Analysis and design of an unequal termination impedance power divider with bandpass filtering response

The design of an unequal termination power divider (PD) with a bandpass filtering response and wide out-of-band suppression characteristics is presented. The two-cascaded coupled lines can be designed with a low impedance transforming ratio. For the validation, a 50-to-5 Ω termination impedance PD was implemented at a centre frequency (f 0) of 2.6 GHz. The measured results are in good agreement with the simulations, showing input and output return losses that are better than 19 dB over a passband bandwidth of 190 MHz (2.51–2.7 GHz), and an out-of-band suppression that is better than 19.6 dB from DC to 2.25 and 2.9 to 7.2 GHz. The isolation between the output ports is 39.2 dB at f 0, and it is better than 19 dB with a broadband frequency (DC to 7.2 GHz).