Reconfigurable microwave filters文档.pdf

Reconfigurable Microwave Filters 159 7 x Reconfigurable Microwave Filters Ignacio Llamas-Garro and Zabdiel Brito-Brito Technical University of Catalonia Spain 1. Introduction Reconfigurable microwave filters make microwave transceivers adaptable to multiple bands of operation using a single filter, which is highly desirable in today’s communications with evermore growing wireless applications. Tunable filters can replace the necessity of switching between several filters to have more than one filter response by introducing tuning elements embedded into a filter topology. Microwave tunable filters can be divided in two groups, filters with discrete tuning, and filters with continuous tuning. Filter topologies presenting a discrete tuning generally use PIN diodes or MEMS switches. On the other hand, filter topologies using varactor diodes, MEMS capacitors, ferroelectric materials or ferromagnetic materials are frequently used to obtain a continuous tuning device. Filter topologies can mix continuous and discrete tuning by combining tuning elements as well, e.g. the use of switches and varactors on