Designs of Diplexing Power Dividers

A diplexer with different-frequency power dividers cascaded to its output ports can split a signal into different frequency bands for power dividing functions. However, the design of a diplexer usually requires two different frequency filters. This paper presents three new microstrip diplexing power dividers (DPDs) to achieve duplexing power division without requiring additional filters. Moreover, to increase selectivity, each of the proposed DPDs has the flexibility of adding a dual-band filter to its input port. In particular, the proposed DPDs have matching circuits integrated in the dividers, enabling each divider with imaginary input impedance to reach the required open condition; this is achieved by designing a 50-Ω transmission line of appropriate length or a quarter-wavelength (λ/4) transmission line.