Electrically Small, High-gain, Multi-band Antennas using Compact Yagi and Artificial Magnetic Conductor (AMC) Ground Plane

A compact antenna package using an electrically small Yagi antenna and a small Artificial Magnetic Conductor (AMC) ground plane with multi-band and high gain characteristics has been developed [25,26]. A preliminary antenna design is first simulated with a closely spaced Yagi antenna over an electromagnetic band-gap (EBG) ground plane (Fig. 1a). The closely spaced Yagi is composed of two elements including a driver and a director. The driver is folded to step up the low radiation resistance due to the close spacing between the driver and the director. The total height from the top of the EBG ground plane to the director of the Yagi is 0.03λ. Two resonances (see Fig. 1b) are attained and each band shows high gain. The first resonance is due to the driver of the Yagi over the EBG ground plane. This resonant frequency is similar to the case when only the driver of the Yagi is placed over the same EBG ground plane (driver mode). Furthermore, the second resonance is created due to the Yagi antenna itself (Yagi mode). The gains at the dipole mode and the Yagi mode are 7.84dB and 8.75dB, respectively. The separation of these two bands can be altered easily by tuning the closely spaced Yagi antenna. In order to realize a truly small antenna package together with the Yagi and the ground plane, a miniaturized Yagi over a small AMC ground plane will be designed. The expected design will be placed in a small cylinder volume, while maintaining multi-band and high gain characteristics. All designs will be optimized by using the Genetic Algorithm (GA).

Tasks and deliverables

  1. Optimized designs based on gain, matching, and bandwidth using the Genetic Algorithms to design the electrically small Yagi and the AMC ground plane.
  2. Simulation & measured results with variety of antenna shapes over the small AMC ground plane.
  3. Prototypes of the optimized design.
Fig. 1a. Prototype of the compact Yagi antenna over the EBG ground plane. Fig. 1b. Measured return loss.

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