Experimental proof-of-principle of a passive, nearly reciprocal, transistor-based tuneable RF inductance

An innovative approach for tuneable reactances using the example of electronic inductances is introduced and the operation principle affirmed by measurement. Hitherto solutions for variable inductances often lack applicability in serial paths or do not exhibit passive behaviour. The presented circuit shows, even though transistor-based, a passive and reciprocal tuneable inductive behaviour at its terminals over a broad range of biasing conditions and frequencies. Thereby it accommodates more degrees-of-freedom in circuit design and possibilities for interesting applications, e.g., in integrated circuit design for a multitude of relevant applications in sensing and mobile communications. A test board was implemented and measured, confirming the principle-of-operation in agreement with numerical simulations, demonstrating a transistor-based, passive, tuneable, nearly reciprocal inductance over a frequency range larger than a decade.