Low frequency load pull tuner using dielectric filled spiral airline
View Patent ↗A new harmonic slide screw impedance tuner for VHF-UHF frequencies uses a reduced overall length spiral slabline structure and three rotating carriages allowing reducing the linear size of the tuner from originally L=3λ/2 to a spiral length L=2πRN of a cylinder with 2R diameter and a height H made up of N floors (example: F=100 MHZ, λ=300 cm, R=10 cm, N=10 floors of 2 cm each, yields a 20×20 cm cylinder versus a 450 cm linear slabline; a core reduction of 450/20=23). The slabline stands vertically on the bench table surface and the carriages, including the tuning probes rotate and wind up and down around a vertical axis through the center of the spiral slabline, controlled by a rack-and pinion spiral arrangement on the edge of the spiral slabline. The rotation of the carriages controls the phase of GAMMA and the insertion of the tuning probes into the channel of the slabline controls its amplitude.
1 . A slide screw impedance tuner, comprising:
a test port, an idle port and a spiral slabline immerged in dielectric fluid, between the ports having two conductive sidewalls forming a spiral channel and a spiral center conductor, and
up to three remotely controlled mobile carriages rolling on a periphery of the sidewalls of the spiral slabline and carrying at least one reflective (tuning) probe each, remotely insertable into the spiral channel and coupled capacitively with the spiral center conductor;
wherein
the periphery of the sidewalls is indented forming a spiral rack;
and wherein
the mobile carriages include remotely controlled teethed wheels (pulleys), engaged with the indentations of the spiral rack on the sidewalls ensuring travelling of the carriages along the periphery of the sidewalls in a rack-and-pinion configuration;
and wherein
an available linear length of the spiral slabline is at least equal to the number of mobile carriages used, times one half of a wavelength (λ/2) at a lowest frequency of operation of the slide screw tuner;
and wherein
the spiral center conductor is centered between the sidewalls and runs at constant depth from the periphery of the sidewalls.
2 . The slide screw impedance tuner of claim 1 ,
wherein the characteristic impedance of the in dielectric fluid immerged spiral slabline is 50 Ohms.
3 . The slide screw impedance tuner of claim 1 ,
wherein the dielectric fluid, in which the spiral slabline is immerged, is a mixture of dielectric fluids of different dielectric permittivity (ε r ).
4 . The slide screw impedance tuner of claim 3 ,
wherein the mixture of dielectric fluids is recirculated.
5 . The slide screw impedance tuner of claim 3 ,
wherein the dielectric fluid is a mixture of high dielectric permittivity (Er) fluid and low dielectric permittivity fluid.
6 . The slide screw impedance tuner of claim 1 ,
wherein
the tuning probes are conductive slugs, slide-fitting into the spiral channel of the slabline and having a concave bottom surface matching the shape of the spiral center conductor of the slabline.