Analysis of Rectangular Notch Antenna for Dual-Band Operation

Transcription

1 Engineering, 00,, 9-96 doi:0.436/eng.00.0 Publised Online February 00 (ttp:// Analysis of Rectangular Notc Antenna for Dual-Band Operation Abstract Rajes Kumar Viswakarma, Sanjay Tiwari Scool of Studies in Electronics, Pt. Ravisankar Sukla University, Raipur, Cattisgar (C.G) Received August 7, 009; revised September 4, 009; accepted September 0, 009 In tis paper a design of single layer rectangular notc microstrip antenna for dual-band is proposed and experimentally investigated. Tis antenna is excited by microstrip line. Direct microstrip coupling wit proper matcing transformer as been used. Design is made for optimized notc dimension for two resonant frequencies. Tese resonance frequencies cange wit te variation in lengt and widt of te notc. Te input impedance and VSR ave been measured wit te elp of Network analyzer. It is found tat te input impedance and VSR depends variation in lengt and widt of te notc microstrip antenna. Keywords: Microstrip Antenna, Notc Antenna, Dual-Band Antenna, Matcing Transformer. Introduction Microstrip antennas are receiving muc attention at present because tey offer many practical advantages suc as small size, ligtweigt, low cost and a low profile ease of fabrication and integration wit RF devices []. In te recent years, radar, satellite communication wireless networks suc as global positioning system (GPS), syntetic aperture radar (SAR), often require dual frequency patc antenna to avoid te use of two different antennas. An ideal dual-frequency antenna sould ave similar performance in bot operating modes. One of te principal disadvantages of suc antenna is narrow bandwidt. Recently several papers [ 4] ave been publised treating notc microstrip antenna to acieve dual band caracteristics. Te major limitation of microstrip antenna lies in its limited bandwidt. Several metods ave been reported in te literature [5 7] to improve te bandwidt of te microstrip antenna suc as ticker substrate use of parasitic elements, proximity coupling of te feed line, and stacked microstrip antennas. Recently Palit [8] et al as reported a microstrip antenna by properly cutting a notc inside te radiating element. Tis properly fields enoug B for dual band frequency and broadband operation. In tis case dual resonance is obtained by a dipole loaded notc antenna [9], notc loaded patc antenna [0], and notc triangular microstrip antenna [] at te radiating edge of patc. Te idea is extended by designing variation of lengt and widt of te notc antenna. In te present work, and te ect of notc lengt and widt on te resonance frequencies ave been carried out.. Feeding Network Te microstrip line metod is easy to fabricate simple to model and matc by controlling te inset cut position in te patc in te (Figure ). Matcing transformers transform te input resistance of patc to 50 om coaxial cable. Te ratio / of te microstrip line used for feeding network can patc to found as to follows. Te ective dielectric constant cange wit te ratio of strip widt to tickness as [] ε ε 0.5 r r 0 ε () w wen ten define Zo Z ε () were Z is te strip impedance. Te formula for Z 0 = for / can be given as Z 0 8H w Z 0 60In for (3) w 4 0π for e can find te impedance wen / is known but most design problem required te oterwise i.e. give Z (4)

2 9 R. K. VISHAKARMA ET AL. L L Notc g / 4 Feed Point using te new we find and a new value of Z 0. A good starting value for te iteration is found from 0 98 (9) Z 0 Iteration metod as been done from Equations to 9 and converges in a few cycles. 3. Measurement Tecniques Figure. Te notc rectangular microstrip antenna. fin /, So Equations () and (3) or (4) in an interactive process are used to find / wen / =, e first find Z 0 of / = and ten and impedance are calculated as. and ε r ε r ε (5) Z Z o o Z Z () (6) were Z If Z 0 is greater tan Z 0 () ten / using is less or equal Case en ten Z0 Z0 exp exp 8 (7) starting wit we solve for using tis value. e find from equation. Ten it is substituted back in 3 to find a new value of Case wen we use Newton s metod of te finding function zero to form an integration equation. Let X= new X X 6 0 X.4 X Z X X (8) Te network analyzer is used to perform te measurement. Glass epoxy substrate wit tickness of =.59 mm and approximate dielectric constant r 4. 5 was used. Several patces were fabricated wit te variation of notc lengt and widt. Te variation of lower and upper resonance frequencies wit notc lengt and widt are sown in te Figures 6 and 6. Te variation of upper and lower resonance frequencies ratio (f /f ) wit notc lengt and widt are sown in te Figures 7 and 7. Te resulting data are sown in Tables to. 4. Design Procedure and Design Parameters Te actual dimension of te antenna designed is magnified two times in order to acieve te desired accuracy in te final design. Te antenna sape of enlarged dimension is taken times in rubylit film. Tis enlarge sape is poto reduced using a ig precision camera to produce a ig-resolution negative, wic is later used for exposing te poto resist. Te laminate is cleaned to insure proper adesion of te poto resist and necessary resolution in te poto development process. Te poto resist is now applied to bot sides of te laminate using a laminator. After wards, te laminate is allowed to stand to normalize to room temperature prior to exposure and development. Te potograpic negative is now eld in a very close contact wit te cover seet of te applied Table. Variation of resonance frequencies wit notc lengt for a given widt =0mm. Lengt (mm) (f ) GHz (f ) GHz Frequencies ratio (f /f ) GHz Table. Variation of resonance frequencies wit notc widt for a given lengt =mm. idt (mm) (f ) GHz (f ) GHz Frequencies ratio (f /f ) GHz

3 R. K. VISHAKARMA ET AL. 93 poto resist, to assure te fine line resolution required wit exposure to proper wave lengt ligt, polymerization of te exposed poto resist occurred, making it insoluble in developer solution. Te backside of te antenna is completely exposed witout a mask, since te copper foil is retained to act as a ground plane. Te protective cover seet of te poto resist is removed and te antenna is now developed in developer, wic remove te soluble poto resist material. Ten te antenna is etced. Visual inspection is used to assure proper etcing. Ten excess poto resist is removed using a stripping solution. For stack antenna, te passive antenna are made wit single side PCB same as done for active antenna. Te various design parameters of te antenna are as follows: Substrate material used Glass Epoxy Tickness of te dielectric substrate =.59 mm Relative permittivity of te substrate r = 4.5 Design frequency f = 3.0 GHz Tickness of te patc t = 0.008cm and designed values were calculated using te standard equations, wic are Te widt of te rectangular patc = 30.5 mm Te lengt of te rectangular patc L = 3.04 mm Te lengt of te notc L =.0 mm to 5 mm at fixed widt = 0mm Te widt of te notc = 6 mm to 0 mm at fixedlengt = mm 5. Discussion of Results ) Te variation of input impedance wit frequency for different notc lengt for a given widt is sown in Figures to (d). It is observed tat notc microstrip antenna sows dual resonance in wic lower and upper resonance frequencies increases wit increasing notc lengt from mm to 5mm. ) Te variation of input impedance wit frequency for different notc widt for a given lengt is sown in Figures 3 to 3(d). It is observed tat notc microstrip (c) (d) Figure. Variations of input impedance wit frequency for notc lengt=mm at widt =0mm; Variations of input impedance wit frequency for notc lengt=3mm at widt =0mm; (c) Variations of input impedance wit frequency for notc lengt = 4mm at widt =0mm; (d) Variations of input impedance wit frequency for notc lengt=5mm at widt =0mm.

4 94 R. K. VISHAKARMA ET AL. antenna sows dual resonance in wic lower resonance frequency increases wit increasing notc widt from 6mm to 9mm,were as upper resonance is all most constant wit varying notc widt. (d) Figure 3. Variations of input impedance wit frequency for notc widt = 6mm at lengt =mm; Variations of input impedance wit frequency for notc widt = 7mm at lengt =mm; (c) Variations of input impedance wit frequency for notc widt = 8mm at lengt =mm; (d) Variations of input impedance wit frequency for notc widt = 9mm at lengt =mm. 3) Te variation of VSR wit frequency for different notc lengt for a given widt are sown in Figures 4 to 4(d) It is observed tat te value of VSR corresponding to lower resonance frequency is decreased from.7 to. wit increasing notc lengt were as (c) Figure 4. Variations of VSR wit frequency for notc lengt = mm and 3 mm notc at widt =0 mm; Variations of VSR wit frequency for notc lengt = 4 mm and 5 mm at notc widt =0 mm.

5 R. K. VISHAKARMA ET AL. 95 corresponding to te upper resonance frequency te value of VSR is increased from.0 to.69. 4) Te variation of VSR wit frequency for different notc widt for given lengt are sown in Figures 5 to 5(d). It is observed tat te value of VSR corresponding to lower resonance frequency is decreased from. to.08. 5) Te variation of resonance frequencies wit notc dimensions is sown in te Figures 6 to 6. It is observed tat bot resonance frequencies are increased wit notc dimensions. 6) Te variation of resonance frequency ratio f /f wit notc dimensions is sown in te Figures 7 to 7. It is observed tat bot resonance frequencies are increases wit notc dimensions. Frequencies (GHz) Notc widts (mm) 8 9 Figure 6. Variations of resonance frequencies wit notc lengts for a given widt; Variations of resonance frequencies wit notc widt for a given lengt. f f 3 f /f.5 (f/f) (GHz) Notc lengts (mm) 4 5 f /f Figure 5. Variations of VSR wit frequency for notc widt = 6 mm and 7 mm at notc lengt = mm; Variations of VSR wit frequency for notc widt = 8 mm and 9 mm at notc lengt = mm. 4.7 (f/f) (GHz) Frequencies (GHz) Notc Lengt (mm) 4 5 f f 6 7 Notc widts (mm) 8 9 Figure 7. Variation of frequency ratios (f /f ) wit notc lengt for a given widt; Variation of frequency ratios (f/f) wit notc widt for a given lengt. 6. Acknowledgment Te autors would like to tank Professor Arun Kumar and Sri R. K. Malaviya of te Space Application Centre, Indian Space Researc Organization Amedabad, for

6 96 R. K. VISHAKARMA ET AL. providing te measurement facilities. 7. References [] I. J. Bal and P. Barta, Microstrip Antenna, Artec House, Massacusetts, USA, 980. [] S. K. Polit and A. Hamad, Dual-band notc microstrip antenna for mobile communications, Asia Pacific Microwave Conference Proceeding New Deli, Vol., pp , pp. 7 0, December 996. [3] H. Nakano and K. Vicien, Dual-frequency square patc antenna wit rectangular notc, Electronics Letters, Vol. 5, No. 6, pp , August 989. [4] L. I. Basilio, A. K. Jery, T. illiams, and A. S. Long, Te dependence of te input impedance on feed position of probe and microstrip line fed patc antenna, IEEE Transactions on Antennas Propagation, Vol. AP 49, pp January 00. [5] E. Cang, S. A. Zong, and. F. Ricards, An experimental investigation of electrically tick rectangular microstrip antenna, IEEE Transactions on Antennas Propagation, Vol. AP 34, pp , 986. [6] D. M. Pozar and B. Kaufman, Increasing te band widt of a microstrip antenna by proximity coupling, Electronics Letters, Vol. 3, No. 8, pp , April 987. [7] H. F. Pues and A. V. V. De Capelle, An impedance matcing tecnique increasing te band widt of microstrip antenna, IEEE Transactions on Antenna and Propagation, Vol. AP 37, No., pp , November 989. [8] S. K. Palit Broad band microstrip antenna design, Cinese Journal of radio science, August 995. [9] C. L. Li, C. F. en, and Y. K. Ling, Dual-band dipole-loaded notc antenna, Te 3rd International Tecnical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 008), pp. No [0] Sivnarayan and B. R. Visvakarma, Analysis of notc loaded patc for dual-band operation, Indian journal of Radio and Space Pysics, Vol. 35, pp , 006. [] J. Y. Hui, and Z. S. si, Notc triangular microstrip antenna for dual-frequency operation, Journal of Sangai University, pp. No , 003. [] M. V. Scneider, Microstrip lines for microwave integrated circuits, Bell System Tecnology Journal, Vol.48, pp , May June 969.