High frequency, high reflection pre-matching tuners with variable zero initialization

Abstract

Automatic microwave pre-matching tuners with new zero positioning capability allowing for a minimum idle airline section between pre-matching and tuning section, thus minimizing insertion loss and enhancing high reflection tuning capability at high frequencies and tuner calibration algorithm of the pre-matching section over one half of a wavelength and of the tuning section over one full wavelength at each operation frequency and associated tuning and measurement operation algorithms.

What I claim as my invention is: 
     
       1. An automatic RF impedance tuner comprising an input port and an output port, a slotted airline connecting both ports, means of remotely positioning two independent mobile carriages carrying a wideband RF probe each, said probes being a primary, or pre-matching probe and a secondary, or tuning probe, said probes can be inserted into the slot and moved parallel to the axis of the airline and can be precisely positioned in such a manner as to generate adjustable microwave reflection factors, and whereas said secondary probe has means for a variable and frequency dependent initial horizontal position relative to the initial position of the primary probe. 
     
     
       2. A method for initializing horizontally the RF probes of the tuner as in  claim 1 , where the zero position of the primary probe is at a position closest to the tuner test port, adjacent to the device under test, and the zero position of the secondary probe is at a position adjacent to the primary probe, when said primary probe is at its initial (or zero) position, both zero positions being frequency independent. 
     
     
       3. A method for initializing horizontally the RF probes of the tuner where the zero position of the primary probe is at a position as in  claim 2  and the zero position of the secondary probe is at a frequency dependent position adjacent to the far end of the carriage of the primary probe, when the primary carriage is at one half of a wavelength away from its initial (zero) position, at the operating frequency. 
     
     
       4. A method for initializing and calibrating automated RF impedance tuner,
 said tuner comprising a test port, an idle port and a slotted airline (slabline) between the ports and two independent remotely controlled mobile carriages sliding along the slabline, carriage 1 closest to the test port and carriage 2 closest to the idle port,   said tuner having frequency dependent initial horizontal position,   each said carriage having a vertical axis carrying a wideband RF tuning probe, the carriage 1 carrying probe 1 (pre-matching probe) and the carriage 2 carrying probe 2 (tuning probe);   said probes being remotely insertable into the slabline at adjustable distance from the center conductor of the slabline and moving parallel to the axis of the airline;   whereby the probe 2 has variable and frequency dependent initial horizontal position relative to the initial position of the probe 1;   whereby each carriage comprises at least one horizontal limit (zero positioning) switch, and whereby frequency independent zero position occurs when the switch of the carriage 1 hits the tuner wall and the switch of the carriage 2 hits the wall of the carriage 1;   said method comprising the following steps:   a) attaching the tuner to a pre-calibrated vector network analyzer (VNA);   b) initializing (placing to zero position closest to the test port) the carriage 1 and withdrawing the probe 1 from the slabline;   c) moving the carriage 2 at least one wavelength at a test frequency away from the carriage 1 towards the idle port and withdrawing the probe 2 from the slabline;   d) inserting the probe 1 into the slabline progressively, measuring the reflection factor (S11) at the test port with the VNA and saving vertical positions at incremental S11 steps of approximately 0.1, up to S11 approximately 0.9;   e) moving the probe 1 to the vertical positions determined in step d) and, for each vertical position of probe 1, moving the carriage 1 in a multitude of steps from zero to half a wavelength (λ/2) at the test frequency, measuring a four s-parameters of the tuner and saving;   f) initializing the carriage 1 and withdrawing the probe 1 from the slabline;   g) initializing the carriage 2 (placing to zero position closest to the carriage 1);   h) repeating step d) for the probe 2;   i) moving the probe 2 to the values determined in step h) and, for each vertical position of the probe 2, moving the carriage 2 in a multitude of steps from zero to full wavelength (λ) at the test frequency, measuring the four s-parameters of the tuner and saving.    
     
     
       5. A tuning (impedance synthesis) method for RF impedance tuner, calibrated as in claim 4, comprising the following steps:
 a) loading calibration data into computer memory;   b) defining a requested impedance;   c) calculating horizontal positions for probe 1 (X1) and probe 2 (X2) as required to generate the requested impedance;   d) if (X2≦X1) replacing X2 by (X2+λ/2);   e) calculating vertical positions for probe 1 (Y1) and probe 2 (Y2), as required to generate the requested impedance;   f) moving the probe 1 to (X1,Y1) and the probe 2 to (X2,Y2).