Abstract
A wafer probe-to-waveguide adapter is transformed to a load pull device by integrating in the straight section of the waveguide a two-slug tuner with fixed penetration into diametral slots in the waveguide controlled by linear stepper actuators crossing over and sharing the same section of the waveguide.
Claims
1. A wafer probe to waveguide adapter comprising: a bent waveguide transmission line between a waveguide flange and the wafer probe and an integrated automated slide screw tuner, having two remotely controlled tuning probes; wherein the waveguide transmission line has two broad walls, a top broad wall, and a bottom broad wall, and two narrow sidewalls, and two slots parallel to a longitudinal axis of the waveguide transmission line, placed facing each-other, one on the top and one on the bottom broad wall; wherein the slots are positioned offset of a center line of the waveguide transmission line by at least a thickness of the tuning probes, and wherein two remotely controlled stepper actuators A#1 and A#2 are mounted opposite to each-other, one on the top broad wall and one on the bottom broad wall, and control associated tuning probes P#1 and P#2, which are inserted diametrical into the slots at a fixed penetration into and move along the waveguide transmission line, sharing this way a section of the waveguide transmission line; and wherein actuator A#1 moves probe P#1 to a position X1, and actuator A#2 moves probe P#2 to a position X2.
2. The wafer probe to waveguide adapter of claim 1, wherein the slots are at least one half of a wavelength (λ/2) long at a lowest frequency of operation (Fmin).
3. The wafer probe to waveguide adapter of claim 1, wherein the tuning probes are at least partly metallic or metallized rods.
4. The wafer probe to waveguide adapter of claim 1, wherein the tuning probes are at least partly metallic or metallized blocks.
5. The wafer probe to waveguide adapter of claim 1, wherein the tuning probes traverse the slots in a contactless manner.
Description
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
(1) The invention and its mode of operation will be better understood from the following detailed description when read with the appended drawings, in which:
(2) FIG. 1 depicts prior art: a typical generic automated load pull test system.
(3) FIGS. 2A through 2B depict prior art: a single probe waveguide impedance tuner; FIG. 2A depicts a front view of the entire tuner; FIG. 2B depicts a cross section of the tuning probe (typically a conductive rod) entering the waveguide slot.
(4) FIG. 3 depicts partly prior art: a Smith chart and two possible trajectories of impedance synthesis (tuning) to reach a target impedance starting from the origin of 50Ω. Reaching target-1 uses the prior art single-probe technique with horizontal and vertical control; reaching target-2 uses the new two-probe technique with horizontal only and no vertical control.
(5) FIG. 4 depicts a cross-section through a waveguide with two conductive tuning rods.
(6) FIG. 5 depicts a side view of the waveguide tuner with two crossing over tuning probes.
(7) FIG. 6 depicts the Smith chart coverage mechanism using two-probe impedance tuner with fixed probe penetration.
(8) FIG. 7 depicts prior art: vertical axis of waveguide slide screw tuner.
(9) FIGS. 8A through 8B depict the integration of tuner in wafer probe waveguide adapter; FIG. 8A depicts a side view; FIG. 8B depicts a top view.
(10) FIG. 9 depicts a side view of an alternative wafer-probe to waveguide adapter with integrated load pull tuner.
(11) FIG. 10 depicts a commercially available system setup.
DETAILED DESCRIPTION OF THE INVENTION
(12) This invention discloses a high frequency (microwave, millimeter wave), wafer-probe to waveguide adapter with integrated computer-controlled impedance tuner, suitable for load pull measurements. The tuner (FIGS. 4 and 5) uses the adapter waveguide-transmission line 40, which includes two broad top walls, two narrow side walls and two slots 46 cut into the broad walls, one on the top and one on the bottom (see cross section 41, 44 in FIG. 5). The slots run parallel to the waveguide longitudinal axis and are positioned opposite to each other and slightly offset from the symmetry center line of the waveguide. The offset eccentricity is selected to allow two tuning probes (typically metallic or metallized rods 42) to cross over (pass next to each other) without touching. This structure is chosen for economy of limited space (FIG. 9), because it uses slots of a total length of one half of a wavelength 56 at the lowest frequency of operation (Fmin) plus the thickness of one tuning rod. The horizontal control of the carriages 52 and 53 is ensured using miniature stepper actuators 54. An alternative configuration, where the slots would be on the same broad wall and the tuning rods would not cross over, would, in principle, also work, but the slot plus the actuator would have to be twice as long, which in our case of a waveguide adapter is not available.
(13) FIG. 5 shows a front view cut through the wafer probe-waveguide adapter with integrated load pull tuner; the two actuators A#1 (54) and A#2 control an ACME rod, on which are attached the small carriage blocks 52 and 53, which hold the tuning probes 55 and slide smoothly on a straight section of the external broad waveguide wall in which two diametral slots 46 have been machined. The slots are slightly offset (see FIG. 4), therefore the lower slot is not visible in FIG. 5. The waveguide is bent and terminates with the wafer probe 50 towards the DUT, which is accessed via the probe tips 57, and towards the auxiliary equipment via the waveguide flange 56. The tuning probes are inserted to a fixed depth inside the slots and move only horizontally and may cross over each other. The distances L1 and L2 determine the tuning state. L1 is chosen to be as small as possible. L2 varies between 0 and λ/2 at any test frequency. The position of the tuning probes is given by coordinates X1 and X2 and by convention it is agreed that if X1<X2 then probe 1 (55) is closer to the test port (or DUT) and if X2<X1 then probe 2 (52) is closer.
(14) FIG. 6 shows how the two crossing over tuning probes inserted at a constant depth into the slots create reflection factors 101 covering the whole area if the Smith chart: one probe creates a circle 100 around the center 102, this is vector 103; the second probe rotates around a point on the trajectory 100 and creates a vector 104. The vectorial sum of both creates the total reflection 105. If vectors 103 and 104 are in phase we get maximum reflection; if they are in opposite phase, we get zero (or the center 102 of the Smith chart). It is obvious that this epicycloid movement covers the entire Smith chart completely, or S11(X1,X2)=S11(X1)+S11(X2), all referred to the DUT (or test port) reference plane.
(15) FIG. 8 shows an embodiment of the wafer-probe to waveguide adapter with integrated load pull tuner. The tips 80 of the wafer probe are transited inside the body 87 to waveguide 83; the straight waveguide section 83 is slotted close to the bend into the top and bottom broad surface slightly offset and at least λ/2 long parallel to the axis of the waveguide. The two actuators 82 and 84 are mounted on the opposite broad surfaces of the waveguide and hold the tuning probes 85 and 86 secured inside the slots 88 at a fixed depth and movable along the slots of the waveguide. The vectorial sum of the reflection of both tuning probes creates the total reflection 81. The whole assembly makes up the wafer-probe to waveguide adapter with integrated load pull tuner. FIG. 8B depicts a top view of the assembly of FIG. 8A, we recognize the top slot 801, the tuning probe holder 802 and the top actuator 803.
(16) The same embodiment on a shorter adapter is shown in FIG. 9: The actuators 90, 91 are mounted on the linear section of the waveguide 92 and control tuning probes 93, 94 as in FIG. 8A. The waveguide flange 95 and probe tips 96 are also shown and define the test and idle ports of the adapter.
(17) FIG. 10 shows a real commercially available test assembly and the benefit of integrating the tuner at positions A and B much closer to the wafer-probes as before possible is obvious.
(18) Obvious alternative embodiments to the herein described wafer probe to waveguide adapter with integrated automated load pull tuner shall not impede the value of the invention.
