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In this paper, a printed loop antenna with current reconfiguration technique is proposed to improve the usability of the loop as a multiband antenna for UWB applications ranging from 3.1 GHz to 10.6 GHz. The current reconfiguration is achieved using a capacitive gap along the circumference of the loop antenna. The shift in the location of the capacitive gap changes the current distribution in the antenna and new bands are generated. It is found that using a single capacitive gap along the loop, the antenna can be operated as a wide band antenna whose frequency ranges from 6 GHz to 10.8 GHz with % bandwidth of 57. The proposed loop can also be used as dual and triple band antenna in the frequency range from 6 GHz to 10.8 GHz by simply switching ON and OFF the switches. The proposed antenna generates the highest numbers of bands at the minimum expense of switches. The proposed loop without capacitive gap is capable of covering only 24% out of the 3.1 GHz-10.6 GHz range. The range of band can be varied from 24% to 57% using the switches. The proposed antenna very well rejects the WLAN and WiMAX bands.
Keywords: Capacitive Gap, Current Reconfiguration, Loop Antenna, Multiband, Wide Band
Reconfigurable antennas are required for the better selectivity of the desired band of operation. These are also used to have desired radiation pattern at different frequencies of operation. The reconfigurability in any antenna is achieved by introducing physical changes in the antenna structure. These changes in antenna structure bring change in antenna current distribution which changes antenna impedance. The performance of antenna changes as the antenna impedance changes. There are several techniques to achieve reconfigurability features in antenna. These techniques use electronic switches, optical, mechanical and electromechanical switches (Mohamed Nasrun Osman et.al, 2015). The change in current is introduced either in the antenna itself or in the ground plane (DGS: defected ground structure) as shown in (Mohammed Al-Husseini et. al., 2010) and (Xuelin Liu et. al., 2015). The structural modification in the antenna is used to control the orientation of the current in the antenna to generate different bands (Sonia Sharma and Chandra C. Tripathi, 2015).
A single loop antenna is not capable of generating multiple bands which restricts the wide application of loop antenna. The proposed method of current reconfiguration in the loop antenna using switches improves the number of bands. The proposed technique successfully demonstrates the enhancement of loop bandwidth using a single switch and can be extended to any dimension of the loop. It is also found that the antenna can be used as a dual or triple band antenna using a single switch at different locations. Therefore it can also be concluded that the location of the switch not only generates different bands but also influences the bandwidth of the produced bands. The proposed loop without a switch is capable of covering only 24% of the entire band of UWB ranging from 3.1 GHz to 10.6 GHz due to the unstable radiation pattern. The range of band can be varied from 24% to 57% using the switches.
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