated Receivers July 23, 2010 Matt Morgan, Rick Fisher, and Tod Boyd

Analog/Digital/Photonic Receiver Program To develop receivers and wide bandwidth data transport systems which are lower cost, more compact, more reliable, lower weight, more reproducible, and more stable than the best current systems. To integrate the conversions from RF to baseband, from analog to digital, and from copper to fiber into a single compact package. To digitize the signal as close to the antenna feed as possible – this inevitably involves transferring some functionality from analog hardware to the digital domain. 2

Integrated Receiver Concept 3

Three-Probe Planar OMT With Integrated LNAs 4 The incoming signals from some arbitrary number of probes in a circular waveguide are digitized independently and recombined with calibrated weighting coefficients to synthesize accurate polarizations. Corrects for all amplitude and phase errors of the probe geometry as well as the receiver chains attached to them. Prototypes shown at the left are for X-Band (8-12 GHz)

DOMT Gain Matrix Representation Gain matrix relates sky signal vector to output voltage vector: or where 5

Moore-Penrose Pseudo-Inverse Provides a Least-Squares Fit Direct inversion is not possible (unless N=2), but we can estimate where 6

Four Channel Downconverter for Testing the DOMTs 7

Laboratory Measurement Setup 8

Polarization Results Isolation (Linear) Axial Ratio (Circular) 9

copper traces on 5-mil thick Kapton substrate lithography sufficient for 3 mm band application easy to parallelize Flex Ribbon Thermal Transition 10 smaller, lighter, and cheaper than stainless steel coax or waveguide shorter (physically and electrically) for the same thermal isolation

Predicted Results: K Transitions for 50 Dual-Polarized Beams… TransitionsSpecifications Heat load Length 50 GHz 50 GHz Total weight * 100 waveguides WR-22 thin-wall stainless steel with 40  ” gold plate 5 W13.1 in.0.29 dB kg 100 coaxial cables 0.085” stainless steel coax with teflon 5 W4.4 in2.50 dB g 10 flex ribbons with 10 stripes on each 0.005” Kapton with ½ oz. copper cladding 5 W2.8 in.1.38 dB5.23 g 11 * Not including the flanges, or the extra height of the dewar.

Digital Sideband Separating Mixer With Integrated ADCs 12 L-Band Module Analog SideDigital Side ADCs RF BoardIF Channels Analog Inputs Digital Outputs

Digital Sideband-Separating Mixer (DSSM) I- and Q-channels digitized and recombined with calibrated complex weighting coefficients. Corrects for LO, RF, and IF analog amplitude and phase errors. Extremely stable design: 50 dB sideband-suppression without re- calibration over a 12 °C temperature change. No increase in digital data rate: requires two ADC's with half the sample rate for a given processed bandwidth °C 40°C

Designed for Calibration Stability Short electrical paths, elimination of standing waves, and the lack of intermediate cabling and connectors lead to smooth, stable complex gain curves. Sideband suppression >52 dB in the passband. Measurement performed six days after calibration. Only calibrated 10 points across the band – 80% of the points shown use interpolated calibration coefficients. 14

Snapshot of L-Band Spectrum on the GBT 15

Internal ADCs Introduce No Measurable Interference 16 expected clock harmonic (12.5 minute integration)

Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array LNA Design and Construction at the CDL July 23, 2010 Matt Morgan, Rick Fisher, and Tod Boyd

Chip and Wire IF Amplifiers for ALMA Band 6 18

Band 6 IF Amplifier Fabrication Resistors, capacitors, and substrates installed by an outside vendor (Advanced Control Components) CRYO3 FETs from NGST and MAP FETs from HRL installed here Final tuning and pair-matching is performed here with cold-testing by an experienced technician in the Band 6 group (Mike Lambeth). Similar units and techniques used for EVLA production... 19

300 Amplifiers Complete, About 50 To Go... 20

MMIC LNA Development (35nm NGC process) 21

New MMIC Designs in Fabrication 22

New MMIC Designs in Fabrication Eric has also developed LNA designs for GHz and GHz bandwidths. We are also experimenting with hybrid approaches: – MMIC partial-LNA with an off-chip quartz matching network – discrete-FET first-stage plus MMIC second-third-fourth-stage 23