A four-device power combiner used as a lossless high power switch at 94 GHz

It is noted that in the millimeter-wave range p-i-n-diode switches are rather lossy (about 2 dB at 94 GHz). Additionally, the power-handling capability of beam-led diodes is limited to some 100-mW average power. To overcome switching problems in high-power applications, e.g. for a pulse radar, the injection power for a symmetrical four-coupler power combiner is switched from one of its two input ports to the other. Hence, the combined power alternately appears at one of the two output ports. If power and phase of the combined oscillators are balanced within 0.5 dB and +or-10 degrees , the power level at the difference port is more than 25 dB below the power level at the sum port. In this manner, the insertion loss of the lossy single-port, double-throw p-i-n-diode switch reduces only the low-level injection power while the combined power of the four devices is switched losslessly between the two output ports of the combiner network. This approach is used to switch the radar transmit power from left- to right-hand circular polarization.<>