Investigation of a Curtain Antenna Array for TIGER Quang Nguyen, Dr - PowerPoint PPT Presentation

Investigation of a Curtain Antenna Array for TIGER Quang Nguyen, Dr John Devlin Electronics Engineering Dept La Trobe University Australia

Problems of currently used antennas • Structural problem 1. Broken long elements (wind 47 m/s) 2. Tower bent along wind direction 3. Twisted of horizontal boom • Questioning of antenna performance

Objectives • Modification of the Log periodic antenna to achieve a robust structural that requires minimal maintenance. • Implementation of frequency independent array to ensure a broadband operation.

Possibility of compact LPDA − τ 1   − 1 α = tan 0.25   sigma tau tau 0.95 0.95 0.2 σ 4   0.9 0.9 0.15 0.1 0.85 0.85 0.05 0.8 0.8 l 40 τ = + n 1 l 30 l n alpha 20 α n 10 s 0 s n , + n 1 , + n n 1 σ = 2 l n

L/Alpha/Bs relationship L 4 3.5 3 2.5 2 Bs = 3.46 1.5 1 0.5 Bs = 2 α 0 5 10 15 20 25 30 35

A Different Approach s − τ 1 1 , 2 = − N 1 − τ L 1

Bs/Tau/N/S 1 /L relationship n Contour lines of s1/L 35 30 25 20 L / 1 15 s g n i s a 10 e r c n I 5 Bs = 3.46 τ 0.8 0.85 0.9 0.95 1

Broaden Structure Bandwidth

Control of electrical height

Dipole over ground h

Inverted-V dipole over ground h

New LPDA Structure

Gain over 8-20 MHz band 10 9.5 9 8.5 8 Gain (dB) 7.5 7 6.5 6 5.5 5 8 10 12 14 16 18 20 F (MHz)

Smith Chart and VSWR VSWR of lp8m1.nec 2 Smith Chart of lp8m1.nec Zc=100 1.9 1 0.5 2 1.8 1.7 5 0.2 1.6 VSWR 1.5 0.2 0.5 1 2 5 0 1.4 -0.2 1.3 -5 1.2 -2 -0.5 1.1 -1 1 8 10 12 14 16 18 20 MHz

Lp8m1f8c.dat

Lp8m1f14c.dat

Azimuth pattern of lp8m1f17.dat G=8.39dB,F/B=24.74dB(theta=51,phi=180) Vertical pattern of lp8m1f17.dB G=8.39dB,F/B=20.66dB(theta=68,phi=0) 0 0 330 330 30 30 300 300 60 60 90 270 270 90 -25 -20 -15 -10 -5 -40 -30 -20 -10 0 0 240 240 120 120 210 150 210 150 180 180

Lp8m1f17c.dat

Lp8m1f20c.dat

LPDA Linear Array • Non constant electrical spacing • Variation of gain • Impedance effects • Beamwidth variation

Electrical Spacing E 1 0.8 0.6 0.4 0.2 ψ −3π/2 −π −π/2 0 π/2 π 3π/2 2π Broaden

Beamwidth Variation

Semi-Circular Array

Conclusion • Inverted-V LPDA • Implementation of semi-circular array