Load-pull measurements are a powerful aid in identifying impedance matches for RF/microwave components. In a load-pull simulation of an active device, the impedances presented to the source and load of the device are swept across a range of values, and the effects on performance are measured. The performance contours are then plotted on a Smith chart (Fig. 1) to show how the changes in impedance impact device performance. By knowing how active-device performance is related to the input and output impedance of a power amplifier (PA), for example, key attributes such as output power and linearity can be fine-tuned for optimum performance...
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