4 ports lumped element 3dB coupler (new in V2330)

When you need to split or combine two signals which have to be 90 degree shifted than a 3dB Hybrid coupler is the solution. This calculator is based on lumped elements and is in priciple a narrow band solution. When a large bandwidth is required than a transmission line based design is the better choise.

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.