In this paper, a noteworthy compact dual band wireless power transfer (DB-WPT) system is presented and studied. This system is proposed using interdigital capacitor which reduced the size of the whole system and accomplished high efficiencies. An interdigital capacitor is printed in the ground plane of the design and loaded with a chip capacitor to produce dual bands. The operation of the system is verified by fabricating the proposed DB-WPT system, which shows measured coupling efficiencies of 96 % and 98.8 % at 0.53 and 1.1 GHz, respectively at a transfer space of 12 mm. The fabricated structure has dimensions of 13.5 mm × 20 mm. The results show good agreement between the circuit model and the measurements. The idea of this design makes it applicable for compact near field WPT applications.

In this paper, two new compacts halved size single and UWB antennas are proposed for WiFi and UWB applications. The single-band compact halved size slot antenna is proposed for WiFi applications at 2.4 GHz. The resonant frequency of the conventional slot antenna can be reduced by cutting the antenna into two halves and without using any lumped elements inside the slot. Moreover, the impedance and radiation characteristics of the proposed halved-size antenna are suitable for WiFi applications at 2.4 GHz. The proposed WiFi antenna has a miniaturized size of 25 × 16.5 × 0.813 mm3. Then, an octagonal blended-shape antenna (OBSA) for UWB applications is proposed. By applying the same cutting concept, the halved size OBSA covers the UWB band from 3.1 GHz to 10.6 GHz. Furthermore, a grounded L-stub is added on the top side to improve the reflection coefficient. The proposed OBSA has a compact size of 28 × 13 × 0.813 mm3 with stable omnidirectional radiation patterns. Simulation and measured results are in good agreement.