As devices continue to demand more power and run in multiple octaves, people need the accompanying couplers to increase the versatility of their equipment. Quadrature couplers are an excellent way to achieve many power goals, and there are multiple types to understand.
Quadrature Coupler Basics
A quadrature coupler splits the input into two signals 90 degrees apart. There are several types of quadrature couplers, including overlay and lange. Branchline is another name for the quadrature hybrid coupler. The most common use of a quadrature coupler is to match device pairs. The 90-degree phase spacing of the through and coupled arms allows reflections to be terminated separately from the coupler input. Quadrature couplers can provide power for power combine amplifiers, and the pairing of these two devices is typically called a balanced amplifier. Assuming the amplifiers are mirrored, this increases the user’s freedom to modify the network to their particular power needs.
Carriers are trying to add updated, next-generation capabilities but don’t want to spend more on equipment. Combining a pair of transmitters with a hybrid coupler allows both transmitters to use the same antenna so that one is left open for the overlay. A hybrid coupler is a device with three to four ports, which is used to split an input signal that has a resultant 90-degree phase shift from one port to the other. These couplers can put two signals together while retaining a significant degree of isolation between ports.
Although these have not been very popular for the last 40 years, they are coming back into popularity for use in multilayer media. However, they still have the problem with being difficult to design. Users tend to spend a significant amount of time running simulations to get it right, as opposed to planar quadrature models.