Frequency-Tunable Electrically Small Diversity Patch Antennas for Cognitive Radio Applications

Electrically small antennas (ESAs) are less efficient and more difficult to design than longer antennas. ESAs have been an integral part of communications engineering since its inception. Whether they are small in comparison to the extremely long wavelengths used at the lowest radio frequencies, or they are designed to save space in GHz-range wireless devices. In this paper, design, and investigation of a frequency-tunable loaded electrically small microstrip patch antenna using RF switch (frequency tuning switch) has been presented. The proposed antenna designs have compact size
$(5\times 5\ \ \text{mm}^{2}$
or smaller) and single shorting post close to feeding point location. The simulated and the practical measurement results of the proposed antenna designs are compared and analyzed. The proposed design has been analyzed, fabricated, and practically validated with area size reduction up to 90.7 % to meet the compact space requirements of the wireless miniaturized systems and cognitive radio applications.