Simple waveguide load pull tuner
View Patent ↗A simple low-profile waveguide load pull tuner uses a horizontally only moving reflective probe and an adjustable attenuator placed between the DUT and the tuning probe. Both controls are using stepper attenuators mounted on the waveguide. This simplifies the design and minimizes the cost of manufacturing. The tuner has wideband 50 Ohm tuning capability allowing minimum risk of transient spurious oscillations. A de-embedding adapter removal calibration method allows generating thousands of calibrated points in a small fraction of the time needed for calibration of the full permutations.
1. A load pull tuner system comprising:
A waveguide load pull tuner comprising:
a waveguide transmission line having two broad walls and two narrow walls, a test and an idle port, at least one slot centered along a broad wall, and
a remotely controlled mobile carriage travelling along the waveguide and holding a reflective tuning probe which is inserted into the at least one slot at a fixed penetration,
and
a RF energy-absorbing sliver, remotely insertable at adjustable penetration into the at least one slot;
wherein
the RF energy-absorbing sliver is placed at a fixed position along the waveguide between the test port and the reflective tuning probe;
and a waveguide load pull tuner calibration method comprising:
connecting the tuner to a pre-calibrated vector network analyzer,
measuring s-parameters of the tuner at a multitude of penetrations of the RF energy-absorbing sliver and positions of the reflective tuning probe along the waveguide and saving in a calibration file for later use.
2. The load pull tuner system of claim 1 ,
wherein the tuning probe of the waveguide load pull tuner is inserted into a first slot, which is at least one half of a wavelength long at a lowest frequency of operation of the waveguide load pull tuner, and the RF energy-absorbing sliver is inserted into a second slot, which is placed between the test port and the first slot.
3. The load pull tuner system of claim 1 ,
wherein the RF energy-absorbing sliver and the tuning probe of the waveguide load pull tuner are cascaded and inserted into the same slot,
and wherein the RF energy-absorbing sliver is inserted between the test port and the reflective tuning probe.
4. The load pull tuner system of claim 1 ,
wherein the RF energy-absorbing sliver of the waveguide load pull tuner is an oval disc rotating eccentrically around an axis perpendicular to the slot and inserted gradually into the slot between full extraction and maximum penetration.
5. The load pull tuner system of claim 4 ,
wherein the axis controlling the RF energy-absorbing sliver of the waveguide load pull tuner is remotely controlled by a second stepper motor and gear.
6. The load pull tuner system of claim 1 ,
wherein the mobile carriage of the waveguide load pull tuner is remotely controlled by a first stepper motor and gear.
7. A calibration method for load pull tuner system as in claim 1 ,
wherein the waveguide load pull tuner is connected with a pre-calibrated vector network analyzer, comprising the following steps:
a) the RF energy-absorbing sliver is withdrawn out of the waveguide, defining a rotation angle Φo=0;
b) the reflective tuning probe is moved close to the test port, defining a horizontal position Xo=0;
c) s-parameters of the waveguide load pull tuner are measured and saved in an init matrix [S0];
d) s-parameters of the waveguide load pull tuner are measured for a multitude of rotation angles Φm of the RF energy-absorbing sliver between a minimum value Φmin, corresponding to withdrawal, and a maximum value Φmax corresponding to maximum insertion and saved;
e) the RF energy absorbing sliver is withdrawn back to angle Φo=0;
f) s-parameters are measured for a multitude of positions Xn of the reflective tuning probe and saved;
g) the invers init matrix [S0] −1 is cascaded with the s-parameters of step f) and saved;
h) all permutations of s-parameters of steps d) and g) are cascaded and saved in a tuner calibration file comprising tuner s-parameters Sij (Φm, Xn) for {i,j}={1,2}.