| CPC G01R 31/2607 (2013.01) [G01R 35/005 (2013.01)] | 6 Claims |
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1. A calibration method for an active load pull system, which includes:
a device under test (DUT), a first vector signal generator (VSG #1) injecting radio frequency (RF) power P1 into an input port #1 of the DUT, a second vector signal generator (VSG #2) injecting RF power P2 into an output port #2 of the DUT, and measurement capability of the RF signal power waves entering (<a1>,<a2>) into the input and departing (<b1>,<b2>) from the output port of the DUT,
comprising the following steps:
a) a setup step:
install and bias the device under test (DUT);
define a multitude of M frequencies Fi, with 1≤i≤M,
define a minimum and a maximum input power supplied by the first VSG #1;
and,
b) a scaling step:
set a medium frequency F=F1+(FM−F1)/2;
determine a center signal phase Pc of the second VSG #2 as follows:
set the input signal power of the first VSG #1 to create a substantial |<b2>|;
set the signal power P2 of the second VSG #2 to create |<a2>|≈|<b2>|;
and,
in a phase control loop:
increase phase Φ2 of the second VSG #2 in 10-degree increments from 0 to 360 degrees, measure Γ=|<a2>|/|<b2>| and select Φc-Φ2 for maximum Γ;
set Φ2-Φc;
and,
in a scaling process:
increase the input power of the first VSG #1 from the minimum to the maximum value in approximately 10 equal increments, and, for each input power P1 setting, measure the departing signal |<b2>| and set the signal power P2 of the second VSG #2 to create entering signal |<a2>| approximately equal to |<b2>| and save a ratio A (F, P1,|<b2>|)=P2/P1;
and,
c) in a calibration pattern measurement process:
for each frequency of the multitude M of frequencies Fi:
step through the input power P1 settings of the scaling process and set P2=A(Fi)*P1,
and, for each input power P1 setting:
step through the phase Φ2 of the second VSG #2 from 0 to 360 degrees in 10-degree increments,
measure Gamma=<b2>/<a2> and save in a calibration file CF in a format (Fi, P1, P2, Φ2, Gamma).
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