EVLA FrontEnd CDR WVR Option

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EVLA Front-End CDR

• Water Vapor Radiometer
• Option

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Water Vapor Radiometer

• Development project
• Not in EVLA baseline plans
• If successful, has implications for EVLA

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WVR.why?

• Water vapor emission in the atmosphere increases
  electrical path length resulting in phase
  fluctuations in the astronomical data
• The effect of these fluctuations is greater at
  shorter wavelengths
• Measuring fluctuation of the amplitude of water
  vapor emission at 22 GHz enables a phase
  correction to be generated and applied to
  astronomical data

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Current WVR system

• The current WVR detection scheme uses three
  channels centered on the water line
• The bandwidth and frequency of the channels are
  limited by RFI generated in the present LO scheme

(From Butler 1999)
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ScientificRequirements

• Defined by need to measure Q band phase
  fluctuations to 10 deg rms
• Fractional amplitude stability of 104
• Timescales 2 sec to 30 min

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VLA WVR block diagram
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WVR prototype stability measurements, using a K
band noise diode as source
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Correlation between phase and WVR output for two
VLA antennas
Baseline length 800 m, sky clear, 22 GHz
Baseline length 2.5 km, sky cover 50-75,
forming cumulus, 22 GHz
BLUE Phase corrected using the scaled WVR
output RED Uncorrected phase GREEN Scaled WVR
output
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EVLA Compact WVRPrototype Module

• The Compact WVR concept uses an integrated module
  with MMIC and drop-in devices (amps, switches,
  detectors) and microstrip filters
• Cheaper than a connectorized version
• Smaller size less mass
• Better thermal stability
• Easier to mass produce
• More frequency bands (5 filters rather than 3)
• Dark Current switch allows DC offsets to be
  determined
• Input switch allows selection between LCP RCP
  signals or between Rx a Termination (or Noise
  Source) for calibration

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CWVR MMIC

• 15 MMIC chips
• 23 chip caps
• 7 circuit substrates
• 110 wire bonds
• 30 initial savings vs. connectorized version

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EVLA K-Band with Compact WVR(Multiplexed Dual
Channel)
Dewar
KL Filter 13FV10- 22250/U8500
MICA T-318S30
Quinstar QLN-2240J0 Pogt10dBm NF lt 2.5 dB
MICA T-318S30
Miteq TB0440LW1 Pogt9dBm CL lt 10dB
MICA T-708S40
TTT Filter K4906- 8-16.5G
MICA T-318S20
MICA T-318S20
Krytar 262210
MICA T-318S20
MICA T-708S35
RCP IF Out 8-18 GHz
RF/IF Box
NRAO CDL
Pamtech KYG2121-K2 (w/g)
WVR Box
10 dB
32dB
RCP
35dB
8-16 GHz
Temperature Stabilized Plate
LNA
Ditom DF2806 13.5-21.5 GHz
x2
15-18 GHz
18-26 GHz
Noise/COM NC 5242 (w/g)
MDL 42AC206
Atlantic Microwave AB4200
MICA T-318S20
Doubler
TCal
Compact WVR
Pol
Noise Diode
29-37 GHz
0 dBm
18 dBm
WR-42 To SMA
0?3 dBm
Krytar 6020265 2-26.5 GHz
x2
MAC Tech PA82072H (2F) 13.5-21.5 GHz (16.0-19.3
GHz)
LO Ref
Doubler
Norden Doubler
LNA
8-16 GHz
35dB
LCP
32dB
10 dB
NRAO CDL
Pamtech KYG2121-K2 (w/g)
Old
LCP IF Out 8-18 GHz
KL Filter 13FV10- 22250/U8500
MICA T-318S30
Quinstar QLN-2240J0 Pogt10dBm NF lt 2.5 dB
MICA T-318S30
Miteq TB0440LW1 Pogt9dBm CL lt 10dB
MICA T-318S20
MICA T-708S40
MICA T-708S35
TTT Filter K4906- 8-16.5G
MICA T-318S20
MICA T-318S20
Krytar 262210
Some New
New
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Prototype Compact WVR
Frequency Multiplexer
Matched Detectors
DC Amp Gain 50
Digital Attenuator
Fixed Pad
LCP In
DC
F 19.25
19.25 / 1.50 GHz
Dark Current Switch
Input Mode Switch
Digital Attenuator
Second Post-amp
DC
21.00 / 0.75 GHz
F 21.00
35dB
22.25 / 1.00 GHz
DC
F 22.25
NF lt 5 dB PO gt 20 dBm
0, 3 6 dB IL 3 dB PO gt 15 dBm
IL 1.5 dB PO gt 15 dBm
IL 1.5 dB PO gt 15 dBm
DC
23.50 / 0.75 GHz
F 23.50
Termination
25.25 / 1.50 GHz
DC
F 25.25
RCP In or Termination
(Chopper Stabilized)
(Linearity Temp)
(Optional)
0, 3 6 dB IL 3 dB PO gt 15 dBm
IL 2.5 dB
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Matt Morgans MMIC Module
MMMMICM
5 channel V-F
Noise Diode
FIBER OUTPUTS
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EVLA CWVR
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EVLA K-BandImpact of WVR on Rx Performance (with
TLNA10K)
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Preliminary CWVR data
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Future CWVR plans

• Continue evaluating MMIC module in the lab using
  a noise source and then a K band receiver
• Evaluate RFI environment in an EVLA antenna to
  determine filter bandpasses
• Design/Test 5 channel MIB interface
• Contingent on funding and manpower