# Design of SWB Antenna with Triple Band Notch Characteristics for Multipurpose Wireless Applications
### Literature Review
By adding an inverted T-shaped stub and a pair of elliptical slots on the radiator, three interfering frequencies of 3.74 GHz (under WiMAX band), 5.45 GHz (under WLAN band), and 7.65 GHz (under X band) were eliminated. In [9], by embedding a fractal stub on the radiating patch and by etching a pair of modified rectangular slots, triple notch bands from WiMAX (3.30-3.80 GHz), WLAN (5.150-5.825 GHz), and DSS (7.25-7.75 GHz) were encountered. Alternately, meander lines have also been used for notch antenna design, because they resonate at different independent frequencies. Meandering means turning or winding. If the number of turns are increased, the meander stub resonates at lower frequencies, and vice versa. It is well known fact that the surface current primarily distributes at the periphery of the microstrip line, and in the meander stubs, the magnitude of surface current will be greater at the corners/bending portion, which provides a coupling to the microstrip line, thus providing the notch at that particular frequency. In [10], a microstrip-fed elliptical-shaped planar monopole antenna with three notch band properties was demonstrated. With the aid of three sets of meandered ground stubs, triple notch band characteristics were obtained. Two notch bands of 3.3-3.6 GHz and 5.15-5.35 GHz were derived from two sets of meandered stubs near the feedline, and another notch band of 5.725-5.825 GHz was yielded from a meandered stub on the upper edge of the ground plane. Another technique to obtain notch bands in a wideband antenna is by introducing parasitic elements near the radiator. A parasitic element is an element that operates under the influence of other's feed. The parasitic element behaves like a passive resonator that modifies the radiation pattern emitted by the patch antenna. Thus, the parasitic element helps to provide wideband characteristics and notch functionality. [PERSON] et al. [11], presented a circular monopole radiator with a parasitic resonator for adding wideband characteristics. By embedding I-shaped and inverted-U-shaped parasitic resonators at the rear side of the radiating patch, dual band notch functions at 5-5.35 GHz and 7.85-8.4 GHz were achieved. Wide bandwidth was also achieved by introducing parasitic elements in addition to slot concepts in antenna design. A tapered triangular microstrip-fed circular monopole antenna with dual band notch characteristics was demonstrated by exploring the parasitic element and slot concept in [12]. By inserting a U-shaped parasitic component in proximity of the ground plane and an inverted T-shaped stub inscribed within the patch, a first stop band at 3.2-4.4 GHz was obtained. For the second stop band at 7.2-8.4 GHz, a U-shaped slot was etched out from the ground plane. Another illustration of a parasitic element-based wideband antenna with band notch characteristics can be seen in [13], where a hemi ellipse-shaped radiating patch with a parasitic element and an elliptical slot was used to hold a single notch band (5.15-5.825 GHz) in the complete frequency band of 3-17 GHz. In another approach, a split ring resonator (SRR) and complementary SRR (CSRR) have been significantly used for designing antenna with band notch capability. The SRR and CSRR can produce strong electric and magnetic coupling from LC resonance and thus are used for band stop filter modelling. In [14], by etching two CSRRs on the radiating patch and by using a set of rectangular SRRs beside the feed line, three notch bands of 3.3-3.8 GHz (WiMAX), 5.15-5.85 GHz (WLAN), and 7.9-8.4 GHz (X-band) were brought in the complete frequency band of 2.21-11.71 GHz. In another example of a CSRR-basedwideband antenna, a miniaturized microstrip-fed planar monopole antenna with three band notch features was designed by [PERSON] et al. [15]. There, triple band notch (3.4 GHz, 5.2 GHz, and 5.8 GHz) functionality was achieved by defining a set of slots around the edges of the patch, a circular-shaped CSRR at the center of the patch, and a set of rectangular-shaped CSRRs on either side of the ground.