Reconfigurable Power Combiner and Miniature Filter

Abstract

Microwave communication systems have undergone tremendous changes in the past two decades. There is an ever-growing demand for devices with higher performance, lower cost and smaller size. Hence, more focus is given to improving the operational efficiency of individual devices. Microwave filters and power combiners are essential parts of such communication systems. This thesis presents a novel reconfigurable power combiner and a unique design for a miniature filter design, which can operate either as an ultra wide band (UWB) filter or a dual-band filter. A Gysel power combiner (GPC) is used to combine input signals from two high power amplifiers. However, the performance of conventional GPC degrades in the case of an imbalance between inputs. With the failure of one of the power amplifiers, only half the power of the other amplifier is delivered to the output port. The other half is dissipated in the load resistors. To circumvent this issue a reconfigurable Gysel combiner is proposed. The reconfigurable Gysel combiner operates efficiently in the normal operational mode. In the case of a failure of one of the amplifiers, it delivers the full power of the other amplifier to the output port. The new design for the reconfigurable Gysel combiner incorporates six SPST switches and a stub matching network. A filter is a two-port device used for frequency selectivity in microwave communication. Among which the UWB filters have a wide pass-band (>20%) and support high data rates, while the dual-band filters are used in multi-band communications. This thesis introduces a unique method to design miniature UWB and dual-band filters. A capacitively coupled distributed microstrip filter with N resonators is integrated with lumped capacitors to effectively produce 2N+1 resonators. This filter can be transformed into a UWB or a Dual-band filter depending on the value of the lumped capacitor. Prototype units for the reconfigurable Gysel combiners, UWB filter and dual-band filter have been developed, fabricated and tested.