Low Profile, Miniaturized, Inductively Coupled Capacitively Loaded Monopole Antenna

A novel high-gain low-profile miniaturized antenna with omnidirectional vertically polarized radiation, similar to a short dipole is presented. The proposed design focus is on increasing the gain and improving the polarization purity of the radiated field in the horizontal plane. The gain and polarization improvement are achieved by isolating the feed structure from a miniaturized resonant radiating structure composed of an in-plane capacitor and a structurally embedded transformer. The antenna topology is developed, based on circuit model and through full-wave simulations the equivalence is established. The equivalent circuit model assists in the initial design, and then minor modifications are required to achieve the desired frequency of operation. The initial topology of the proposed antenna, the so-called Inductively Coupled Capacitively Loaded Monopole Antenna (ICCLMA), consists of two metal layers, a feeding pin and a shorting pin. The performance of the proposed antenna is compared to that of an ordinary inverted F antenna and a more recent low profile vertically polarized antenna (LMMMA) [1]. It is shown that the gain of ICCLMA is 9 dB and 4 dB higher than that of the conventional inverted-F antenna and the LMMMA, respectively. To simplify the fabrication process a modified single-layer ICCLMA topology is presented and optimized. Finally, a design procedure to further reduce the lateral dimension of ICCLMA is presented. A procedure for accurate measurement of antennas with small ground planes is also presented.