Abstract
This paper presents a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna, using a novel active electromagnetic band gap (EBG) structure. The EBG surface employs identical metallic rectangular patch arrays on both sides of a thin substrate, but rotated by 90 $^{\circ}$ from each other. The active bias circuits are also orthogonal for each surface, enabling the reflection phases for orthogonal incident waves to be tuned independently in a wide frequency range. By placing a wideband coplanar waveguide (CPW) fed monopole antenna above the EBG surface, and properly tuning the bias voltages across the varactors in each direction, CP waves can be generated at any desired frequency over a broad band. In accordance with simulations, the measured 3 dB axial ratio (AR) bandwidth reaches 40% (1.03–1.54 GHz), with good input matching $(S_{11})$ and radiation patterns at six presented sampling frequencies. The polarization reconfigurability is verified by simulations and measurements, and shown to be capable of switching between left hand circular polarization (LHCP) and right hand circular polarization (RHCP).
Highlights
E LECTROMAGNETIC BAND GAP (EBG) structures have drawn great interests in Þeld of electromagnetics for many years [1]–[3]
Frequency and polarization reconÞgurability of a tunable electromagnetic band gap (EBG) reßector based antenna has been realized by both simulations and measurements
A novel dual-polarized tunable EBG structure has been presented, which is incorporated in the design of a frequency and polarization reconÞgurable circularly polarized (CP) antenna
Summary
E LECTROMAGNETIC BAND GAP (EBG) structures have drawn great interests in Þeld of electromagnetics for many years [1]–[3]. To simplify the structure and the biasing connection, a design based on the conÞguration in [3] was presented in [15], adopting a resistive-lumped-element biasing grid that was introduced in [16] In this design, vias were required in order to provide uniform bias voltages. A new dual-polarized tunable EBG is proposed, in which the reßection phase of orthogonally polarized incident plane waves can be tuned independently. By independently tuning the bias voltages on each side of the surface, the operating frequency to generate CP waves is tuned between 1–1.6 GHz. the conÞguration provides the capability of agile polarization switching between LHCP and RHCP.
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