A 90 Degree Hybrid Coupler is a one of the few hybrid coupler types, the others include 180 degree hybrid couplers and 0 degree hybrid couplers. 90-degree hybrid couplers are also known as quadrature couplers/hybrids, as any signal injected into any port will result in two 90 degree out-of-phase signals present on the other two ports. The output signals in a 90-degree hybrid coupler are typically split evenly between the two output ports, meaning that the signal energy is 3dB (half signal strength) less at the outputs than the inputs, but otherwise identical except for being out-of-phase by 90 degrees.
Common 90-degree hybrid coupler applications:
These quadrature signals can be useful for a variety of communication and sensing applications and are a common component found in transmitter and receiver signal chains. As long as the 90-degree hybrid coupler is electrically and mechanically symmetrical, then the response of a 90-degree hybrid coupler is the same regardless of what port the input signal is injected. As perfect symmetry isn’t possible in real systems, the 4th port on a 90-degree hybrid coupler serves the function of absorbing the reflection of the signals due to mismatch. 90-degree hybrid couplers are used for both splitting and combining signals and provides significant isolation between the ports.
- Combiners
- Splitters
- Image-rejection mixers
- Balanced mixers
- Phase shifters
- Diplexers
- Switches
- Antenna feed networks