EM COMPONENTSUPDATE & PERFORMANCE RESULTS

S. Srikanth

Critical Design Review

GBT K-Band Focal Plane Array

January 30-31, 2009

OUTLINE OF TALK

1. Feed – Measured Results

2. Array Performance

3. Efficiency Comparison

4. Phase Shifter – Measured Results

5. OMJ – Measured Results

KFPA FEED

Frequency 18-26.5 GHzFeed taper -13 dBCompact/Profile taper hornRing-loaded corrugations

Aperture ID = 2.93”* (5.5λ22)OD = 3.4”Length = 6.658”Pitch = 0.082” (λ18/8)Vane = 0.026”Depth = 0.13” (0.28λ26.5)69 corrugationsΘi = 8º ; Θmax = 17º*ID of linear taper horn=5.55”

Measured Patterns & Taper

H-plane; z=-2.975

-60

-50

-40

-30

-20

-10

0

-60 -45 -30 -15 0 15 30 45 60

Azimuth (deg.)

Am

pli

tud

e (d

B) 18

20

22

24

26

28

Freq.

(GHz)

H-pln

(dB)

E-pln

(dB)

18 -11.7 -11.2

19 -12.6 -12.3

20 -13.2 -13.6

21 -13.7 -14.2

22 -13.7 -14.2

23 -13.5 -14.0

24 -13.2 -13.6

25 -13.0 -13.4

26 -13.0 -14.3

26.5 -13.9 -14.7

Avg. -13.2 -13.5

E-plane; z=-2.975

-60

-50

-40

-30

-20

-10

0

-60 -45 -30 -15 0 15 30 45 60

Azimuth (deg.)

Am

pli

tud

e (d

B) 18

20

22

24

26

28

22 GHz; Theory & Measured

22 GHz; H-Plane

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Angle (degrees)

Ampl

itude

(dB) Theory

Measured

22 GHz; E-Plane

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Angle (degrees)Am

plitu

de (d

B) Theory

Measured

H-plane E-plane

Measured Cross-polarization in 45 deg. plane

45 deg. plane; Cross-pol.

-80

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Azimuth (deg.)

Am

plit

ud

e (d

B) 17

17.4

18

19

20

45 deg. plane; Cross-pol.

-80

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Azimuth (deg.)

Am

plit

ud

e (d

B)

21

22

24

25

45 deg. plane; Cross-pol.

-80

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Azimuth (deg.)

Am

plit

ud

e (d

B)

26

27

28

29

Measured Input Return Loss

GBT K-band array receiver feeds

-50

-40

-30

-20

-10

0

17 19 21 23 25 27

Frequency

Ret

urn

Lo

ss (

dB

)

# 01

# 02

# 03

Ø36.00"

Azimuth/Asym.plane

Elev./Symm. plane

LAYOUT OF ELEMENTS (61 Feeds)

Element spacing 3.45”1+6+12+18+24

22 GHz; Telescope beams in Azimuth (asym.) planeHPBW = 34”

X” Throw

(arcsec)

Throw

(HPBW)

0 0 0

3.45 94 2.7

6.9 189 5.5

10.4 284 8.2

13.8 378 11.0

17.3 473 13.7

Azimuth beams; 0,1,2-0.63; 3-0.62; 4-0.59; 5-0.55

20

30

40

50

60

70

80

90

-0.1000 -0.0500 0.0000 0.0500 0.1000 0.1500 0.2000

Azimuth (deg)

Am

plit

ud

e (d

B)

0

3.4

6.92

10.4

13.9

17.3

Beam throw 27.4”/inch; 0.43HPBW/λ

* Theoretical feed patterns used

22 GHz; Telescope beams in Elevation (symm.) planeHPBW = 34”

y” Throw

(arcsec)

Throw

(HPBW)

0 0 0

6 164 4.8

12 331 9.6

18 498 14.5

Elevation beams; 0,1-0.63; 2-0.62; 3-0.60,

20

30

40

50

60

70

80

90

-0.1000 -0.0500 0.0000 0.0500 0.1000 0.1500 0.2000

Elevation (deg)

Am

plit

ud

e (d

B) 0

6

12

18

Beam throw 27.4”/inch; 0.43HPBW/λ

* Theoretical feed patterns used

Circle #1 (3.4”rad): 62.9% min.

Circle#2 (6.9”rad): 62.9% min.

Circle#3 (10.4”rad): 61.7% min.Circle#4 (13.8”rad): 58.9% (az) -6.3%; 61.6% (el) -2%

Circle 18.0” rad: 54.7% (az); 60.2% (el)

FEED OFFSET & APERTURE EFFICIENCY

Aperture Eff. Vs Feed offset; 22 GHz; OD=3.4"

0 3 69

12 15

18

0.5

0.52

0.54

0.56

0.58

0.6

0.62

0.64

0 5 10 15 20

Offset (inch)

Eff

icie

ncy Asym

Sym

Ø36.00"

Azimuth/Asym.plane

Elev./Symm. plane

-2%; measured -5% at 8.4”offset

Ø36.00"

Elev./Symm. plane

62.9%

61.7%

58.9%54.7%

58.9%

61.5%

Optimum orientation of Elements

62.9%

61.7%

54.7%

60.7%

60.7%

61.4%

62.9%

61.7%

54.7%

60.7%

60.7%

61.4%

Beam width & Beam spacing

Freq.

(GHz)

HPBW Beam Spacing

(HPBW)

18 40” 2.3

22 34” 2.7

24 31” 3.0

26.5 29” 3.2

Element spacing 3.45”; Beam spacing 94arcsec Beam throw 27.4 arcsec/”

Measured 20 GHz; E-plane

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Angle (degrees)

Po

wer

(d

B)

Prof

LinL

Measured 20 GHz; H-plane

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Angle (degrees)

Po

wer

(d

B)

Prof

LinL

KFPA FEED Vs. 20 GHz FEED

Measured patternsKFPA Feed – Profile Horn (-13.5,-13.3 dB)20 GHz Feed – Linear Taper Horn (-11.7,-12.8 dB)

GBT Beam; Sym. plane; 20 GHz

20

30

40

50

60

70

80

90

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Angle (degrees)

Po

we

r (d

B)

Lin

Prof

GBT Beam; Sym. plane; 18 GHz

20

30

40

50

60

70

80

90

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Angle (degrees)

Po

we

r (d

B)

Lin

Prof

GBT Beam; Sym. plane; 22 GHz

20

30

40

50

60

70

80

90

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Angle (degrees)

Po

we

r (d

B)

Lin

Prof

Freq.

(GHz)

Linear taper Profile ήapl- ήapp

------------------

ήapl

(%)

Edgetaper (dB)

ήapl Edge taper (dB)

ήapp

18 -12.64 0.6995 -11.45 0.6965 0.43

20 -12.23 0.7284 -13.41 0.6560 9.94

22 -14.07 0.6888 -13.95 0.6189 10.15

KFPA FEED Vs. 20 GHz FEEDTelescope beam patterns, Efficiency

Measured 24 GHz; E-plane

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Angle (degrees)

Po

wer

(d

B)

Prof

LinH

Measured 24 GHz; H-plane

-70

-60

-50

-40

-30

-20

-10

0

-90 -60 -30 0 30 60 90

Angle (degrees)

Po

wer

(d

B)

Prof

LinH

KFPA FEED Vs. 24 GHz FEED

Measured patternsKFPA Feed – Profile Horn (-13.7,-13.3 dB)24 GHz Feed – Linear Taper Horn (-12.1,-13.1 dB)

GBT Beam; Sym. plane; 22 GHz

20

30

40

50

60

70

80

90

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Angle (degrees)

Po

we

r (d

B)

Lin

Prof

GBT Beam; Sym. plane; 24 GHz

20

30

40

50

60

70

80

90

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Angle (degrees)

Po

we

r (d

B)

Lin

Prof

GBT Beam; Sym. plane; 26.5 GHz

20

30

40

50

60

70

80

90

-0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

Angle (degrees)

Po

we

r (d

B)

Lin

Prof

Freq.

(GHz)

Linear taper Profile ήapl- ήapp

------------------

ήapl

(%)

Edgetaper (dB)

ήapl Edge taper (dB)

ήapp

22 -12.10 0.6770 -13.95 0.6189 8.58

24 -12.58 0.6669 -13.48 0.6050 9.28

26.5 -12.46 0.6456 -14.32 0.5864 9.17

KFPA FEED Vs. 24 GHz FEEDTelescope beam patterns, Efficiency

S. Srikanth, “A Wide-Band Corrugated Rectangular Waveguide Phase Shifter for Cryogenically CooledReceivers”, IEEE Microwave and Guided Wave Letters, Volume 7, pp. 150-152, June 1997.

18-26.5 GHz Phase Shifter

0.474 x 0.452; Length 4.84”

Serial #01; Return Loss; Perp. 0.474

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

17 18 19 20 21 22 23 24 25 26 27

Frequency (GHz)

Ret

urn

Lo

ss (

dB

)

S11

Serial #01; Return Loss; Perp. 0.452

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

17 18 19 20 21 22 23 24 25 26 27

Frequency (GHz)R

etu

rn L

oss

(d

B)

S11

MEASURED RETURN LOSS

Serial #01; Insertion Loss; Perp. 0.474

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

17 18 19 20 21 22 23 24 25 26 27

Frequency (GHz)

Ret

urn

Lo

ss (

dB

)

S11

Serial #01; Insertion Loss; Perp. 0.452

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

17 18 19 20 21 22 23 24 25 26 27

Frequency (GHz)

Ret

urn

Lo

ss (

dB

)

S11

MEASURED INSERTION LOSS

Serial # 01; Differential phase

65

70

75

80

85

90

95

100

105

110

115

17 18 19 20 21 22 23 24 25 26 27

Frequency (GHz)

Dif

fere

nti

al p

has

e (d

egre

es)

Delta

Serial # 03; Differential phase

65

70

75

80

85

90

95

100

105

110

115

17 18 19 20 21 22 23 24 25 26 27

Frequency (GHz)D

iffe

ren

tial

ph

ase

(deg

rees

)

Series1

MEASURED DIFFERENTIAL PHASE

ORTHO MODE JUNCTION

E. Wollack, “A Full Waveguide Band Orthomode Junction”, EDIR No. 303, NRAO, May 16, 1996

WR42 waveguide; 4.5” x 2.8”Septum 0.010” (Beryl. Cu)Pin 0.040” dia. (Beryl. Cu)

353 Leaded brass; Weight 1 lb

ORTHO MODE JUNCTION

6061-T6 Aluminum; Weight 0.33 lb

6061-T6 ALUMINUM Vs. 353 LEADED BRASS

Property 353 Leaded Brass 6061-T6 Aluminum

Composition

(%)

Cu 62, Pb 1.8, Zn 36.2

Al 97.92, Si 0.6, Mn 0.28, Mg 1.0, Cr 0.2

Density

(lb/in3)

0.307 0.098

Thermal conductivity

(BTU/ft. h.°F)

104 96

Coeff. of thermal expansion

(ppm/°C)

18.4 23.6

Electrical Resistivity

(μΩ.cm)

6.6-3.5 5.0-4.0

K-Band OMT S/N 35 - Insertion & Input Return Loss(RHH : 20 Feb 2008)

-1.0

-0.9

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

18 19 20 21 22 23 24 25 26 27 28

Frequency (GHz)

Ins

ert

ion

Lo

ss

(d

B)

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Re

turn

Lo

ss

(dB

)

IL - Main Arm

IL - Side Arm

RL - Main Arm

RL - Side Arm

Measured S-parameters- Brass OMJ

Measured by R. Hayward, NRAO, Socorro, NM

Main arm Side arm

Measured S-parameters- Aluminum OMJ

Measured by R. Simon, NRAO, Green Bank, WV

#1: 18 GHz; #2: 26.5 GHz; #3; 27.5 GHz

CONCLUSION

All EM components have been validated.

Feed: 3 nos.

Phase shifter: 2 good ones; 6 being electroformed

OMJ: 3 nos. of aluminum OMJ

Circular-rectangular transition, 45 twist: 10 nos of each being processed.

Pc 3”-4.2”

22-26.5 Feed: ID=4.54 OD=4.85 L=8.14 pc=5.9

Phase patterns & Phase centers

H-plane; z=-2.975

-80

-60

-40

-20

0

20

40

60

80

-30 -20 -10 0 10 20 30

Azimuth (deg.)

Pha

se (d

eg.)

17

17.4

18

19

20

21

H-plane; z=-3.627

-80

-60

-40

-20

0

20

40

60

80

-30 -20 -10 0 10 20 30

Azimuth (deg.)

Ph

ase

(deg

.)

20

21

22

23

24

H-plane; z=-4.126

-80

-60

-40

-20

0

20

40

60

80

-30 -20 -10 0 10 20 30

Azimuth (deg.)

Ph

ase

(deg

.)

24

25

26

26.6

27

28

PC at 18 GHz

PC at 22 GHz

PC at 26 GHz

Aperture Efficiency & System Temperature

3.4 “ OD Feed 2.8” OD Feed

Freq

(GHz)

Ap.Eff. System Temp

(K)

90 30

G/T (K/Jy)

90 30

Freq

(GHz)

Ap.Eff System Temp

(K)

90 30

G/T (K/Jy)

90 30

18 0.6911 54.9

6.7

62.1

7.1

0.0358 0.0317 18 0.7006 58.5 66.0 0.0341 0.0302

22 0.6287 45.6

4.9

63.3

5.3

0.0392 0.0283 22 0.6500 47.2 65.0 0.0392 0.0284

26.5 0.5900 42.2

4.1

55.5

4.3

0.0398 0.0302 26.5 0.6131 41.1 54.3 0.0424 0.0321

Tspill