1. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 1 EVLA Front-End CDR Water Vapor Radiometer Option

2. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 2 Water Vapor Radiometer Development project Not in EVLA baseline plans If successful, has implications for EVLA

3. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 3 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

4. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 4 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)

5. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 5 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

6. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 6 VLA WVR block diagram

7. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 7 WVR prototype stability measurements, using a K band noise diode as source

8. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 8 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

9. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 9 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

10. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 10 CWVR MMIC 15 MMIC chips 23 chip caps 7 circuit substrates 110 wire bonds 30% initial savings vs. connectorized version

11. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 11 EVLA K-Band with Compact WVR (Multiplexed Dual Channel) LO Ref 35dB RCP IF Out 8-18 GHz 18-26 GHz Noise Diode Pol LNA Old New 29-37 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 13FV10- 22250/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 15-18 GHz Norden Doubler Ditom DF2806 13.5-21.5 GHz MAC Tech PA82072H (2F) 13.5-21.5 GHz (16.0-19.3 GHz) Krytar 6020265 2-26.5 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 262210 MICA T-318S20 K&L Filter 13FV10- 22250/U8500 MICA T-318S30 Quinstar QLN-2240J0 Po>+10dBm NF < 2.5 dB MICA T-318S20 MICA T-318S30 MICA T-318S20 Krytar 262210 Miteq TB0440LW1 Po>+9dBm CL < 10dB MICA T-318S20 MICA T-708S40 MICA T-708S35 TTT Filter K4906- 8-16.5G Miteq TB0440LW1 Po>+9dBm CL < 10dB MICA T-318S20 MICA T-708S40 MICA T-708S35 TTT Filter K4906- 8-16.5G 0  3 dBm

12. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 12 Prototype Compact WVR 35dB 19.25 / 1.50 GHz 21.00 / 0.75 GHz 22.25 / 1.00 GHz 23.50 / 0.75 GHz 25.25 / 1.50 GHz DC F = 19.25 F = 21.00 F = 22.25 F = 23.50 F = 25.25 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

13. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 13 Matt Morgan’s MMIC Module 5 channel V-F FIBER OUTPUTS MMMMICM Noise Diode

14. EVLA CWVR

15. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 15 EVLA K-Band Impact of WVR on Rx Performance (with T LNA =10°K)

16. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 16 Preliminary CWVR data

17. Brent WilloughbyEVLA Front-End CDR – WVR Option 24 April 2006 17 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