Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April EVLA Front-End CDR Water Vapor Radiometer Option

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April Water Vapor Radiometer Development project Not in EVLA baseline plans If successful, has implications for EVLA

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 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

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 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)

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April Scientific Requirements Defined by need to measure Q band phase fluctuations to 10 deg rms Fractional amplitude stability of 10 –4 Timescales 2 sec to 30 min

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April VLA WVR block diagram

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April WVR prototype stability measurements, using a K band noise diode as source

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April Baseline length = 800 m, sky clear, 22 GHz Baseline length = 2.5 km, sky cover 50-75%, forming cumulus, 22 GHz Correlation between phase and WVR output for two VLA antennas *BLUE: Phase corrected using the scaled WVR output *RED: Uncorrected phase *GREEN: Scaled WVR output

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April EVLA Compact WVR Prototype 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

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April CWVR MMIC 15 MMIC chips 23 chip caps 7 circuit substrates 110 wire bonds 30% initial savings vs. connectorized version

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April EVLA K-Band with Compact WVR (Multiplexed Dual Channel) LO Ref 35dB RCP IF Out 8-18 GHz GHz Noise Diode Pol LNA Old New GHz0 dBm 18 dBm x2 Doubler x2 Doubler Dewar RF/IF Box NRAO CDL 35dB LNA NRAO CDL Pamtech KYG2121-K2 (w/g) Pamtech KYG2121-K2 (w/g) Noise/COM NC 5242 (w/g) 8-16 GHz Some New 8-16 GHz 32dB K&L Filter 13FV /U8500 MICA T-318S30 Quinstar QLN-2240J0 Po>+10dBm NF < 2.5 dB MICA T-318S20 MICA T-318S30 LCP IF Out 8-18 GHz GHz Norden Doubler Ditom DF GHz MAC Tech PA82072H (2F) GHz ( GHz) Krytar GHz WVR Box Temperature Stabilized Plate RCP LCP T Cal WR-42 To SMA MDL 42AC206 Atlantic Microwave AB4200 Compact WVR 10 dB 32dB 10 dB MICA T-318S20 Krytar MICA T-318S20 K&L Filter 13FV /U8500 MICA T-318S30 Quinstar QLN-2240J0 Po>+10dBm NF < 2.5 dB MICA T-318S20 MICA T-318S30 MICA T-318S20 Krytar Miteq TB0440LW1 Po>+9dBm CL < 10dB MICA T-318S20 MICA T-708S40 MICA T-708S35 TTT Filter K G Miteq TB0440LW1 Po>+9dBm CL < 10dB MICA T-318S20 MICA T-708S40 MICA T-708S35 TTT Filter K G 0  3 dBm

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April Prototype Compact WVR 35dB / 1.50 GHz / 0.75 GHz / 1.00 GHz / 0.75 GHz / 1.50 GHz DC F = F = F = F = F = Frequency Multiplexer 0, 3 & 6 dB IL = 3 dB P O > 15 dBm Matched Detectors DC Amp Gain ~ 50 Termination LCP In “Dark Current” Switch Input Mode Switch Digital Attenuator (Chopper Stabilized) (Linearity &Temp) IL = 2.5 dB IL = 1.5 dB P O > 15 dBm NF < 5 dB P O > 20 dBm IL = 1.5 dB P O > 15 dBm RCP In or Termination Digital Attenuator 0, 3 & 6 dB IL = 3 dB P O > 15 dBm Fixed Pad (Optional) Second Post-amp

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April Matt Morgan’s MMIC Module 5 channel V-F FIBER OUTPUTS MMMMICM Noise Diode

EVLA CWVR

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April EVLA K-Band Impact of WVR on Rx Performance (with T LNA =10°K)

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April Preliminary CWVR data

Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 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