An Extremely Compact Frequency Reconfigurable Self-Diplexing Antenna Employing Dielectric Liquids

The letter presents an extremely compact frequency reconfigurable Self-diplexing antenna based on fluidic channels for sub-6 GHz applications. The self-diplexing antenna is realized by using slot-loaded half-mode(HM) and quarter-mode (QM) substrate-integrated rectangular cavities, which takes an extremely compact size. The high isolation is obtained by employing the loading slot and the orthogonal feed lines, and three fluidic vias are bored from the bottom plane and filled with different dielectric liquids to enable frequency reconfigurability with little effect on the antenna radiation. To illustrate the antenna mechanism, the equivalent circuit, electric field distributions, and parameter studies are analyzed. For validation of the concept, an antenna diplexer is built and demonstrated. The constructed antenna prototype has a small footprint of 0.078$\lambda _{g}^{2}$ with 15% and 16% of reconfigurability in the lower and upper frequency bands, respectively. The measured results show 31.3 dB isolation, 3.28 dBi gain for the low-band and 4.5 dBi gain for the high-band, respectively. A good consistency is obtained in between full-wave simulations and measurement.