Articles
Cascading Tuners For High-VSWR And Harmonic Load Pull
February 3, 2009
By Steve Dudkiewicz and Roman Meierer, Maury Microwave Corporation
ABSTRACT:
For the first time ever, two or three tuners can be cascaded externally to achieve extremely high magnitudes of reflection (VSWR in the order of 100:1-200:1, G>0.98) as well as control multiple impedances at multiple frequencies (wideband harmonic tuning). Due to the use of calibrated and interpolated data for all tuners, we are able to achieve an overall system-level accuracy of greater than 40-80dB at highest G's.
Mechanical Slide-Screw Tuner
A mechanical slide screw-tuner consists of a 50O slabline and a reflective probe, referred to as a slug. Ideally, when the slug is fully retracted, the tuner presents a 50O impedance. As the slug is lowered into the slabline (y-direction), it interrupts the electric field and creates a capacitance, thereby increasing the magnitude of reflection. As the slug travels along the slabline (x-direction), the phase of the reflection is rotated. We are therefore able to recreate any and all impedances without the need of discrete components (lumped elements or transmission lines).
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