Design of an ultra compact electronically tunable microwave impedance transformer

Abstract : A novel ultra compact microwave tuneable impedance transformer topology is proposed. It consists of a classical /spl pi/ CLC network where an equivalent tuneable inductance is realised with a high impedance transmission line in series with fixed inductance and a diode's varactors. The realised hybrid prototype at 900 MHz operating frequency is only 0.06λ-long. Impedance loads from 16.5 to 280 Ω can be matched with a return loss better than -20 dB, and the relative bandwidth equals ±36% for a fixed 50 Ω load.