Atacama Large Millimeter/submillimeter Array

Expanded Very Large ArrayRobert C. Byrd Green Bank Telescope

Very Long Baseline Array

Integrated Receivers

July 23, 2010Matt 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.

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Integrated Receiver Concept

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Three-Probe Planar OMT With Integrated LNAs

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• 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

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y

x

jNy

jNx

jy

jx

jy

jx

N

ss

eaea

eaeaeaea

v

vv

NyNx

yx

yx

22

11

22

11

2

1

GSV

jesS

sincos

0

Moore-Penrose Pseudo-Inverse Provides a Least-Squares Fit

• Direct inversion is not possible (unless N=2), but we can estimate

• where

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GSV

HVS

TT GGGH1

Four Channel Downconverter for Testing the DOMTs

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Laboratory Measurement Setup

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Polarization Results

Isolation (Linear) Axial Ratio (Circular)

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• copper traces on 5-mil thick Kapton substrate

• lithography sufficient for 3 mm band application

• easy to parallelize

Flex Ribbon Thermal Transition

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• smaller, lighter, and cheaper than stainless steel coax or waveguide

• shorter (physically and electrically) for the same thermal isolation

Predicted Results: 15-300K Transitions for 50 Dual-Polarized Beams…Transitions Specifications Heat

load Length Loss@ 50 GHz

Wavelengths @ 50 GHz

Total weight*

100 waveguides WR-22 thin-wall stainless steel with 40m” gold plate 5 W 13.1 in. 0.29 dB 47.2 1.215 kg

100 coaxial cables 0.085” stainless steel coax with teflon 5 W 4.4 in 2.50 dB 6.5 195 g

10 flex ribbons with 10 stripes on each

0.005” Kapton with ½ oz. copper cladding 5 W 2.8 in. 1.38 dB 5.2 3 g

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*Not including the flanges, or the extra height of the dewar.

Digital Sideband Separating Mixer With Integrated ADCs

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L-Band Module

Analog Side Digital SideADCsRF Board IF 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.

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28°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

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Internal ADCs Introduce No Measurable Interference

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expected clock harmonic

(12.5 minute integration)

Atacama Large Millimeter/submillimeter Array

Expanded Very Large ArrayRobert C. Byrd Green Bank Telescope

Very Long Baseline Array

LNA Design and Construction at the CDL

July 23, 2010Matt Morgan, Rick Fisher, and Tod Boyd

Chip and Wire IF Amplifiers for ALMA Band 6

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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...

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MMIC LNA Development (35nm NGC process)

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New MMIC Designs in Fabrication

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New MMIC Designs in Fabrication

• Eric has also developed LNA designs for 67-95 GHz and 68-116 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

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