Abstracts - Dipartimento di Elettronica Applicata

Meta 2010 & FEM 2010 – Rome, 13-15 December 2010
Design formulas of High-Impedance Surfaces with
circular patch arrays.
D. Ramaccia, F. Bilotti and A. Toscano
(1) University RomaTre, Department of Applied Electronics
Rome, Italy – E-mail: davide.ramaccia@gmail.com
Originally photonic band gap materials were introduced with the goal to control the
optical properties of materials. Frequency Selective Surfaces (FSS) materials offer the
same control for the electromagnetic properties of the materials at microwave
frequencies. These periodic metallic arrays are employed in the design of High
Impedance Surfaces (HIS) [1], [2].
A typical high–impedance surface with square patches, its equivalent circuit
representation and the circular patch pattern are shown in Figure 1a, 1b and 1c,
respectively.
b) c)
Figure 1: HIS a) typical structure with square patches. b) equivalent circuit model. c) circular patch
array.
It is well known that although the array with square and circular patches have the
same periodicity D and the same separation d, the different geometry of the elements
causes a different behavior in frequency. It is taken into account modifying the
expression the separation gap d between two adjacent patches. The new parameter deq
for circular patches is deq ��D�� d,
where the coefficients � and � have been
determined geometrically.
The resonance frequency of the circuit in Figure 1b corresponds to the frequency
when the structure present a 0 degree phase shift of the reflected wave. From the
resonant circuit theory, it is �0 � 1 LC and consequently the gap d can modify the
resonant frequency of the structure. Fixing � 0 , the geometrical parameters of the
structure can be used to define the bandwidth of operation.
References
[1] O. Luukkonen et al., "Simple and Accurate Model of Planar Grids and High–Impedance Surfaces
Comprising Metal Strips or Patches," IEEE Trans. Antennas Propag., 56, 1624–1632, 2008.
[2] D. Sievenpiper et al., "High-Impedance Electromagnetic Surfaces with a Forbidden Frequency
Band," IEEE Transaction Microwave Theory Tech., 47, 1999.
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a)