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This study presents the design and implementation of a 6.78 MHz wireless power transfer (WPT) system that uses magnetically coupled resonance for 5 W mobile phone charger applications. For a resonant WPT system, one of the most significant design issues is the power receiver because of its resonant characteristics. A compact resonant-type power receiver is required for high efficiency and robustness. To realise a compact size, a fully integrated 5 W power receiver that includes an on-chip AC-DC converter and a DC-DC converter is implemented. A protection circuit that operates only during initial power-up is proposed to protect the power switches in the receiver. The proposed receiver was implemented using a 0.18 µm bipolarcomplementary metal-oxide-semiconductor-double-diffused metal-oxide-semiconductor process with a die area of 3.5 mm × 3.5 mm. The measured maximum power transfer efficiency of the receiver and peak efficiency of the system was 81 and 51%, respectively.

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This paper represents CMOS direct down-conversion mixer for L-band application based on 0.18 um CMOS technology. The proposed mixer uses current bleeding technique and common-mode feedback (CMFB) circuit. The transconductance stage PMOS transistors that concurrently amplify RF signal and bleed current offer reduction of current in the LO transistors while still maintain the mixer output voltage to reference value. Reduction of current through the LO transistors and resistive loads offers better noise performance as well as better conversion gain.