Impedance tuners with resonant probes
View Patent ↗Slide screw impedance tuners use resonant probes in order to avoid uncontrollable reflection factors at harmonic frequencies in high power load pull transistor testing. The tuners use either coaxial slotted airlines or slablines. The probes are coupled capacitively with the central conductor of the airline and are either slotted with associated spring loaded effect for better galvanic ground contact, or solid dielectrically coated or anodized and carefully machined for slide fitting into the slabline opening or the coaxial line slot, for capacitive contact with the ground plane. The probes allow for selective reflection behavior over a given frequency range, which does not include unwanted frequencies, such as harmonic or sub-harmonic frequencies.
1. An impedance tuner comprising an input (test) port, an output (idle) port and a low loss slotted transmission airline between said ports, said slot being parallel to the center conductor, in which one or more conductive or metallic probes are mounted on mobile carriages and can be inserted and moved to various distances from the center conductor and across the length of said airline by means of appropriate gear and remotely controlled electrical motors;
said probes having the form of cubical blocks with a concave bottom which matches axially the center conductor and being divided in two sections: one section being grounded on the walls of the slotted airline and one floating section;
said grounded section being capacitively or galvanically connected with the sidewalls of said slotted airline, and said floating section being made as a protrusion of the probe(s)' concave bottom tails inside the cavity of the slotted airline;
said probes being resonant;
said resonance being created by a capacitance and an inductance in series;
said capacitance being created by the proximity of the concave bottom part of said probe(s) and the center conductor of said slotted airline;
said inductance being created by the floating protrusion tails of the lower part of the body of said probe(s) inside the cavity of said slotted airline;
said protrusion being the non-grounded (floating) section of said probe(s)' body beyond the area where said probe(s) make capacitive or galvanic ground contact with the sidewalls of said slotted airline.
2. An impedance tuner as in claim 1 , comprising two independent carriages in the same airline each said carriage holding one or more different resonant probes, each probe being dimensioned for a different frequency range.
3. An impedance tuner as in claim 1 , comprising two independent carriages in the same airline with identical or similar resonant probes each.
4. A cascade of two tuners as in claim 1 , each said tuner using a single resonant probe.
5. An impedance tuner as in claim 1 , in which said airline is a coaxial airline with a slot, parallel to the center conductor, said slot having a trapezoidal (slanted) cross section, in which said metallic probes are inserted and make galvanic ground contact, said slot having its narrow opening towards the center of said airline.
6. A cascade of two tuners as in claim 5 , each said tuner using a single resonant probe.
7. An impedance tuner as in claim 5 , in which a resonant metallic probe is used, said probe being made of a solid block with a concave bottom channel, dimensioned in order to match the diameter of the center conductor and having its tails extend vertically beyond the center conductor of the airline, and having a thickness dimensioned in order to slide-fit into the slot of the airline in order to make galvanic contact with the body of said airline and having a probe length, parallel to the center conductor, dimensioned such as to cover a certain frequency band.
8. An impedance tuner as in claim 5 , in which a resonant metallic probe is used, said probe being made of a block having a vertical slot and a cavity in the center, in direction of the center conductor of said airline and having a concave bottom channel, dimensioned in order to match the diameter of the center conductor and having its tails extend vertically beyond the center conductor of the airline, and a thickness dimensioned in order to slide-fit into the trapezoidal slot of the airline and a probe length, parallel to the center conductor, dimensioned such as to cover a certain frequency band, said slot serving in creating spring loaded effect of the tails of said probe and making galvanic contact with the body of said airline.
9. An impedance tuner as in claim 5 , comprising two independent carriages in the same airline with different resonant probes, each dimensioned for a different frequency range.
10. An impedance tuner as in claim 5 , comprising two independent carriages in the same airline with identical or similar resonant probes each.
11. An impedance tuner as in claim 1 , in which said airline is a coaxial airline with a slot, parallel to the center conductor, said slot having a trapezoidal (slanted) cross section, in which said metallic probes are inserted and make galvanic ground contact, said slot having its wide opening towards the center of said airline.
12. An impedance tuner as in claim 11 , comprising two independent carriages in the same airline with different resonant probes, each dimensioned for a different frequency range.
13. An impedance tuner as in claim 11 , comprising two independent carriages in the same airline with identical or similar resonant probes each.
14. A cascade of two tuners as in claim 11 , each said tuner using a single resonant probe.
15. An impedance tuner as in claim 1 , in which said airline is a slotted coaxial airline;
the cross section of said slot being rectangular, having two lateral internal walls parallel to each other.
16. An impedance tuner as in claim 15 , comprising two independent carriages in the same airline with different resonant probes, each dimensioned for a different frequency range.
17. An impedance tuner as in claim 15 , comprising two independent carriages in the same airline with identical or similar resonant probes each.
18. A cascade of two tuners as in claim 15 , each said tuner using a single resonant probe.
19. An impedance tuner as in claim 1 , in which said airline is a parallel plate airline (slabline).
20. An impedance tuner as in claim 19 , in which a resonant metallic probe is used, said probe being made of a solid block with a concave bottom channel, dimensioned in order to match the diameter of the center conductor and having its tails extend vertically beyond the center conductor of the airline, and having a thickness dimensioned in order to slide-fit into the slot of the airline in order to make capacitive contact with the body of said slabline and having a probe length, parallel to the center conductor, dimensioned such as to cover a certain frequency band, said probe being anodized or dielectrically coated.
21. An impedance tuner as in claim 19 , in which a resonant metallic probe is used, said probe being made of a block having a vertical slot and a cavity in the center, in direction of the center conductor of said airline and having a concave bottom channel, dimensioned to match the diameter of the center conductor and having its tails extend beyond the center conductor of the airline, and a thickness dimensioned to slide-fit into the rectangular slot of the airline and a probe length dimensioned to cover a certain frequency band, said slot serving in creating spring loaded effect of the tails of said probe and making galvanic contact with the body of said airline.
22. An impedance tuner as in claim 19 , in which a resonant metallic probe is used, said probe being made of a block having a vertical slot and a cavity in the center, in direction of the center conductor of said airline and having a concave bottom channel and a top guidance section, which slide fits into the slabline and guides the probe horizontally and vertically and a narrower bottom section dimensioned such as to leave small gaps on each side between said probe and the lateral walls of said slabline, said slot creating a spring effect between said probe and slabline for reliable galvanic ground contact between said top guidance section of said probe and the lateral walls of said slabline.
23. An impedance tuner as in claim 22 , in which each lateral side gap has different height, each dimensioned to create a resonance at a different frequency band.
24. An impedance tuner as in claim 19 , in which the sidewalls of said slabline are anodized or otherwise dielectrically coated.
25. An impedance tuner as in claim 24 , in which a resonant metallic probe is used, said probe being made of a solid block with a concave bottom channel, dimensioned in order to match the diameter of the center conductor and having its tails being indented in order to leave a small gap between the body of said probe and the walls of said slabline and extend vertically beyond the center conductor of the slabline, and having a thickness dimensioned in order to slide-fit into the slot of the slabline, in order to make capacitive contact with the sidewalls of said slabline and having a probe length, parallel to the center conductor, dimensioned such as to cover a certain frequency band.
26. An impedance tuner as in claim 19 , in which a resonant metallic probe is used, said probe being made of a solid block with a concave bottom channel, and having a top guidance section, which slide fits into the slabline and guides the probe horizontally and vertically and a narrower bottom section dimensioned such as to leave small gaps on each side between said probe and the lateral walls of said slabline, said probe being dielectrically coated or anodized so that the top guidance section makes reliable capacitive ground contact with the lateral walls of said slabline.
27. An impedance tuner as in claim 26 in which said slabline is anodized or otherwise dielectrically coated.
28. An impedance tuner as in claim 26 , in which each lateral side gap has different height, each height dimensioned to create a resonance at a different frequency band.