Tunable impedance matching network with wide impedance coverage for multi frequency standards RF front-end

Abstract

Tunability in RF front-end improves the link quality by maintaining low VSWR in operating environment through correcting the impedance to counteract the sudden impedance change in a user fluctuating operating environment. Introducing tunability to the RF front-end provides great benefits but carries also losses in the impedance network. A large number of RF switches tend to be used in impedance networks in order to achieve large impedance coverage at multi-operating frequencies. However, this increases the losses, sizes and also the implementation complexity of an impedance network. For this reason, a design technique is proposed in order to achieve a wide impedance coverage with a reduced number of RF switches in the impedance network through identifying the electrical distance for the maximum impedance coverage. The required electrical distance of series transmission line of the Pi-network topology for the maximum impedance coverage has first been determined at a single operating frequency and then the electrical length has been reconfigured when switching to other operating frequency. Nearly 85% of the impedance coverage has been conserved by using the proposed technique compared to only 30% of the coverage remained in the conventional Pi-network while switching to other frequency. This technique significantly enhances the impedance coverage and reduces the number of RF switches needed in the impedance matching network especially at the multi frequency standards.