Abstract
In this paper, a design approach for a microstrip Yagi antenna with a switched beam using resonant TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes is proposed. The antenna consists of a driven patch and two parasitic patches. Initially, a driven patch radiator with two symmetric probes is investigated to determine whether TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> or TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode of this patch can be generated by properly exciting the dual feeding ports. The operating bands of the dual modes are reallocated in close proximity to overlap with each other by introducing the shorting pins and narrow slots. Then, two smaller-sized parasitic patches are placed on the right side of the driver to achieve switchable tilted-beam radiation patterns. The results demonstrate that the smaller-sized parasitic patches act as either directors or reflectors when their TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode or TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode is excited, respectively. Therefore, the quasi-end-fire beams can be satisfactorily generated and steered in the E-plane by switching these two radiative modes by feeding probes. Finally, a proposed antenna is designed and measured. The measured results show that the antenna operating in TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes can achieve a common band of 3.03-3.19 GHz, and their beams are oriented at the directions of +27° and -42° in E-plane patterns, respectively. Most importantly, no RF switches are introduced in our design, thus significantly reducing the complexity and cost of the proposed antenna.
Highlights
The demand for high-speed and high-quality data transmission has increased greatly with the development of wireless communication systems
Monopole and dipole antennas are the two forms used as switched-beam antenna elements [1]-[2]
The results show that these parasitic patches act as directors or reflectors when their TM10 mode or TM20 mode is excited, respectively
Summary
The demand for high-speed and high-quality data transmission has increased greatly with the development of wireless communication systems. The data rate drops dramatically as the transmission distance increases due to the multipath fading. Antennas with switchable beams are well-known solutions used to overcome this problem. A series of antennas that focus on switched beams have been proposed [1]-[4]. Monopole and dipole antennas are the two forms used as switched-beam antenna elements [1]-[2]. Slot antennas are a simple form used to realize beam switching [3]-[4]. Various patch antennas that make use of different radiating modes to achieve beam switching have been proposed [5,6]
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