A Semi-Lumped Miniaturized Spurious Less Frequency Tunable Three-port Divider\Combiner with 20 dB Isolation Between Output Ports

We propose a new topology based on a semi-lumped complex impedance transformer for the design of a frequency tunable three-port power divider. A prototype has been realized in a hybrid technology with commercially available varactor diodes. Our design is based on an impedance transformer in the input branch (with electrical length of 20.4deg), and a loop in the output branches (with electrical length of 2times24deg). This leads to a miniaturized device, more than two times shorter than a classical Wilkinson power divider. This divider can be tuned over plusmn30% around 1.35 GHz (from 0.95 GHz to 1.75 GHz) with insertion loss lower than 0.3 dB, return loss better than 20 dB and isolation between the two output ports better than 20 dB. Moreover, the low-pass behavior of the input impedance transformer leads to a good rejection of the second harmonic