Improved Shield Design for Split-Ring Resonator Tahir Ejaz, Syed Afaq Ali Shah, Hamood Ur Rahman, Tahir Zaidi Department of Electrical Engineering, College of Electrical & Mechanical Engineering, National University of Sciences & Technology (NUST), Islamabad, Pakistan. tahir.ejaz@ceme.nust.edu.pk, ali.shah82@hotmail.com, hamood@ceme.nust.edu.pk, tahirzaidi@ceme.nust.edu.pk Abstract—Shield or cavity around split-ring resonators is used for enhancing its output performance. Shield parameters which influence resonator performance include dimensions, material, electrical and mechanical properties. Performance is generally measured in terms of quality factor and resonant frequency. This paper presents an approach for designing a shield for attaining better quality factor. Shields have been modeled around predesigned split-ring resonators. Various aforesaid parameters were used for obtaining improved values of performance parameters. These parametric values were utilized to design a new shield. Developed algorithm was verified for the correctness of results. Keywords— Quality factor, shield, simulation, split-ring resonator. I. INTRODUCTION Quality (Q) factor is an important figure of merit in various application fields. Benefits of improved Q factor include better selectivity [1], increased permittivity sensing [2], longer coherence times [3] etc. A number of techniques have been investigated to increase Q factor of various components [1], [2], [4]. Yet there is a dire need to improve this important parameter pertaining to other components and achieve benefits in relevant field. Split-ring resonator (SRR) [5] also known as loop-gap resonator (LGR) [6]–[8] or open-loop resonator [9] is used in filters, oscillators, frequency meters, tuned amplifiers and other applications. SRRs are characterized with low phase noise, moderate Q factor, low cost and ease of fabrication. A number of design equations are available for quantifying output parameters [5]–[8]. SRR performance is enhanced in terms of Q factor, stability and noise rejection when it is enclosed in a shield or cavity. Q factor is affected by conductivity of shield material [10]. Various parameters like dimensions, material, electrical and mechanical properties were varied while designing an effective shield for SRR. Different sets of performance parameters like resonant frequency and Q factor were also observed. These observations motivated to explore various parameters for designing improved shield for SRR. In this work improved Q factor has been obtained through optimizing geometric dimensions of shield by using an algorithm developed for parameterization. II. PREDESIGNED MODELS A SRR in its simplest form is shown in figure 1 [6], [7], [11]. A cylindrical resonator with a longitudinal gap is enclosed inside a shield or cavity. SRR shown in the figure can be considered as a single turn inductor connected with a gap capacitor [9]. Various forms of SRRs have been designed including planar forms [9], geometrical shapes [12], multiple rings [13], etc. Fig. 1. The split-ring resonator and cross-sectional view Three predesigned SRR design structures were used [11], [14], [15] to study the effect of shield on resonant frequency and Q factor. These SRR designs have been devised/used for design formulations, calculations, simulations and applications. Table I presents design parameters used for different structures. Inner radius of shield for design ‘C’ [15] has been selected with provided design guidelines [6], [7]. TABLE I. DESIGN PARAMETERS Parameters SRR Designs A [11] B [14] C [15] Inner radius of shield ‘R0’ (mm) 18 12 20 Inner radius of resonator ‘r0’ (mm) 10 3 13 Width of resonator ‘W’ (mm) 1 3 2 Length of resonator ‘Z’ (mm) 10 3 5 Gap of resonator ‘t’ (mm) 1 0.4 6 III. SIMULATION Simulation models were developed for three design structures [16]. Additional parameters were provided including shield and resonator material, shield height (in the direction of SRR length) and its wall thickness. Several materials can be used for formulation of shield and resonator [7], [14]. Copper was used for SRRs whereas cylindrical shields were designed using aluminum. Shield height should be as large as possible whereas shield radius should be much smaller than the resonant wavelength [6], [7]. Design structure of SRR enclosed in shield is shown in figure 2. Design parameters for analysis are presented in table II. ISBN: 978-1-4799-5679-1 ©2015 IEEE 207 Proceedings of The Third International Conference on Technological Advances in Electrical, Electronics and Computer Engineering, Beirut, Lebanon 2015