1NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

Broadband Arrays and Switching Antennas

Dan Palecek, SD School of Mines and Technology, Rapid City, SD

Dr. Anthony Martin, Clemson University, Clemson, SC

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Overview Background

Simulation SoftwareGenetic Algorithms5:1 Antenna System

Objectives and Strategies / ResultsBroadband ArraySwitching Antenna

Conclusions and Further Research

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Software Solves electric field integral equation

via method of momentsTraditional triangle basis functionsPulse test functions

Approximates geometry with straight wire segments

Utilizes genetic algorithm (GA) optimization

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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How Do GAs Work? Encode Parameters

Generate Initial Population

Evaluate and Assign Fitness Values

Select Parents Based on Fitness

Reproduce Through Recombination

Mutation

Chromosome

p1

{ { {p2 p3 p4

[ 0101 0011 1101 0101 ]{

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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5:1 Antenna System

L = 0.22 HR = 470

a = 0.4 mm

2a

L R

hL = 11.6 cm

h = 21.25 cm

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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5:1 Antenna System

Matching Network

Lm ZA

Transmission Line

Z0 = 50

1 : 4

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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5:1 Antenna System Bandwidth criteria

VSWR < 3.5 System gain > -4.0 dBi

2

1010log 1 90 dBisys eff AG M G

max

min

Bandwidthff

Cost Function - VSWR and Gain Penalty

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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5:1 Antenna System

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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5:1 Antenna System

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Broadband Array

ObjectiveDetermine if array retains broadband

characteristics

StrategyPlace 5:1 elements in array configurationVary spacing between elements and observe

effects

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Broadband Arrayh = 21.25 cm

hL = 11.6 cmd

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Broadband Array

Matching NetworkTransmission

Line

Z0 = 50

1 : 2

Lm

ZA

ZA

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Broadband Array

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Broadband Array

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Broadband Array200 MHz

300 MHz

400 MHz

500 MHz

600 MHz

700 MHz

800 MHz

900 MHz

1000 MHz

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

16

Switched Antenna

ObjectiveExtend bandwidth of 5:1 antenna via

switching

StrategySwitch in various loaded wire segmentsOptimize for lower frequency bandOpen switch, examine effects on 5:1 band

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Switching Antenna

Switch Open for 5:1 Band

Loaded Segment

5:1 Antenna

Switch

Switch Closed for New Band

Loaded Segment

5:1 Antenna

Switch

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Switching Antenna

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Switching Antenna

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Conclusions

Broadband ArrayBroadband performance can be

maintained

Switching AntennaBandwidth can be increased

NSF SURE Program, Summer 2002 / Clemson University, Clemson, SC

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Further Research

Broadband Array Feedline between matching network and array

elements Matching network

Switching Antenna Switching mechanism Software modifications