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  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME 1 EFFECT OF FEEDLINE ON RESONANT MODE OF SQUARE MICROSTRIP ANTENNA Dr. Nagraj Kulkarni Department of Electronics, Government College, Gulbarga-585105,Karkataka, India ABSTRACT In this paper the effect of microstripline feed on resonant mode of the square microstrip antenna is studied. The antenna is constructed with its structure of dimension 8 X 5 X 0.16 cm3 . The microstripline feed arrangement along with quarter wave transformer is used to excite the proposed antenna. The antennas exhibits a broadside and linear radiation characteristics. The results are presented and discussed. This antenna may find its applications in S-band communication system. Key words: Square Microstrip Antenna, Feedline, Resonance. 1. INTRODUCTION In the recent years the microstrip antennas (MSAs) have gained popular position in communication system because of their inherent attractive features like light weight, planar in structure, ruggedness, different geometries and shapes, easy installation, low fabrication cost [1] etc. In this paper the effect of microstrip feedline on the resonant modes of the antenna is presented. This study may be useful for switching of bands applications. This kind of study is found to be rare in the literature. 2. DESIGNING The low cost glass epoxy substrate material of area A × B, thickness h = 0.16 cm and dielectric constant εr = 4.2 is used to fabricate the proposed antenna. The artwork of the antenna is sketched using computer software Auto CAD to achieve better accuracy. Photolithography process is used to fabricate the antenna. INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2014): 6.8310 (Calculated by GISI) www.jifactor.com IJEET © I A E M E
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME 2 Figure 1: Top view geometry SMSA-1 Figure 1 shows the top view geometry of square microstrip antenna (SMSA-1), which is designed for the resonant frequency of 3.5 GHz using the equations available in the literature for the design of square microstrip antenna [2]. The SMSA-1 consists of a square radiating patch of equal length (L) and width (W). The Lf and Wf are the length and width of the microstripline used to excite the patch. The SMSA-1 has Lf equal to λ0/4. A semi miniature-A (SMA) connector of 50 impedance is used at the tip of the microstripline to feed the microwave power. A quarter wave transformer of length Lt and width Wt is used to match the impedances between lower radiating edge of the patch and microstripline feed. Figure 2: The top view geometry SMSA-2 Figure 2 shows the geometry of modified square microstrip antenna (SMSA-2). The SMSA-2 has the entire dimension same as that of SMSA-1, the modification is made in microstrip feedline length of SMSA-2, which is reduced to λ0/6. Table 1 gives the design parameters of SMSA and SMSA-2. Table 1: Design parameters of SMSA and DOSMSA ( cm ) Antenna L W Lf L’ f Wf Lt Wt A B SMSA-1 2.04 2.04 2.18 - 0.32 1.09 0.06 5 8 SMSA-2 2.04 2.04 - 1.416 0.32 1.09 0.06 5 8
  • International Journal of Electrical Engineering and Technology (I ISSN 0976 – 6553(Online) Volume 5, Issue 3. EXPERIMENTAL RESULTS The Agilent Technologies make is used to measure the experimental return loss of Figure 3: Variation of retur Figure 3 shows the variation of return lo this figure it is seen that, the SMSA designed frequency of 3.5 GHz, while SMSA toward lower frequency side is due to the reduction in length of the resonant mode helps in switching action of band applications. The bandwidth SMSA-1 and SMSA-2 are 3.61% and 2.94% respectively. Figure 4: Radiation pattern of SMSA measured at 3.43 GHz Figure 5: Radiation pattern of Fig 4 and 5 show the radiation patterns of from these figures that, the patterns are broadside and linearly polarized. The cross is much lower when compared to the co The gain of SMSA-1 and SMSA-2 is calculated using the absolute gain method given by the relation, International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME 3 make (Agilent N5230A: A.06.04.32), Vector Network Analyzer is used to measure the experimental return loss of SMSA and SMSA-2. Variation of return loss versus frequency of SMSA-1 and SMSA shows the variation of return loss versus frequency of SMSA-1 and SMSA-1 resonates at 3.43 GHz of frequency which is nearer to the while SMSA-2 resonates at 2.64 GHz. This shift of resonant mode toward lower frequency side is due to the reduction in length of the microstrip feedline. This shift of helps in switching action of band applications. The bandwidth BW and 2.94% respectively. Radiation pattern of SMSA measured at 3.43 GHz Radiation pattern of SMSA-2 measured at 2.20 GHz show the radiation patterns of SMSA-1 and SMSA-2 respectively. from these figures that, the patterns are broadside and linearly polarized. The cross-polar power level is much lower when compared to the co-polar power level indicates the broad nature of radiation. is calculated using the absolute gain method given by the relation, JEET), ISSN 0976 – 6545(Print), ), Vector Network Analyzer SMSA-2 nd SMSA-2. From which is nearer to the This shift of resonant mode feedline. This shift of BW1 and BW2 of respectively. It can be noted polar power level polar power level indicates the broad nature of radiation. is calculated using the absolute gain method given by the relation,
  • International Journal of Electrical Engineering and Technology (I ISSN 0976 – 6553(Online) Volume 5, Issue ( ) 10 log - ( ) - 20logG dB G dB dB=       where, Gt is the gain of the pyramidal horn antenna and R is the distance between the transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘P power transmitted by standard pyramidal horn antenna ‘P measured for SMSA-1 is found to be 0.8 0.92 dB. 4. CONCLUSION From this detailed study, it is concluded that lower frequency side when length of the same as that of SMSA-1. The radiation characteristics of linearly polarized. This antenna may find its a REFERENCES 1. G. Kumar and K. P. Ray, Broadband Microstrip Antennas, MA (2003). 2. Antennas: John D Kraus: MacGraw Hill Pub Co.Ltd. 3. Kishan Singh and Shivasharanappa N Mulgi Compact Square Microstrip Antenna Electronics and Communication Engineering & Technology (IJECET), Volume 2010, pp. 99 - 106, ISSN Print: 0976 BIO-DATA Dr. Nagraj K. Kulkarni Electronics from Gulbarga Universi respectively. He is working as an Assistant professor Electronics Government Degree C field of Microwave Electronics. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 6553(Online) Volume 5, Issue 3, March (2014), pp. 01-04 © IAEME 4 0 ( ) 10 log - ( ) - 20log 4 r t t P G dB G dB dB P R λ π           (2) is the gain of the pyramidal horn antenna and R is the distance between the transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘P power transmitted by standard pyramidal horn antenna ‘Pt’ is measured independently. is found to be 0.8 dB maximum and the peak gain of SMSA From this detailed study, it is concluded that the resonant mode of SMSA lower frequency side when length of the microstrip feedline is reduced keeping all other dimensions The radiation characteristics of SMSA-1 and SMSA-2 are broadside and This antenna may find its applications in S-band communication system. P. Ray, Broadband Microstrip Antennas, MA: Artech House, Norwood, : MacGraw Hill Pub Co.Ltd. Shivasharanappa N Mulgi, “Complementary-Symmetric Corner Truncated Compact Square Microstrip Antenna for Wide Band Operation”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume , ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. Kulkarni received his M.Sc, M.Phil and Ph. D degree in Applied Electronics from Gulbarga University Gulbarga in the year 1995, respectively. He is working as an Assistant professor and Head, in the Department of Electronics Government Degree College Gulbarga. He is an active researcher field of Microwave Electronics. JEET), ISSN 0976 – 6545(Print), (2) is the gain of the pyramidal horn antenna and R is the distance between the transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘Pr’ and the ’ is measured independently. The gain SMSA-2 is found to be of SMSA-2 shifts towards feedline is reduced keeping all other dimensions are broadside and communication system. : Artech House, Norwood, Symmetric Corner Truncated ”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 1, Issue 1, degree in Applied ty Gulbarga in the year 1995, 1996 and 2014 in the Department of active researcher in the