MHz range harmonic impedance tuner and method
View Patent ↗An electro-mechanical MHz range harmonic load pull tuner is made as a cascade of filter sections and independent tuning sections; the filter section includes three parallel series resonant circuits, each set including one inductor and one adjustable capacitor. The tuning section includes three parallel tuning modules; each module comprising three adjustable shunt air capacitors inter-connected using coaxial cables of appropriate length. Each capacitor is remotely adjustable to 10 or 20 values (settings); the tuner creates independently controllable impedances at three (harmonic) frequencies in octave size frequency bands between 5 and 150 MHz. An Error Function-based optimization algorithm allows impedance tuning at three frequencies independently, by optimized searching among the more than 20 9 =512*10 9 possible combined tuner states. Stepper motors, drivers and control software are used to automate, calibrate and use the harmonic tuner for automated harmonic load pull measurement.
1. A MHz range harmonic impedance tuner comprising
an input port and an output port
and a cascade of a filter section and an impedance tuning section;
wherein
the filter section comprises at least two independent serial resonance circuits of inductor and adjustable capacitor connected in parallel;
and wherein
the tuning section comprises at least two independent tuning modules, each module comprising at least three adjustable shunt capacitors interconnected using transmission lines;
and wherein
the cascades of filter sections and tuning sections are connected in parallel, the common terminal of the filter sections being the input port of the tuner and the common terminal of the tuning sections being the output port of the tuner.
2. The tuner of claim 1 ,
wherein
the filter section comprises three filter resonant circuits and the tuning section comprises three tuning modules.
3. The tuner of claim 2 ,
wherein
the series resonance frequencies of the filter resonant circuits are tuned independently to harmonic frequencies Fo (fundamental), 2Fo (first harmonic) and 3Fo (second harmonic).
4. The tuner of claim 3 ,
wherein
the tuning modules are designed and configured to create maximum tuning range at the frequency range of the associated resonant filter circuit.
5. The tuner of claim 4 ,
wherein
the capacitors of the filter resonant circuits and of the tuning modules are remotely controlled using stepper motors, electronic control, appropriate gear and control software.
6. A calibration method for tuner as in claim 5 comprising the following steps:
a) adjusting the filter resonant circuits to the fundamental (Fo) and harmonic frequencies (2Fo and 3Fo);
b) initialize (disengage) all capacitors of all tuning modules;
c) measure s-parameters of the tuner at the fundamental Fo and harmonic frequencies 2Fo and 3Fo between input and output ports and save in matrix [S0(N*Fo)], N=1,2,3;
d) measure s-parameters of the tuner at Fo, 2Fo and 3Fo for a multitude of capacitor settings of the Fo tuning module, de-embed s-parameters of all capacitors, except the one closest to the input port by cascading with [S0(N*Fo)] −1 and save;
e) initialize the capacitors of the tuning module in step d) and measure s-parameters of the tuner at Fo, 2Fo and 3Fo for a multitude of capacitor settings of the 2Fo tuning module, de-embed s-parameters of all capacitors except the one closest to the input port by cascading with [S0(N*Fo)] −1 and save;
f) initialize the capacitors of the tuning module in step e) and measure s-parameters of the tuner at Fo, 2Fo and 3Fo for a multitude of capacitor settings of the 3Fo tuning module, de-embed s-parameters of all capacitors except the one closest to the input port by cascading with [S0(N*Fo)] −1 and save;
g) create, in computer memory, all permutations of s-parameters of steps d) to f) and save in tuner calibration file(s).
7. A tuning (impedance synthesis) method for the tuner calibrated as in claim 6 comprising the following steps:
a) select tolerances T(Fo), T(2Fo) and T(3Fo);
b) select weight factors W(Fo), W(2Fo) and W(3Fo);
c) select target reflection factors Γ(Fo), Γ(2Fo) and Γ(3Fo);
d) load the tuner calibration file in memory;
e) divide the reflection factor surface (Smith chart) in approximately 100 or more adjacent segments;
f) identify the segment of step e) comprising the target Γ(Fo);
g) search through all capacitor Ci settings generating reflection factors at Fo (Γ(Fo)) inside the segment of step f), calculate the Error Function (EF(Fo, 2Fo, 3Fo)) and save the smallest value EFmin and associated capacitor settings, Cio;
h) starting with settings Cio repeat step g) using interpolated s-parameters, until a global minimum of EF (EFopt) is reached at capacitor settings Ciopt;
i) save capacitor settings and move all capacitors to their optimum settings Ciopt.
8. The calibration method of claim 6 , applied to the tuner of claim 5 for only fundamental (Fo) and one harmonic (2Fo or 3Fo) filter resonant circuits and two associated tuning modules.
9. The tuning method of claim 6 , applied to the tuner of claim 5 comprising only two filter resonant circuits and two tuning modules.