Digital fabrication techniques gives the possibility of producing elements with very thin and precise features which could allow the modification of UHF structures to reduce ink usage while still achieving similar performance. This paper investigates the case where dipole elements are modified into Frame Dipoles by removing areas where the surface current tends to be very low

Batchelor, John C.

Parker, Edward A.

Sanchez-Romaguera, Veronica

Schubert, US

Turki, Badredin

Wünscher, Sebastian

Yeates, Stephen

Ziai, Mohamed A.

English

Kent Academic Repository

 Inkjet Fabrication of Frame Dipole FSS Badredin M.Turki1, Edward A.Parker1, John C. Batchelor1, M. Ali Ziai1, S.Wünscher2, V. Sanchez-Romaguera3,Stephen G. Yeates3, U.S. Schubert2 1School of Engineering University of Kent, Canterbury, UKj.c.batchelor@kent.ac.uk 2Laboratory of Organic and Macromolecular Chemistry, Friedrich-Schiller-Universität Jena, Jena, Germany 3Organic Materials Innovation Centre (OMIC), School of Chemistry, University of Manchester, UK Abstract—Digital fabrication techniques gives the possibility of producing elements with very thin and precise features which could allow the modification of UHF structures to reduce ink usage while still achieving similar performance. This paper investigates the case where dipole elements are modified into Frame Dipoles by removing areas where the surface current tends to be very low. Keywords; Frequency selective surfaces; Inkjet printing; Indoor radio propagation;Electromagnetic architecture; security. I.  INTRODUCTION  Wireless communication in indoor environments endures degradation in performance due to over use of the radio spectrum, especially in the unlicensed bands. Frequency selective surfaces have been considered as a means of improving wireless communication within indoor environments and have been shown to reduce co-channel interference by rejecting the interfering signals [1-2].  Inkjet printing technology is considered as a potentially useful future means of manufacturing electromagnetic designs with very fine details, especially as new printers are introduced capable of producing pico-Litre and femto-Litre sized droplets. The drop-on-demand (DoD) technology allows printing of very thin traces, in the order of a few tens of micrometers that could not be achievable with chemical etching.  Repeatable droplets (on demand) are deposited to achieve the required design dimensions which could lead to a reduction the amount of waste associated with the chemical etching process. It also allows the use of inexpensive recyclable substrate materials, which cannot be used with the conventional etching technique [3].  The performance of frequency selective screens in indoor environments has been reported in [4-5] and the performance of inkjet printed FSS showed signal rejection levels very similar to equivalent copper etched FSS [6].  This paper utilizes the thin precise features that can be achieved by inkjet printing, and introduces printed frame elements where conductors are deposited only where the surface current is likely to be maximum, at the dipole edges.  The solid and frame elements are arranged on a skewed lattice geometry [7].    II. DESIGN METHODOLOGY  The FSS arrays contained 374 patch dipoles in total, arranged in a skewed lattice format with length L and periodicity P equal to 9 and 10.4mm respectively, with horizontal spacing ܦݔ ൌ 1mm , and vertical spacing  ܦݕ ൌ2mm, as shown in Figs. 1 and 2. The dipole width w was 1mm and conductor thickness was 0.01mm.   Fig.1 Skewed lattice solid dipole FSS   Two equivalent Frame dipole FSS were made with frame widths of ܨݓ ൌ 0.2 & 0.15 ݉݉ respectively.    Fig.2 Skewed lattice frame dipole FSS   The FSS was etched onto a polyester substrate of 0.045mm thickness and relative permittivity ߳௥ ൌ 3.5  with loss tangent  ൌ 0.02 . The physical size of the array was  280 ൈ190 mm2. LDx Dy Fw 2014 Loughborough Antennas and Propagation Conference (LAPC) 10 - 11 November 2014, UK978-1-4799-3662-5/14/$31.00 (C)2014 IEEE 347 In addition, 2 FSS screens were also produced by inkjet printing using a nanoparticle silver ink: 1 Solid and 1 Frame, with the same L and P, and vertical and horizontal spacing, but with dipole width w=0.4mm and Fw=70 µm, as shown in Fig.3 (a and b).   (a) Solid dipoles   (b) Frame dipoles Fig.3 Inkjet printed FSS III. RESULTS A. Transmission response (S21) The measured transmission responses (S21) of the chemically etched and inkjet printed FSS are shown in Fig.4 and Fig.5 respectively.    Fig.4 Chemically etched FSS; Transmission response (S21)   The resonant frequency of the frame dipole FSS is less than the solid dipole FSS by about 300 and 450MHz for frame widths of 0.2 and 0.15 mm respectively.   Fig.5 Inkjet printed FSS; Transmission response (S21)   The resonant frequency of the inkjet printed frames is less than the inkjet solid dipoles by only 50MHz, as shown in Fig.5.  B. Current distribution  Fig.6 shows the surface current across the solid and frame dipoles; red shows that current is maximum and blue is minimum.    (a) Solid dipoles    (b) Frame dipoles Fig.6 Surface current across the dipole elements; red shows that current is maximum and blue is minimum.  IV. DISCUSSION AND CONCLUSIONS Inkjet printing costs for producing large FSS arrays could be reduced by printing only dipole elements as outer frames where the current is maximum. This could save up to 50% of the amount of ink used compared to the solid complete elements, while still achieving a very good reflectivity of more than the 20dB benchmark  within the operating frequency band [8]. With some design modification, the resonant frequency could be adjusted to meet the solid counterpart, while still saving ink.  -40-35-30-25-20-15-10-5010 11 12 13 14 15 16 17 18 19 20S21-dBFrequency GHzSolid dipolesFrame dipoles Fw=0.15mmFrame dipoles Fw=0.2mm-30-25-20-15-10-508 9 10 11 12 13 14 15 16 17 18S21-dBFrequency GHzSolid dipolesFrame dipoles348 The difference in the resonance frequency is less in the case of the printed FSS, as the ratio between dipole width and frame width is greater for the etched FSS. ACKNOWLEDGMENT The authors wish to acknowledge the contribution of the UK EPSRC in funding this research through grant EP/J000086/1.  REFERENCES [1] M. Philippakis, C. Martel, D. Kemp, S. Appleton, R. Pearson, and E.A. Parker, “Application of FSS Structures to Selectively Control the Propagation of signals into and out of buildings, Annex 3,” Ofcom ref AY4464, pp. 1–54, 2004. [2] A. H. Wong, M. J. Neve, and K. W. Sowerby, “Performance analysis for indoor wireless systems employing directional antennas in the presence of external interference,” 2005 IEEE Antennas Propag. Soc. Int. Symp., vol. 1A, pp. 799–802, 2005. [3] V. Sanchez-Romaguera, M. A. Ziai, D. Oyeka, S. Barbosa, J. S. R. Wheeler, J. C. Batchelor, E. A. Parker, and S. G. Yeates, “Towards inkjet-printed low cost passive UHF RFID skin mounted tattoo paper tags based on silver nanoparticle inks,” J. Mater. Chem. C, vol. 1, no. 39, p. 6395, 2013. [4] E. A. Parker, J. C. Batchelor, R. Chiang, A. G. Williamson, B. Sanz-Izquierdo, M. J. Neve, and K. W. Sowerby, “Frequency selectively screened office incorporating convoluted FSS window,” Electron. Lett., vol. 46, no. 5, p. 317, 2010. [5] E. A. Parker, J.-B. Robertson, B. Sanz-Izquierdo, and J. C. Batchelor, “Minimal size FSS for long wavelength operation,” Electron. Lett., vol. 44, no. 6, p. 394, 2008. [6] J. C. Batchelor, E. A. Parker, J. A. Miller, V. Sanchez-Romaguera, and S. G. Yeates, “Inkjet printing of frequency selective surfaces,” Electron. Lett., vol. 45, no. 1, p. 7, 2009. [7] S. M. A. Hamdy and E. A. Parker, “Influence of lattice geometry on transmission of electromagnetic waves through arrays of crossed dipoles,” IEE Proc. H Microwaves, Opt. Antennas, vol. 129, no. 1, p. 7, 1982. [8] B. M. Turki, E. A. Parker, J. C. Batchelor, M. A. Ziai, S. G. Yeates, and V. Sanchez-Romaguera, “Influence of defective elements on performance of frequency selective surfaces,” Electron. Lett., vol. 49, no. 17, pp. 1054–1055, Aug. 2013.   349

Frequency selectively screened office incorporating convoluted FSS window,”

Influence of defective elements on performance of frequency selective surfaces,”

Influence of lattice geometry on transmission of electromagnetic waves through arrays of crossed dipoles,”

Inkjet printing of frequency selective surfaces,”

Minimal size FSS for long wavelength operation,”

Performance analysis for indoor wireless systems employing directional antennas in the presence of external interference,”

Towards inkjet-printed low cost passive UHF RFID skin mounted tattoo paper tags based on silver nanoparticle inks,”

Inkjet Fabrication of Frame Dipole FSS

http://kar.kent.ac.uk/46012/1/IJ%20fab%20of%20frame%20dipole%20FSS.pdf

Inkjet Fabrication of Frame Dipole FSS

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