Abstract
In this paper, we present an offset microstrip-fed ultrawideband antenna with band notch characteristics.The antenna structure consists of rectangular radiating patch and ground plane with rectangular shaped slot, which increases impedance bandwidth upto 117.73%(2.9-11.2GHz).A new modified U slot is etched in the radiating patch to create band-notched properties in the WiMAX (3.33.7GHz) and C-band satellite communication (3.7-4.15GHz).Furthermore, parametric studies have been conducted using EM simulation software CADFEKO suite(7.0) and optimized with stable radiation pattern which satisfied UWB requirement for VSWR<2.A prototype of antenna is fabricated on 1.6mm thick FR-4 substrate with dielectric constant of 4.4 and loss tangent of 0.02.The designed antenna exhibits bidirectional and omni directional radiation patterns along E and H-plane with stable gain and efficiency over entire operating band except notch frequency band. Simulated results are in good agreement with the measured results of the proposed antenna which makes it a good candidate for UWB application.
Highlights
According to FCC UWB is a very promising technology that have a large unlicenced bandwidth of 7.5GHz ranging from 3.1GHz to 10.6GHz [1].Since UWB communication system has been favourable due to various advantages such as high data transmission rate, low cost and ease of integration
These narrowband systems are WiMAX(IEEE802.16) operating in the frequency band of 3.33.7GHz,C-band satellite communication operating in the frequency band of 3.7-4.15GHz,WLAN operating in the frequency band of 5.15-5.825GHz,X-band satellite communication operating at 7.25-7.75GHz band
It is observed that antenna radiation characteristics describe the energy directed by the antenna in azimuth plane (Φ=0°) and elevation plane (Φ=90°) at 3.1GHz,5.5GHz and 10.1GHz frequencies.It is shown that for all frequencies elevation radiation patterns have almost bidirectional and dipole like radiation patterns because the alternating electric current enters the antenna through feed line and patch junction and leaves the antenna through edges of the radiating patch which results in formation of electric field pattern with maximum field at the radiating edges in the direction of radiation and minimum field at the centre of the patch.The designed antenna is radiated as an omnidirectional in H-plane(Φ=0°).It is observed that as frequency increases radiation patterns are distorted due to reduction in efficiency at higher frequency range
Summary
According to FCC UWB is a very promising technology that have a large unlicenced bandwidth of 7.5GHz ranging from 3.1GHz to 10.6GHz [1].Since UWB communication system has been favourable due to various advantages such as high data transmission rate, low cost and ease of integration. It is essential to design UWB antenna with band notched characteristics in the frequency band of 3.3-3.7GHz,3.7-4.15GHz,5.15-5.825GHz,7.25-7.75GHz respectively to reduce interference between WiMAX, C-band, WLAN, X-band and UWB system To reduce this interference,many significant band-notched techniques have been used in UWB antennas,including etching an angle-shaped parasitic slits[2],C-shaped slot and L-shaped stub[3], a pair of S-shaped slits and elliptical ring slot[4], inverted U and fork-shaped parasitic structures[5].Band rejection characteristics are obtained by embedding different shapes of the slots such as a square ring[6] and folded trapezoid[7].In [8]-[9] dual band antenna operating in bluetooth and UWB proposed but without band-notched characteristics.In [10] the UWB antenna with integrated Bluetooth and band-notched characteristics are investigated ,so as to reduce interference between narrowband and UWB systems. The effect of ground length(Lg) is presented in fig..It shows simulated results for different values of length of ground(Lg) such as 8,9 and 10mm.When Lg=8mm S11 gets disturbed at higher frequency range.For Lg=10mm return loss is very poor at 4.3GHz frequency.Only for Lg=9mm we achieved satisfied UWB
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