30 are of identical construction as may be seen by the layout of the couplers 28 and 30 presented in fig1 and by the end view presented in fig2 the coaxial transmission lines 22 are fabricated in a convenient fashion by milling out channels 50 within the base plate 24 to provide the outer conductors 40 of the transmission lines 22 the center conductors 32 are then placed within the channels 50 and supported in their respective positions by the supports 42 thereupon the assembly is completed by installing the cover plate 26 on top of the base plate 24 both the base plate 24 and the cover plate 26 as well as the center conductors 32 may be fabricated of an electrically conducting material which is readily machined such as aluminum as will be explained in further detail hereinafter with reference to fig9 the crossover 20 acts to couple an electromagnetic wave from one of the input ports to the diagonally opposite output port for example from the second input port 38 to the first output port 44 this is accomplished by virtue of the even splitting of power at each of the couplers 28 and 30 with the phase lag of 90 degrees this resulting in a cancellation of waves at one of the output ports so that all of the power of the input wave exists from the other output port it is noted that a particular feature of the invention is the construction of the crossover 20 including all components of the couplers 28 and 30 and.