7. Simulation of dual-band resonator design with multiple rectification techniques

By applying single-coil approach, Figure 8 depicts an example of dual-band printed spiral resonator simulated with full-wave electromagnetic simulator, CST Microwave Studio separated at transfer distance of 15 mm. Three rectification techniques are implemented specifically resonator design, resonator configuration, and impedance transformation network. Since dimension constrictions are of paramount concern in near-field WET system, the overall dimension of transmitting resonator is limited to 75 mm by 82.5 mm. Other parameter properties are detailed in Table 4 after optimization of parametric studies via geometrical layout tuning.

designing a superimposed dual-band DGS instead of coplanar or coaxial

metrical configuration technique between a pair of coupled resonators.

Impedance transformation network functions as alleviative measures of mutual inductance disparities triggered by spatial distance or load fluctuations between near-field coupled resonators. Resonance tuning and impedance matching, also referred to as compensation network, are commonly applied as front-end resonator design before AC-DC rectification. Implementing appropriate reactive compensation is necessary toward realizing maximum power transfer efficiency at preferred resonance frequency. Figure 7 illustrates capacitive compensation topologies which can be generally categorized into symmetrical and asymmetrical compensation network (CN) for single-band near-field WET system. Single capacitive compensation commonly employed each at transmitting and receiving resonator sides encompasses series-series (S-S), parallel-parallel (P–P), series-parallel (S-P), and

Symmetrical compensation network topologies: (i) series-series (S-S); (ii) parallel-parallel (P–P); (iii) series parallel-series parallel (SP-SP); (iv) parallel series-parallel series (PS-PS). Asymmetrical compensation network topologies: (v) parallel-series (P-S); (vi) series-parallel (S-P); (vii) series parallel-parallel series

6.3 Impedance transformation network

Recent Wireless Power Transfer Technologies

Furthermore, isolation techniques such as antiparallel loop structure [42] and frequency selective loop [40] structure functioning as band-pass filter have proven effective in rectifying interference caused by multi-coil mode. Band-stop filter in [31] filters' undesired parasitic eddy current from higher frequency induced across lower frequency coil path. The design is then revised in [32] with minimization of large spacing between low and high frequency coils and discrete inductor size along with total number of inverters. With careful combination of impedance values and coil-winding track, magnitude and phase of higher frequency voltage are fine-tuned to attain nil summation of total voltage across lower frequency path. As for displacement countermeasure, constructing more than one loop in an array structure reinforces tolerance toward detrimental consequences caused by imperfect orientations between transmitting and receiving resonators [62]. Robustness toward lateral displacement with wider coverage area is validated in [31] by incorporating asym-

configurations.

Figure 7.

58

(SP-PS); (viii) parallel series-series parallel (PS-SP).

Parameters Value L1tx 4.15 μH C1tx 8.5 pF Cstx 94.65 pF Cptx 184.69 pF L1rx 2.25 μH C1rx 4.32 pF Csrx 77.58 pF Cprx 269.10 pF

DOI: http://dx.doi.org/10.5772/intechopen.89218

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

Symmetrical hybrid compensation properties for dual-band printed spiral resonator design adopting single-coil

Simulated S-parameter plots of dual-band printed spiral resonator design adopting single-coil approach.

Simulated power transfer efficiency plot of dual-band printed spiral resonator design adopting single-coil

Table 5.

approach.

Figure 10.

Figure 11.

approach.

61

#### Figure 8.

Dual-band printed spiral resonator design adopting single-coil approach: (i) transmitter's top layer; (ii) transmitter's bottom layer; (iii) 3D model of transmitting and receiving resonators.


#### Table 4.

Parameter properties for dual-band printed spiral resonator design adopting single-coil approach.

Combined with asymmetrical configuration technique, receiving resonator is designed at two-thirds of transmitting resonator's size. Symmetrical hybrid compensation network topology which comprises of inductor and capacitors is incorporated in order to achieve simultaneous conjugate matching at 6.78 and 13.56 MHz as shown in Figure 9. LC tank is added with series-parallel capacitive compensation topology for single-coil approach. Values of optimized lumped elements are detailed in Table 5. Figure 10 shows simulated S11 and S21 plots. Despite attaining two distinct resonance frequencies at the intended f1 and f2, feasibility in supporting data transmission at higher frequency is affected as the corresponding 3 dB fractional bandwidth is unfortunately low at approximately 5%. Nevertheless, it is observed that the highest simulated PTE is realized at lower frequency, while

#### Figure 9.

Symmetrical hybrid compensation network topology for dual-band printed spiral resonator design adopting single-coil approach.

Dual-Band Resonator Designs for Near-Field Wireless Energy Transfer Applications DOI: http://dx.doi.org/10.5772/intechopen.89218


#### Table 5.

Symmetrical hybrid compensation properties for dual-band printed spiral resonator design adopting single-coil approach.

Figure 10. Simulated S-parameter plots of dual-band printed spiral resonator design adopting single-coil approach.

#### Figure 11.

Simulated power transfer efficiency plot of dual-band printed spiral resonator design adopting single-coil approach.

Combined with asymmetrical configuration technique, receiving resonator is designed at two-thirds of transmitting resonator's size. Symmetrical hybrid compensation network topology which comprises of inductor and capacitors is incorporated in order to achieve simultaneous conjugate matching at 6.78 and 13.56 MHz as shown in Figure 9. LC tank is added with series-parallel capacitive compensation topology for single-coil approach. Values of optimized lumped elements are detailed in Table 5. Figure 10 shows simulated S11 and S21 plots. Despite attaining two distinct resonance frequencies at the intended f1 and f2, feasibility in supporting data transmission at higher frequency is affected as the corresponding 3 dB fractional bandwidth is unfortunately low at approximately 5%. Nevertheless, it is observed that the highest simulated PTE is realized at lower frequency, while

Symmetrical hybrid compensation network topology for dual-band printed spiral resonator design adopting

Parameter properties for dual-band printed spiral resonator design adopting single-coil approach.

Dual-band printed spiral resonator design adopting single-coil approach: (i) transmitter's top layer;

Parameters Value (mm) Substrate thickness,Ts 0.4 Conductor thickness, tc 0.035 Overall dimension (width length) 75 82.5 Outermost side length of transmitting resonator, do\_tx 55.8 Innermost side length of transmitting resonator, di\_tx 6.45 Outermost conductor's width of transmitting resonator, wo\_tx 2.85 Innermost conductor's width of transmitting resonator, wi\_tx 0.98 Outermost conductor's spacing of transmitting resonator, so\_tx 1.5 Innermost conductor's spacing of transmitting resonator, si\_tx 3.75 Size ratio of transmitting to receiving resonators, Tx:Rx 1.5:1

(ii) transmitter's bottom layer; (iii) 3D model of transmitting and receiving resonators.

Recent Wireless Power Transfer Technologies

Figure 8.

Table 4.

Figure 9.

60

single-coil approach.

minimum variation of PTEs is preserved as depicted in Figure 11. Positioned at perfect alignment, PTE for each frequency is 90.11 and 80.56% at 6.78 and 13.56 MHz, respectively. Variation of PTEs at 9.55% is satisfactory considering ratio between frequencies is significantly small at only two for single-coil approach.

Symbol Parameter

DOI: http://dx.doi.org/10.5772/intechopen.89218

PL load power Vs voltage source

n turns

Author details

Lai Ly Pon1

Rennes, France

63

wc conductor's width

sc conductor's spacing

Ts substrate thickness tc conductor thickness

, Mohamed Himdi<sup>2</sup>

provided the original work is properly cited.

zop\_fn optimal transfer distance

ARX area, area of receiving resonator

M mutual inductance

Q1,2 Q-factor transmitting or receiving resonator

L1,2 inductance of transmitting or receiving resonator

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

do\_tx,0\_rx outermost side lengths of transmitting or receiving resonator di\_tx,i\_rx innermost side length of transmitting or receiving resonator

wo\_tx outermost conductor's width of transmitting resonator wi\_tx innermost conductor's width of transmitting resonator

so\_tx outermost conductor's spacing of transmitting resonator si\_tx innermost conductor's spacing of transmitting resonator

L1tx,1rx simulated inductor at transmitting or receiving resonator C1tx,1rx simulated capacitor at transmitting or receiving resonator Cstx,srx simulated series capacitor at transmitting or receiving resonator Cptx,prx simulated parallel capacitor at transmitting or receiving resonator

1 Wireless Communication Center, School of Electrical Engineering, Faculty of

2 Institute of Electronics and Telecommunication of Rennes, University of Rennes 1,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia

\*Address all correspondence to: mohamed.himdi@univ-rennes1.fr

\*, Sharul Kamal Abdul Rahim<sup>1</sup> and Chee Yen Leow<sup>1</sup>
