Fail-safe power combining and switching network

Under non-fault conditions the power from two equal power transmitters A and B having a relative phasing of 90 DEG is combined in the network of this invention to provide at an output thereof a power of A + B. The network preferably comprises two 3db short-slot 90 DEG couplers connected in cascade with the first coupler normally operating and the second coupler shorted or decoupled in the coupling slot region by means of shorting posts or the like. If transmitter B fails this condition is sensed and the second coupler has its associated decoupling means withdrawn so that the couplers form a zero db cross-over coupler delivering the total power of transmitter A to the output. For a failure condition of transmitter A a decoupling means is also associated with the first coupler so the entire network can be decoupled delivering the total power of transmitter B to the output under that condition. With a failure of either transmitter A or B there is the possibility of inoperation of the decoupling means. Under this condition the network is fail-safe with half of the available power from the operative transmitter being delivered to the output with the network still being matched.