A New Class of Highly-Miniaturized Reconfigurable UWB Filters for Multi-Band Multi-Standard Transceiver Architectures

Modern wireless communication systems typically employ multiple frequency bands for several standards. A new class of miniaturized ring filters with tuning capability is introduced for this purpose. The proposed filter structure is based on a single multi-mode resonator with variable section impedances in microstrip technology. The bandwidth of the filter can be significantly extended to cover the whole ultra wideband (UWB) frequency range with high adjustability. Moreover, a tunable bandnotch is introduced within the filter response, which can be arbitrarily placed according to the required application. Varactor and PIN diodes are also utilized to facilitate a high tuning capability throughout the different filter characteristics with respect to bandwidth, center frequency, and bandnotch frequency. Based on the symmetry of the filter, even-odd mode analysis is applied to investigate the different filter design characteristics. In addition, a comprehensive transmission line model is investigated within this paper which showed excellent agreements with full-wave simulations and measurements. The implemented UWB filter is investigated with respect to its frequency-domain characteristics and group delay response. The realized filter has a fractional bandwidth of more than 119% with a low group delay. All measured results are in a very good agreement with analysis and simulations. The overall filter dimensions, including housing, do not exceed 25 mm× 25 mm.