Two-Stage Design Method for Enhanced Inductive Energy Transmission with Q-Constrained Planar Square Loops

Abstract

Q-factor constraints are usually imposed on conductor loops employed as proximity range High Frequency Radio Frequency Identification (HF-RFID) reader antennas to ensure adequate data bandwidth. However, pairing such low Q-factor loops in inductive energy transmission links restricts the link transmission performance. The contribution of this paper is to assess the improvement that is reached with a two-stage design method, concerning the transmission performance of a planar square loop relative to an initial design, without compromise to a Q-factor constraint. The first stage of the synthesis flow is analytical in approach, and determines the number and spacing of turns by which coupling between similar paired square loops can be enhanced with low deviation from the Q-factor limit presented by an initial design. The second stage applies full-wave electromagnetic simulations to determine more appropriate turn spacing and widths to match the Q-factor constraint, and achieve improved coupling relative to the initial design. Evaluating the design method in a test scenario yielded a more than 5% increase in link transmission efficiency, as well as an improvement in the link fractional bandwidth by more than 3%, without violating the loop Q-factor limit. These transmission performance enhancements are indicative of a potential for modifying proximity HF-RFID reader antennas for efficient inductive energy transfer and data telemetry links.

Dual-Band Resonator Designs for Near-Field Wireless Energy Transfer Applications

“…Since the design is based on multi-coil mode, compromise should be made in selecting optimum separation distance between outermost side length of loop operating at f 1 and f 2 . The relationship between optimal transfer distance, z op_fn , and outermost side length of loop, d o_f1,f2 , at maximum excited magnetic field derived in [58] for a square spiral resonator yields:…”

Printed Spiral Resonator for Displacement-Tolerant Near-Field Wireless Energy Transfer

“…By taking precedence of space circumscription comprising of width and length of substrate as well as adequate length for SubMiniature Version A (SMA) connection, the outer side length is predetermined at 52 mm. The correlation between optimal transfer distance, z op and outermost diameter length of bottom layer's loop, db o at maximum excited magnetic field derived in [31] and [36] yields…”

“…Compromise should be exercised in deciding displacement mitigation strategy between performance, complexity, cost and space constraints. The ultimate drawback of using surface mount device (SMD) components is the additional losses incurred apart from the fact that designers have to deal with negative consequences of having excessive or insufficient amount of soldering on printed circuit board (PCB) which might leads to the occurrence of significant frequency shift from the targeted operating frequency [25], [31]. Moreover, the precise values of SMD components required for impedance matching might not be similar to the available offthe-shelf capacitors.…”

Displacement-Tolerant Printed Spiral Resonator With Capacitive Compensated-Plates for Non-Radiative Wireless Energy Transfer

“…The design and enhancement steps for printed spiral coil (PSC) commences in the preliminary stage with the aid from a full-wave electromagnetic simulator, CST Microwave Studio as depicted in Fig.2. The relationship between optimal transfer distance, z op and outermost diameter length of loop, o at maximum excited magnetic field derived in [17] and [18] yields…”

“…3, L-match network comprises of a series capacitor, C stx,srx and a parallel capacitor, C ptx,prx connected to a pair of symmetrical transmitting and receiving printed spiral resonator which is represented by L tx,rx . These values are determined from inbuilt search algorithm in full-wave electromagnetic solver [18]. Lumped elements of capacitors are used as impedance matching network in the initial design.…”