Recent Advances in Microwave Filters

This paper will describe recent advances in techniques for the design and realisation of microwave filters for a variety of applications including mobile and satellite communications, and radar. The first area, lossy filters, is that of the synthesis of filters with finite dissipation loss. This enables the realisation of highly selective filters with lower resonator Q factor than conventional design approaches, consequently reducing the physical size of filters in receiver applications. The second approach, frequency selective limiters, is a non-linear filtering technique which reduces the dynamic range of signals across a wide frequency band, enabling simpler A-D conversion of radar signals. The third technique, reconfigurable filters, is a new method for constructing tunable bandpass filters with low loss and high intercept point. Finally we will present results on techniques for the design of multi-mode patch antennas with filtering characteristics, enabling wider band and multiband operation.