Raisa Georgiana Pesel
Impedance Matching Networks for Wireless Applications
Impedance matching, also known as tuning, implies maximum power transfer from source to load as well as minimum signal re ection from the load, in an RF system. This explains the importance of impedance matching networks and their continuously increasing use in many electronic applications, as for example RF power ampli ers, source-pull and load-pull power transistor characterization or impedance matching devices such as Antenna Tuning Units. The focus of this thesis is on the design, fabrication and test of such impedance matching networks, printed on an Alumina substrate with gold metalization and having CPW load lines. Many di erent types of practical IMNs are available which is why, in a rst place, detailed investigation and analysis is to be done in order to nd the most suitable topology for the network. The analysis conducted in this sense indicates in favor of a -network topology consisting in a xed inductor connected to two shunt variable capacitors, as tuning elements. A new approach is introduced regarding the tuning elements of the chosen topology: the use of RF MicroElectroMechanical Systems (MEMS) to design a switch-capacitor bank that would replace the commercially available variable capacitors. In a rst place, several RF switches are analyzed and simulated so that their behavior is known when applied to the capacitor bank. Multiple capacitor banks were designed and fabricated for the purpose of this thesis. The above mentioned approach provides better performance, wider capacitance ranges are achieved, compared to the conventional varactors and it also allows the design of similar circuits, but with di erent bandwidths and speci cations, that can be used as part of a dynamically recon gurable automatic match control circuit, for a wide variety of wireless devices and intelligent RF front ends. For comparison purposes, an impedance matching network using commercial varactors is also designed and its Smith Chart coverage is presented. The designed circuits are fabricated and measured, the results indicating satisfactory performance and good agreement with the circuit simulations.