An Overview of Directional Couplers

A directional coupler is an electronic component that has applications in different industries and types of equipment. There are several different types of couplers that can perform unique tasks. However, all couplers are designed to route an input signal and power to different ports. Depending on how a coupler is set up and used, signals may be combined, isolated, or eliminated. Manipulating the input signal may be important in power monitoring applications. A directional coupler can also be used in experiments or tests that require certain signal measurements. Here is an overview of how this component works.

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Ports

Directional couplers generally have four unique ports. The input port allows a signal to enter into the coupler. There is also a transmission (through) port, which serves as the exit point for most of the incident signal. A fixed portion of the signal may be routed to the coupled port. In most cases, the signal at the coupled port is expressed in units of dB. The last piece is the isolated port. In many cases, this port is terminated.

Key Specifications

A directional coupler is essentially a passive reciprocal network, which means that certain aspects of the ports and the circuit matter. Ideally, the ports should be interchangeable, meaning the signal transmission should be good no matter what the direction of propagation is. The circuit should also be as lossless as possible. Other important aspects of a directional coupler include operational bandwidth, directivity factor, and input power. The coupling ratio is another essential feature to notice. This term describes how the input power is split between the coupled and output ports. Different applications may require different coupling ratios.

A directional coupler is an essential component in many applications that use microwaves, such as consumer electronics. Choosing the right coupler for a specific application may require understanding the basic design of couplers and the most favorable specifications.