Hybrid Load Pull Tuning for Wide-Range Low-Power Impedance Matching
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Solution Overview
Problem
Traditional load pull testing systems for microwave transistors face limitations in tuning range, power handling, and universality due to electro-mechanical slide screw tuners, which introduce signal transformation and insertion loss, and active tuners require high power amplifiers for high-speed operation but are costly and nonlinear.
Innovation Solution
A digital hybrid load pull system combining high-speed active digital and passive electro-mechanical tuning with calibration and impedance synthesis algorithms, featuring a closed-loop digital electronic tuner and a mechanical pre-matching tuner section, allowing for high power handling with minimized active power injection and real-time impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electro-mechanical slide screw tuners are used, then tuning range is improved, but insertion loss increases and power handling is limited
Solution Approach 1:
The tuner is divided into two independent sections: a passive electro-mechanical slide screw tuner for wide tuning range and an active digital electronic tuner for precise control. Each section operates in its optimal regime, with the passive section providing broad coverage and the active section enabling fine adjustments without mechanical wear or excessive insertion loss.
Solution Approach 2:
The patent combines passive electro-mechanical tuning elements with active digital electronic tuning elements into a unified hybrid tuner system. This merging allows the system to leverage the advantages of both approaches: the wide tuning range of mechanical tuners and the low insertion loss, high speed, and precision of electronic tuners.
2Speed
If active tuners are used for high-speed operation, then tuning speed is improved, but power requirements increase and cost increases
Solution Approach 1:
The active digital electronic tuner operates at low power levels sufficient for control and measurement functions, while the passive electro-mechanical tuner handles the bulk of power handling requirements. This partial action approach allows high-speed electronic control without requiring the active section to be oversized for full power handling.
Solution Approach 2:
The passive electro-mechanical tuner section acts as an intermediary that handles high power levels, allowing the active digital electronic tuner to operate at lower power levels for precise control. The passive section mediates between the high-power DUT and the low-power electronic control circuitry.
3Speed
If active tuners are used, then tuning speed is improved, but linearity deteriorates
Solution Approach 1:
The tuning function is segmented between passive electro-mechanical elements that provide linear, predictable impedance transformations and active digital elements that provide fast switching and control. The passive section ensures linearity while the active section provides speed.
Solution Approach 2:
The patent replaces purely mechanical tuning with a hybrid system where digital electronic control supplements mechanical tuning. The digital section can rapidly switch between predefined impedance states, providing high-speed tuning without the non-linearities associated with fully active electronic tuners operating at high power.
Data Source
AI summary
A digital high-speed hybrid load pull test system comprises a slide screw automatic passive tuner, a digital active forward injection loop in a closed loop transmission configuration, calibration and tuning algorithms. The forward active injection loop comprises at least one adjustable coupler, a digital electronic tuner and feedback power amplifier; the passive tuner comprises one or more metallic tuning probes, used to create passive reflection factors. Small signal calibration of the passive and active tuners create a global calibration data base, used to pre-tune in the area of the target impedance and final high power (nonlinear) tuning employs a in-situ signal power wave search and measurement for digital impedances around the small signal pattern. The system provides for high speed low injected power tuning with maximum reflection factor at DUT reference plane reaching unity.