International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017
p-ISSN: 2395-0072
www.irjet.net
Microstrip-fed broadband circularly Polarized monopole antenna Gauri K.Kirve, Premanand K. Kadbe 1Student 2Assistant
Dept. Of E&TC, VPKBIET, Baramati, Maharashtra, India Professor, Dept. Of E&TC, VPKBIET, Baramati, Maharashtra, India
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Abstract - A microstrip-fed broadband circularly polarized (CP) monopole antenna studied. Impedance bandwidth and large axial ratio bandwidth (AR-BW) obtained at a time. This antenna used a monopole architecture, except for it ground plane and asymmetric feeding.The asymmetric-feeding used to provide an orthogonal component different from its linearly polarized wave. Also, by adding a rectangular slit and a stub on the ground plane of antenna produce CP wave and to obtain an impedance bandwidth. As per the simulated results, the impedance bandwidth was 6.72 GHz with a return loss of a 10 dB, which covered a range of 2.09– 8.20 GHz. The AR-BW was 1.37 GHz for a 3 dB AR, which covered a range of 3.52–4.89 GHz.
Key Words: Microstrip, Stub, Slit, Monopole, Asymmetric. INTRODUCTION Recent applications of circularly polarized (CP) waves have attracted much attention due to their significance in resisting inclement weather as compared to linearly polarized (LP) waves. They employed in modern communication systems that are sensitive to climatic variations, such as satellite systems and mobile communication systems radar tracking, navigation, [1]. The hazard caused by misalignment can be ignored to simplify antenna mounting as well as to improve reception efficiency. Exciting a CP wave requires two conditions: first, the amplitudes of two near degenerate equal orthogonal E vectors; second, t p s r n PD tw n t two ort o on l E v tors must pprox m t ly 9 R t- n r ul r pol r z t on RHCP or l t- n r ul r pol r z t on LHCP n n y 9 p s l or l Tr t on lly pol r s r s r qu r or exciting a quadrature phase contribution to producing CP. Some approaches have employed couplers, dividers or phase shifters to provide a 908 PD [2]. These mechanisms have referred to as the so-called dual-feed technique. On the other hand, some researchers established a cavity model to estimate the central frequency of CP and the polarized sense based on the physical dimensions and feeding positions of the antenna [3–5]. These configurations enabled CP capability to be realized using a singlefeed method, which simplified the feeding. In addition to microstrip antennas, many types of antennas can efficiently achieve CP, such as slotted antennas [6], and arrays [8]helical antennas [7]. In last years, numerous studies designed CP asymmetric antennas.Ojiro in 1998, used a monopole feed and a symmetrical loop to generate a traveling wave current and realize CP [9]. A coplanar waveguide (CPW)- antenna utilized to produce a circular polarization mode between the sleeve and monopole antenna [10]. Paper states an asymmetric microstrip-fed monopole antenna to obtain a wide impedance bandwidth and broad axial ratio bandwidth. This antenna contains a rectangular radiator with asymmetric feed line and a ground plane with an embedded slit and stub. Asymmetric feeding achieves an impedance bandwidth and excites an elliptically polarized (EP) wave. By changing the shape of the plane, antenna produces a broad impedance bandwidth and wideband CP simultaneously. The work presents parametric studies of the antenna geometry, and the measured results show that this antenna generates a wide impedance bandwidth of 102.5% at a center frequency of 5.43 GHz and a wide CP radiation wave of 32.6% on a center frequency of 3.8 GHz.
1 THE OPERATION OF CIRCULAR POLARIZATION Feeding structures typically classify into two categories, central feeding and asymmetric feeding, which can cause different surface current distributions on an antenna. Fig. 1a shows the surface current distribution for symmetric feeding, which can divide by horizontal and vertical currents. The orientation of the horizontal current excites two components t t r 8 out o phase. Therefore the radiation in the far field in the horizontal direction is weak. Thus, it is tough for a conventional monopole antenna to excite CP. Asymmetric feeding produces two currents, which consist of horizontal and vert l urr nts s s n F T r PD n mpl tu s o not v CP r qu r m nt so t symm tr n t n qu n n r t n EP w v CP v y two ort o on l E v tors w t qu l mpl tu s n 9 PD It n s © 2017, IRJET
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