Directional Coupler: Some Quick Facts

If you’ve done experiments in science class during high school or college, or if you’ve visited an electronics laboratory, you’ve probably seen, or even handled, an equipment called a “directional coupler”. But perhaps, when you saw this device, you never had an idea what it does, or what it’s good for. Here are a couple of helpful and useful facts about directional couplers, especially those that operate on the 5 – 1000 MHz range.

The Basic Uses Of Directional Couplers

What are the basic uses of directional couplers? For the uninformed, or for those who are not too keen on studying electronics, a directional coupler 5-1000 MHz is defined as a “passive device which is used in the field of radio technology, and they couple a certain amount of electromagnetic power in a transmission line, to a port which enables the signal to be used in another circuit”.

A directional coupler (whether microstrip, stirpline, coax and waveguide) is used for sampling a signal, and they are widely utilized in super high-frequency equipment or apparatus, with frequencies ranging from 30 megahertz (MHz) to 300 gigahertz (GHz)  for splitting or combining the energies of waves, or for determining wave direction, power and phase, as well as for other applications.

This equipment is designed as a passive 4-port device, which accepts an input RF signal and divides it into 2 output signals, of which the output signals are unequal in amplitude. This device is also utilized in a lot of circuit and system applications, including RF amplifiers, transmitters and receivers, as well as in test & measurement.

How Are Directional Couplers Constructed?

In constructing directional couplers, a wide array of techniques are utilized, from stripline to coaxial, lumped element and others. These are also packaged in different formats, from using solder pins to substrate carriers and others.
These devices are designed as 4-port devices, of which the four ports are: Input (Port 1), Transmitted (Port 2, Output), Coupled (Port 3) and Isolated (Port 4). The terms in the brackets refer to the port’s alternative names.

Electronics and communications experts stress that the main line is between port 1 and 2, which would normally be suited to carry high power levels, and it may be equipped with larger RF connectors (if it’s a unit that has RF connectors).

Yet despite the different construction techniques employed, what these directional couplers have in common is their ability to tap a sample of the input power, without considerably affecting the original signal.
The other ports are generally suited for lower power levels, since they are only intended to carry a small segment of the main power line. Port 3 and 4 may even have much smaller connectors, so it would be easier to distinguish them from the directional coupler’s main line ports.

In conclusion, a directional coupler 5-1000 MHz (which is also referred to as ”Taps”) is used in super high-frequency equipment or apparatus for splitting or combining energy waves, and its three important parameters to check include insertion loss, isolation and tap loss.