# Design of SWB Antenna with Triple Band Notch Characteristics for Multipurpose Wireless Applications
### Literature Review  
The major difficulty in implementing an SWB communication system is eliminating the authorized and unauthorized license bands such as WiMAX, WLAN, AWS, C, X, etc., from the assigned SWB bandwidth. Each of these communications has its defined frequency bands, and the SWB system has to separate out those bands to make the communication interference resistant. Various researchers have addressed the aforementioned challenge to some extent by introducing SWB antennas with multi notch characteristics. Several techniques such as the introduction of a slot in the patch/ground plane [1; 2; 3]; insertion of a slit on the patch/ground plane [4; 5]; placing stubs [6; 7; 8; 9], meander grounded stubs [10], and parasitic elements [11; 12; 13]; and employing a split ring resonator [14; 15] have been used in SWB antenna design to filter out undesired frequency bands. Placing a slot on the patch or ground plane empirically helps to reject a particular frequency band and thus brings band notch characteristics to the SWB antenna. Various shapes and sizes of slots have been investigated, and combinations of slots with other geometries have been examined for rejecting a desired band of frequencies. In [1], the bandwidth of a square-shaped antenna was enhanced by placing a dumbbell-structured parasitic resonator at the upper side of the partial ground plane. Further, by adding two similar inverted J-shaped slots and a reverse F-shaped slot, two notch bands were obtained at 3.3-4.2 GHz and 5.1-5.4 GHz frequencies. Again, in [2], a triple notch band SWB antenna was designed by exploring the slot on patch concept. First, a notch band at 3.5 GHz (WiMAX) was realized by cutting an E-shaped slot in the upper portion of the antenna, while a rectangular slot and a C-shaped slot along with a set of two parasitic patches provided two more notch bands at 5.2 GHz and 5.8 GHz (lower and upper) WLAN, respectively. A monopole printed circular radiating patch with a coplanar waveguide (CPW)-fed level-shaped ground plane is demonstrated in [3]. By etching two C-shaped slots on the radiating patch and a pair of C-shaped slots in the ground plane, three frequency bands, namely 3.43-3.65 GHz, 4.95-5.25 GHz, and 5.36-5.85 GHz, were eliminated. Introduction of slits on the patch results in multiband frequency operation because of the disruption caused to the average current paths of any resonant mode. The surface current paths become elaborated around the slits, and because of this, resonant frequency decreases leading to multiband frequency operation. In [4], a modified circular radiating patch with a pair of open ended quarter wavelength slits was realized to suppress dual notch bands of 5.15-5.35 GHz and 5.725-5.825 GHz. In another example of the slit concept, a CPW-fed single band notch circular fashioned antenna was demonstrated in [5]. With the help of a set of stubs and slits adopted inside the tapered slot and circular patch, a notch band of 5.0-5.8 GHz was realized. Another method to bring notches in wideband antennas is by loading the stub on the antenna structure. Stub loading on the patch or ground plane transfuses the fundamental and harmonics in quadrature and thus eliminates the required band of frequencies. [PERSON] et al. presented a square-shaped radiating patch with a modified ground plane for developing a dual notch band wideband antenna. By introducing an inverted T-shaped stub on the patch and a set of U-shaped stubs adjacent to the feed line, stop bands of 3.3-4.0 GHz (WiMAX) and 5.05-5.90 GHz (WLAN) were achieved [6]. In [7], a quasi-U-shaped patch with a stepped slot in the ground plane was presented to bring wide bandwidth in antenna characteristics. Two inverted L-shaped stubs in the radiating patch realized two notch bands of 4.97-5.48 GHz and 5.69-5.99 GHz for removing lower and upper WLAN bands, respectively. A guitar-shaped CPW-fed monopole radiator with triple band notch functionality was presented by [PERSON] et al. [8].