Design of reduced size power divider for lower RF band using periodically loaded slow wave structure

In conventional Wilkinson power divider the quarter wave transformers are used to match the split ports to the common port. These are realized by 90deg transmission lines, which are quite large especially at lower RF range of frequencies. This paper reports the design and development of a reduced size two-way Wilkinson power divider at 850 MHz and 620 MHz. Approximately, 25%-35% length reduction is achieved by loading transmission line by capacitance at fixed intervals, which reduces the phase velocity and hence physical length at the desired frequency of operation. The required dimensions of the periodically loaded line are calculated using basic transmission line theory. The paper describes the method of theoretical calculation of the factor by which phase velocity is reduced at the desired frequency of operation. The EM simulation and experimental results validates the design approach. The circuit is realized with microstrip technology and hence can easily be fabricated using conventional printed circuit processes.