Array of Quasi Rhomboid Shaped Element Bowtie Antenna with Reflector for Ultra Wideband Applications

The demands for broadband services by wireless communication systems are rapidly growing. An ultra wideband radio technology has become an important topic for microwave communication because of its low cost and low power consumption. The ultra wideband technology is specified the frequencies ranging from 3.1 GHz to 10.6 GHz by Federal Communication Commission (FCC), which has a bandwidth ratio (defined as higher frequency versus lower frequency) of approximately 3.3:1 [1]. The essential equipment for their wireless communication systems are the antenna that it is used for transmitting and receiving a signal. There are many types of antenna to choose for applying in the appropriate function and system. But one the major requirement of an ultra wideband application is a compact and extremely wideband antenna covering the ultra wideband spectrum. Microstrip patch antennas are well candidates for ultra wideband applications due to their exhibit small size, light weight, low manufacturing cost and easy method of fabrication. However, microstrip antennas have very narrow bandwidth. Therefore, the ultra wideband antenna design is going to the main challenges for ultra wideband system. The goal of the ultra wide band antenna designer is to make an antenna with small size, simple structure that produces low distortions but can provide large bandwidth. Recent ultra wideband antenna development tends to focus on small planar antennas such as bow-tie antennas [2] elliptical antennas [3], slot antennas and array antennas [4]. Most of the reported all these antennas have omni-directional radiation patterns and the gain of these antennas are relatively low, about 2-4 dB. When these omni-directional antennas are attached to wall or metals, it is suspected that the antenna performances can be degraded due to the omni-directionality. In order to avoid degradation of the antenna performance, we considered placing a flat reflector behind the quasi rhomboid shaped bowtie antenna. In addition, if the directivity of the ultra wideband antenna increases as a result of the reflector, higher speed and lower power consumption communication system can be realized. In this paper, we propose array of quasi rhomboid shaped element bowtie antenna design by using a flat reflector for ultra wideband communication systems. The proposed antenna consists of two elements quasi rhomboid shaped and aluminium flat reflector. This antenna is designed on FR-4 substrate and antenna analysis was conducted by using the IE3D program. The proposed antenna is realized and experimentally examined, since it is small size, light weight, easy method fabrication and low manufacturing cost. In measurement, it is found that the propose antenna have impedance bandwidth of 122.22% (2:1 VSWR) which covered frequency range 2.8-11.6 GHz. This antenna has uni-directional radiation patterns over the frequency range of 3.1-10.6 GHz for ultra wideband technology. For comparison purposes antenna, the average gain of the quasi rhomboid shaped bowtie antenna with and without the reflector, which average gain achieved in the quasi rhomboid shaped bowtie antenna using a flat reflector is much greater than without the reflector about 2 dB. The advantage of the proposed antenna is that it can be used to design impulse receive transmit system for ultra wideband applications. The 2009 International Symposium on Antennas and Propagation (ISAP 2009) October 20-23, 2009, Bangkok, THAILAND