Progress in OTM Loop Antennas - · PDF fileHFIA Loop Presentation assuredcommunications™...

4 February 2010HFIA Loop Presentation assuredcommunications™

Progress in OTM Loop Antennas

M.J. PackerHarris Corporation,

RF Communication Division 1680 University Avenue, Rochester, NY, USA, 14610

[email protected]

THIS INFORMATION WAS REVIEWED IN ACCORDANCE WITH INTERNATIONAL TRAFFIC IN ARMS REGULATIONS, 22 CFR 120-130 AND EXPORT ADMINISTRATION REGULATIONS, 15 CFR

730-774: BASIC MARKETING INFORMATION OF DEFENSE ARTICLES PER ITAR 120.10(a)(5). EXPORT LICENSE IS NOT REQUIRED


Agenda

• Background/History• Benefits/Issues• Numerical Treatment• On-Air-Measurements• Summary and Conclusions


Background

• Continuous Search for the Better OTM HF Antenna

• Today’s Communication Environment – Dry Deserts to Rugged Mountains limits LOS– Limited Satellite Bandwidth– Users Want to Own & Control Hardware– Repeaters are Vulnerable

• Users Perception – Small Cellular Phone talks around the world


HF Propagation

• Refraction from Ionosphere• Ionosphere Thickness and Density is Variable• Variability - Man can not Control but can Predict

• Diurnal Variation (24 hour cycle)• Seasonal Variation (365 day cycle)• Solar Variation (11 year cycle)

EARTH

Tx Rx

Skywave Channel


History

• General Loop History– 1913 Farrand, two triangular loops for direction finding– 1915 Kolster, multi turns loop– 1930 Loops went out of favor for long wires– 1938 Loops started to appear again – 1940 Russian Military adapted Vehicular Loops– 1970 Ferrite Rod loops– 1970 Active loops commercially available

• Harris Progress– 1994 Experimented with Digital Tuned Loops– 2004 Half-loop Interfaced to Harris Radios

• Operation in both 2G ALE• Issues – Mounting, Complexity, Cost

– 2009 Full Loop Seamless Interface with Harris Coupler/Radios


Loop Antennas Benefits

• Basic Theory: For a Given Volume, a Magnetic Antenna is more efficiency than an Electric Antenna

• Ideal Radiation Pattern for NVIS Comm with Limited Real Estate.

• Omni-direction at High to Medium TOA• Figure-8 at Low TOA

– Potential Elimination of Undesired Signals and Noise

• Full loop does not Require a Gnd Plane


Loop Antenna Tribulations

• Why Are They Not Everywhere?• Mounting Complex Relative to Whip• Radiation Resistance Very Small• Inductance Very High• Fixed Capacitor – Single Freq. Solution• Digitally Tuning Difficult without Inherent

Losses• High Current Flow


Vehicular Loop Antennas

2005 Half-Loop

2009 Full-Loop


Half-loop to Full Loop

ah

Ah

A=a2

R=10A2Io2

P=1/2Io2R

Q=6In(a/ao)/3

af

Image

GndPlane

Ah=3.14*0.92=2.54m2

Af=3.14*0.732=1.68m2

Seems the Half-loop is a better Antenna

Only true if gnd plane is infinite

So, half-loop has Area = Ah/2

Therefore Ah=1.27m2

ao


Loop Components

• Interfaces Directly to Harris Couplers (RF-382 and RF-5382)• Fully compatible with 2G and 3G ALE. • Works with all 20W, 125Watt and 150 Watt systems.• Lightweight (15lb) and low profile yet Robust (passed Oak beam test)• Mounts to standard NATO 5.4 inch bolt circle• Designed for the Severe Military Environmental Conditions• The Antenna Includes:

• One piece fiber-glass radiating element• Spring mounted Support rod, • Low-profile tower unit • Control cable• Manual


Numerical Meshed Models

• Loop Simple | Better Feed System• NEC: 103 segments | HFSS: 22,098 tetrahedra• NEC: < 1min | HFSS: 12 minutes on 3.2 GHz PC

HFSS ModelNEC Model


Numerical Modeling

• Twin Loop Elements• Feed System Coil• Loading Capacitor

– Binominal Switched Capacitors modeled by one Capacitor

– Feed Lines to Coupler

• Free Space• With Ground Plane• On HMMWV• Over Real Ground


Capacitor Loading

• Loading with a Capacitor to Tune Loop to 6 MHz• Increases Resistance 600m to 100• Reactance Resonance

0.1

1

10

100

2 3 4 5 6 7 8 9 10 11 12Frequency (MHz)

Res

ista

nce

(Ohm

s)

1

10

100

1000

Rea

ctan

ce (O

hms)

With Loading Capacitor

Without Loading Capacitor


-200

-100

0

100

200

300

400

1.950 1.975 2.000 2.025 2.050

Frequency (MHz)

Impe

danc

e (O

hms)

Zr MeasZi measZi ModelZr Model

Capacitor Tuning

2.0 MHz

1590 pF

-400

-200

0

200

400

600

800

3.85 3.90 3.95 4.00 4.05 4.10

Frequency (MHz)

Impe

danc

e (O

hms)


4 MHz

385 pF

-400

-200

0

200

400

600

800

1000

1200

7.80 7.85 7.90 7.95 8.00 8.05 8.10

Frequency (MHz)

Impe

danc

e (O

hms)


8 MHz

90 pF

• 2, 4, and 8 MHz

• Measurements and Modeling

• Results match Well on BW

• Measurements have higher Values


Surface Current Magnitude

• Surface Current (A/m)• Uniform Current Density over Loop• Feed Loop higher Current Density


3D Radiation Patterns

• Loop 1.5m above Real Earth (12/.005)• Peak Gain towards Zenith• Omni Pattern at High Elevation• Figure-8 Pattern at low Elevation

2 MHz

16 MHz

8 MHz4 MHz


Gain - Theory and Numerical

-30

-25

-20

-15

-10

-5

0

2 4 6 8 10 12 14 16 18Frequency (MHz)

Gai

n (d

Bi)

Small Loop TheoryLoop 1.5 above real GndNEC Tilt Whip


Field Testing

Loop on 10x10-ft2Ground Plane Loop w/o Gnd Plane


Measured Bandwidth and “Q”

1

10

100

1000

0 2 4 6 8 10 12 14 16Frequency (MHz)

Ban

dwid

th (K

Hz)

and

Qua

lity

Fact

or

Tilt Whip/Coupler "Q" of Tilt WhipFull Loop/Coupler "Q" of Full LoopHalf Loop "Q" of Half Loop


Tune Script Results

• Step every 10KHz, Tune for VSWR• Only NVIS band shown• Tunes from 2 to 30 MHz• Without Ground Plane

0

25

50

75

100

125

150

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0Frequency (MHz)

Forw

ard

Pow

er (W

)0

0.5

1

1.5

2

2.5

3

VSW

R (X

:1)Fwd Pwr

Rfl PwrVSWR


Measurement System

• Use Radio Link Testing to Compare Antenna Performance• PC Controls Two Radios Systems in Mobile Platform • Each System Runs 3G LQA Sequentially Every Minute• Systems Runs Autonomously Until Stopped• Saves Radio Raw Data and GPS data as Platform is Traveling

PRE

+

_VOL

+

_

1 2 3

CLR

ENT

FALCONZ

LD

RV

FLL

II

DATA

J3

0J2

GPS

ABCCALL LT MODE

DEF GHI

4 5 6JKLSQ ZERO

MNO PQR

7 8 9STUOPT PGM

VWX YZ

RT-1694D(P)/(C)/U

CCI

AUDIOJ1

ANTENNA

ACCESSORY

J6

PTCC

CT

OFF

J7J16RECEIVER/TRANSMITTER

PRE

+

_VOL

+

_

1 2 3

CLR

ENT

FALCONZ

LD

RV

FLL

II

DATA

J3

0J2

GPS

ABCCALL LT MODE

DEF GHI

4 5 6JKLSQ ZERO

MNO PQR

7 8 9STUOPT PGM

VWX YZ

RT-1694D(P)/(C)/U

CCI

AUDIOJ1

ANTENNA

ACCESSORY

J6

PTCC

CT

OFF


PRE

+

_VOL

+

_

1 2 3

CLR

ENT

FALCONZ

LD

RV

FLL

II

DATA

J3

0J2

GPS

ABCCALL LT MODE

DEF GHI

4 5 6JKLSQ ZERO

MNO PQR

7 8 9STUOPT PGM

VWX YZ

RT-1694D(P)/(C)/U

CCI

AUDIOJ1

ANTENNA

ACCESSORY

J6

PTCC

CT

OFF


Loop/150W

Tilt-whip/150W

Fan Dipole/150W

Ground Wave


Mobile Testing Ground Wave

• 150W/Dipole to OTM 150W/loop & TW at 2/4MHz• LQA scores in 3G• Platform drove from 0 to 70km and then back• All Ground Wave – some NVIS hits - Early Afternoon• Loop and Tilt-whip have Equivalent Performance

2 MHzLoopTilt-Whip

4 MHzLoopTilt-Whip


Loop and Half-loop Comparison

• 150W/1912 to OTM 150W/loop and HL/van• LQA scores in 3G• Van drove from 0 to 70km and then back• At 2.8 MHz, Many NVIS events • Performance Increase when Vehicle Stops

2.8 MHzLoopHalf-Loop


0-50 km LQA Comparisons 20W/2MHz

• 20W/Dipole to OTM 20W/loop and TW/van• LQA scores in 3G• Van drove from 0 to 50km and then back• Difference in Parallel versus Perpendicular GW

performance of Loop


Measurement System

• Same System as Before – Now at Fixed Sites

PRE

+

_VOL

+

_

1 2 3

CLR

ENT

FALCONZ

LD

RV

FLL

II

DATA

J3

0J2

GPS

ABCCALL LT MODE

DEF GHI

4 5 6JKLSQ ZERO

MNO PQR

7 8 9STUOPT PGM

VWX YZ

RT-1694D(P)/(C)/U

CCI

AUDIOJ1

ANTENNA

ACCESSORY

J6

PTCC

CT

OFF

J7J16RE CEIVER/TRA NSM ITTE R

PRE

+

_VOL

+

_

1 2 3

CLR

ENT

FALCONZ

LD

RV

FLL

II

DATA

J3

0J2

GPS

ABCCALL LT MOD E

DEF GHI

4 5 6JKLSQ ZERO

MNO PQR

7 8 9STUOPT PGM

VWX YZ

RT-1694D(P)/(C)/U

CCI

AUDIOJ1

ANTENNA

ACCESSORY

J6

PTCC

CT

OFF

J7J16RECEIVER/TRANSMIT TER

PRE

+

_VOL

+

_

1 2 3

CLR

ENT

FALCONZ

LD

RV

FLL

II

DATA

J3

0J2

GPS

ABCCALL LT MODE

DEF GHI

4 5 6JKLSQ ZERO

MNO PQR

7 8 9STUOPT PGM

VWX YZ

RT-1694D(P)/(C)/U

CCI

AUDIOJ1

ANTENNA

ACCESSORY

J6

PTCC

CT

OFF


Loop/150W

Tilt-whip/150W

RF-1912/150W

160km Hop


0

20

40

60

80

100

12017

:06

19:3

9

22:1

9

1:02

3:44

6:27

9:08

11:4

9

14:3

0

17:1

0

19:5

1

22:3

0

1:12

3:54

6:37

9:18

11:5

8

14:3

8

17:1

8

19:5

8

22:3

7

1:19

4:03

6:45

4.41 MHz FLP-1912 4.41 MHz HLP-191225 per. Mov. Avg. (4.41 MHz FLP-1912) 25 per. Mov. Avg. (4.41 MHz HLP-1912)

160 km Link in 2G - Loop and HLp

• Loop and Half-loop to 150W Fan Dipole• Very Limited scores at 2.7 and 6 MHz• Diurnal Variations Noticeable


160 km Link in 3G - Loop and TWP

0

10

20

30

40

50

60

70

80

90

16:4

5

18:4

8

20:5

2

22:5

5

0:58

3:01

5:04

7:07

9:10

11:1

4

13:1

7

15:2

0

17:2

3

19:2

7

21:3

0

23:3

3

1:36

3:39

5:43

7:46

9:49

11:5

2

13:5

5

15:5

9

18:0

2

20:0

5

22:0

4

23:5

8

1:52

3:46

5:40

7:34

2.73 MHz TWP-19122.73 MHz FLP-191225 per. Mov. Avg. (2.73 MHz TWP-1912)25 per. Mov. Avg. (2.73 MHz FLP-1912)

TWP out of SYNC

• Loop (w/o GP) and Tilt-whip Linking with 150W Fan Dipole at 2.7 MHz• Single Hop HF Link Available 24 hours a day• During Day 3 Initiator Lost Sync• Real LQA data highly variable – bold lines are 25 pt moving averages

Day 1 Day 2 Day 3


0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

16:45

18:56

21:07

23:18

1:29

3:40

5:50

8:01

10:12

12:23

14:34

16:45

18:56

21:07

23:17

1:28

3:39

5:50

8:01

10:12

12:23

14:34

16:45

18:56

21:07

23:08

4 .4 1 M H z T W P -1 9 1 24 .4 1 M H z F L P -1 9 1 22 5 p e r . M o v . A v g . (4 .4 1 M H z T W P -1 9 1 2 )2 5 p e r . M o v . A v g . (4 .4 1 M H z F L P -1 9 1 2 )

Same Link at 4.4 & 6.2 MHz

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

16:45

18:56

21:07

23:18

1 :29

3 :40

5 :50

8 :01

10:12

12:23

14:34

16:45

18:56

21:07

23:17

1 :28

3 :39

5:50

8:01

10:12

12:23

14:34

16:45

18:56

21:07

23:08

6 .2 3 M H z T W P -1 9 1 26 .2 3 M H z F L P - 1 9 1 22 5 p e r . M o v . A v g . ( 6 .2 3 M H z T W P - 1 9 1 2 )2 5 p e r . M o v . A v g . ( 6 .2 3 M H z F L P - 1 9 1 2 )

T W P


SNR 3G Performance at 4.4 MHz

0

5

10

15

20

25

30

35

17:21

17:51

18:21

18:51

19:21

19:52

20:22

20:51

21:21

21:51

22:20

22:50

23:20

23:49

0:19 0:48 1:18 1:48 2:18 2:48 3:19 3:50 4:25 4:55 5:25 5:54 6:24 6:54 7:24 7:54

loop-(d1 )H lp -(d1)10 p er . M ov . A vg . (loo p-(d1))10 p er . M ov . A vg . (H lp -(d 1))

Tx SNR

0

5

1 0

1 5

2 0

2 5

3 0

17:21

17:51

18:21

18:51

19:21

19:52

20:22

20:51

21:21

21:51

22:20

22:50

23:20

23:49

0:19 0:48 1:18 1:48 2:18 2:48 3:19 3:50 4:25 4:55 5:25 5:54 6:24 6:54 7:24 7:54

lo o p -(d 0 )H lp -(d 0 )1 0 p e r . M o v . A v g . (lo o p -(d 0 ))1 0 p e r . M o v . A v g . (H lp -(d 0 ))Rx SNR

• Tx SNR Perform comparison of Transmit (Rx SNR at the Dipole End)• Rx SNR Performance Comparison of Receive• Overall: Loop and Half-loop have equal SNR performance


Conclusions/Summary

• Numerical Modeling Provides Loop Parameters which are difficult to Measure– Includes Ground Losses/ vehicular/ comparison of Ground Planes

• Testing: – 0 to 70km Mobile Ground Wave – NVIS 160km fixed testing

• Tilt-whip, Half-loop, Full-loop all Provide HF Link Closure • Loops are Omni-Directional for High TOA & Directional for Low TOA• Full Loop

– Less Complex than Half-Loop– Simple Mounting– No need for Extensive Ground Plane – Allows User to Swap Between Loop and Whip in the Field– Allows use of Standard HF Coupler for Larger Tactical HF antenna to

Fulfill At-The-Pause HF Requirements

Progress in OTM Loop Antennas - · PDF fileHFIA Loop Presentation assuredcommunications™...

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