Adaptive Microwave Filters and Multiplexers for Communication Systems

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The use of multi-band microwave systems is increasing, especially for cellular networks. Many cell phones today can transmit different types of coded signals over multiple frequency bands. Radio frequency filters are essential devices in the communication of these signals. With a proper multi-band filter design, a two terminal device can be made that performs the needed filtering for the multiple frequency bands used by a cell phone or by base stations. This reduces the amount and total size of the filters and eliminates the need for switches and multiple chip sets for each type of transmitted signal. The spectral efficiency of a microwave system can be improved by implementing adaptive filtering architectures. A switched filter bank has traditionally been used to achieve this type of architecture. Tunable multi-band filters allow for bandwidth to be assigned as needed by the microwave system. The design of adaptive duplexers and multiplexers will further offer flexibility into the microwave communication system. The filtering provided by tunable multi-band filters and tunable multiplexers can adapt correspondingly to satisfy the demand in bandwidth. The adaptive devices will be developed, designed, fabricated, and characterized. Their linearity performance will also be characterized while considering their loss and tuning range. Computer aided design algorithms will be developed to control the tuning of these adaptive filters and multiplexers. The main goals of this research program are to develop, fabricate and characterize multi-band microwave filters, to develop, fabricate and characterize novel adaptive multi-band microwave filters, to develop, design, fabricate and characterize adaptive multiplexers, to characterize the linearity performance as a function of frequency, loss and tuning range for the adaptive filters and multiplexers, and to develop computer aided design programs for determining the optimum tuning states for the fabricated filters and multiplexers.