Multi-function microwave components based on implantable filters

This paper presents some multi-function microwave components based on implantable filters. It is found that some bandpass filters (BPFs) have the properties of ±K-inverters, meaning that they can be utilised to replace 90° or 270° transmission lines in passive microwave components such as in-phase and out-of-phase power dividers and rat-race couplers to realise both filtering and power-splitting functions. The ±K-inverter properties also mean that the proposed filters can be employed as impedance transformers in output-matching networks (OMNs) of power amplifiers for efficiency improvement and harmonic suppression. As a demonstration, some power combining and dividing components and power amplifiers are implemented based on the implantable filters, which exhibit dual functions, good performance and compact size.