The purpose of a quadrature coupler is to take an input signal, split it into two signals and then ensure that both signals are 90 degrees apart in their phase. With quadrature couplers, there are many varieties. For instance, you could have a lange coupler, branchline coupler and a quadrature hybrid coupler. Each has its own purpose.
Uses for Quadrature Couplers
One of the most common uses for a quadrature coupler includes impedance matching pairs of devices. The devices are arranged in a way that ensures their reflections are terminated in a load that is completely isolated from the coupler’s input. How is this possible? It is something that can only be done with the 90 degree phase difference between the signals.
Another common use for quadrature couplers, most often lange or overlay couplers, is to create a diplexer. With a diplexer, you have one port that passes DC while the other port is passing RF. Such a contraption is often utilized as a bias tree.
New Coupler Technology
The past few years have seen the technology for hybrid and quadrature couplers evolve in an impressive way. Not only are couplers more compact and efficient, but they are also able to handle a broad range of coupling values. The best couplers are able to handle between 6 dB to 30dB.
A lot of people are not aware that hybrid couplers and similar components are an enormous help to the military. Since these devices are used as part of signal monitoring and communications networks, the military is always at the forefront of requesting better technology.
In fact, many of the companies that produce couplers receive funding and grants from the military to improve their tech. While the military is the one that gets the first use out of these devices, they do trickle down into commercial and industrial use.