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S. Srikanth EVLA Feed/FE PDR February 12-13, 2002 EVLA FEEDS DESIGN S. Srikanth NRAO/Charlottesville

EVLA FEEDS DESIGN

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EVLA FEEDS DESIGN. S. Srikanth NRAO/Charlottesville. VLA Cassegrain Geometry Drawing. Current Receiver Bands. VLA Vertex Feed Cone. EVLA Receiver Bands. Selection of Bands. Minimize number of receivers Use existing technology - PowerPoint PPT Presentation

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Page 1: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

EVLA FEEDS DESIGN

S. SrikanthNRAO/Charlottesville

Page 2: EVLA FEEDS DESIGN

VLA Cassegrain Geometry Drawing

Page 3: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Current Receiver Bands

Page 4: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

VLA Vertex Feed Cone

Page 5: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

EVLA Receiver Bands

Page 6: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Selection of Bands

• Minimize number of receivers

• Use existing technology

• Performance at the band edges - feeds, polarizers, amplifiers etc.

Page 7: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Selection of Feed Type and Parameters

• Nominal taper of -13 dB at 9.25 degrees

• Compact horns where space is limited

• Ring-loaded slots (except for Q-band)

• Number of corrugations/wavelength - 3.8

Page 8: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Conventional Corrugations

Page 9: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Ring-Loaded Corrugations

Page 10: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

VSWR – Conventional and Ring-Loaded

Page 11: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 12: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 13: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 14: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 15: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 16: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 17: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Linear Taper Horn 75" OD – 1.0 GHz

Page 18: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Linear Taper Horn 75" OD – 1.4 GHz

Page 19: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Page 20: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of 75" OD and 62" OD Feeds

Feed Taper at 9 Degrees (dB)75" OD 62" ODFreq.

(GHz) H E X H E X 0.85 -5.0 -3.4 -19.0 -3.7 -6.6 -14.1

1.0 -6.8 -7.3 -5.1 -4.81.1 -8.7 -8.1 -6.0 -5.81.2 -10.0 -10.0 -7.2 -7.01.4 -10.3 -11.3 -10.0 -9.91.6 -11.0 -10.5 -10.2 -11.41.8 -9.4 -11.0 -10.5 -9.92.0 -10.5 -11.6 -12.4 -12.12.3 -8.5 -9.0 -9.0 -9.7 -22.4

1-2 GHz Average taper -10.0 dB1-2 GHz Average taper - 9.3 dB1.2-2 GHz Average taper -10.2 dB

Page 21: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Compact Horn – 75" OD 1.0 GHz

Page 22: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Compact Horn – 62" OD 1.0 GHz

Page 23: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Compact Horn – 75" OD 1.4 GHz

Page 24: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Compact Horn – 62" OD 1.4 GHz

Page 25: EVLA FEEDS DESIGN

VLA Cassegrain Geometry Drawing

Page 26: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

ANALYSIS METHODOLOGY 

 

Page 27: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

ANALYSIS METHODOLOGY

= /max = /sinmax

6. Grids on the reflector surface

Page 28: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of Subreflector Patternsat 1.5 GHz ( = 0°)

JPL Software NRAO Software

Page 29: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of Subreflector Patternsat 1.5 GHz ( = 90°)

JPL Software NRAO Software

Page 30: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of Main Reflector Patterns

at 1.465 GHz

Measured

NRAO Software -4 -2 0 2 4

Page 31: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 1.4 GHzCompact Horn - 75" OD

Symmetric Plane

Page 32: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 1.4 GHzCompact Horn - 62" OD

Symmetric Plane

Page 33: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 1.4 GHzCompact Horn - 75" OD

Asymmetric Plane

Page 34: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 1.4 GHzCompact Horn - 62" OD

Asymmetric Plane

Page 35: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 1.4 GHzCompact Horn - 62" OD

Symmetric Plane

Page 36: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 1.4 GHzCompact Horn - 62" OD

Asymmetric Plane

Page 37: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Main Reflector Pattern – 1.4 GHzCompact Horn - 75" OD

Page 38: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Main Reflector Pattern – 1.4 GHzCompact Horn - 62" OD

Page 39: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of 75" OD and 62" OD Feeds

Effc. 75" & 62" OD Feeds

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

Frequency (GHz)

Eff

icie

nc

y

75" OD

62" OD

Page 40: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Compact Horn –75" OD

Spillover Temp. 75" OD

0

10

20

30

40

50

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

Frequency (GHz)

Ts

pill

(K

) Elev.90

Elev.60

Elev.30

Elev.20

Page 41: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Compact Horn – 62" OD

Spillover Temp. 62" OD

0

10

20

30

40

50

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

Frequency (GHz)

Tsp

ill

(K) Elev.90

Elev.60

Elev.30

Elev.20

Page 42: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of 75" OD and 62" OD Feeds

Gain/Tsys. 90 deg.

0

0.1

0.2

0.3

0.4

0.5

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

Frequency (GHz)

G/T

(1/J

y*10

E-2

)

75: OD

62" OD

Trx=8

Tsk=4,6

Tsc=2,3

Page 43: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of 75" OD and 62" OD Feeds

Gain/Tsys. 60 deg.

0

0.1

0.2

0.3

0.4

0.5

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

Frequency (GHz)

G/T

(1/J

y*10

E-2

)

75" OD

62" OD

Trx=8

Tsk=4,6

Tsc=2,3

Page 44: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison of 75" OD and 62" OD Feeds

Gain/Tsys. 30 deg.

0

0.1

0.2

0.3

0.4

0.5

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

Frequency (GHz)

G/T

(1/J

y*10

E-2

)

75" OD

62" OD

Trx=8

Tsk=4,6

Tsc=2,3

Page 45: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

The hybrid lens feed

Page 46: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Measured Pattern – Current Feed

E-1.53 GHz (raw)

-45-40-35-30-25-20-15-10-505

-100 -50 0 50 100

Angle (deg)

Lev

el (

dB

)

#20;-18.6

#2;-17.4

#4:-17.6

Page 47: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Corrected Pattern – Current Feed

E,1.53 GHz;Avg.

-45

-35

-25

-15

-5

5

-100 -50 0 50 100

Angle (deg)

Lev

el (

dB

)

Raw;-17.9

Prcd;-12.5

Page 48: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Measured Pattern – Current Feed

H-1.53 GHz (raw)

-45-40-35-30-25-20-15-10-505

-100 -50 0 50 100

Angle (deg)

Lev

el (

dB

)

#20;-18.7

#2;-18.7

#4;-20.7

Page 49: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Corrected Pattern – Current Feed

H,1.53 GHz;Avg.

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

-100 -50 0 50 100

Angle (deg)

Le

ve

l (d

B)

Raw;-19.4

Prcd;-13.0

Page 50: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

Efficiency

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.5 1 1.5 2 2.5

Freq. (GHz)

Eff

icie

ncy

New

Current

Page 51: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

Current Feed

0102030405060708090

100

0.5 1 1.5 2 2.5

Freq. (GHz)

Tsy

s (K

)

Elev. 90

Elev. 60

Elev. 30

Elev. 20

Trx=8

Tsk=4,6

Tsc=2,3

Page 52: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

New Design

0102030405060708090

100

0.5 1 1.5 2 2.5

Freq. (GHz)

Tsy

s (K

)

Elev. 90

Elev. 60

Elev. 30

Elev. 20

Trx=8

Tsk=4,6

Tsc=2,3

Page 53: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

Elevation 90

00.05

0.10.15

0.20.25

0.30.35

0.40.45

0.5

0.5 1 1.5 2 2.5

Freq. (GHz)

G/T

(1/J

y*10

E-2

)

New

Current

Page 54: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

Elevation 60

0

0.1

0.2

0.3

0.4

0.5

0.5 1 1.5 2 2.5

Freq. (GHz)

G/T

(1/

Jy*1

0E-2

)

New

Current

Page 55: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

Elevation 30

0

0.1

0.2

0.3

0.4

0.5

0.5 1 1.5 2 2.5

Freq. (GHz)

G/T

(1/

Jy*1

0E-2

)

New

Current

Page 56: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Comparison: New Design & Current Feed

L-Band

Elevation 20

0

0.1

0.2

0.3

0.4

0.5

0.5 1 1.5 2 2.5

Freq. (GHz)

G/T

(1/

Jy*1

0E-2

)

New

Current

Page 57: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 3.0 GHz-11 dB Taper

Page 58: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Subreflector Scatter Pattern – 3.0 GHz-18 dB Taper

Page 59: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Gain/Tsys Analysis

Effic. at 3 GHz

0.5

0.55

0.6

0.65

0.7

0.75

0.8

-20-18-16-14-12-10

Taper (dB)

Eff

icie

nc

y

Efficiency

Page 60: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Gain/Tsys Analysis

Tsys. ; 3 GHz

0

10

20

30

40

50

-20-18-16-14-12-10

Feed Taper (dB)

Ts

ys

. (K

)

Elev. 90

Elev.60

Elev.30

Elev.20

Tr=13

Tsk=4,6

Tsc=2,3

Page 61: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Gain/Tsys Analysis

G/Tsys ; 3 GHz

0

0.1

0.2

0.3

0.4

0.5

-20-18-16-14-12-10

Feed Taper (dB)

G/T

(1

/Jy

*10

E-2

)

Elev. 90

Elev.60

Elev.30

Elev.20

Tr=13

Tsk=4,6

Tsc=2,3

Page 62: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

EVLA – Predicted Performance

Page 63: EVLA FEEDS DESIGN

S. Srikanth EVLA Feed/FE PDRFebruary 12-13, 2002

Future Work

1. Gain/Tsys vs. feed taper analysis at 10

GHz and 30 GHz.

2. Effect of phase center travel on pointing.

3. Optimization of the feed pointing.

1. Gain/Tsys vs. feed taper analysis at 10

GHz and 30 GHz.