20 dB directional coupler

The 20dB Directional Coupler – An Inside Look at Directional Coupler Basics, Design and Its Applications

In communications today, radio frequency (RF) and microwave (MW) are increasingly important, and, as such, components like the directional coupler have become practically indispensable. Not only are they fairly accurate, but they’re also simple to include in a system, and they’re convenient.

There’s no such thing as one size fits all when it comes to directional couplers, however; in fact, there is a wide range of packages and configurations. Still, they can easily be distinguished by either their sampling capabilities, or their intended use. A 20dB directional coupler, for instance, can be either coaxial or waveguide, single or dual-directional, or else a combination.

The Inside of a Directional Coupler

Directional couplers are typically devices consisting of 4 ports. The first port is called the incident, or input; the second is the output, or transmitted. The third and fourth ports are called the forward coupled or just coupled, and reverse coupled or isolated ports, respectively.

Typically, the coupler’s main line is the one found between ports 1 and 2, is more suited to carrying high power levels and therefore may have bigger connectors, if the coupler comes with those. The other ports, on the other hand, are best suited for lower power levels in comparison.

Despite the labels, any of the ports can be the input; when this happens, the port directly across from it becomes the transmitted port. Meanwhile, the one beside it becomes the coupled port, and the one diagonally across is the isolated port.

Applications for Directional Couplers

The directional coupler may find itself being used a power splitter from time to time, but many of its usual applications sees it used as a power sampler in measurement systems. This is because it can sample power from a transmission line and do so through a definite known amount. Accordingly, accurate measurements can be taken without interrupting the system’s operations.

Directional couplers can also be used to measure frequencies, in a similar fashion to when it’s used to measure power in a system. In operating systems where it’s the frequency that matters, you’ll be hard pressed to find a more fitting component than a directional coupler.

Signal levelling is another application for directional couplers, particularly when you want to eliminate uncertainty caused by cables and other similar components. By eliminating the levelling loop or simplifying the one currently in use, you streamline the testing procedure. This way, you don’t have to select and match detectors and couplers.

Choosing Directional Couplers

There are several terms used in selecting directional couplers for various applications. Among these are the coupling coefficient, the directivity, residual standing wave ratio (VSWR), and insertion loss.

Typically, a higher directivity is more desirable as this means there are less chances of power being reflected back to one of the other ports and therefore interfering with, say, measurement. On the other hand, insertion loss and residual VSWR should be as low as possible to ensure high performance. The coupling coefficient, though, will vary depending on the application’s needs.

Make sure to contact AWG Tech

To be sure you’re getting the right 20dB directional coupler or otherwise, don’t be afraid to consult with experts at companies like AWG Tech. That way, you’re sure to get the right components for your applications each time.