Active Load Pull System

Active load pull tuning is essential for overcoming the limited tuning range of passive tuners, which is further reduced by fixture and probe insertion loss. This method allows test engineers to achieve |Γload|=1 (RDUT=0Ω), matching any DUT at its reference plane. In closed-loop active tuning, a portion of the extracted RF power from the DUT is amplified and fed back into the DUT output port, creating a virtual load. Since the re-injected power can exceed the original extracted power, Γ can be >1, compensating for insertion loss. Using two or more synchronized (coherent) sources enables open-loop active and harmonic tuning by closing the loop at IF through synchronization, rather than at RF.