Tri-mode electric ring resonator and adjustable UWB triple band-notched antenna

The reference ultra-wideband (UWB) planar antenna was designed as a circular metallic patch fed by a coplanar waveguide structure (CPW). This antenna provides a stable radiation pattern and impedance bandwidth of the wideband response from 2.5 GHz to 12 GHz. To achieve the band-notched characteristics at desirable frequencies, the electric ring resonator (ERR) is proposed to use in the planar configuration of the UWB antenna. The triple notched band can be obtained by placing a single tri-mode ERR beneath the CPW structure of the antenna. Each of the notched frequency band can be easily tuned by proper changing the dimensions of the ERR structure. Reconfigurability of the first (low frequency) notched band is provided by using a variable capacitor (DVC) instead of ERR's quasi-lumped capacitance. Reconfigurability of the second (middle frequency) or the third (high frequency) notched band is provided by using a pair of variable capacitors (DVC) inserted into the middle of the ERR's rings corresponding to the chosen mode (middle or high frequency).