Compact and Spherical Range Design, Application and Evaluation

Walter D. Burnside and Inder J. Gupta

The Ohio State UniversityElectroScience Laboratory

1320 Kinnear RoadColumbus, Ohio 43212

(614) 292-5747 and (614) 292-5951

Presented on September 21-22, 2005 for Raytheon (Tucson, AZ).

Course Outline

Basic Range Design Guidelines (Burnside) Compact Range Reflector Design (Gupta) Absorber Design and Layout (Burnside) Critical Range Evaluation (Gupta)

Second Half Day

First Full Day

R-Card Fences for Outdoor Ranges (Gupta) Summary of Range Design Issues (Burnside)

R-card Fences to Suppress Ground Bounce Term in Outdoor Facilities

Inder (Jiti) Gupta

ElectroScience LaboratoryDept. of Electrical and Computer Engineering

The Ohio State University1320 Kinnear Road, Columbus, OH 43212

Phone: (614) 292-5951Fax: (614) 292-7297

Email: gupta.11@osu.edu

Introduction(1)

In outdoor facilities, the ground bounce term can be a limiting factor.

The ground bounce term can destructively interfere with the direct path term reducing the signal level in the quiet zone.

The transmit antenna height is adjusted so that the direct ray and the ground bounce term add in phase.

– Narrowband solution

Alternatively, metallic fences are used to steer the ground bounce term away from the quiet zone.

Introduction(2)

R-card Fences

R-card fences have varying resistance where the resistance varies smoothly from a very low value (purely conductor) to very high values.

– Metallic fence can be replaced with a R-card fence.

Transmit signal through the fence can end up in the quiet zone.

Outdoor Facility with R-card Fences

Multiple R-card fences can be used to eliminate the ground bounce term in the quiet zone.

OSU-ESL has designed and built R-card fences for outdoor facilities.

Experimental Outdoor Test Range

30 meters longRadar antenna height is 60 cmCenter of target zone is 3 meters above

ground6-18 GHz frequency bandSix R-card fencesFences are tilted 20° towards the feed.

30 Meter Outdoor Test Range

30 Meter Outdoor Test Range

R-card Fences

Each fence is 60 cm tall.

Bottom one third of a fence is pure metal.

Resistance increases smoothly from pure metal to 1150 ohms.

Built using ten layers of flat resistively coated thin films.

Resistive taper on both sides, too.

An R-card Fence

Field Probe Data

Radar – HP8510 network analyzer

Radar Antenna – SA 8-12 GHz standard gain horn

Probe Antenna – AEL 2-18 GHz horn

LNA behind the AEL horn to compensate for the cable loss

Horizontal and vertical polarization

A vertical scan (center 3 meters above ground)

A horizontal scan (3meters above ground)

Range with Linear Scanner

Field Probe Data - Horizontal Scan

No fences With fencesVertical Pol

Field Probe Data - Horizontal ScanHorizontal Pol

No fences With fences

Field Probe Data - Vertical Scan

Vertical PolNo fences With fences

Field Probe Data - Vertical ScanHorizontal Pol

No fences With fences

Field Probe Data - Vertical Scan

Horizontal Pol8 GHz 12 GHz

Calibrated Field Probe Data – Vertical Scan

No fences With fencesHorizontal Pol

Backscatter Measurements

1-foot corner reflector

Backscattered fields along the boradside direction

Corner reflector at various heights

8.5 GHz to 12.5 GHz frequency band in 2 MHz steps

Two separate antennas for transmit and receive to perform S12 measurements

Time gating (25 point smoothing) to isolate the corner reflector return

Measured Backscattered Fields – Corner Reflector

Horizontal PolNo fences With fences

Measured Backscattered Fields – Corner ReflectorHorizontal Pol

6 R-card fences

Multilayered R-card Fences

The R-card fences discussed until now have strong reflected field term.

In some applications, the reflection term is also undesired.

Multilayered R-card fences have been designed and built for these applications

The R-card Layout: Layer 1

The R-card Layout: Layer 2

The R-card Layout: Layer 3

The R-card Layout: Layer 4

The R-card Layout: Layer 5

Near Field Data for Single Layer R-Card Fence Design

Plot Convention: #L#C##L: number of layers per R-Card Fence#C: number of R-Card Fences#: Separation between two adjacent R-Card Fences

Total Field at Receiver Site Reflected Field at Transmitter Site

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Reflected Field Back to the Source0.56 inch Foam

Vertical Probe Position (meters)

0 1 2 3 4 5 6

Sca

tter

ed F

ield

at

Tra

nsm

itter

(dB

)0

5

10

15

20

25

30

35

40

1L1C001L3C081L3C12 1L3C16

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Total Field 0.56 inch Foam

Vertical Probe Position (meters)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

Tot

al P

robe

Fie

ld a

t R

ecei

ver

(dB

)

0

5

10

15

20

25

30

35

40

Direct1L1C001L3C081L3C121L3C16

3 Fences

Near Field Data for 3 Layer R-Card Fence Design

Plot Convention: #L#C##L: number of layers per R-Card Fence#C: number of R-Card Fences#: Separation between two adjacent R-Card Fences

Total Field at Receiver Site Reflected Field at Transmitter Site

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Total Field 0.56 inch Foam

Vertical Probe Position (meters)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

Tot

al P

robe

Fie

ld a

t R

ecei

ver

(dB

)

0

5

10

15

20

25

30

35

40

Direct3L1C003L3C083L3C123L3C16

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Reflected Field Back to the Source0.56 inch Foam

Vertical Probe Position (meters)

0 1 2 3 4 5 6

Sca

tter

ed F

ield

at

Tra

nsm

itter

(dB

)0

5

10

15

20

25

30

35

40

3L1C003L3C08 3L3C12 3L3C16

3 Fences

Near Field Data for 5 Layer R-Card Fence Design

Plot Convention: #L#C##L: number of layers per R-Card Fence#C: number of R-Card Fences#: Separation between two adjacent R-Card Fences

Total Field at Receiver Site Reflected Field at Transmitter Site

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Reflected Field Back to the Source0.56 inch Foam

Vertical Probe Position (meters)

0 1 2 3 4 5 6

Sca

tter

ed F

ield

at

Tra

nsm

itter

(dB

)0

5

10

15

20

25

30

35

40

5L1C005L3C085L3C125L3C16

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Total Field 0.56 inch Foam

Vertical Probe Position (meters)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

Tot

al P

robe

Fie

ld a

t R

ecei

ver

(dB

)

0

5

10

15

20

25

30

35

40

Direct5L1C005L3C085L3C125L3C16

3 Fences

Near Field Data for 5 Layer R-Card Fence Design

Plot Convention: #L#C##L: number of layers per R-Card Fence#C: number of R-Card Fences#: Separation between two adjacent R-Card Fences

Total Field at Receiver Site Reflected Field at Transmitter Site

3 Fences

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Reflected Field Back to the SourceOne inch Foam

Vertical Probe Position (meters)

0 1 2 3 4 5 6

Sca

tter

ed F

ield

at

Tra

nsm

itter

(dB

)0

5

10

15

20

25

30

35

40

5L1C005L3C08 5L3C12 5L3C16

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Total Field One inch Foam

Vertical Probe Position (meters)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

Tot

al P

robe

Fie

ld a

t R

ecei

ver

(dB

)

0

5

10

15

20

25

30

35

40

Direct5L1C005L3C085L3C125L3C16

1.0” Foam

Near Field Data for 5 Layer R-Card Fence Design

Plot Convention: #L#C##L: number of layers per R-Card Fence#C: number of R-Card Fences#: Separation between two adjacent R-Card Fences

Total Field at Receiver Site Reflected Field at Transmitter Site

2 Fences

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Reflected Field Back to the SourceOne inch Foam

Vertical Probe Position (meters)

0 1 2 3 4 5 6S

catt

ered

Fie

ld a

t T

rans

mitt

er (

dB)

0

5

10

15

20

25

30

35

40

5L1C005L2C14 5L2C22 5L2C30

Field Probe Pattern at Z=80 metersFrequency = 1575 MHz

Total Field One inch Foam

Vertical Probe Position (meters)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

Tot

al P

robe

Fie

ld a

t R

ecei

ver

(dB

)

0

5

10

15

20

25

30

35

40

Direct5L1C005L2C145L2C225L2C30

1.0” Foam

Measurement Setup

Tx

Rx

260 ft

95 ft 95 ft70 ft

~10 ft

90 in

70 in8' High R-Card Fences

Measurement Setup Behind ESL

Transmit Antenna Receive Antenna

R-card Fences

Receiving Antenna Transmit Antenna

Measurement Setup Behind ESL

Ohio University R-Card Fence Measured Probe DataHorizontal Polarization, Tx Antenna Height = 10'

Frequency = 1576 MHz

Receiving Antenna Height (inches)

90 100 110 120 130 140 150 160

Pro

be F

ield

(dB

)

-120

-115

-110

-105

-100

-95

-90

With FenceWithout Fence

Ohio University R-Card Fence Measured Probe DataVertical Polarization, Tx Antenna Height = 10'

Frequency = 1576 MHz

Receiving Antenna Height (inches)

90 100 110 120 130 140 150 160

Pro

be F

ield

(dB

)

-120

-115

-110

-105

-100

-95

-90

With FenceWithout Fence

Probe Field at 1575 MHz

Summary

R-card fences can be used for performance enhancement of outdoor facilities.

Multi-layered R-card fences can be designed to act like absorber (low-level transmission and reflection).

References

Y. Kim and E.K. Walton, “Ground bounce reduction using a tapered resistive sheet fence,” AMTA2000, pp. 222-227, Philadelphia, PA, October 2000.

I.J. Gupta and W.D. Burnside, ”Performance of an experimental outdoor RCS range with R-card fences,” AMTA2001, pp.400-405, Denver, CO, October 2001.

T.-H. Lee and W.D. Burnside, “Applications of multilayer resistive strips (R-card) in EM measurements,” AMTA2003, pp 420-425, Irvine, CA, October 2003.