- Email: [email protected]
5.8 GHz Applications
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ScienceDirect Procedia Computer Science 46 (2015) 1311 – 1316
International Conference on Information and Communication Technologies (ICICT 2014)
A Dual Band SIR Coupled Dipole Antenna for 2.4/5.2/5.8 GHz Applications U. Deepaka,*, T. K. Roshnaa and P. Mohanana a
Centre for Research in Electromagnetics and Antennas (CREMA), Department of Electronics, Cochin University of Science and Technology, Cochin -682022, Kerala, India
Abstract A novel planar, dual band antenna for 2.4, 5.2 & 5.8 GHz ISM band applications, on a substrate of relative permittivity 4.3 is proposed. The wide band at higher resonance is due to the modified planar dipole and the lower resonance is achieved by a stepped impedance resonator (SIR), which is electrically coupled to the modified dipole. The 2:1 VSWR impedance bandwidth of the proposed antenna is 95MHz for the first resonance and 1.38GHz for the second resonance. The radiation patterns are nearly omnidirectional and the maximum measured gain is 2.6dBi and 3.6dBi at 2.48 GHz and 5.35 GHz respectively. © 2015 2014 The The Authors. Authors. Published Published by by Elsevier ElsevierB.V. B.V.This is an open access article under the CC BY-NC-ND license © Peer-review under responsibility of organizing committee of the International Conference on Information and Communication (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the International Conference on Information and Communication (ICICT 2014). Technologies Technologies (ICICT 2014) Keywords: Dual band antenna;Bended dipole;Stepped impedance resonator.
1. Introduction The 2.4 GHz, 5.2 GHz and 5.8 GHz ISM bands are very common and widely used for different applications like wireless local area networks and many other wireless devices like wireless printers, bluetooth etc. Because of the wide use of this band, devices operating at this band require multiband capability to comply with IEEE 802.11, 802.11a, 802.11b, 802.11g, ETSI HiperLAN1, HiperLAN2 standards. Owing to the greater demand for applications in these frequency bands, many attempts have been done for making compact and efficient antennas operating in these bands. Later, dual band antennas which operate at both these bands are introduced. Planar inverted F antennas
* Corresponding author. Tel.: +91 9747594592. E-mail address: [email protected]
1877-0509 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the International Conference on Information and Communication Technologies (ICICT 2014) doi:10.1016/j.procs.2015.01.058
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(PIFA) are commonly used in the above bands1,2. The large ground plane of PIFA makes the antenna bulkier. Numerous designs of planar monopole dual frequency antennas are demonstrated, including microstrip fed modified T shaped antenna, dual band CPW fed cross slot antenna, dual band planar slot antenna with an embedded metal strip, S-shaped monopole antenna etc. Most of these antennas also employ a very large ground plane. Antennas which employ parasitic elements for achieving resonance are found in literature. A monopole antenna with a shorted parasitic element is used to achieve a wide band operation3, whereas another monopole with a shorted parasitic element results in a dual band operation4. A microstripline fed, capacitively coupled microstrip patch antenna is used to achieve a broadband operation at 2.5GHz5, a fractal antenna fed by capacitive coupling is employed for achieving multiband operation6. Stepped impedance resonators are well known for their RF and microwave region applications due to their low cost and simple structure. They find application in many RF filters and amplifiers. The ability of SIR to control the higher harmonics and to reduce the size as compared to uniform impedance resonators (UIR) is greatly employed in filters and microwave antennas. A slot SIR in different configurations, fed from a CPW (Coplanar Waveguide) is used to achieve a dual-band/tri-band/broadband operations7, whereas in one of the work by Wen-Hua Tu and Kai Chang, an SIR slot antenna capacitively fed with a CPW transmission line is employed at 3.86GHz. This antenna occupies an area of 80mm x80mm on an RT Duroid 6006 substrate with a permittivity of 6.158. In this work a half wave length UIR slot dipole is replaced with an SIR slot dipole to bring the compactness to the antenna structure. A 31% reduction in length is achieved in comparison with the UIR loaded antenna. This novel modified planar dipole antenna along with a folded SIR parasitic element offers a dual band operation. The total size of the antenna is very small and offers considerably good gain with less complexity to the structure. Apart from other antennas in literature which uses slot SIR, a coplanar stripline SIR is utilized in this proposed design. A desirable bandwidth of 95 MHz and 1.38 GHz with 2:1 VSWR reflection coefficient in both lower and higher band is achieved, respectively.
Fig. 1. Geometry of the proposed antenna.
2. Antenna design & geometry Fig. 1 shows the geometry of the proposed antenna. The antenna occupies an overall size of 25 x 20 mm2 on a substrate of permittivity (εr) 4.3 and thickness 1.6mm. A planar dipole of length 10mm is initially designed with an optimized width of 2mm, and then modified by bending it with an inner radius of 7mm. The arc length of the bended dipole is made same as that of the length of planar dipole. This dipole resonates at 5 GHz, where the length of the dipole is equal to λg/2, where λg is the guided wavelength in the structure at the resonant frequency. To eliminate the problem of return current, the dipole is modified as a double sided structure as shown in Fig. 1. A folded stepped impedance resonator (SIR), with lengths L1, L2, L3, widths W1 and W2 is utilized as a parasitic
U. Deepak et al. / Procedia Computer Science 46 (2015) 1311 – 1316
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element to the dipole. The total length of the SIR is selected as λ g/2 at 2.4 GHz. This antenna is fed with a microstrip line with an impedance transformer for better impedance matching. The physical dimensions of the antenna are given in Table 1. The design and optimization of the antenna is done with Ansoft HFSS. Table 1. Dimensions of the proposed antenna. Parameter
Dimension (mm)
L1 L2 L3 L4 L5 W1 W2 W3 R1 R2 C G H
6.7 9.62 7.3 4 7 2 0.2 3 7 9 0.4 1 4.1
Fig. 2. Measured and Simulated Reflection Coefficient.
3. Results and discussion All the measurements are done using PNA E8362B Network Analyzer. Fig. 2 shows the measured and simulated reflection coefficients of the antenna. Both the measured and simulated results are in good agreement and the slight variation is due to the fabrication tolerance. 3.1. Analysis of Electric Field, Surface Current and Polarization of the Antenna At the fundamental mode of the SIR (2.4 GHz), the E-field in the dipole ends is at maximum. These ends are electromagnetically coupled to the SIR. The electric field of bended dipole structure at 2.4 GHz is given in Fig. 3, which confirms the electrical coupling between dipole and the SIR.
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Fig. 3. Electric field distribution in the structure at 2.4GHz.
In the SIR at 2.4 GHz, the current along the Y direction on either side is antiparallel and will cancel at far field, leaving behind a net current in the X direction. At 5.2 GHz the Y components of the current on either side of the dipole is antiparallel and will cancel at far field, leaving behind a net current in the X direction. This results in the polarization of the antenna along X direction, which is experimentally verified. 3.2. Analysis of Parasitic Element & Modeling The SIR used in the proposed antenna is modeled as an open ended composite Coplanar Striplines (CPS) instead of using a microstrip transmission line model9. The symmetrical CPS has two 2mm wide strips, and the asymmetrical CPS consists of 0.2mm and 2mm wide strips, as in Fig. 4. The simulated plain wave excitation of the coplanar SIR shows a resonance at 2.2 GHz. The two important parameters of an SIR which determines the resonant frequencies are the impedance ratio k and length ratio α, given by10,
k
Z2 Z1
D
T2 T1 T 2
(1)
(2)
Fig. 4. Stepped Impedance Resonator.
The resonance of an SIR is calculated by evaluating the condition, k tan T1 * tanT 2
(3)
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Here θ1 & θ2 are the electrical lengths of the SIR corresponding to the physical length l1 & l2, and Z1 & Z2 are the characteristic impedance of the two CPS lines, as given in Fig. 4. The calculated values of k and α are 0.45644 and 0.7306, respectively.
Fig. 5. Measured radiation pattern(a) at 2.4 GHz; (b) at 5.2 GHz.
Fig. 6. Measured gain and efficiency of the antenna (a) in 2.4GHz band; (b) in 5 GHz band.
3.3. Radiation Pattern, Gain and Efficiency The radiation patterns of the antenna at 2.4 GHz and 5.2 GHz are shown in the Fig. 5. The pattern is nearly omnidirectional in both the bands. The Fig. 6 depicts the gain and efficiency of the antenna. At 2.4 GHz band, it gives a nearly uniform gain with an average gain of 1.4 dBi and a peak gain of 2.6 dBi at 2.48 GHz. In the 5-6 GHz band, the average gain is 2.2 dBi with a peak gain of 3.6 dBi at 5.35 GHz. The measured peak efficiency using Wheeler Cap method11, in the lower and higher bands are 88.6% and 96.87%, respectively. The antenna shows a 2:1 VSWR bandwidth of 95 MHz in the 2.4 GHz band from 2.405 GHz to 2.5 GHz and 1.38 GHz in the 5-6 GHz band from 4.52 GHz to 5.9 GHz.
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4. Conclusion A novel compact coplanar dual band antenna is proposed and investigated. The antenna resonates at 2.4 & 56GHz bands with a 2:1 VSWR bandwidth of 95 MHz and 1.38 GHz, respectively. The average gain of the small sized antenna is 1.4 dBi and 2.2 dBi at 2.4 GHz and 5 GHz band, with a peak gain of 2.6 dBi and 3.6 dBi at 2.48 and 5.35 GHz, respectively. The antenna shows a nearly omnidirectional radiation pattern at both frequency bands. The efficiency is 88.6% and 96.87% at 2.45 and 5.4 GHz, respectively.
Acknowledgements The authors acknowledge University Grant Commission (UGC) and Department of Science & Technology (DST) under Government of India for the financial support. References 1. Young Jun Cho, Yong Sun Shin, Seong-Ook Park. An internal PIFA for 2.4/5 GHz WLAN applications. Microwave conference proceedings, APMC, Suzhou, China, 2005. p. 1-3.
2. Wenjun Huang, Terence S. P See, Zhi Ning Chen. 2.4/5-GHz dual-band PIFA for portable devices. APSURSI, Pokane, Washington, USA, 2011. p. 430-433.
3. C. F. Tseng, C. L. Huang, C. H. Hsu. Microstrip fed monopole antenna with a shorted parasitic element for wideband application. Progress in Electromagnetic Research Letters 2009;7:115-125.
4. C. Y. Huang, P. Y. Chiu. Dual-band monopole antenna with shorted parasitic element. Electronics Letters 2005;41(21):1154 – 1155. 5. Hitesh Baheti, Deepak Kumar Pathak, Usha Kiran Kommuri. Broadband and high gain low profile (thin) capacitive coupled microstrip antennas for wireless applications. Annual IEEE India Conference, IIT Bombay, Mumbai, India, 2013. p. 1-5.
6. Norakamon Wongsin, Thanakarn Suangun, Chatree Mahatthanajatuphat, Prayoot Akkaraekthalin. A multiband fractal ring antenna fed by capacitive coupling. The 8th Electrical Engineering Electronics, Computer, Telecommunications and Information Technology (ECTI) Association of Thailand - Conference 2011, Khon Kaen 2011. p. 204-207. 7. Shih-Wei Chen, Deng-Yin Wang, Wen-Hua Tu. Dual-band/tri-band/broadband CPW-fed stepped-impedance slot dipole antennas. IEEE Transactions on Antennas and Propagation 2014;62(1):485-490. 8. Wen-Hua Tu, Kai Chang. Miniaturized CPW fed slot antenna using stepped impedance resonator. Antenna and propagation society international symposium, 2005. p. 351-354. 9. M. Sagawa, M. Makimoto, S. Yamashita. Geometrical structure and fundamental characteristics of microwave stepped impedance resonators. IEEE Transactions on microwave theory and technique 1997;45:1078-1085. 10. Arnaud Vena, Etenne Perret, Smail Tedjini. Chipless RFID tag using hybrid coding technique. IEEE Trans Microwave Theory Tech 2011;59:3356-3364. 11. H. A. Wheeler. The radiationsphere around a small antenna. Proc. IRE 1959;47:1325-1333.
ScienceDirect Procedia Computer Science 46 (2015) 1311 – 1316
International Conference on Information and Communication Technologies (ICICT 2014)
A Dual Band SIR Coupled Dipole Antenna for 2.4/5.2/5.8 GHz Applications U. Deepaka,*, T. K. Roshnaa and P. Mohanana a
Centre for Research in Electromagnetics and Antennas (CREMA), Department of Electronics, Cochin University of Science and Technology, Cochin -682022, Kerala, India
Abstract A novel planar, dual band antenna for 2.4, 5.2 & 5.8 GHz ISM band applications, on a substrate of relative permittivity 4.3 is proposed. The wide band at higher resonance is due to the modified planar dipole and the lower resonance is achieved by a stepped impedance resonator (SIR), which is electrically coupled to the modified dipole. The 2:1 VSWR impedance bandwidth of the proposed antenna is 95MHz for the first resonance and 1.38GHz for the second resonance. The radiation patterns are nearly omnidirectional and the maximum measured gain is 2.6dBi and 3.6dBi at 2.48 GHz and 5.35 GHz respectively. © 2015 2014 The The Authors. Authors. Published Published by by Elsevier ElsevierB.V. B.V.This is an open access article under the CC BY-NC-ND license © Peer-review under responsibility of organizing committee of the International Conference on Information and Communication (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the International Conference on Information and Communication (ICICT 2014). Technologies Technologies (ICICT 2014) Keywords: Dual band antenna;Bended dipole;Stepped impedance resonator.
1. Introduction The 2.4 GHz, 5.2 GHz and 5.8 GHz ISM bands are very common and widely used for different applications like wireless local area networks and many other wireless devices like wireless printers, bluetooth etc. Because of the wide use of this band, devices operating at this band require multiband capability to comply with IEEE 802.11, 802.11a, 802.11b, 802.11g, ETSI HiperLAN1, HiperLAN2 standards. Owing to the greater demand for applications in these frequency bands, many attempts have been done for making compact and efficient antennas operating in these bands. Later, dual band antennas which operate at both these bands are introduced. Planar inverted F antennas
* Corresponding author. Tel.: +91 9747594592. E-mail address: [email protected]
1877-0509 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the International Conference on Information and Communication Technologies (ICICT 2014) doi:10.1016/j.procs.2015.01.058
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U. Deepak et al. / Procedia Computer Science 46 (2015) 1311 – 1316
(PIFA) are commonly used in the above bands1,2. The large ground plane of PIFA makes the antenna bulkier. Numerous designs of planar monopole dual frequency antennas are demonstrated, including microstrip fed modified T shaped antenna, dual band CPW fed cross slot antenna, dual band planar slot antenna with an embedded metal strip, S-shaped monopole antenna etc. Most of these antennas also employ a very large ground plane. Antennas which employ parasitic elements for achieving resonance are found in literature. A monopole antenna with a shorted parasitic element is used to achieve a wide band operation3, whereas another monopole with a shorted parasitic element results in a dual band operation4. A microstripline fed, capacitively coupled microstrip patch antenna is used to achieve a broadband operation at 2.5GHz5, a fractal antenna fed by capacitive coupling is employed for achieving multiband operation6. Stepped impedance resonators are well known for their RF and microwave region applications due to their low cost and simple structure. They find application in many RF filters and amplifiers. The ability of SIR to control the higher harmonics and to reduce the size as compared to uniform impedance resonators (UIR) is greatly employed in filters and microwave antennas. A slot SIR in different configurations, fed from a CPW (Coplanar Waveguide) is used to achieve a dual-band/tri-band/broadband operations7, whereas in one of the work by Wen-Hua Tu and Kai Chang, an SIR slot antenna capacitively fed with a CPW transmission line is employed at 3.86GHz. This antenna occupies an area of 80mm x80mm on an RT Duroid 6006 substrate with a permittivity of 6.158. In this work a half wave length UIR slot dipole is replaced with an SIR slot dipole to bring the compactness to the antenna structure. A 31% reduction in length is achieved in comparison with the UIR loaded antenna. This novel modified planar dipole antenna along with a folded SIR parasitic element offers a dual band operation. The total size of the antenna is very small and offers considerably good gain with less complexity to the structure. Apart from other antennas in literature which uses slot SIR, a coplanar stripline SIR is utilized in this proposed design. A desirable bandwidth of 95 MHz and 1.38 GHz with 2:1 VSWR reflection coefficient in both lower and higher band is achieved, respectively.
Fig. 1. Geometry of the proposed antenna.
2. Antenna design & geometry Fig. 1 shows the geometry of the proposed antenna. The antenna occupies an overall size of 25 x 20 mm2 on a substrate of permittivity (εr) 4.3 and thickness 1.6mm. A planar dipole of length 10mm is initially designed with an optimized width of 2mm, and then modified by bending it with an inner radius of 7mm. The arc length of the bended dipole is made same as that of the length of planar dipole. This dipole resonates at 5 GHz, where the length of the dipole is equal to λg/2, where λg is the guided wavelength in the structure at the resonant frequency. To eliminate the problem of return current, the dipole is modified as a double sided structure as shown in Fig. 1. A folded stepped impedance resonator (SIR), with lengths L1, L2, L3, widths W1 and W2 is utilized as a parasitic
U. Deepak et al. / Procedia Computer Science 46 (2015) 1311 – 1316
1313
element to the dipole. The total length of the SIR is selected as λ g/2 at 2.4 GHz. This antenna is fed with a microstrip line with an impedance transformer for better impedance matching. The physical dimensions of the antenna are given in Table 1. The design and optimization of the antenna is done with Ansoft HFSS. Table 1. Dimensions of the proposed antenna. Parameter
Dimension (mm)
L1 L2 L3 L4 L5 W1 W2 W3 R1 R2 C G H
6.7 9.62 7.3 4 7 2 0.2 3 7 9 0.4 1 4.1
Fig. 2. Measured and Simulated Reflection Coefficient.
3. Results and discussion All the measurements are done using PNA E8362B Network Analyzer. Fig. 2 shows the measured and simulated reflection coefficients of the antenna. Both the measured and simulated results are in good agreement and the slight variation is due to the fabrication tolerance. 3.1. Analysis of Electric Field, Surface Current and Polarization of the Antenna At the fundamental mode of the SIR (2.4 GHz), the E-field in the dipole ends is at maximum. These ends are electromagnetically coupled to the SIR. The electric field of bended dipole structure at 2.4 GHz is given in Fig. 3, which confirms the electrical coupling between dipole and the SIR.
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Fig. 3. Electric field distribution in the structure at 2.4GHz.
In the SIR at 2.4 GHz, the current along the Y direction on either side is antiparallel and will cancel at far field, leaving behind a net current in the X direction. At 5.2 GHz the Y components of the current on either side of the dipole is antiparallel and will cancel at far field, leaving behind a net current in the X direction. This results in the polarization of the antenna along X direction, which is experimentally verified. 3.2. Analysis of Parasitic Element & Modeling The SIR used in the proposed antenna is modeled as an open ended composite Coplanar Striplines (CPS) instead of using a microstrip transmission line model9. The symmetrical CPS has two 2mm wide strips, and the asymmetrical CPS consists of 0.2mm and 2mm wide strips, as in Fig. 4. The simulated plain wave excitation of the coplanar SIR shows a resonance at 2.2 GHz. The two important parameters of an SIR which determines the resonant frequencies are the impedance ratio k and length ratio α, given by10,
k
Z2 Z1
D
T2 T1 T 2
(1)
(2)
Fig. 4. Stepped Impedance Resonator.
The resonance of an SIR is calculated by evaluating the condition, k tan T1 * tanT 2
(3)
U. Deepak et al. / Procedia Computer Science 46 (2015) 1311 – 1316
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Here θ1 & θ2 are the electrical lengths of the SIR corresponding to the physical length l1 & l2, and Z1 & Z2 are the characteristic impedance of the two CPS lines, as given in Fig. 4. The calculated values of k and α are 0.45644 and 0.7306, respectively.
Fig. 5. Measured radiation pattern(a) at 2.4 GHz; (b) at 5.2 GHz.
Fig. 6. Measured gain and efficiency of the antenna (a) in 2.4GHz band; (b) in 5 GHz band.
3.3. Radiation Pattern, Gain and Efficiency The radiation patterns of the antenna at 2.4 GHz and 5.2 GHz are shown in the Fig. 5. The pattern is nearly omnidirectional in both the bands. The Fig. 6 depicts the gain and efficiency of the antenna. At 2.4 GHz band, it gives a nearly uniform gain with an average gain of 1.4 dBi and a peak gain of 2.6 dBi at 2.48 GHz. In the 5-6 GHz band, the average gain is 2.2 dBi with a peak gain of 3.6 dBi at 5.35 GHz. The measured peak efficiency using Wheeler Cap method11, in the lower and higher bands are 88.6% and 96.87%, respectively. The antenna shows a 2:1 VSWR bandwidth of 95 MHz in the 2.4 GHz band from 2.405 GHz to 2.5 GHz and 1.38 GHz in the 5-6 GHz band from 4.52 GHz to 5.9 GHz.
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U. Deepak et al. / Procedia Computer Science 46 (2015) 1311 – 1316
4. Conclusion A novel compact coplanar dual band antenna is proposed and investigated. The antenna resonates at 2.4 & 56GHz bands with a 2:1 VSWR bandwidth of 95 MHz and 1.38 GHz, respectively. The average gain of the small sized antenna is 1.4 dBi and 2.2 dBi at 2.4 GHz and 5 GHz band, with a peak gain of 2.6 dBi and 3.6 dBi at 2.48 and 5.35 GHz, respectively. The antenna shows a nearly omnidirectional radiation pattern at both frequency bands. The efficiency is 88.6% and 96.87% at 2.45 and 5.4 GHz, respectively.
Acknowledgements The authors acknowledge University Grant Commission (UGC) and Department of Science & Technology (DST) under Government of India for the financial support. References 1. Young Jun Cho, Yong Sun Shin, Seong-Ook Park. An internal PIFA for 2.4/5 GHz WLAN applications. Microwave conference proceedings, APMC, Suzhou, China, 2005. p. 1-3.
2. Wenjun Huang, Terence S. P See, Zhi Ning Chen. 2.4/5-GHz dual-band PIFA for portable devices. APSURSI, Pokane, Washington, USA, 2011. p. 430-433.
3. C. F. Tseng, C. L. Huang, C. H. Hsu. Microstrip fed monopole antenna with a shorted parasitic element for wideband application. Progress in Electromagnetic Research Letters 2009;7:115-125.
4. C. Y. Huang, P. Y. Chiu. Dual-band monopole antenna with shorted parasitic element. Electronics Letters 2005;41(21):1154 – 1155. 5. Hitesh Baheti, Deepak Kumar Pathak, Usha Kiran Kommuri. Broadband and high gain low profile (thin) capacitive coupled microstrip antennas for wireless applications. Annual IEEE India Conference, IIT Bombay, Mumbai, India, 2013. p. 1-5.
6. Norakamon Wongsin, Thanakarn Suangun, Chatree Mahatthanajatuphat, Prayoot Akkaraekthalin. A multiband fractal ring antenna fed by capacitive coupling. The 8th Electrical Engineering Electronics, Computer, Telecommunications and Information Technology (ECTI) Association of Thailand - Conference 2011, Khon Kaen 2011. p. 204-207. 7. Shih-Wei Chen, Deng-Yin Wang, Wen-Hua Tu. Dual-band/tri-band/broadband CPW-fed stepped-impedance slot dipole antennas. IEEE Transactions on Antennas and Propagation 2014;62(1):485-490. 8. Wen-Hua Tu, Kai Chang. Miniaturized CPW fed slot antenna using stepped impedance resonator. Antenna and propagation society international symposium, 2005. p. 351-354. 9. M. Sagawa, M. Makimoto, S. Yamashita. Geometrical structure and fundamental characteristics of microwave stepped impedance resonators. IEEE Transactions on microwave theory and technique 1997;45:1078-1085. 10. Arnaud Vena, Etenne Perret, Smail Tedjini. Chipless RFID tag using hybrid coding technique. IEEE Trans Microwave Theory Tech 2011;59:3356-3364. 11. H. A. Wheeler. The radiationsphere around a small antenna. Proc. IRE 1959;47:1325-1333.