VSWR Estimation via Correlation to Suppress Interference
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Solution Overview
Problem
In wireless transmission systems, monitoring the condition of antennas and cable/connector systems is challenging due to noise in reflected signals, leading to false alarms and inaccurate return loss measurements, especially with complex modulation and co-siting scenarios.
Innovation Solution
A method involving correlation analysis between forward and reflected signal samples to determine the maximum correlation value, which is associated with the return loss of the cable/connector system, effectively suppressing interfering signals and providing accurate return loss estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional power detectors are used to measure reflected power, then the measurement process is simple, but the measurement precision deteriorates due to noise from co-sited transmitters and complex modulation signals
Solution Approach 1:
The patent extracts only the relevant reflected signal component by correlating the received signal with a known copy of the transmitted signal. This extraction process separates the desired reflected power information from the interfering noise and co-sited transmitter signals, thereby improving measurement precision without requiring complex hardware modifications
Solution Approach 2:
The patent introduces correlation processing as an intermediary step between signal reception and power measurement. This intermediary process uses the known transmitted signal as a reference to filter and isolate the reflected signal component, enabling accurate return loss measurement in the presence of complex interference conditions
2Adaptability or versatility
If log detectors are used for complex modulation and multiple carriers, then the detection covers wide bandwidth, but the measurement precision deteriorates because log detectors are not true power detectors
Solution Approach 1:
The patent replaces the conventional log detector mechanism with a correlation-based power measurement system. Instead of using logarithmic detection that varies with signal type, the system uses correlation processing followed by true power calculation, which provides consistent and accurate measurements across all modulation types and carrier configurations
Solution Approach 2:
The patent changes the measurement parameter approach by using correlation magnitude squared as the basis for power calculation rather than logarithmic detection output. This parameter change ensures that the measurement accurately reflects true power regardless of modulation complexity, carrier number, or signal bandwidth
3Difficulty of detecting and measuring
If directional couplers and bridges are used to separate forward and reflected signals, then the signal separation is effective, but the measurement precision deteriorates due to noise in the reflected signal path
Solution Approach 1:
The patent extracts the reflected signal component through correlation processing, effectively removing the noise and interference that contaminates the reflected signal path in conventional directional coupler systems. This extraction method achieves clean separation of forward and reflected power measurements without the noise amplification problems of passive directional devices
Data Source
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AI summary
A method includes accessing sets of correlation values, each set corresponding to a correlation performed between a number of first samples and a same number of second samples. The sets of correlation values were determined by aligning the number of the first samples with selected second samples and sliding the number of first samples across the second samples to select different sets of the second samples. The first samples are samples of a forward signal transmitted over a cable/connector system to one or more antennas, and the second samples are samples of a reflected RF signal that comprises a reflected version of the forward signal. The method includes determining a maximum value from the plurality of sets of correlation values, and associating the maximum value with a return loss of the cable/connector system. Apparatus, computer programs, and program products are also disclosed.