Universal Design Approach for Multiport Filtering Power Divider

This paper presents a universal design approach of multiport filtering power divider with the arbitrary power-division ratio, which is applicable for the designs of the single-ended/balanced circuit or hybrid of them. The power allocation in a specified passband is fulfilled by relying on two key factors in building a filter, i.e., coupling coefficient and external <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-factor (<inline-formula> <tex-math notation="LaTeX">$Q_{\mathrm {e}}$ </tex-math></inline-formula>). After synthesis for the bandpass response, the total input/output <inline-formula> <tex-math notation="LaTeX">$Q_{\mathrm {e}}$ </tex-math></inline-formula> and the total coupling coefficient at each power dividing level can be determined. Subsequently, according to the desired power-dividing ratio, the coupling coefficient between the two coupled resonators and <inline-formula> <tex-math notation="LaTeX">$Q_{\mathrm {e}}$ </tex-math></inline-formula> of each output can be easily determined. Once the parameters for filtering response are fixed, the power allocation can be determined by <inline-formula> <tex-math notation="LaTeX">$Q_{\mathrm {e}}$ </tex-math></inline-formula> without effect on the filtering response. Thus, the two functions of bandpass and power dividing can be designed independently, which provides tremendous freedom for the overall design with the arbitrary order of filtering and number of output ports. The proposed topology has several advantages, such as flexibility, cost efficiency, and simple design procedure, which would be a good candidate for multiple-path operation in the current and future MIMO systems.