Frequency-Shifted PIM Cancellation for Lower RF Sampling Rates
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Solution Overview
Problem
Conventional PIM reduction algorithms in RF systems require high sampling rates to avoid aliasing, leading to increased power consumption and design complexity, especially in scenarios where carrier signal spacing is narrow.
Innovation Solution
Implementing frequency shifting of signal components to reduce the frequency spacing between TX carrier signals, allowing the PIM filter coefficient estimation algorithm to run at a lower sampling rate, thereby reducing power consumption and design complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PIM reduction algorithms are used with high sampling rates to avoid aliasing, then measurement precision is improved, but use of energy increases and device complexity increases
Solution Approach 1:
The patent applies frequency shifting to change the frequency domain parameters of the signal, specifically shifting the carrier signals to reduce their spacing. This parameter transformation allows the PIM reduction algorithm to operate at lower sampling rates while maintaining estimation accuracy, thereby reducing power consumption without sacrificing measurement precision
2Measurement precision
If conventional PIM reduction algorithms are used with high sampling rates to avoid aliasing, then measurement precision is improved, but device complexity increases
Solution Approach 1:
By transforming the frequency domain parameters through frequency shifting, the patent enables the system to use lower sampling rates. This reduces the complexity of the PIM reduction circuit and algorithm implementation while maintaining the same level of coefficient estimation accuracy, thus resolving the contradiction between precision and complexity
3Use of energy by moving object
If frequency shifting is applied to reduce frequency spacing between TX carrier signals, then use of energy decreases and device complexity decreases, but the signal frequency characteristics change
Solution Approach 1:
The patent applies frequency shifting as a preliminary transformation before PIM reduction processing. This preliminary action modifies the signal's frequency characteristics temporarily to enable lower sampling rates, but the original frequency information is preserved and restored through the algorithm, preventing permanent harmful frequency distortion
Solution Approach 2:
The PIM filter coefficient estimation algorithm uses feedback from the frequency-shifted signals to calculate correction coefficients. These coefficients are then applied to compensate for the frequency shifting effects, ensuring that the final output signal maintains its original frequency characteristics while benefiting from the reduced power consumption and complexity
Data Source
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AI summary
A system for reducing or eliminating PIM interference in an RX signal is disclosed. The system is configured to use RX and TX signals to generate a frequency-shifted output that includes a RX carrier signal component of the RX signal, as well as first and second TX carrier signal components of the TX signal, positioned in a frequency spectrum so that a frequency spacing between the first and the second TX carrier signal components and a frequency spacing between the RX carrier signal component and a closest one of the first and the TX second carrier signal components is smaller than a frequency spacing between the first and the second TX carrier signal components in the TX signal. The system may then use the frequency-shifted output to generate an estimate of a PIM signal component in the RX signal.