RF Signal Level Measurement Circuit Using Phase Shifting
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Solution Overview
Problem
Existing RF signal measurement technologies face challenges in accurately measuring signal levels over a wide frequency range and under varying load impedance conditions, particularly in multiradio devices, due to issues with directional couplers such as high losses, poor directivity, and inaccuracy, as well as difficulties in miniaturization and integration with other circuit elements.
Innovation Solution
A method and measurement circuit that utilize two versions of an RF signal with a phase difference, where one version is inverted and the phase difference is replicated in the other, allowing for the combination of phase-inverted and phase-shifted signals to produce an output indicative of the RF signal level, independent of frequency and impedance mismatch, enabling calibration to compensate for errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a directional coupler is used to measure RF signal levels, then signal level measurement capability is provided, but measurement precision deteriorates due to high losses, poor directivity, and inaccuracy
Solution Approach 1:
The patent replaces the mechanical/electromagnetic directional coupler structure with a signal processing approach using phase shifters and hybrid couplers. Instead of relying on the physical directional coupling mechanism, the invention uses phase manipulation (shifting and inverting) combined with hybrid coupling to achieve accurate power measurement without the losses and directivity issues of traditional directional couplers
Solution Approach 2:
The invention changes the measurement approach by manipulating signal parameters (phase and amplitude) rather than relying on the directional coupler's physical parameters. By introducing phase shifters that create specific phase differences and using hybrid couplers with defined coupling ratios, the system achieves accurate power measurement through parameter transformation rather than direct physical coupling
2Volume of moving object
If a directional coupler is miniaturized to reduce device size, then device complexity is reduced, but measurement precision deteriorates due to unacceptably high losses and poor directivity
Solution Approach 1:
The patent replaces the miniaturized directional coupler with an integrated circuit implementation using phase shifters and hybrid couplers. This substitution allows the measurement function to be implemented in a compact form factor while maintaining measurement accuracy, as the phase shifting and hybrid coupling mechanisms can be efficiently integrated without suffering from the same miniaturization penalties as directional couplers
3Measurement precision
If calibration is applied to compensate for directional coupler inaccuracies, then measurement precision improves, but ease of operation deteriorates due to inability to calibrate under varying impedance conditions
Solution Approach 1:
The patent incorporates a feedback mechanism where the measurement system continuously monitors the RF signal and adjusts its operation based on the measured values. The system uses the measured power level information to control the amplifier section, creating a closed-loop system that automatically compensates for variations without requiring manual calibration, thus maintaining both high precision and ease of operation under varying impedance conditions
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 provides accurate RF signal level measurement across a wide frequency range and varying impedance conditions, facilitating integration with other RF circuits and optimizing transmitter device performance by removing frequency dependency and allowing for calibration to enhance measurement accuracy.
Implementation Method 1
a transmission phase shifter
Implementation Method 2
a measurement circuit configured to combine a signal coming through said second coupling with a phase-inverted version of a signal coming through said first coupling to produce a first output signal indicative of a power level
Data Source
AI summary
On a radio frequency signal path a transmission phase shifter causes a phase shift. From a first end of said phase shifter comes a first sample, and from a second end of said phase shifter comes a second sample. Another phase shifter changes the phase of the second sample by the same magnitude as said transmission phase shifter. A measurement circuit combines the phase-shifted second sample with a phase-inverted version of the first sample to produce an output indicative of a power level of the original signal on the radio frequency signal path.