Integrated PCB Design of UWB Balun and Log-Periodic Antennas
Date Issued
2009
Date
2009
Author(s)
Wu, Han-Yang
Abstract
The log-periodic dipole antenna (LPDA) is categorized as a frequency independent antenna with linear polarization and stable gain patterns; therefore it is suitable for the source antenna in EMI/Antenna measurement. Traditional LPDA is made of metal cylinders fed by coaxial cables making the antenna heavy and difficult to fabricate. Planar printed circuit board (PCB) LPDA was proposed recently; however, its unshielded and unbalanced feeding line may cause the cross-polarization too high to be used for practical applications. In this thesis, we propose a balun-based feeding scheme integrated with the planar LPDA using the multi-layered PCB technology. In the first half of the thesis, we design a Marchand balun in a multi-layered PCB with measured amplitude and phase balance within 1.0 dB and 10 degrees respectively over the 0.66~5.71 GHz band. In the second half of this thesis, we integrate the developed balun with the planar LPDA on the same PCB. Two designs are demonstrated for the 0.8~3.2 GHz and 0.8~6.0 GHz bands respectively. Both designs show good results in the wideband impedance matching, stable broadside gain range 0~6 dBi, and the highly isolated cross-polarization of 20 dB over the entire band.
Subjects
Balun
cross-polarization isolation
LPDA, planar antenna
broadband
Type
thesis
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ntu-98-R96942081-1.pdf
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