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Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization
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Design and development of low profile, dual band microstrip antenna with enhanced bandwidth, gain, frequency ratio and low cross polarization

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  • 1. InternationalJournal of Electronics and Communication Engineering & Technology (IJECET), International Journal of Electronics and CommunicationEngineering 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME ISSN 0976 – & Technology (IJECET) IJECETISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online)Volume 1, Number 1, Sep - Oct (2010), pp. 88-98 ©IAEME© IAEME, http://www.iaeme.com/ijecet.html DESIGN AND DEVELOPMENT OF LOW PROFILE, DUAL BAND MICROSTRIP ANTENNA WITH ENHANCED BANDWIDTH, GAIN, FREQUENCY RATIO AND LOW CROSS POLARIZATION Suryakanth B Department of PG Studies and Research in Applied Electronics Gulbarga University, Gulbarga E-Mail: surya_recblk@yahoo.co.in Shivasharanappa N Mulgi Department of PG Studies and Research in Applied Electronics Gulbarga University, Gulbarga E-Mail: s.mulgi@rediffmail.com ABSTRACT This paper presents the experimental investigations carried out for obtaining dual band operation of an antenna by placing two short circuited stubs along the non-radiating boundaries of the conventional rectangular microstrip antenna. The frequency ratio is found to be 1.23. Further, by embedding two parallel slots in the patch and vertical slots in the stubs, the antenna shows the property of virtual size reduction without changing the frequency ratio. However by placing slot loaded stub along the radiating edge of the patch the upper operating bandwidth can be enhanced to 21.13% and frequency ratio to 1.43. This technique also enhances the gain to 12.13 dB and minimizes the cross polar power level to -20 dB down with respect to co-polar. The enhancement of bandwidth, gain, frequency ratio and reduction of cross-polar power level does not affect the nature of broadside radiation characteristics. The design concepts of antennas are presented and experimental results are discussed. Keywords: microstrip antenna, dual band, stubs, slots. 88
  • 2. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME1. INTRODUCTION The microstrip antennas (MSAs) are widely used for the last few years due totheir attractive features such as light weight, low volume, ease in fabrication and low cost[1]. However, two major disadvantages associated with MSAs are low gain and narrowbandwidth. The traditional MSAs have typical gain of about 6 dB and bandwidth nearly2 to 5% [1-2], which restricts their many useful applications. Number of studies has beenreported in the literature for enhancing the bandwidth [3-6] and gain [7-8]. Further inmodern communication systems, such as satellite links or radar communications, dualband MSAs are more attractive as they avoid use of two separate antennas fortransmit/receive applications. The dual band antennas are realized by many methodssuch as by using shorting pins on the patch [9-10], using aperture coupled parallelresonators [11], reactively loaded patch [12] etc. However, the antennas adopted thesedesigns have narrow operating bandwidths, usually in the order of 2% or less than that.But in this presentation enhanced dual band antenna is realized by using short circuitedstubs along the non radiating edges of the conventional rectangular patch. Further theproposed antennas are also capable for the enhancement of frequency ratio, gain andreduction of cross polar power level by placing rectangular slots in the patch and stubsand by loading slots in the stub connected along the radiating edge of the patch, withoutaffecting the nature of broadside radiation characteristics.2. DESCRIPTION OF ANTENNA GEOMETRY The art work of proposed antennas are developed using computer softwareAutoCAD-2006 and are fabricated on low cost glass epoxy substrate material ofthickness h=1.4 mm and permittivity εr=4.4. The conventional rectangular microstripantenna (CRMA) has been designed using the equations available in the literature [1, 13].Figure 1 show the geometry of conventional rectangular microstrip antenna which isdesigned for the resonant frequency of 9.4 GHz. The antenna is fed by usingmicrostripline feeding. This feeding has been selected because of its simplicity and it canbe simultaneously fabricated along with the antenna element. Figure 1 consists of aradiating patch of length L and width W, quarter wave transformer of length Lt and widthWt, used between the patch and 50Ω microstripline feed of length Lf and width Wf. At 89
  • 3. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEthe tip of microstripline feed, a 50Ω coaxial SMA connector is used for feeding themicrowave power. Figure 2 shows the geometry of dual stub rectangular microstripantenna (DSRMA). The two short circuited stubs of length L1 and width W1 are placedalong the centre axis of the non radiating boundaries of the patch. The dimensions of thestubs are taken in terms of λ0, where λ0 is the free space wavelength in cm correspondingto the designed frequency of 9.4 GHz. The feed arrangement of Figure 2 remains same asthat of feed arrangement of Figure 1. Figure 3 shows the geometry of dual stub slotloaded rectangular microstrip antenna (DSSRMA). In this antenna two parallel slots oflength L2 and width W2 are embedded on the patch at a distance of 1 mm from the non-radiating edges of the patch. Also a slot of length L3 and width W3 is embedded on boththe stubs. The slot in the stub is placed at a distance of 1 mm from the non-radiating edge(L) of the patch. The feed geometry of this antenna remains same as that of Figure 1. Figure 4 is the extension of Figure 3. In this antenna a slot loaded stub used inFigure 3 along the length (L) of patch is also connected along the width (W) of the patch.The slot in this stub is placed vertically at a distance of 1 mm from upper radiating edgeof the patch. This antenna is named as triple stub slot loaded rectangular microstripantenna (TSSRMA). The feed geometry of this antenna remains same as that of Figure 1.The proposed antennas are fabricated using photolithography process. Table 1 shows thelist of designed parameters of the proposed antennas. The substrate area of the all theantennas is A=M×N. Figure 1 Geometry of CRMA Figure 2 Geometry of DSRM 90
  • 4. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME Figure 3 Geometry of DSSRMA Figure 4 Geometry of TSSRMA Table 1 Design Parameters of Proposed AntennasAntenna Dimensions Antenna Dimensions Antenna DimensionsParameters in mm Parameters in mm Parameters in mm L 7.06 mm W 9.89 mm Lt 3.16 mm Lf 4.10 mm L1 3.99 mm Wt 4.18 mm Wf 3.16 mm W1 3.16 mm L2 5.06 mm M 25 mm L3 2.16 mm W2 1.00 mm N 25 mm W3 1.00 mm3. EXPERIMENTAL RESULTS The bandwidth over return loss less than -10 dB for the proposed antennas ismeasured. The measurement is taken on Vector Network Analyzer (Rhode & Schwarz,Germany Make ZVK model 1127.8651). Figure 5 shows the variation of return lossversus frequency of CRMA. From this figure it is seen that the antenna resonates veryclose to its designed frequency of 9.4 GHz. This validates the design concept of CRMA.From Figure 5 the bandwidth is calculated by using the equation,  fH − fL  Bandwidth =  × 100 % (1)  fC  91
  • 5. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME Figure 5 Variation of return loss versus frequency of CRMA Where, fH and fL are the upper and lower cut-off frequency of the bandrespectively when its return loss becomes -10 dB and fc is the center frequency betweenfH and fL. Hence by using equation (1) the bandwidth BW1 of CRMA as shown in Figure1 is found to be 4.4%. The theoretical impedance bandwidth of this antenna is calculatedusing [7].  A× h  W (2) Bandwidth ( % ) =  × λ 0 εr    L Where, A is the correction factor, which is found to be 180 as per [7]. Thetheoretical bandwidth of CRMA is found to be 4.42 % which is in good agreement withthe experimental value. For the calculation of the gain of antenna under test (AUT), the power transmitted‘Pt’ by pyramidal horn antenna and power received ‘Pr’ by AUT are measuredindependently. The gain G in dB is given by [14],  Pr   λ0 (G ) dB = 10 log   - (Gt ) dB - 20 log   dB (3)  Pt   4π R  Where, λ0 is the operating wavelength in cm, R is the distance between thetransmitting and receiving antenna and Gt is the gain of the pyramidal horn antenna. With 92
  • 6. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEthe help of these experimental data, the maximum gain G (dB) of CRMA measured inBW1 using the equation (3) and is found to be 5.26 dB. Figure 6 shows the variation of return loss versus frequency of DSRMA. Fromthis figure it is seen that the antenna resonates at two frequencies FL=9.28 GHz andFH=11.37 GHz. The bandwidth BW2 and BW3 as shown in Figure 6 are found to be3.54% and 3.52% respectively. The BW2 is due to the fundamental mode of the patch andBW3 is due to the use of stubs in DSRMA. Hence the use of stubs is effective in gettingdual band operation. The ratio of two resonance frequencies FH/FL is 1.23. Figure 7 showsthe variation of return loss versus frequency of DSSRMA. From this figure it is seen thatthe antenna again resonates for dual bands BW4 and BW5 with an impedance bandwidthof 0.5% and 6.4% respectively. The resonant frequency of BW4 and BW5 are 7.27 GHz(FL) and 8.98 GHz (FH) respectively. It is clear from this figure that the use of slots in thepatch and stubs does not affect the dual band property of antenna but enhances the upperband BW5 from 3.52% to 6.4% and decreases the lower band BW4 from 3.54% to 0.5%,when compared to BW3 and BW2 of Figure 6 respectively. However, the ratio FH/FLremains same as that of DSRMA. Further from Figure 7 it is seen that the DSSRMAshifts the resonant frequency FL from 9.28 to 7.27 GHz and FH from 11.37 GHz to 8.98GHz respectively, when compared to the resonant frequency of DSRMA as shown inFigure 6. This is one of the useful property of virtual size reduction of DSSRMA. Figure 6 Variation of return loss versus frequency of DSRMA 93
  • 7. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME Figure 7 Variation of return loss versus frequency of DSSRMA Figure 8 Variation of return loss versus frequency of TSRMA Figure 8 shows the variation of return loss versus frequency of TSSRMA. Fromthis figure it is seen that the antenna resonates for dual bands. The magnitude ofbandwidth of BW6 and BW7 is found to be 2.69% and 21.13% respectively. From thisfigure it is seen that the slot loaded stub used along the radiating edge of the antenna doesnot affect much the resonant frequency FL in BW6 but enhances the BW6 from 0.5% to2.69% and BW7 from 6.4% to 21.13% when compared to BW4 and BW5 as shown inFigure 7 respectively. The ratio FH/FL is also increases from 1.23 to 1.43. This isolationratio is 16.08% better when compared to the literature value [12]. The gain of DSRMA, 94
  • 8. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEDSSRMA and TSSRMA are measured in their operating bands using the equation 3 in asimilar manner as explained for the measurement of gain of CRMA. The obtained valuesare shown in Table 2. From this table, it is seen that the maximum gain of 9.51dB in BW6and 12.13dB in BW7 is achieved respectively in case of TSSRMA. Hence, TSSRMA isquite effective in enhancing the gain of antenna when compared to the gain of otherantennas mentioned in Table 2. The various antenna parameters of proposed antennas arealso given in Table 2 for the sake of comparison. Table 2 Experimental results of proposed AntennasAntenna Number of Resonant Maximum Bandwidth FL/ FH bands frequency Gain (dB) (%) (GHz)CRMA 1 Fr = 9.11 5.26 4.40DSRMA 2 FL=9.28 3.72 3.54 1.23 FH=11.37 5.62 3.52DSSRMA 2 FL= 7.27 4.33 0.5 1.23 FH=8.98 6.16 6.4DSSRMA 2 FL= 7.27 4.33 0.5 1.23 FH=8.98 6.16 6.4TSSRMA 2 FL= 7.81 9.51 2.69 1.43 FH=11.17 12.13 21.13 Figures 9-12 show the typical co-polar and cross-polar radiation patterns ofCRMA, DSRMA, DSSRMA and TSSRMA respectively measured at their operatingbands. From these figures, it can be observed that the patterns are broadsided and linearlypolarized. The TSSRMA gives the cross polar power level of -20 dB down whencompared to its co-polar power level, which is minimum among the proposed antennas. Figure 9 Co-polar and cross polar radiation patterns of CRMA measured at 9.11GHz 95
  • 9. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME Figure 10 Co-polar and cross polar radiation patterns of DSRMA measured at 11.38 GHz Figure 11 Co-polar and cross polar radiation patterns of DSSRMA measured at 8.98 GHz Figure 12 Co-polar and cross polar radiation patterns of TSRMA measured at 7.81 GHz 96
  • 10. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME4. CONCLUSION From the detailed experimental study it is concluded that by placing the stubsalong the non-radiating edges of CRMA results into dual band operation with frequencyratio of 1.23. Further by embedding parallel slots on the patch and slots in the stubs,antenna gives dual bands with same frequency ratio but shows the property of virtual sizereduction. However by placing slot loaded stub along the radiating edge i.e. TSSRMA theantenna resonates for two bands with frequency ratio of 1.43. This technique enhancesthe bandwidth to 21.13 % and gain 12.13 dB and reduces the cross polar power to -20 dBdown with respect to its co-polar power level. The enhancement of impedance bandwidthand gain does not change the nature of broadside radiation characteristics. The proposedantennas are simple in their design and fabrication and they use low cost substratematerial. These antennas may find application in microwave communication systemsparticularly in synthetic aperture radar (SAR), where dual bands are required.ACKNOWLEDGEMENTS The authors would like to thank Dept. of Science & Technology (DST), Govt. ofIndia, New Delhi, for sanctioning Vector Network Analyzer to this Department underFIST project.REFERENCES1. Bhal I. J. and Bharatia P (1980), Microstrip antennas, Artech House, New Delhi, 1981.2. Pozar D. M. (1992), “Microstrip antennas,” IEEE, proc. Vol. 80, No. 1, pp. 79-91.3. Pues H. F. and Van de Capelle A. R. (2002), “An impedance matching technique for increasing the bandwidth of microstrip antennas,” IEEE Trans. Antennas Propagat., Vol. 37, No. 11, pp. 1345-1354.4. K. Oh., et. al. (2004), “Design of dual and wideband aperture stacked patch antenna with double-sided notches,” Electron. Lett., Vol. 40, No. 11, pp. 643-645.5. Sze J. Y. and Wong K. L. (2000), “Slotted rectangular microstrip antenna for bandwidth enhancement,” IEEE Trans. Antennas Propag, Vol. 48, No. 8, 1149-1152. 97
  • 11. International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME6. Kumar G and Gupta K. C. (2003), “Broad-band microstrip Antennas using additional resonators gap-coupled to the radiating edges,” IEEE Trans. Antennas Propag, Soc. Int. Symp. Vol. 1, No. 12, pp. 1375-1379.7. Kumar G and Ray K. P. (2003), “Broadband Microstrip Antennas”, Artech House, Norwood.8. David R. Jackson and Nicolaos G. Alexopoulos (2002), “Gain enhancement method for printed circuit antennas,” IEEE Trans. Antennas Propag, Vol. 33, No. 9, 976-987.9. Waterhouse R. B. (1999), “Broadband stacked shorted patch,” Electron. Lett., Vol. 35, No. 2, pp. 98-100.10. Bao F. Wang and Yuen T. Lo (1984), “Microstrip antennas for dual- frequency operation,” IEEE Trans. Antennas Propagat, Vol. 32, No. 9, 938-943.11. Fredric Croq and Pozar D. M. (1992), “Multi-frequency operation of microstrip antennas using aperture coupled parallel resonators,” IEEE Trans. Antennas & Propagat., Vol. 40, No. 11, pp. 1367-1374.12. Richards W. F., et. al. (1985), “Dual-band reactively loaded microstrip antenna,” IEEE Trans. Antennas & Propagat., Vol. 33, No. 5, pp. 556-561.13. Kishan Singh., et. al. (2010), “Dual band Microstrip Antennas,” IUP Journal of Telecommunications, Vol. 2. No. 3, pp.45-54.14. Balanis C A (1982), “Antenna theory analysis and Design”, John Wiley and Sons, New York. 98

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