Comprehensive Study of Microstrip Patch Antenna using different Feeding Techniques

Abstract

For modern wireless communication systems, miniaturized multiband antennas with enhanced bandwidth and gain are desired to achieve optimum system performance. A planar microstrip patch antenna is preferred because of its small size, low cost, and ease of fabrication. For impedance matching, a conductive metallic patch can be fed by different techniques to deliver the maximum power to the microstrip antenna. The various configurations of inset feed, co-axial feed, aperture feed, and proximity feed, CPW feed which are used to excite micro-strip patch antennas are reviewed in this research work. Different feeding mechanisms are discussed to improve antenna performance in terms of S₁₁ parameter, bandwidth, gain and radiation pattern suitable for different wireless communication applications.

In a wireless communication system, antenna is the key component that serves the most important function. For low frequency applications, special antennas were employed that were merely positioned outside the electronic devices. The antennas were quite enormous, and they only supported single frequency band with limited bandwidth. To overcome these issues, a new antenna was developed in 1953, named microstrip antenna for wireless communication. Microstrip patch antennas are used to get Single-band, multi-band, and broadband frequency responses with the majority of the features we use most often. It is used in many applications, such as mobile communications (GSM, LTE), Bluetooth and WiFi coverage, global positioning satellites (GPS), direct broadband satellite systems (DBS), remote sensing, and non-Satellite based applications such as medical hyperthermia. This has seen an increase in data transmission speed due to the rapid advancement in communication technology which is successful only if the transmission bandwidth and efficiency is maintained by an equally effective antenna to enable multiple services, standards and systems. [1,2].

Microstrip antenna has a thin profile, light weight, easy to fabricate with low cost characteristics [3,4]. In this paper, a review of microstrip patch antennas with different feeding techniques is presented and the improvement in the performance parameters is compared for with respect to S₁₁ parameters. Microstrip patch antenna is composed of a metallic patch, dielectric substrate, and perfect electrically conducting ground plane as shown in the fig.1(a). The patch may be in different shapes such as square, rectangular, circular, and elliptical as shown in fig.1(b). Feeding structurescause an efficient power transfer from the transmission line to the radiation structure and help in matching their impedance. The choice of feeding technique depends on the application chosen for wireless communication. Some feed structures give greater bandwidth performance, better efficiency, better gain, return loss, and better radiations as compared to others. However, the main drawbacks of microstrip antennas include narrow bandwidth and low gain. This can be compensated by increasing radiation efficiency to overcome these drawbacks.

The antenna's input impedance should be the same as the source's, which is 50 ohms for all RF and microwave sources. Because the antenna is pointed towards space, it works as an impedance transducer between the 50 ohms source and the 377 ohms free space. As a reason, a feed point on the antenna should be selected so that the input impedance of the antenna reaches 50 ohms at that point. Feeding techniques [3] which are implemented in microstrip patch antenna can either be direct contacting (feed line in contact with patch) or  non-contacting ( not in contact with patch). The feed of microstrip antenna can have many configurations like microstrip feed, coaxial feed [4], aperture coupled feed and proximity feed. The microstrip feed and coaxial feed are relatively easier to fabricate. There are the significant key roles of the feeding techniques.

                                     (a)                                                                                 (b)

Fig.1 Microstrip Patch Antenna (a) Structure (b) various Shapes of Microstrip Patch