Design, Implementation, and Evaluation of High-Efficiency High-Power Radio-Frequency Inductors

Radio-Frequency (RF) power inductors are critical to many applications such as communications, RF heating, and plasma generation for semiconductor processing. Their high loss and large size can often be major contributors to the overall system size and loss. Inductors for high frequency and high power (e.g., tens of MHz and hundreds of watts and above) have traditionally been implemented as air-core solenoids to avoid high-frequency core loss. These designs have more turns than magnetic-core inductors and thus high copper loss. We propose a magnetic-core inductor design approach that leverages NiZn ferrites with low loss at RF, distributed gaps and field balancing to achieve improved performance at tens of MHz and at hundreds of watts and above. We demonstrate this approach with a 13.56 MHz, 500 nH, 80 Apk magnetic-core inductor design for a plasma generation matching network that achieves a quality factor of >1800 in simulation and >1100 experimentally. Additionally, we describe the difficulties in experimentally measuring inductor quality factors with very high current and very low loss at high frequency.