Compact Loaded PIFA for Multifrequency Applications

A new multifrequency microstrip patch antenna is presented. The antenna can be considered a PIFA since it has a metallic wall on one of its sides. The different bands of operation are independent of each other, and different radiation patterns for each band can be achieved if desired. In addition, a circuital model is introduced to explain the operation of the antenna. This model presents some similarities with composite right left handed models presented in the literature. Some prototypes have been manufactured and measurements of return losses, efficiencies and radiation patterns, have been performed for a thorough characterization of the antenna as well as to validate the simulation results.

I. Introduction

Modern telecommunication devices are required to be small and able to integrate several functionalities. The antennas used for these wireless systems must hence possess multiband capabilities but yet remain compact. One of the most common types of antenna used for conventional devices are patch antennas, due to their low cost of manufacture and lightweight nature. In addition, they have a high radiation efficiency [1], [2]. Patch antennas are resonant antennas that typically operate at the frequency whereby the length of a dimension is half a wavelength. This requirement may render the antenna too large for low-frequency applications. Consequently, some recent studies have focused on achieving compact patch antennas that can still function at lower frequencies [3]–[5]. A classical and simple method for reducing the operational electrical-size of patch antennas is to implement a modified structure known as PIFA (Planar Inverted F Antenna), which has a metallic wall on one of the sides. In this way, the antenna fulfils the boundary conditions with a quarter wavelength distance between the open and the short-circuit, instead of the half wavelength between two open boundaries in conventional patch antennas [2], [6].