Thus if we start with an output impedance as shown in red in the figure and we have a transmission line, it’s going to rotate around a quarter wavelength to the other side to the input impedance shown in blue. Here’s a quick reminder that a quarter wavelength transformer takes us from one side of the Smith chart to the other. ![]() Ultimately we are not only going to see how the incoming signals combine at but also how well they’re isolated from one another. We want our input impedance to look exactly like our PA impedance so that our impedances match in this example. For this we use a PA, which stands for power amplifier. Notice that each line has a resistor at one end as shown bythe schematic on the right.Īs an example, we’re going to assume that we’re using micro-strip transmission lines as shown at the bottom of the figure and that we have some source impedance. He used transmission lines and put them in a radial configuration with the inputs, combining them to a single output as shown on the left side of the figure. It was invented in the nineteen sixties and is still the most used topology. The solution to this problem is called a Wilkinson power combiner. As you will see shortly, the typical layout for a Wilkinson combiner looks a bit strange! Theory of Operation At the same time the transmission lines need to be far away from one another so the two paths do not couple. To connect it between the two ports, the transmission lines need to be “bent” to almost touch so the connection to the resistor is short. ![]() The difficulty in realizing a Wilkinson divider is that balance resistor is a discrete element and much smaller than the transmission lines. The Wilkinson divider achieves excellent isolation through the use of quarter-wavelength transmission lines and a balance resistor between the inputs/outputs. Unlike the branchline coupler, the Wilkinson will split a signal into two signals with 0 phase shift between them. The Wilkinson Divider is used to both divide and combine signals, maintaining their phase. In this part of the workshop, you will design a 0.95GHz 3dB Wilkinson Power Divider circuit.
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