Essentially these are multi-port power splitters used in reverse to combine multiple inputs that are in-phase and of equal amplitude. This type of combiner offers no form of isolation between inputs in that if there is an imbalance of either phase or amplitude, there will be significant power reflected back towards the input source. There are no loads in this device and as long as the inputs are equal power and phase, this form of combining is very efficient and cost effective.
Hybrid Network Combiner
Using a corporate, or linear arrangement of 4-port hybrids, multiple inputs can be combined to a single output. This type of combiner can have multiple inputs of different amplitude and/or phase and offer the feature that the input port will always present a matched load, no matter the state of the other input sources. The loads present on the “isolation” port of the each hybrid absorbs the imbalance portion of the source power. The insertion loss of this traditional type of power combining tends to be the highest of three types.
Like the impedance combiner, multiple input sources can be combined in a low insertion loss manner. However, the Gysel combiner includes an additional network structure to provide isolation much in the same manner as the hybrid network, but in a very compact system. This system requires one load per input that does not see any power unless there is an unbalance in the amplitude or phase of the sources. Additionally, the loads need only be rated to approximately 75% of a single input source, contrary to the hybrid combiner, where the load rating needs to commensurate with the actual power present in that particular hybrid.