We present a series of designs for uniplanar electromagnetic bandgap structures for antennas and microwave circuits. The proposed, easy to fabricate configurations, are based solely on metallic surfaces on layer interfaces, without the use of vias or other kinds of vertical connections. Their use in low profile antenna applications and mutual coupling reduction of planar radiating elements is investigated through an efficient and versatile technique, since the only information needed is the reflection phase and the dispersion diagram of the unit cell.

The accurate and fully 3-D analysis of graphene surface conductivity models by means of a frequency-dependent finite-difference time-domain method is introduced in this paper. For the infinite sheet to be consistently simulated, the novel technique uses a set of periodic boundary conditions that lead to a unit cell excited with a spectral scheme in terms of a total-field/scattered-field formulation. On the other hand, graphene itself is modeled through a subcell approach and a complex surface conductivity concept defined by quantum mechanical equations. This conductivity model is next converted to a volume one in order to permit a realistic time-domain study. Numerical outcomes, addressing a variety of applications, reveal a promising coincidence with those acquired from analytical closed-form expressions.

The uniplanar cross-like compact EBG structure is thoroughly assessed by means of a computational FEM-based eigenvalue analysis. A careful inspection of the dispersion diagram reveals the existence of a nearly-TEM mode that compromises the bandgap behavior, a fact that is also confirmed in coupling performance investigations. The structure is then modified and optimized to maximize the resulting bandgap zone, for mutual coupling reduction in WiMAX MIMO arrays.

Antenna array beamforming (BF) refers to a realtime procedure that aims at calculating proper feeding weights applied to the array elements in order to create a main lobe and a number of nulls towards respective preassigned directions. Most of the research performed on BF has been based on a simplified mathematical model, which ignores the non-isotropic radiation pattern of the array elements and the element mutual coupling. This paper introduces an innovative way to incorporate the actual radiation pattern of the array elements and the element coupling into two popular deterministic BF methods, thus making these methods applicable to realistic antenna arrays. The two modified methods are applied in several scenarios, where a desired signal and several interference signals with various directions of arrival are received by a realistic microstrip linear antenna array. The statistical analysis performed in every scenario demonstrates the validity and effectiveness of the proposed modification.