Waveguide slide screw tuner and method

A calibration method for a waveguide slide screw tuner having a test port and an idle port, and two tuning probes, a first tuning probe and a second tuning probe, inserted diametrically and laterally offset to each other into slots on opposite broad walls of the waveguide and movable at constant penetration along the waveguide, comprising the following steps:

• a) connect the tuner to a VNA pre-calibrated at a frequency F;
• b) move the tuning probes to initial positions, the first tuning probe to X1.0 and the second tuning probe to X2.0;
• c) measure s-parameters of the tuner and save in an init matrix [S0];
• d) in a first move-measurement loop
• d1) move the first tuning probe from X1=X1.0 to at least X1=X1.0+λ/2 in N steps of ΔX=λ/(2N),
• d2) measure s-parameters and save in a file S1 including Sij(X1,X2.0);
• e) return the first tuning probe to position X1=X1.0;
• f) in a second move-measurement loop
• f1) move the second tuning probe from X2=X2.0 to at least X2=X2.0+λ/2 in N steps of ΔX=λ/(2N),
• f2) measure s-parameters and save in a file S2 including Sij(X1.0,X2);
• g) in a third move-measurement loop
• move the first tuning probe from X1=X1.0 to at least X1=X1.0+λ2 in steps of ΔX and, for each movement of the first tuning probe, move the second moving probe from X2=X1−M*ΔX to X2=X1+M*ΔX in steps of ΔX, with M=0, 1, 2, 3 . . . and measure s-parameters and save in files SK including Sij(X1,X2), for 3≤K≤3+2M;
• h) in a numerical cascading loop for all permutations {X1,X2}
• if the first tuning probe is closer to the test port (X1≤X2) de-embed s-parameters of the second tuning probe:
• cascade s-parameters [S1]*[S0]−1*[S2] and save in file C1;
• if the second tuning probe is closer to the test port (X1>X2) de-embed the first tuning probe:
• cascade s-parameters [S2]*[S0]−1*[S1] and save in file C2;
• i) concatenate s-parameters of files C1 with C2, replace s-parameters with data from files SK and save s-parameters Sij(X1,X2) in a tuner calibration file C(F).