Low-Loss Loop Coupler for High-Frequency Load-Pull Characterization
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Solution Overview
Problem
Existing loadpull measurement methods face significant energy losses and measurement inaccuracies due to the placement of distributed directional couplers between the device-under-test and the tuner, leading to noisy measurements and sensitivity loss, especially when dealing with high or low resistive impedances and harmonic frequencies.
Innovation Solution
The introduction of a low insertion loss loop type coupling structure between the device-under-test and the tuner, which connects to both coupled arms of the coupler, minimizing energy loss and allowing for accurate voltage and current waveform sensing without affecting impedance matching or calibration complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If distributed directional couplers are placed between the device-under-test and the tuner, then voltage and current waveforms can be sensed, but significant energy losses occur and measurement sensitivity is reduced
Solution Approach 1:
The patent extracts the sensing function from the main signal path by using a resistive bridge that samples the signal through a high-impedance node. The distributed directional coupler is replaced with a sensing mechanism that does not require the signal to pass through lossy coupling structures, thereby eliminating insertion losses while maintaining waveform sensing capability
Solution Approach 2:
The patent introduces a resistive bridge as an intermediary sensing element that couples to the signal through a high-impedance node. This intermediary structure allows waveform measurement without requiring the main signal path to pass through lossy distributed couplers, thus reducing energy loss while enabling precise measurement
2Measurement precision
If distributed directional couplers are used for sensing, then voltage and current waveforms can be measured, but measurement accuracy deteriorates due to noisy measurements and sensitivity loss
Solution Approach 1:
The sensing function is extracted from the main signal path by using a high-impedance sampling node that does not require the signal to pass through lossy distributed couplers. This extraction eliminates the source of measurement noise and sensitivity loss while maintaining accurate waveform measurement capability
Solution Approach 2:
A resistive bridge is introduced as an intermediary sensing element that couples to the signal through a high-impedance node. This intermediary structure provides a clean measurement path that is isolated from the noise and sensitivity issues affecting distributed directional couplers, thereby improving measurement reliability
3Measurement precision
If existing loadpull measurement methods are used, then device characterization can be performed, but complex calibration procedures are required and impedance matching is affected
Solution Approach 1:
The sensing function is extracted from the main signal path using a high-impedance sampling node, which eliminates the need for complex calibration procedures required by distributed directional couplers. This extraction simplifies the overall measurement system while maintaining device characterization capability
Solution Approach 2:
A resistive bridge is introduced as an intermediary sensing element that provides a straightforward measurement path without requiring complex calibration. This intermediary structure decouples the sensing function from the impedance matching network, thereby reducing system complexity while maintaining measurement precision
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
This approach reduces energy loss and maintains measurement accuracy by minimizing the impact of energy reflection on the device-under-test, providing clear and precise data on voltage and current waveforms, including harmonic frequencies, without the need for complex calibration procedures.
Implementation Method 1
a low insertion loss loop type coupling structure between the device-under-test and the tuner
Data Source
AI summary
An impedance tuning measurement setup and method for characterizing high frequency devices-under-test whereby one inserts an extremely low loss directive coupling structure between the terminal of the device-under-test and that part of the impedance tuner that generates the variable impedance. One or both coupled arm outputs of the directive coupling structure are connected to the inputs of a broadband RF receiver. By using the extremely low loss directive coupling structure one avoids the loss of energy caused by the distributed directional couplers or the resistive bridges used in prior art. The low loss directive coupling structure is formed by a small piece of conductive wire, which is inserted into the electro-magnetic waveguiding structure that guides the RF signals towards and from the DUT terminals. The ends of the small piece of conductive wire are connected to the center conductors of two electromagnetic waveguiding structures, which act as the coupling arms.