Design of Frequency Reconfigurable Antennas Using the Theory of Network Characteristic Modes

This paper demonstrates a design procedure for frequency tunable reconfigurable antennas based on the application of reactive loads. Unlike other design procedures, antennas of arbitrary geometry can be tuned utilizing the proposed design framework. The design technique utilizes the theory of network characteristic modes to systematically compute reactive load values required to resonate any antenna at many frequency points in a wide frequency range. For simplicity, a 1.2 m dipole antenna is used to demonstrate the design procedure by tuning it at four loading ports along the antenna body. Both simulations and measurements demonstrate wide frequency tunability characteristics of the dipole input impedance (tunability range wider than 1:4) while preserving the radiation pattern and polarization at seven different frequency states. Lastly, a loaded PIFA is briefly examined as a more complex application of the procedure.