Load pull tuner for waveguide wafer probe
View Patent ↗A waveguide to wafer-probe adapter includes an integrated computer-controlled load pull tuner forming a compact and handy assembly. The adapter includes a horizontal, a vertical and a sloped straight section, joined with two knee junctions. The tuner is simple and includes two, only along the sloped waveguide section moving at fixed penetration tuning probes without cumbersome vertical axis mechanisms. The sloped cavity section of the waveguide includes niches at the knee junctions, in which the probes can be moved and hidden, thus allowing a for low residual reflection and original transmission behavior. When the probes are hidden the adapter can be used for instantaneous s-parameter measurement still maintaining full load pull capacity. High-speed calibration and tuning algorithms allow efficient operation.
1. A load pull tuner incorporated in a waveguide-to-wafer-probe adapter comprising:
a partly slotted waveguide-to-wafer-probe adapter, and
two mobile reflective tuning probes, a first tuning probe and a second tuning probe, and remote control of the tuning probes,
wherein
the partly slotted waveguide-to-wafer-probe adapter comprises:
a rectangular waveguide transmission line having a top and a bottom broad wall and two narrow side walls and is divided into three sections joined by knee junctions: a sloped section between a vertical section and a horizontal section, the vertical section being attached to a wafer-probe head and the horizontal section being attached to a waveguide flange;
and wherein
the sloped section includes two slots, centered on the top broad wall along the waveguide, a first slot towards the vertical section and a second slot towards the horizontal section, said slots comprising a portion inside the sloped section and a protrusion inside and traversing the knee junctions;
and wherein
two mobile carriages, a first mobile carriage and a second mobile carriage, are saddled on and slide along the sloped section of the waveguide, controlled using stepper motors and appropriate gear;
and wherein
the first tuning probe is attached to the first mobile carriage and the second tuning probe is attached to the second mobile carriage;
and wherein
the tuning probes are inserted contactless at fixed penetration into the slots, the first tuning probe into the first slot and the second tuning probe into the second slot.
2. The load pull tuner incorporated in a-waveguide-to-wafer-probe adapter of claim 1 , wherein
the tuning probes are at least partly metallized rods.
3. The load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 1 , wherein
the tuning probes are at least partly metallized dielectric pellets.
4. The load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 1 , wherein
the tuning probes are initialized by moving them to withdrawal positions inside the protrusion of the slots into the sloped-to-vertical and the sloped-to-horizontal knee junctions defining associated initialization (withdrawal) positions X 1 =0 and X 2 =0,
and wherein
the first carriage moves the first tuning probe to a position X 1 from the initialization position X 1 =0 and the second carriage moves the second tuning probe to a position X 2 from the initialization position X 2 =0.
5. A calibration method for the load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 4 , comprising the following steps:
a) connect the waveguide-to-wafer-probe adapter to a VNA calibrated at a frequency F, associated with a half wavelength of XMAX motor steps;
b) move the first tuning probe to the initialization position X 1 =0 and the second tuning probe to the initialization position X 2 =0;
c) measure s-parameters and save in an init matrix [S 0 ];
d) in a first move-measurement loop
d1) move the first tuning probe from X 1 =0 to at least X 1 =XMAX in a multitude of N>10 steps of ΔX=int (XMAX/N),
d2) measure s-parameters and save in a file S 1 (X 1 , X 2 =0);
e) return the first tuning probe to the initialization position X 1 =0;
f) in a second move-measurement loop
f1) move the second tuning probe from X 2 =0 to at least X 2 =XMAX in a multitude of N steps of ΔX=int (XMAX/N),
f2) measure s-parameters and save in a file S 2 (X 1 =0, X 2 );
g) retrieve s-parameters Sij(X 1 ,O) from file S 1 and Sij (0, X 2 ) from file S 2 ;
h) in a numerical loop cascade (convert to transfer T-format, multiply and convert back to s-format) all s-parameter permutations for {X 1 , X 2 } from step g) as follows: [T 1 ]*[T 0 ] −1 *[T 2 ], convert back to s-format and save as Sij(X 1 ,X 2 ) in a calibration file C(F).
6. An impedance synthesis (tuning) method for the load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 5 comprising the following steps:
a) enter a frequency F;
b) enter a complex target reflection factor Gamma=Real (Gamma)+j*Imag (Gamma);
c) load s-parameters Sij (X 1 , X 2 ) from the calibration file C(F) in dynamic computer memory;
d) in a search loop
d1) compare S 11 (X 1 , X 2 ) with Gamma for all combinations {X 1 , X 2 };
d2) if the amplitude of the vectorial difference |S 11 (X 1 , X 2 )-Gamma| is minimum, move the first tuning probe to X 1 and the second tuning probe to X 2 ;
e) terminate.
7. The load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 1 , wherein
the portion of the slots inside the cavity are at least one half of a wavelength (λ/2) long at a minimum operation frequency (Fmin) of the waveguide-to-wafer-probe adapter.
8. The load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 1 , wherein
the carriages are moved by remotely controlled stepper motors and appropriate gear.
9. The load pull tuner incorporated in a waveguide-to-wafer-probe adapter of claim 1 , wherein
the tuning probes are inserted into the slots without contacting the waveguide walls.