yesA frequency tuned antenna has been designed to meet the coverage requirements of the DCS, PCS, UMTS and WLAN bands. The antenna consists of a main patch, and a planar inverted L (PIL) slot. The radiator patch is fed, and shorted, using simple feed lines with broadband characteristics. The handset represents the finite ground plane, and a varactor diode is mounted across the middle of the slot for tuning purposes. Initial tuning was obtained by placing lumped capacitors, instead of the varactor, over the radiator. Good agreement is obtained between the predicted and measured input return loss, gain and radiation pattern over the tuned frequency range.MSCR

Abd-Alhameed, Raed A.

Abusitta, M.M.

Alhaddad, A.G.

Elfergani, Issa T.

Hraga, Hmeda I.

Hussaini, Abubakar S.

Rodriguez, Jonathan

See, Chan H.

YesA frequency tuned antenna has been designed to meet the coverage requirements of the DCS, PCS, UMTS and WLAN bands. The antenna consists of a main patch, and a planar inverted L (PIL) slot. The radiator patch is fed, and shorted, using simple feed lines with broadband characteristics. The handset represents the finite ground plane, and a varactor diode is mounted across the middle of the slot for tuning purposes. Initial tuning was obtained by placing lumped capacitors, instead of the varactor, over the radiator. Good agreement is obtained between the predicted and measured input return loss, gain and radiation pattern over the tuned frequency range.MSCR

Abd-Alhameed, Raed

Bradford Scholars

 The University of Bradford Institutional Repository http://bradscholars.brad.ac.uk This work is made available online in accordance with publisher policies. Please refer to the repository record for this item and our Policy Document available from the repository home page for further information. To see the final version of this work please visit the publisher’s website. Where available access to the published online version may require a subscription. Author(s): Elfergani, I. T. E., Hussaini, A. S., Abd-Alhameed, R. A., See, C. H., Abusitta, M. M., Hraga, H. I., Alhaddad, A. G. and Rodriguez, J. Title: Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range. Publication year: 2011 Conference title: Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, March 20-23, 2011. Publisher:  The Electromagnetics Academy. Link to original published version:  http://www.piers.org/piersproceedings/piers2011MarrakeshProc.php Citation: Elfergani, I. T. E., Hussaini, A. S., Abd-Alhameed, R. A., See, C. H., Abusitta, M. M., Hraga, H. I., Alhaddad, A. G. and Rodriguez, J. (2011). Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range. In: Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, March 20-23, 2011. Cambridge, MA: The Electromagnetics Academy, pp 443-447. Copyright statement: © 2011, The Electromagnetics Academy. Reproduced in accordance with the publisher's self-archiving policy. 1Frequency Tuned Planar Inverted F Antenna with L Shaped SlitDesign for Wide Frequency RangeI. T. E. Elfergani1, Abubakar Sadiq Hussaini1, 2, R. A. Abd-Alhameed1, C. H. See1,M. M. Abusitta1, H. I. Hraga1, A. G. Alhaddad1, and Jonathan Rodriguez21Mobile and Satellite Communications Research Centre, University of BradfordBradford, West Yorkshire, BD7 1DP, UK2Instituto de Telecomunicac¸o˜es, Aveiro, PortugalAbstract— A frequency tuned antenna has been designed to meet the coverage requirementsof the DCS, PCS, UMTS and WLAN bands. The antenna consists of a main patch, and aplanar inverted L (PIL) slot. The radiator patch is fed, and shorted, using simple feed lineswith broadband characteristics. The handset represents the finite ground plane, and a varactordiode is mounted across the middle of the slot for tuning purposes. Initial tuning was obtainedby placing lumped capacitors, instead of the varactor, over the radiator. Good agreement isobtained between the predicted and measured input return loss, gain and radiation pattern overthe tuned frequency range.1. INTRODUCTIONPIFA designs tend to be low profile, light weight and efficient space filling structures, and as such,are particularly attractive for handset and terminal applications. Conventional PIFA designs haveconstrained bandwidth; however, it is possible to realize novel structures which are electronicallytunable over most of the wireless communication bands. Tunable multi-functional handset modulesemploy the same basic design aims to provide favorable trade-offs in terms of volume, weightand performance. Many interesting PIFA, and more general tuned printed antennas, have beenproposed [1]. Various switching technologies, such as RF switches, MEMs switches, PIN diodesand varactor diodes have been used in reconfigurable antenna designs [2–4]. The varactor diodesin particular seem to offer a rich possibility for future designs over a wide frequency range, due totheir excellent DC voltage controlled reactance property.The increasing trend for slimmer, highly integrated mobile handsets and terminals, operatingover several distinct and over-lapping frequency bands, has created a need for reconfigurable (tuned)antenna designs [5]. However, this trend towards slimmer, more space efficient integrated designs,poses a significant problem for the antenna designer. The trade-off between small antenna size,adequate bandwidth, and high efficiency, creates a difficult competing multi-objective optimization,which is also subject to fundamental physical constraints. To some extent this coverage problemcan be solved by using multiple antennas, but the design of such an antenna module would addmutual coupling effects to an already substantial list of physical constraints.Planar inverted F antennas (PIFA) may be modified to operate over multiple frequency bands byusing, e.g., parasitic elements, and/or by the formation of several surface current paths through theintroduction of slots in the radiator element. Recently, PIFA structures providing comprehensivecoverage of the frequency ranges of six operating standards have been presented [6]. A commonapproach to tuning the operating frequency of a PIFA is to reconfigure a short circuit connectionwith an external tuning circuit. This has been used in single and dual band designs [7, 8]. Otherreported tuning methods include the use of adjustable reactive components between the PIFA patchand a ground plane [9, 10], and switched tuning stubs, which have been applied in both single anddual band designs [3, 11].2. ANTENNA DESIGN CONCEPTThe design optimization for this study requires an antenna structure compatible with contemporaryhandset chassis dimensions. The structural and lumped element parameters were simulated usingthe general electromagnetic analysis packages HFSS [12]. The optimization was tracked in terms ofthe antenna return loss, radiation patterns and power gain. Initial frequency tuning is tested andevaluated by placing lumped capacitors in the range of 0.5 to 3.3 pF along the slot of the radiator.2This process is equivalent to replace the varactor operation. The design was further constrainedby the impedance matching requirements covering a frequency range comprising the DCS, PCS,UMTS and W-LAN bands.The prototype radiator patch is suspended over a 50mm× 80mm (Wboard, Lbroad) ground planewith a 2mm× 7mm shorting pin, and the antenna is fed by means of a vertical plate, of maximumheight 6.5mm and width 2mm as shown in Fig. 1. It is also connected to the feeding probe throughthe slot in the ground plane for which the effective substrate is considered air. The rectangularpatch dimensions, (Lant, Want), are 14mm× 50mm. The L-slot has a uniform width (Ss) of 1mm,and the lateral dimensions, (LS , WS , and Wgap), are 8mm, 17.5mm, and 15mm.3. IMPACT OF THE LOADING ON THE ANTENNAThe impact of the loading capacitance on overall antenna performance, including the return loss,gain and radiation pattern needs to be investigated both in simulation, and through performanceassessments on the physical prototype. For comparison purposes in simulation, we require a fullycharacterized reference antenna which omits the varactor; this structure resonates at 2.47GHz (seeFig. 2). A loading capacitor with values selected from {0.5–3.3}pF is placed over the slot radiatorin a fixed location, making the antenna resonate over wide range 1.75 ≤ f0 ≤ 2.4GHz. In thefirst instance the tuning is investigated via a lumped (ceramic) capacitor, instead of a varactor,therefore the DC bias and circuit parasitic effects are excluded. The effects of lumped capacitorshave been tested on the working prototype, in order to find out how the loaded capacitors couldaffect the antenna performance; and the optimal location on the slot ‘arm’. The working prototypein Fig. 3 was tested without the bias circuit. The loading capacitor was varied over [0.5, 3.3] pF,(a) (b)Figure 1: Basic antenna structure. (a) Top view, (b) 3D.1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5-35-30-25-20-15-10-5Frequency in GHzReturn loss in dB  Antenna without LoadingFigure 2: Return loss of antenna prototype, withoutloading capacitor present.Figure 3: The prototype (loaded) antenna structure.3which was found to be sufficient to control the antenna response.4. SIMULATED AND MEASURED RESULT DISCUSSIONSThis tuned antenna design relies on the introduction of the L-shaped slot on the radiator arm,and a varactor diode is attached to a location over the slot to achieve the required tuning. As thecapacitance is varied, tuning is exhibited over a wide frequency band. The first resonance occursat 2400MHz, and then shifts, to the lower frequency band of 1750MHz. However, the resonantfrequencies are not only be controlled by changing the value of applied capacitance of the varactor,but also by its location along the slot.Figure 4 illustrates the simulated and the measured return loss, the simulated was generated byusing HFSS software package while the measured was obtained using a HP 8510C VNA. Fivefrequencies were selected: 1750MHz, 1850MHz, 2040MHz, 2200MHz, and 2400MHz, respec-tively. The results show a satisfactory agreement between the results achieved by both simulationand measurement. It can be seen that the antenna is capable of covering the frequency rangesof digital cellular system (DCS: 1710–1880MHz), personal communication service (PCS: 1850–1990MHz), universal mobile telecommunications system (UMTS: 1900–2200MHz), wireless LAN(WLAN: 2400MHz).1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5-45-40-35-30-25-20-15-10-5Frequency in GHzReturn Loss in dB  Cv=0.5pf MeasuredCv=1pf   MeasuredCv=1.5pf MeasuredCv=2.4pf MeasuredCv=3.3pf MeasuredCv-0.5pf SimulatedCv=1pf   SimulatedCv=1.5pf SimulatedCv=2.4pf SimulatedCv=3.3pf SimulatedFigure 4: Measured and simulated return loss.1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.51.522.533.544.555.5Frequency in GHzGain in dBi  Measured gainSimulated gainFigure 5: Simulated and measured antenna gains.-25-20-15-10-50 3021060240902701203001503301800+X+Z-25-20-15-10-50 3021060240902701203001503301800+Z+Y-25-20-15-10-50 3021060240902701203001503301800+X+Z-25-20-15-10-50 3021060240902701203001503301800+Y+Z2400 MHz2200 MHz4-25-20-15-10-50 3021060240902701203001503301800+Z+X-25-20-15-10-50 3021060240902701203001503301800+Y+Z-25-20-15-10-50 3021060240902701203001503301800+X+Z-25-20-15-10-50 3021060240902701203001503301800+Y+Z2040 MHz1750 MHz(a) (b)Figure 6: Measured and simulated normalised radiation field patterns of the proposed antenna for variousoperating frequencies. (a) xz plane, (b) yz plane. ‘ooo’: Simulated co-polar, ‘***’: Simulated cross-polar,‘-----’: Measured co-polar, ‘- - - -’: Measured cross-polar.Figure 5 shows the measured and simulated gains of the proposed antenna across the 2400MHz,2200MHz, 2040MHz, 1850MHz and 1750MHz bands. It can be seen that the maximum measuredgains values for the mentioned five bands were 1.6 dBi, 3.8 dBi, 3.2 dBi, 2.5 dBi, and 5.2 dBi, respec-tively. The maximum simulated gains over the five bands were 3.3 dBi, 3.4 dBi, 3.5 dBi, 3.55 dBi,and 4.1 dBi, respectively.The simulated and measured radiation patterns are quite similar, and are shown in Fig. 6. Theslight variations in these field patterns may be attributed in inaccuracies introduced during fabri-cation, and construction, the patterns are essentially omni-directional. The far field measurementswere performed in an anechoic chamber, the simulated patterns were generated using HFSS. Twopattern cuts were selected for three operating frequencies covering the whole designated bandwidth;radiation patterns in the xz-plane and yz-plane at 2400MHz, 2200MHz 2040MHz, and 1750MHzwere measured.5. CONCLUSIONSIn this paper, a PIFA-tuned antenna is proposed and validated through practical measurement.By carefully selecting different sets of optimal structural and tuning parameters, basically, thisantenna has wide frequency range operation that covers DCS, PCS, UMTS, and WLAN thatmakes it suitable for multifunctional mobile handsets or terminals. By attaching a varactor diodeon the L-slot, the proposed antenna achieved more wideband frequency coverage. In addition, theantenna size was small enough to be fit within the mobile handsets. The proposed frequency-tuningconcept can be extended to more complex PIFA structures as well as other antenna types. Insteadof the varactor diode, RF diode switch, or RF MEMS components may be used to further improvethe electrical performance and functionality of the antenna.REFERENCES1. Wu, J. F., C. J. Panagamuwa, P. McEvoy, J. C. Vardaxoglou, and O. A. Saraereh, “Switch-ing a dual band PIFA to operate in four bands,” IEEE Antennas and Propagation SocietyInternational Symposium, 2675–2678, 2006.52. Chiu, C. W. and F. L. Lin, “Compact dual-band PIFA with multi-resonators,” ElectronicsLetters, Vol. 38, No. 12, 538–540, Jun. 2002.3. Behdad, N. and K. Sarabandi, “A varactor-tuned dual-band slot antenna,” IEEE Transactionson Antennas and Propagation, Vol. 54, No. 2, Part 1, 401–408, Feb. 2006.4. Panaia, P., C. Luxey, G. Jacquemod, R. Staraj, G. Kossiavas, L. Dussopt, F. Vacherand, andC. Billard, “MEMS-based reconfigurable antennas,” IEEE Int. Symp. on Industrial Electronics,Vol. 1, 175–179, 2004.5. Lindberg, P., “Wide-band active and passive antenna solutions for hand held terminals,” Ph.D.Dissertation, Uppsala University, Sweden, Feb. 2007.6. Park, H., K. Chung, and J. Choi, “Design of a planar inverted-F antenna with very wideimpedance bandwidth,” IEEE Microw. Wireless Comp. Lett., Vol. 16, No. 3, 113–115,Mar. 2006.7. Louhos, J. P. and I. Pankinaho, “Electrical tuning of integrated mobile phone antennas,” Proc.Antenna Applications Symp., 69–97, Monticello, IL, 1999.8. Karmakar, N. C., “Shorting strap tunable stacked patch PIFA,” IEEE Transactions on An-tennas and Propagation, Vol. 52, No. 11, 2877–2883, Nov. 2004.9. Panayi, P. K., M. O. Al-Nuaimi, and I. P. Ivrissimtzis, “Tuning techniques for planar inverted-Fantenna,” IEEE Electron. Lett., Vol. 37, No. 16, 1003–1004, Aug. 2001.10. Karmakar, N. C., “Shorting strap tunable stacked patch PIFA,” IEEE Transactions on An-tennas and Propagation, Vol. 52, No. 11, 2877–2883, Nov. 2004.11. Oh, S. K., H. S. Yoon, and S. O. Park, “A PIFA-type varactor-tunable slim antenna with apil patch feed for multiband applications,” IEEE Antennas and Wireless Propagation Letters,Vol. 6, 103–105, 2007.12. Ansoft High Frequency Structure Simulator v10 Uses Guide, CA, USA.

Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range

Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range.

Frequency Tuned Planar Inverted F Antenna with L Shaped Slit Design for Wide Frequency Range.

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