A new design of a hybrid power combiner using double-sided parallel-striplines is proposed for wideband and high power applications. The circuit is used to realize a 4: 1 power combiner. The use of double-sided parallel-strip lines adds flexibility to the design, since different characteristic impedances can readily be realized by simply adjusting the offset between parallel lines, without having to change the width of the lines. Moreover, a new approach using ferrite cores in order to improve low frequency performance of the power combiner is successfully applied. The proposed power combiner is studied analytically; its performance is verified via detailed HFSS simulations and measurements results.