Annular Ring Microstrip Antenna Characterisation

Model Geometry

This article presents the FEKO simulation of an annular ring example from [1].  Figure 1 depicts the geometry from [1, Fig. 2b] with the following dimension:

• Ring inner diameter = 27.44 mm.
• Ring outer diameter = 53.99 mm.
• Coaxial probe feed at coordinates (x, y) = (-20.357, 0) mm.
• Feed pin diameter = 0.5 mm.
  

Figure 1:  Annular Ring Geometry

A single dielectric layer is used:

• ε_r = 2.5
• tan δ = 0.0018
• h = 1.52 mm

The dielectric layer is implemented with a special Green's function as an infinite layer with a ground plane below the annular ring.

Simulation Results

A frequency sweep was performed from 1.524 GHz to 1.6040 GHz and the real input impedance computed and plotted on the Smith chart presented in Figure 2.  The impedance locus crossed the real axis at approximately 1.57 GHz.

Figure 2:  Real input impedance Smith chart

A near field plane was computed 2 mm above the annulus.  The resulting patterns are presented in Figure 3.  The results compare favourably with the results published in [1, Figure 4 and 6].

Figure 3:  Tangential near fields 2 mm above the annulus
(a) Ex (b) Ey
The observation plane is located 2 mm above the dielectric, with sample points at x = y = (-40:0.5:40) mm. The attached models are sampled more coarsely to conserve resources and are sampled at x = y = (-40:2:40) mm.