a hybrid coupler has four ports and is capable of coupling radio frequency signals having a certain frequency from at least one port to at least one other port . the hybrid coupler is implemented as a differential coupler arranged to couple differential radio frequency signals . with such a hybrid coupler a power amplifying circuit can be produced which has sufficiently low ripple on the supply voltage to be integrated together with more sensitive radio circuits , and which is also insensitive to load mismatch such that an isolator can be avoided . a differential hybrid coupler allows the output current to be shared between four transistors or amplifiers , thus reducing the amplitude of the ripple . further , the frequency of the ripple is four times the operating frequency of the circuit , which makes it much easier to filter out the ripple .