4 ports lumped element 3dB coupler (new in V2330)
When you need to split two signals which are 90 degree shifted, or when you have to create from one signal two signals with a 90 degree phase shift the 3dB Hybrid coupler is the solution.
Often there is a requirement for couplers like this where a circular polarization is required. This type of polarization can be left or right handed. Changing between these two polarization modes is just e matter of interchanging the phase shifted signals.
Quite often this requirement is seen in SatCom applications, for example the reception of low orbit weather satellites with a polar track around the earth surface. The signals in the 137 MHz band are circular polarized transmitted to earth which calls for a circular polarized antenna in the down link station.
Next to a Helix antenna, the turnstyle antenna is a popular design created from to 2 element Yagi's mounted 90 degrees between each other in the horizontal plane.
By combining the outputs from the two orthogonal oriented antennas with a 90 degrees hybrid, the required circular polarization radiation pattern is obtained.