Miniaturized Broadband Patch Antenna Partially Loaded With High Permittivity Dielectric

Abstract

A compact microstrip ring antenna using a hybrid substrate of high permittivity dielectric and air is presented. By strategically placing a hollow cylindrical dielectric with high permittivity underneath a concentric ring patch, we can obtain omnidirectional radiation via a center-fed disk-loaded probe over a wide operation band. On the one hand, the centric high permittivity dielectric helps to lower the resonant frequency of high-order TM ₀₃ mode substantially, whereas the outer air dielectric strives to maintain the resonant frequency of dominant TM ₀₂ mode to a great extent, then wideband operation and miniaturization can be attained at the same time. On the other hand, a little modification to the disk-loaded probe feed structure induces an additional probe mode to stabilize the impedance matching between the aforementioned two modes. Furthermore, an omnidirectional dielectric resonator (DR) TM _011+δ mode is also excited at high frequency that further broadens the bandwidth. Consequently, a ring patch antenna with a height of 0.11λ ₀ and an outer radius of 0.22λ ₀ was designed, where λ ₀ is the free-space wavelength of the center frequency. The simulated result shows that -10dB impedance bandwidth of 69.2% is realized.