Bandwidth Enhancement of a Compact Transverse Bilateral Helical Antenna With Parasitic Element for Mobile Device Applications

An electrically small antenna (ESA) designed for portable communication device applications is described. The antenna structure is based on the introduction of parasitic element to the transverse bilateral helical (TBH) antenna to enhance the bandwidth, leading to the TBH antenna with parasitic elements (TBHP). By insertion of a second helix into the core of the host helix, the overall dimensions of the antenna structure are kept the same as the original TBH antenna. A first-order analytical model is developed to gain insight to the design process. Performance of the TBHP antenna is evaluated using finite element method (FEM) electromagnetic simulation. The experimental and simulation data showed that the TBHP antenna has 105% wider bandwidth in a 50-Ω reference system and 74% higher radiation efficiency around the 621-MHz operating frequency compared with the original TBH antenna. Simulation and measurement results are found to be in good agreement.