A high gain microstrip yagi antenna with large bandwidth at frequency of 5.8 GHZ

Presently, unlicensed frequencies have gained a wide popularity due to no license payments need to be paid. These frequencies can be utilized to support point-to-point (P2P) communication, such as Long Term Evolution – Unlicensed (LTE-U). An antenna plays a crucial role in P2P communication system which is used to transmit or receive electromagnetic wave. It is available in many types and microstrip patch antenna is the most widely used in P2P communication due to it has some advantages, such as light weight and easy fabrication. P2P communication system requires a high gain microstrip antenna with large bandwidth in order to enable connectivity across a large area with high data transmission. Numerous methods have been attempted by some researchers to enhance the gain and bandwidth of the microstrip patch antenna, such as employing Yagi antenna design in microstrip patch antenna. This technique is also known as microstrip Yagi antenna which was first introduced by John Huang in around 1989. This thesis proposes a new configuration of microstrip Yagi antenna in order to upgrade the performance of previous works on microstrip Yagi antenna in terms of gain and bandwidth without increasing surface area size. There are two proposed antennas which were designed, simulated, optimized and fabricated. A 1.575 mm thick Arlon CuClad 217 substrate with dielectric permittivity of around 2.2 is selected as substrate of the proposed antennas. The first proposed antenna is called Octagon Microstrip Yagi Antenna (OMYA). Initially, the designed model of OMYA is a derivative of the microstrip Yagi antenna which has been introduced by Gerald R. Dejean et al. It consists of 2 reflector elements, 1 driven element, two bottom director elements and 2 top director elements. In addition, 4 director elements have been modified from square patch geometry into octagonal-shaped in order to reduce surface-waves at the edge of square patch. According to experimental results, bandwidth and gain of the OMYA are 13.8% and 11.1 dB, respectively.The second proposed antenna is the OMYA with two material substrates with permittivity of 10.2 and thickness of around 2.5 mm. The two additional substrates were placed above the OMYA. The primary aim of adding those substrates is to enhance the gain of the OMYA. Upon varying the height of air gaps, the maximum gain enhancement can be reached. The experimental measurement shows that the OMYA is capable to generate 19.82% bandwidth after adding the superstrates. In addition, this second proposed antenna yields higher gain of around 13 dB.

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