PIN-Diode-Controlled X-/Ku-Band Frequency Reconfiguration of a CPW-Fed Quasi-Yagi Antenna
A PIN-diode-reconfigurable quasi-Yagi antenna fed by a coplanar waveguide (CPW) is presented for X-band and Ku-band frequency reconfiguration. PIN diodes are strategically introduced between the driven and parasitic elements to control the effective surface-current paths and thereby modify the operating frequency characteristics. By optimizing the diode locations, number, and switching states, two distinct operating modes are achieved. In Mode I, dual-band operation covering the X-band and Ku-band is obtained, with simulated impedance bandwidths of 9-11 GHz and 12.2-18.8 GHz. In Mode II, a simulated continuous impedance bandwidth from 10 to 14.2 GHz is achieved. The corresponding simulated peak gains are approximately 8 and 7 dBi for Mode I and Mode II, respectively. A prototype is fabricated and experimentally characterized in terms of its S-parameters, and the measured results confirm the frequency-reconfiguration behavior of the proposed antenna. The effects of the number and placement of the PIN diodes on the impedance characteristics are further investigated to clarify their roles in frequency reconfiguration and design complexity. The proposed antenna provides a compact CPW-fed quasi-Yagi configuration with PIN-controlled X-band and Ku-band frequency reconfiguration.