Load pull system using tuner with two dual-state tuning probes

1 . A load-pull tuner system comprising:

a) an automated slide screw tuner with two dual-state tuning probes,

b) tuner calibration methods,

c) an impedance synthesis (tuning) method,

wherein

a) the automated slide screw tuner includes:

a parallel plate airline (slabline) having an input port, an output port, a center conductor and two conductive sidewalls forming a channel, and

two mobile carriages C #1 and C #2, mounted across the channel, opposite to each-other, one on top and one on bottom of the sidewalls, remotely movable along the slabline using a control computer, each said mobile carriage carrying a dual-state tuning probe, carriage C #1 carrying tuning probe P #1 and carriage C #2 carrying tuning probe P #2,

wherein

the dual-state tuning probes are insertable diametral into the channel and settable to two preset states PS #1 and PS #2, state PS #1 corresponding to full withdrawal of the tuning probe from the channel of the slabline and state PS #2 corresponding to insertion of the tuning probe into the channel of the slabline to a fixed distance from the center conductor;

and wherein

each tuning probe has an initial (zero) position X1.0 and X2.0 correspondingly,

relative to the test port, and

carriage C #1 moves tuning probe P #1 to a position X1 relative to the test port, and

carriage C #2 moves tuning probe P #2 to a position X2 relative to the test port;

and wherein

if X1>X2 then tuning probe P #2 is closer to the test port than tuning probe P #1, else if

X1≤X2 then tuning probe P #1 is equal or closer to the test port than tuning probe P #2;

b) the tuner calibration methods comprise:

b1) a first tuner calibration method comprising:

routines for control of a pre-calibrated vector network analyzer (VNA),

positioning the tuning probes to a multitude of distinct positions, measuring s-parameters by the VNA as a function of the multitude of tuning probe positions and acquiring s-parameter data by the control computer, processing the acquired s-parameter data numerically using swapped de-embedding and saving the processed s-parameter data in tuner calibration files in the control computer;

b2) a second tuner calibration method comprising:

routines for control of a pre-calibrated vector network analyzer (VNA),

positioning the tuning probes to a multitude of distinct positions, measuring s-parameters by the VNA as a function of the multitude of tuning probe positions, and saving the processed s-parameter data in tuner calibration files in the control computer;

c) the impedance synthesis (tuning) method comprises:

retrieval of tuner calibration s-parameter data from the tuner calibration files, interpolation of s-parameter data between the distinct calibrated positions and numeric search among the calibrated and interpolated s-parameter data for the tuning probe positions that generate user defined impedances.

2 . The load-pull tuner system of claim 1 ,

wherein

the slabline of the slide screw tuner is at least one half of a wavelength long (λ/2) at a minimum operation frequency (Fmin).

3 . The load-pull tuner system of claim 1 ,

wherein the first tuner calibration method, comprises swapped de-embedding with following steps:

a) connect the tuner to the VNA, pre-calibrated at a frequency F;

b) set both tuning probes to the state PS #1 (withdrawn);

c) measure s-parameters and save in a zero matrix [S0] and set the tuning probe P #1 to the state PS #2 (inserted);

d) in a measurement loop for a multitude M of positions X1 with X1.0≤X1≤X1.0+λ(F)/2:

d1) move the tuning probe P #1 to a position X1;

d2) measure s-parameters Sij, whereby {i,j}={1,2};

d3) save the s-parameters and the associated probe P #1 position in a format (X1, Sij) in a file S1;

d4) when all positions M have been selected:

e) set the tuning probe P #1 to the state PS #1 (withdrawn) and the tuning probe P #2 to the state PS #2 (inserted);

f) in a measurement loop for a multitude N of positions X2 with X2.0≤X2≤X2.0+λ(F)/2:

f1) move the tuning probe P #2 to a position X2; f2) measure s-parameters Sij whereby {i,j}={1,2};

f3) save the s-parameters and the associated probe P #2 position in a format (X2, Sij) in a file S2;

f4) when all positions N have been selected:

g) retrieve s-parameters Sij(X1) from the file S1 and Sij(X2) from the file S2;

h) in a scanning loop through Sij(X1) for the multitude M of positions X1:

 execute a nested scanning loop through Sij(X2) for the multitude N of positions X2:

 if (X1≤X2) then

h1) cascade the inverse s-parameter zero matrix [S0] −1 with the s-parameters Sij(X2) of the file S2 and replace (update) in the file S2;

 else if (X1>X2) then

h2) cascade the inverse s-parameter zero matrix [S0] −1 with the s-parameters Sij(X1) of the file S1 and replace (update) in the file S1;

i) retrieve the s-parameters Sij(X1) from the updated file S1 and Sij(X2) from the updated file S2,

 cascade the s-parameters of the updated file S1 with the s-parameters of the updated file S2 to create Sij(X1,X2) and save (X1, X2, Sij(X1,X2)) in a file TUNER-CAL(F) for later use.

4 . The load pull tuner of claim 1 , wherein the second tuner calibration method further comprises the following steps:

a) connect the tuner to the VNA, pre-calibrated at a frequency F;

b) set both tuning probes in the state PS #2 (inserted);

c) in a measurement loop for a multitude M>1 of positions X1, whereby X1.0≤X1≤X1.0+λ(F)/2,

c1) move tuning probe P #I to a position X1;

c2) in a nested measurement loop for a multitude N>1 of positions X2,

 whereby

X 2.0≤ X 2≤ X 2.0+λ( F )/2,

(i) move tuning probe P #2 to a position X2;

(ii) measure s-parameters Sij, whereby {i,j}={1,2};

(iii) save (X1, X2, Sij) in a file TUNER-CAL(F);

 when all X2 positions of the multitude of N positions have been selected,

 select a next position X1 and return to step (c1);

d) when all X1 positions of the multitude of M positions have been selected, save the file TUNER-CAL(F) for later use.

5 . The load-pull tuner system of claim 4 , wherein the impedance synthesis (tuning) method comprises:

a) define a frequency F and load the tuner calibration file TUNER-CAL(F) in memory;

b) define a tuning target reflection factor Γ=|Γ|*exp(jΦ) and a maximum number of iterations NMAX;

c) search in s-parameter Sij(X1,X2) data of the file TUNER-CAL(F) for an initial calibration point S11(X1o, X2o), for which an error function EF=|S11(X1o, X2o)−Γ| 2 , defined as the vector difference between the test port reflection factor S11 at probe positions X1o and X2o and the target reflection factor Γ, is minimum;

d) set N=1 and search among interpolated s-parameter data S11(X1,X2) in the area surrounding the initial tuner setting (X1o,X2o) for a final tuner setting (X1.final,X2.final) in following steps:

d1) from the initial tuner setting (X1o,X2o) in a first optimization loop as follows: set N=N+1 and change X1o by δX1 to X1o+δX1, with δX1 proportional to the change of the Error Function EF=|S11(X1o+δX1,X2o)−Γ| 2 , until the error function EF reaches a minimum, and set X1o′=X1o+δX1;

d2) from a new tuner setting (X1o′,X2o) in a second optimization loop as follows: set N=N+1 and change X2o by δX2 to X2o+δX2, with δX2 proportional to the change of the Error Function EF=|S11(X1o′,X2o+δX2)−Γ| 2 , until the error function EF reaches a minimum, and set X2o′=X2o+δX2;

d3) set X1o=X1o′, X2o=X2o′ and repeat steps d1) and d2) until there is no further Error Function EF reduction, or if N>NMAX;

d4) define X1.final=X1o′, X2.final=X2o′;

e) insert the tuning probes to the state PS #2 and move the tuning probe P #1 to X1.final and the tuning probe P #2 to X2.final.