30dB Directional Coupler

The 30dB Directional Coupler – Different Types Based on Its Features

In both radio frequency (RF) and microwave (MW) technologies, you’re bound to see devices that are used to combine, distribute, or otherwise transport power from one point to another. These devices could either be active or passive. The former can generate their own power, while the latter are incapable of power gain, not to mention they need an external source of energy.

Directional couplers are on the list of passive devices, and today they’ve become a sought-after measuring tool. That’s because, whether you’re working with a 30dB directional coupler or a different type, it can sample energy with neither adjustment nor moving parts. This makes it a simple and convenient means of measurement.

The directional coupler is also capable of separating reflected power from forward power, meaning the reading you’d get is as accurate as can be.

Features of a Directional Coupler

When it comes to selecting the right component, there are certain traits or features you’ll want to pay attention to. The following are the most important features to look at when you’re choosing directional couplers for your application.

Insertion loss. This is the change in load power when the signal is passed through a component. For some applications, it’s imperative to use directional couplers with as little insertion loss as possible. That’s because the loss in power may affect the overall operation of the application or system.

Bandwidth. This is the range of frequencies that the coupler can operate in, without affecting overall performance.

Coupling coefficient. The ratio of incident power, or power that’s fed into the first port of a coupler, to coupled port power – that is, the power that comes out of the second port. One thing about the measurement is that it is taken when all ports are terminated in a way where the power doesn’t reflect back into the coupler. The ratio is then usually expressed in dB (decibels).

Directivity. The ratio of power output at an auxiliary port when power is transmitted in one direction, to power output at the same port when power is transmitted in the opposite direction. Reflectionless terminations are connected to all other ports when the measure is taken. Like the coupling coefficient, the ratio is shown in dB.

Residual VSWR. This refers to the standing wave ratio measured using a reflectometer coupler with reflectionless termination and fed from a non-reflecting generator. It’s also the directivity expressed as a VSWR.

Tracking. The maximum change in difference between two couplers’ coupling coefficient.

Flatness. The maximum peak-to-peak variation in coupling coefficient that one can expect over a certain frequency band.

Remember, however, that the traits you’ll need to pay close attention to will change depending on your application’s needs, as some of these are practically impossible to achieve in the same coupler. For instance, you cannot have a coupler with high directivity and flatness over a wide bandwidth. So make sure you know what you need before specifying certain traits.

If you’re not sure what kind of coupler you’re looking for, be it a 30db directional coupler or otherwise, the experts at retailers like AWG Tech will be happy to help you find what you need.