A CPW-Fed Quasi-PIFA Antenna Using Quasi-Lumped Resonators for Mobile Phones

Abstract

A novel single CPW-fed Quasi-Planar Inverted-F Antenna (PIFA) using quasi-lumped elements is developed for mobile communication handheld terminals operating at 2.6 GHz. The antenna is composed of an inductor covered by a set of interdigital and parasitic capacitors. The proposed antenna achieves a measured bandwidth of 11% for return loss with the antenna gain of about 4 dBi. The antenna is designed in single layer (zero height) which is appropriate to be used in thin devices where a small room is considered for the antenna. The proposed antenna is suitable for use in Long Term Evolution band 7. The operating frequency of introduced antenna depends on the number of interdigital fingers and inductor length rather than the total resonator patch only, so that the operating frequency can be altered while the total patch size remains unchanged. The calculated operating frequency is confirmed by simulation and measurement. Also the dipole-like simulated radiation pattern is confirmed by measurement.

Lumped Elements and Its Existence in Quasi Lumped Element Resonator Antenna

“…The lumped capacitor can be realized by using an open circuited (ZL = ∞) microstrip sections and a lumped inductor is realizable using a short circuited (ZL = 0) microstrip section. Thus, a small section of the short circuited transmission line behaves as a lumped inductor in series with a resistance R [6]. It is a lumped inductor if the value of the resistance is very small, but where the conductor used in designing the lumped element is Nicr (gold), the value of the resistance is high and the lumped element is resistive.…”

“…The short circuited microstrip line then behaves as an inductor, otherwise when the resistance is very high, as in the case of an inductor in series with a high resistance, for example when Nicr (gold) is used as the conductor, the microstrip section behaves as a resistor [7]. These small sections are called quasi-lumped elements at High Frequency (HF) since the sections are used to replace the actual lumped elements [6]. An ideal lumped element is not realizable at lower microwave frequencies because of the associated parasitic reactance caused by fringing fields [8].…”

“…An ideal lumped element is not realizable at lower microwave frequencies because of the associated parasitic reactance caused by fringing fields [8]. Each component has associated electric and magnetic fields and finite dissipative loss at RF and microwave frequencies [6].…”

“…This constitutes the effect of fringing fields, ground plane, conductor thickness, substrate material and thickness, associated mounting techniques and applications needed, non-uniform current distribution. Note that the non-uniform current distribution is caused either by the field produced by the current itself (skin-effect), the return current (proximity effect) or the current induced in the primary conductor (caused by the field of the return current on the LEs) [6].…”