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Frequency-Tunable Waveguide Antenna for Field Measurement

Research Scholar

Hyo-Dal Park, Electrical and Computer Engineering (South Korea)
Won-Jong Lee, Co-Researcher
Haedong Jang, Co-Researcher
Patrick Roblin, Faculty Mentor


Hyo-Dal Park was born in EuiSung, Korea, in June 1952. He received a bachelor's degree in electronic engineering from Inha University, Korea in 1978, a master's degree from YonSei University, Korea in 1981, and master's and Ph.D. degrees in electronic engineering from École Nationale Supérieure de l'Électronique et de ses Applications, France in 1984 and 1987. He started his career at the Centre National de la Recherche Scientifique (CNRS) and Centre National d'Études Spatiales (CNES) in France, then served as the chief of researcher at Korea Institute of Aerospace Technology. In 1992, he joined the Department of Electronic Engineering at Inha University as an Assistant Professor, where he is currently a professor.

What is the issue or problem addressed in your research?

As many wireless devices have been designed with development of recent telecommunication technology, measuring equipments also have been developed. An issue for wireless device measurements is the required distance between antenna under test (AUT) and probe. In case of near-field antenna measurement, AUT and probe must have about 3~10λ separation. Since this distance often turns out several meters, the measurement chamber that includes all equipments results in large size. To obtain benefits of space by decreasing size of the chamber, AUT and probe must be located close to each other. But in this case, inaccurate measurements can result by multiple reflections between the probe and the AUT. One of the methods of reducing the chamber size is minimization aperture of the waveguide probe. For this method, double ridges have been inserted in waveguide. But in this case, another problem can occur in wave propagation because permittivity becomes negative and permeability becomes positive at the frequency lower than cut-off frequency of the waveguide.

What methodology did you use in your research?

In this paper, in order to circumvent these undesirable material properties at lower frequency while decreasing AUT aperture, inserting varactor-loaded split-ring resonator (VLSRR) in double ridged waveguide is proposed and designed. By loading a varactor to the conventional SRR, the resonance frequency of antenna becomes adjustable using external DC voltage, furthermore the aperture can be reduced.

For adjusting resonance frequency of the proposed antenna, external DC voltage of the varactor need to be varied. Capacitance of the varactor by varying external DC voltage changes resonance frequency of antenna. The tunable frequency range extends from 1.96 to 2.36 GHz (a fractional frequency range of 18.5%). Good results for the reflection coefficient, radiation pattern and gain are obtained by the simulations and experiments. The proposed antenna retains the 70% aperture reduction of previously developed split-ring-resonator-loaded waveguide antennas.

What are the purpose/rationale and implications of your research?

An antenna was designed and measured for demonstration. 70% of aperture reduction, compared to previously developed SRR waveguide antennas, was observed, maintaining other important performance parameters, such as resonant frequency reflection coefficient, radiation pattern and gain, in fairly good range. This method is expected to be able to applied to antenna measurement chamber significantly reducing the dimension and construction cost as well.