Active Impedance Tuner Using Heterodyne Feedback for Base-Band Load Pull
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Solution Overview
Problem
Existing load pull testing systems for RF transistors and active components are limited by the inability to effectively control and measure base-band impedances at very low frequencies, particularly below 10 MHz, due to the insertion loss of wafer-probe access paths and the limitations of passive tuners, which hinder accurate characterization and optimization of RF network performance.
Innovation Solution
A very low frequency active impedance tuner using the heterodyne principle, which mixes low base-band signals into the local oscillator frequency range (1-4 GHz) and converts them back to the low base-band frequencies for amplification and injection into the device under test, allowing for the creation of a virtual active load and bypassing the limitations of conventional tuners and circulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive tuners are used for load pull testing, then the device structure is simple, but the tuning range is limited and insertion loss is high at frequencies below 10 MHz
Solution Approach 1:
The patent introduces an active tuner as an intermediary device that uses a local oscillator and mixing circuitry to translate base-band frequencies to higher RF frequencies where conventional tuners operate effectively. This mediator approach allows accurate impedance control at base-band frequencies without requiring specialized low-frequency passive tuner components
Solution Approach 2:
The patent changes the operating parameters of the tuner by using active electronic components that can dynamically adjust impedance across a wide frequency range. The active tuner modifies its electrical characteristics through electronic control, enabling it to overcome the frequency limitations of passive mechanical tuners
2Area of stationary object
If wafer-probe access paths are used, then the test setup is compact, but insertion loss increases and reduces effective tuning range
Solution Approach 1:
The patent replaces the mechanical passive tuning approach with an active electronic tuning system. The active tuner uses electronic signal processing and active components to compensate for insertion losses in the wafer-probe access paths, thereby maintaining effective tuning range despite the compact test fixture configuration
3Device complexity
If conventional tuners are used at base-band frequencies, then the device complexity is low, but the tuning range is restricted and cannot operate below 10 MHz
Solution Approach 1:
The active tuner acts as an intermediary that bridges the gap between base-band frequencies and the operational range of conventional tuners. By using frequency translation through mixing with a local oscillator, it enables conventional tuner components to effectively operate at frequencies where they would normally be ineffective
Solution Approach 2:
The patent implements a dynamic tuning system where the local oscillator frequency can be varied to adapt to different base-band frequencies. This dynamic adjustment capability allows the tuner to maintain versatility across a wide frequency range, unlike static conventional tuners
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise control and measurement of base-band impedances across a wideband frequency range, enhancing the characterization and optimization of RF network performance, particularly in nonlinear device characterization and large signal linearity testing, by compensating for insertion loss and extending the tuning range beyond the capabilities of passive tuners.
Implementation Method 1
A very low frequency active impedance tuner using the heterodyne principle, which mixes low base-band signals into the local oscillator frequency range (1-4 GHz) and converts them back to the low base-band frequencies
Data Source
AI summary
A base-band (kHz to MHz range) very low frequency active impedance tuner allows controlling the reflection factor at a multitude of frequencies in the base-band for systematic evaluation of the effect of bias networks on nonlinear quantities of a RF transistor, like EVM and ACPR. It comprises an electronically controlled active heterodyne feedback loop, frequency mixing, filtering and a remotely controlled digital electronic tuner. The digital electronic tuning feedback module operates at standard octave band GHz range, which allows controlling impedances over several decades in the base-band frequency range.