A Study of substrate permittivity effects on the gain of planar inverted-F antennas

Effects of Substrate Permittivity on Planar Inverted-F Antenna Performances

“…The structure is encompassed in a rectangular air box, which is defined as a radiation boundary. The air-box boundary is drawn so that the recommended quarterwavelength (λ/4) minimum distance from the sides of the radiating structure (including the ground plane) is satisfied [1], [9]. The structure is excited by a lumped port [9], [14] located at the edge of the patch feeding structure.…”

“…The substrate permittivity (ε r ) combined with the thickness h of a microstrip antenna affect the resonant frequency, gain, matching bandwidth and polarization. Microstrip antenna theory [1]- [5] indicates a degradation in performance when ε r increases. High permittivity substrates reduce antenna size at the cost of the gain and matching bandwidth.…”

“…The short introduces a return path for the facial currents of the antenna and triggers resonance for electrical dimensions smaller than half-a-wavelength (λ/2) as demonstrated in [2], [3], [11]. The resonant frequency of a PIFA is given by [14]: (1) where c is the velocity in free space, l 1 and l 2 are the dimensions of the radiating patch, w is the width of the short, h is the thickness of the substrate and ε eff is the effective permittivity of the substrate material between the radiating patch and the ground plane. The effective permittivity (ε eff ) is approximated using (2):…”

“…From (1), it should be observed that the resonant frequency of a PIFA is affected not only by the physical lengths (l 1 and l 2 ), but also by the width of the short (w) and the thickness (h) of the substrate material. For fixed radiating patch lengths, the resonant frequency increases as w decreases.…”