Filter Synthesis and Design Techniques for Highly Adaptable Systems

Software defined radio and cognitive radio (SDR/CR) are promising concepts toward more optimally using the electromagnetic spectrum for communications and data transfer. These systems are highly agile in terms of modulation technique and frequency of operation due to early digitization and software processing of received radio frequency signals. However, the front ends of SDR/CR systems often use static antennas and switched banks of static, wide bandwidth filters before the digitization process. These components limit the ability of SDR/CR systems to operate in environments with high levels of interference and are therefore a bottleneck in the path to achieving optimal adaptation of wireless systems. This dissertation focuses on tunable and reconfigurable filter synthesis and design techniques that have the potential to alleviate the hardware adaptation bottleneck currently experienced by SDR/CR systems. The presented filter techniques and structures promise the capability to dynamically adapt the center frequency, order, response shape, bandwidth, group delay, passband insertion loss-stopband attenuation tradeoff, and transmission zero spectral location of a filter response in the field. Such reconfiguration capability is made possible through the use of new coupling relationships and structures that enable dynamic reconfiguration between electric, magnetic, and zero coupling values