EVLA Front-End CDR · LNA LNA LCP RCP GHz LN2 Liquid Nitrogen ... • Not always as accurate as SOIDA but allows quick comparison measurements ... R. Hayward EVLA Front-End CDR

R. Hayward EVLA Front-End CDR – Laboratory Receiver Testing 24 April 2006

1

EVLA Front-End CDR

LaboratoryReceiverTesting


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EVLA Ka-Band ReceiverOverview

1) Rx Characterization - SOIDA Rack- EVERETT Rack

2) PNA Measurements - OMT Tweaking- Phase Matching

3) SNA Measurements - General Purpose Measurements- Sensitivity (Y-Factor)- Axial Ratio- Total Power Stability


3

The SOIDA Rack

• The SOIDA Rack consists of a data acquisition PC, two commercial frequency synthesizers, a power meter plus a custom designed Baseband Converter (BBC) unit.

• The system is designed to:• Measure the receiver sensitivity

(i.e., TRx) vs. frequency• Measure the noise diode calibration

(i.e., TCal) vs. frequency• We also have a 2nd test rack which is

affectionately known as the SOS Rack, for “Son of SOIDA”

SOIDA Testing Q-Band Rx


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Cold Load

77°K

Hot Load

295°K

“SOIDA” Hot/Cold LoadEVLA Q-Band - Swept LO1

CharacterizationCV-3

MicrowaveAbsorber

Dewar

RF/IF Box

SOIDA

Key:

ChannelNot Shown

30 dB

30 dB

40-50

NoiseDiode

Pol

LNALNA

RCPLCP

GHz

LN2Liquid

Nitrogen

NoiseDiodeNoiseDiode

GigatronicsSynthesizer1-26 GHz

20 dB 10 dB

HP 8671ASynthesizer2-18 GHz

HP436APowerMeter

DataAcqPC

GPIB Interface

DC-20MHz

LO1 =16.133 to 19.467

GHz

IF = 8.4GHz

LO2 = 8.4 GHz

Baseband Converter

35 dB

39-51 GHz

Warm RF/IF Sub-system

x3


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What SOIDA Sees

)1()(

/

/

−⋅−

=CH

ColdCHHotRx

YTYTT

Hot LoadPower(dBm)

0 10 20 30 40 50

Freq(MHz)

Cold Load

Cold Load + Noise Diode

YH/C

YND/C

)1()( / −⋅+= CNDColdRxCal YTTT


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A Typical SOIDA PlotEVLA Q-Band Receiver

The SOIDA plot is designed to

display thefollowing

information:PHotPColdGainTRxTCal

(SCal)


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The Next Generation Test

Rack• EVLA requires 240 upgraded or new receivers.• Both SOIDA & SOS use obsolete test equipment

- synthesizers & power meters.• The PC’s are ancient 33 MHz machines.• Only able to do one channel at a time.• Takes ~1½ hour to do a single W-Band channel.• Developing a new dual-channel replacement rack

which uses a modern laptop, E4119B power meter, 83630B/24L synthesizers and a new broadband dual-channel BBC.

• Cost $90K each• EVERETT++ = “Expanded Vla Enhanced

Receiver Evaluation & Test Terminal”.• Plan on 2 EVERETT Racks as well as 1 (or 2)

SOIDA Racks (depending on longevity).


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E8364BPrecision Network Analyzer

(PNA)• Agilent’s newest generation of Vector Network Analyzer

• DC – 50 GHz• Electronic Calibration Unit (to 50 GHz)• Mechanical Cal kits

• Coaxial - 3.5 mm• Waveguide - WR-42, WR-28 & WR-22

• Frequency Translation Option• Higher Dynamic Range and faster than the 8510 VNA• Windows Platform• Bought to facilitate Ka & Q-Band MMIC-based modules• Cost -$150K


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Precision Network AnalyzerEVLA Related Measurements

• Return Loss measurements of OMT during tweaking

• Phase Balancing of Cables between OMT & Hybrid

• Measurement of MMIC device and multi-function module S-Parameters using Wafer Probe Station

• Numerous General Purpose Measurements of RF & microwave components and sub-systems

PNA measuring Return Loss on 2nd L-Band OMT


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Scalar Network Analyzer

• Coaxial SNA = 8757C + 83630B Synthesizer10 MHz to 26.5 GHz

• W/G SNA = 8757E + 83623A Synthesizer2 to 20 GHz

Plus Source Modules atKa, Q & W-Band

Acquired enough surplus 8757C’s to build one intothe new EVERETT Racks as well.


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SNA GP MeasurementsFrequency Response

Ka-Band Down-converter

CoaxialSNA

WaveguideSNA


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SNA GP MeasurementsKaDCM Frequency Response

Close up


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Y-Factor Measurement with SNA

• SNA’s can be configured to measurement Y-Factor sensitivity essentially in real-time – 1 minute vs. 15 to 90 minutes on SOIDA– Dual channels simultaneously

• For Lower Frequency Rx’s with no internal frequency conversion or for the EVLA Block Converter Mode receivers, use with the BBC on the SOIDA Rack.

• For Higher Frequency Rx’s with internal mixers, use a narrow filter and post-amp n the IF output.– 8400, 11000, 14200 MHz filters with 100 MHz bandwidth

• Not always as accurate as SOIDA but allows quick comparison measurements (TRx vs. LO Power, bias settings, cpt changes, etc.)


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SOIDA & SNA Measurement Comparison of Receiver Temperature Block Converter Mode on Receiver Q#17

LCP - SOIDA 100 MHz Step Size, 40 MHz Filter Bandwidth & 32 Sample AverageLCP - SNA 25 MHz Step Size. 40 MHz Filter Bandwidth & 8 Sweep AverageRCP - SOIDA 100 MHz Step Size, 40 MHz Filter Bandwidth & 32 Sample AverageLCP - SNA 25 MHz Step Size, 40 MHz Filter Bandwidth & 8 Sweep Average

40 41 42 43 44 45 46 47 48 49 50Frequency (MHz)

20

30

40

50

Rec

eive

r T

empe

ratu

re (K

)


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Lab Measurements of Circular Polarization

• Attempt to measure the response of the receiver to a linearly polarized signal rotated through 360E by injecting it into the receiver and detecting the LCP & RCP output power.

• If the polarizer is perfect, we should see no variation.• If the polarizer has a 1 dB axial ratio, we should see the output power

change by 1 dB.• Best done on an antenna test range

• Would be a pain at L-Band with its 16 ft feed• So lab measurements done using a circular waveguide test fixture

that gives us both a linear polarized signal and a rotary joint.• Initially measurements were taken with a power meter at each

Position Angle (typically every 10 to 20E) for a fixed frequency.• Polarization plotted up in Polar Plots (i.e., “Peanuts”)


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045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

1200 MHzRCP = 18 dB ?LCP = 16 dB ?

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

1300 MHzRCP = 18 dB ?LCP = 20 dB ?

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2Axial Ratio (dB)

L-Band S/N 02Axial Ratio (dB) and Position Angle of Major Axis versus Frequency

Cold Receiver with Bradley Prototype Balanced AmplifiersDrain Voltages & Currents Tweaked to Eliminate LNA Oscillations

(28 Jan 2004)

1400 MHzRCP = 15 dB ?LCP = 17 dB ?

1500 MHzRCP = 17 dB ?LCP = 22 dB ?

1600 MHzRCP = 21 dB ?LCP = 18 dB ?

1700 MHzRCP = 12 dB ?LCP = 13 dB ?

1800 MHzRCP = 10 dB ?LCP = 11 dB ?

FrequencyRCP LNA IRLLCP LNA IRL


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SNA EllipticityMeasurements

• Power Meter measurements truly painful and we were under sampling the frequency response

• Developed new test procedure using the SNA– Full frequency sweep taken at each Position Angle– SNA Reference channel eliminates power variations from

RF cable being twisted.– SNA data “grabbed” by laptop & written to Excel file– Super spreadsheet imports the -100,000 data points and

then calculates the axial ratio for each frequency point • 2.5 MHz @ L-Band or 20 MHz at K-Band

– Scheme also allows smoothing of data before AR calculated so effect of freq ripple in the test setup can be reduced.


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Scalar Network AnalyzerAxial Ratio vs. Freq Measurements

K-Band Ellipticity Test Setup

35 dB

35 dB

18-26 GHz

NoiseDiode

OMT

LNA

LNA

Mod

eC

onve

rter

90 DegreePhase-Shifter

Cir

cula

rT

oSq

uare

Vac

uum

Win

dow

Squa

reto

Cir

cula

r

OMT

Ter

min

atio

n

SynthesizerHP 83630B

Scalar NetworkAnalyzer

HP 8757D

DetectorHP 85025E

Det

ecto

rH

P 85

025EDewar

Det

ecto

rH

P 85

025E

Chan A

Chan B

LCP

RCP

Rotary Joint

Ref

GPIBRF Out-15 dBm

20 dB

Power Divider

HP 11667B

K-BandEllipticity

TestFixture


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K-Band S/N 28Under Test


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K-Band Ellipticity Test Fixtures (KETF’s)

OMTKETFusesspare

WollackOMT

IsolatorKETFuses

FaradayIsolator


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High Resolution SNA Axial Ratio

Scan

18000 20000 22000 24000 26000Frequency (MHz)

0

0.5

1

1.5A

xial

Rat

io (d

B)

0

0.5

1

1.5

Axi

al R

atio

(dB

)

0

0.5

1

1.5

Axi

al R

atio

(dB

)

0

0.5

1

1.5

Axi

al R

atio

(dB

) Iso-KETF

Iso-KETF with Spacer

OMT-KETF

OMT-KETF with Spacer

K#22 Axial Ratio for Various K-Band Ellipticity Test Fixtures

LCP & RCP(15 April 2005)

LCPRCP


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Typical K-Band Axial Ratio Measurement

Measured Axial Ratio on K#22 LCP & RCP Channels using the Iso-KETFversus

Calculated Axial Ratio for Phase-Shifter #23 based on Differential Phase Shift Test Data(Assumes 0 dB Amplitude Inbalance)

15 April 20051 dB Axial Ratio SpecLCP (Unsmoothed)LCP SmoothedRCP (Unsmoothed)RCP (Smoothed)Phase-Shifter #23

18000 19000 20000 21000 22000 23000 24000 25000 26000

Frequency (GHz)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Axi

al R

atio

(dB

)


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AR Test on L#21using VLA-Style OMT


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Simulated LNA Return Loss Measurements

Hybrid Coupler Polarizer in anEVLA Interim L-Band Rx (L#32)

Simulated LNA’s using Terminations and/or Unterminated Pads (L#21)


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Simulated LNA Return Loss

Measurements

1300 1400 1500 1600 1700 1800Frequency (MHz)

0123

Term

inat

ions

0123

IRL=

20 d

B

0123

IRL=

18 d

B

0123

IRL=

16 d

B

0123

IRL=

14 d

B

0123

IRL=

12 d

B

0123

IRL=

10 d

B

0123

IRL=

8 dB

0123

IRL=

6 dB

L#21 Circular Polarizer - Quadridge OMT & Hybrid Coupler Axial Ratio vs. Simulated LNA Input Return Loss

Axial Ratio Key = LCP , RCP & 1 dB Spec (17 Feb 2006)


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SNA Measurement of Total Power Stability

Q-Band S/N 12

• Measure noise power (in 100 MHz BW) across Rx frequency response

• Save in Memory• Look at “Meas-Mem”• Microphonics will

appear as deviations from a flat line

• Whack on dewar

LCP

RCP


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Total Power StabilityLong & Short Term at 48 GHz

Q-Band S/N 12

10 sec sweep 200 ms sweep

Microphonics - 17 ms period

LCP

RCP


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Total Power StabilityAdd Restraining Brackets across

Output WR-22 FlexguideQ-Band S/N 12

RestrainingBracket


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Total Power StabilityShort Term after Fix

Q-Band S/N 12

LCP

RCP


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Summary

• We believe we have the appropriate test equipment and have developed the requisite test techniques to characterize all of the EVLA receivers that will be built over the next 6 years.


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Questions ?


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Backup Slides


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Laboratory ReceiverCharacterization

• The first automated amplifier & receiver test measurement system built at the NRAO was designed by Sandy Weinreb at CDL in the late 70’s & early ’80’s.

• This system used the foremost microcomputer of the day - the Apple II.

• The software for the system was written in BASIC by Sandy’s son, Glenn.

• They gave it the name ADIOS, which stands for “Analog Digital Input Output System”.


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ADIOS, Amigos

• In the 1990’s, as the AOC took on an increasing role in VLA/VLBA receiver development & maintenance, Paul Lilie(former Head of the FE Group) designed a new PC-based test system.

• Ever one for a pun, he endowed it with a name that gave tribute to the original ADIOS system…

• The word SOIDA has become ubiquitous.• Adjective : “Did you do a SOIDA test on the receiver?”• Noun : “I did a SOIDA on it yesterday?”• Verb : “When will you SOIDA this receiver?”• Adverb : “I was SOIDA testing the receiver when it died?”


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Hot/Cold LoadsHigh Frequency Rx’s

Ku, K, Ka & Q-Band• Feeds are considered to

be part of the receiver.• Hot/Cold Loads use

CV-3 Absorber.• Boxes made from

Styrofoam or Zotefoam.• K-Band has a metal plate

to make Cold Load look “colder” (reduce leakage from 300K ambient).

• K-Band Cold Load elevated with fan to eliminate moisture build up on bottom surface.

K-Band Cold Load


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Hot/Cold LoadsLower Frequency Rx’s

L, S, C & X-Band• The feeds for these

receivers are built into the Vertex Cabin.

• So they need circular waveguide Hot/Cold Loads.

• Built from OMT’s with coaxial terminations at ambient or immersed in LN2

• Old VLBA Hot/Cold Loads not broadband enoughSOS Testing a VLBA Ku-Band Rx L-Band Proto with 40” Section


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Hot/Cold LoadsLower Frequency Rx’s

Examples

L-Band Hot/Cold Load Lilie Noise Standard C-Band Hot/Cold Load


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Typical L-Band Axial Ratio Measurement

L#32 : AR & PA vs. Frequency (Unsmoothed) - With Reference Subtraction23 Nov 2004

0

0.5

1

1.5

2

2.5

3

1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Frequency (MHz)

Axi

al R

atio

(dB

)

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

140

160

180

Posi

tion

Ang

le (N

orm

aliz

ed)

AR - LCPAR - RCPPAN - RCPPAN - RCP


40

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

1000 MHz

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

1100 MHz

045

90

135180

225

270

315

-1 0 1 2

045

90

135180

225

270

315

-1 0 1 2

1200 MHz

1300 MHz 1400 MHz 1500 MHz

1600 MHz0

45

90

135180

225

270

315

-1 0 1 2

1700 MHz 1800 MHz0

45

90

135180

225

270

315

-1 0 1 2

RCP

LCP

L-Band S/N 32 (23 Nov 2004) - With Ref SubtractionAxial Ratio (dB) and Position Angle versus Frequency

Cold Receiver with Balanced LN+HP Gain BlocksSNA Captured Data (Unsmoothed)

045

90

135180

225

270

315

-1 0 1 2

1900 MHz0

45

90

135180

225

270

315

-1 0 1 2

2000 MHz0

45

90

135180

225

270

315

Position Angle

-1 0 1 2Axial Ratio (dB)


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L#21 Circular Polarizer - Quadridge OMT & Hybrid Coupler Axial Ratio vs. Simulated LNA Input Return Loss

(19 Feb 2006)IRL = TerminationsIRL = 20 dBIRL = 18 dBIRL = 16 dBIRL = 14 dBIRL = 12 dBIRL = 10 dBIRL = 8 dBIRL = 6 dBAxial Ratio 1 dB Spec

-25

-20

-15

-10

-5

0

nput

Retur

n Los

s (d

B)

1300 1400 1500 1600 1700 1800Frequency (MHz)

-40

-35

-30

I

1300 1400 1500 1600 1700 1800Frequency (MHz)

-40

-35

-30

B)

-25

-20

-15

-10

-5

0

Input Return L

oss (d

LCP RCP

1300 1400 1500 1600 1700 1800Frequency (MHz)

0

1

2

3

Axi

al R

atio

(dB

)

1300 1400 1500 1600 1700 1800Frequency (MHz)

0

1

2

3

Axial R

atio (dB)

LCP RCP


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L#21 Circular Polarizer - Quadridge OMT & Hybrid Coupler Axial Ratio vs. Simulated LNA Input Return LossLCP & RCP IRL = Termination and/or IRL10 dB

Axial Ratio Key = LCP , RCP & 1 dB Spec (17 Feb 2006)

1300 1400 1500 1600 1700 1800Frequency (MHz)

0

1

2

3

LCP=

Term

& R

CP=

Term

0

1

2

3

LCP=

Term

& R

CP=

10dB

0

1

2

3

LCP=

10db

& R

CP=

Term

0

1

2

3

LCP=

10db

& R

CP=

10dB


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General Purpose Test Equipment

• PNA DC-50 GHz (Agilent E8463B)• Coaxial SNA DC-26 GHz (HP8757C + HP83630B)• Waveguide SNA (HP8758E + HP83624A)

• Ka, Q & W-Band Source Modules

• Spectrum Analyzer (Agilent 8563EC)• DC-26, 33-50, 75-110 GHz

• Power Meter (Agilent E4419B)• DC to 110 GHz

• SiteMasters (Anritsu S332B & S820A)

Documents

EVLA Front-End CDR · LNA LNA LCP RCP GHz LN2 Liquid Nitrogen ... • Not always as accurate as SOIDA but allows quick comparison measurements ... R. Hayward EVLA Front-End CDR