Harmonic rejection tuner with adjustable short circuited resonators
View Patent ↗A harmonic rejection tuner, used for reflecting RF power at the harmonic frequencies in a load pull measurement setup, uses adjustable capacitive grounding of half wavelength long resonator stubs in order to vary the electrical length and thus the resonant frequency of the resonators. Since the resonators themselves are by nature narrowband, this frequency adjustability allows for a higher frequency bandwidth and better coverage of operational frequency range of the test setup. Since load pull measurements are carried out mostly at fixed frequencies, adjustment of the capacitive shorts can be either manual or by remote control. Capacitive shorting the resonator stubs allows DC bias to be applicable to the device under test through the tuner.
1. A harmonic rejection impedance tuner comprising:
an input/test port and an output/idle port;
a slotted airline between the two ports;
one or more sets of coaxial resonator assemblies, one set of resonator assemblies for each harmonic frequency; and
wherein each said assembly comprising two cylindrical resonators, each said resonator comprising an external conductive wall and a center conductor, said external wall having perfect galvanic contact with the ground of said slotted airline, said center conductor making on one end perfect galvanic contact with the center conductor of said slotted airline, and at one half-wavelength away from said galvanic contact, perfect capacitive RF ground contact with said external wall of said resonator through a high dielectric permittivity washer/rod, which is fitting between said center conductor and external wall of the resonator.
2. A tuner as in claim 1 , in which the center conductor of said resonator is making perfect sliding galvanic contact with the center conductor of said slotted airline.
3. A tuner as in claim 2 , in which said dielectric washer/rod can slide along said center conductor of said resonator in order to adjust the electrical length of said resonator and thus its half-wavelength resonant frequency.
4. A harmonic rejection tuner, as in claim 1 , in which said center conductors of the resonators are surrounded, on one end, by a metallic cylinder, which slides on the inside of the resonator cavity and makes galvanic contact with the external ground wall of the cavity and is capacitively coupled with said center conductors on the inner side, using a thin film of dielectric material inserted between said surrounding metal cylinder and the center conductors.
5. A harmonic rejection tuner, as in claim 4 , in which the vertical position of the metallic cylinder surrounding the center conductors of the resonators can be adjusted manually.
6. A harmonic rejection tuner, as in claim 4 , in which the horizontal distance between resonator assemblies can be adjusted manually.
7. A harmonic rejection tuner, as in claim 4 , in which the vertical position of the metallic cylinder surrounding the center conductors of the resonators can be adjusted automatically using stepper motors, translation gear and computerized remote control.
8. A harmonic rejection tuner, as in claim 4 , in which the horizontal distance between resonator assemblies can be adjusted automatically, using stepper motors, translation gear and computerized remote control.
9. A harmonic tuner as in claim 8 , wherein the harmonic tuner is calibrated by measuring said tuner's scattering parameters (S-parameters), as a function of frequency and of vertical positions of the metallic cylinders inside the resonator assemblies and as a function of horizontal distance between the resonator assemblies, said frequency being close to and including the resonance frequency of the resonators, said scattering parameters being saved in calibration files for later use.