Multi-Tone Signal Phase Coherent Mixing and Downconversion
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Solution Overview
Problem
Current RF and microwave measurement technologies, such as high-frequency spectrum analyzers and vector signal analyzers, face challenges in maintaining phase coherence between tones, leading to loss of phase information and reduced signal-to-noise ratios when measuring modulated signals.
Innovation Solution
A system and method that uses phase coherent mixing and data acquisition to maintain phase coherence between tones in multi-tone signals, employing a reference signal with fixed phase differences to normalize and downconvert signals, allowing for reconstruction of the original signal through calibration techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency spectrum analyzers are used to measure RF and microwave signals, then amplitude spectrum can be obtained, but phase coherence between tones is lost
Solution Approach 1:
The measurement process is segmented into multiple sequential downconversion steps, with each step handling a specific frequency range or tone. The system divides the multi-tone signal into individual tones and processes them separately while maintaining phase reference to the original signal, thereby preserving phase coherence information that would be lost in a single broadband measurement.
Solution Approach 2:
A reference signal is introduced as an intermediary element that maintains phase coherence with the original multi-tone signal. This reference signal is used to normalize the phase of individual tones during sequential downconversion, acting as a mediator that preserves the phase relationship between tones throughout the measurement process.
2Measurement precision
If vector signal analyzers are used to demodulate modulated high frequency tones, then high signal to noise ratios can be achieved, but phase coherence between fundamental and harmonics is lost
Solution Approach 1:
The system performs preliminary downconversion of the high-frequency signal to an intermediate frequency before final demodulation. This preliminary action maintains phase coherence by preserving the relationship between fundamental and harmonic tones during the frequency translation process, allowing subsequent demodulation to achieve high signal-to-noise ratio without losing phase information.
Solution Approach 2:
An intermediate frequency representation serves as a mediator between the high-frequency input signal and the baseband output. This intermediate representation maintains phase coherence between tones while enabling the high signal-to-noise ratio demodulation capabilities of vector signal analyzers to be applied effectively.
3Reliability
If repetitive sampling oscilloscopes are used to measure modulated signals, then dynamic range is limited, but phase coherence can be maintained with synchronous triggering
Solution Approach 1:
The system replaces the mechanical synchronous triggering mechanism with a digital reference signal normalization approach. Instead of relying on precise mechanical synchronization between the sampling clock and the modulated signal, the system uses digital processing to reference all measurements to a stored phase reference, thereby maintaining phase coherence while enabling larger dynamic range through digital rather than purely time-synchronized measurement.
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 accurate measurement and reconstruction of multi-tone signals with maintained phase coherence, improving dynamic range and signal quality by eliminating arbitrary delays and phase offsets, while allowing for repeatable and determined distortion correction.
Implementation Method 1
phase coherent mixing means for demodulation in connection with data acquisition means for digitization. The mixing means and data acquisition means are fed with the multi-tone signal and with a reference signal comprising said phase coherent tones
Data Source
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AI summary
The present invention is related to a system (1) for determining a representation of a multi-tone signal (2) comprising a plurality of phase coherent tones, at least two of said phase coherent tones being modulated by a modulating signal, said system comprising an input (3) for applying the multi-tone signal (2), phase coherent mixing means (5) for demodulation in connection with data acquisition means (6) for digitization, said mixing means and data acquisition means arranged for being fed with the multi-tone signal and with a reference signal (8) comprising said phase coherent tones, each pair of phase coherent tones having a fixed phase difference, whereby the data acquisition means is arranged for being triggered by a trigger signal (4) for yielding a representation of said modulation signals with fixed delay, processing means (7) arranged for receiving digital signals output from the data acquisition means and for comparing phase information of a downconverted tone of the multi-tone signal after demodulation with phase information derived from the corresponding tone of the demodulated reference signal and further arranged for controlling the phase coherent mixing means for sequential downconversion, such that a representation of said multi-tone signal can be determined.