TX LO Leakage Calibration via Loopback Circuitry
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Solution Overview
Problem
Existing wireless communication systems face challenges in accurately measuring and correcting TX LO leakage due to corruption from LO leakage of measurement circuitry, DC offsets, phase differences, and LO harmonics, especially when using non-linear mixers, which degrades signal quality and compliance with regulatory standards.
Innovation Solution
A method and system for estimating and correcting TX LO leakage using a loopback path with filters, buffers, and switches to isolate and measure DC signals, filter out LO harmonics, and compensate for phase differences, allowing for continuous calibration and correction of TX LO leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a loopback path is used to measure TX LO leakage, then measurement capability is provided, but measurement precision is degraded due to LO leakage of measurement circuitry and DC offsets
Solution Approach 1:
The patent extracts and removes the harmful LO leakage components and DC offsets from the measurement path by using additional mixers and filters that selectively downconvert and filter out these interference signals, allowing the true TX LO leakage to be measured accurately
Solution Approach 2:
The patent introduces intermediary circuitry including additional mixers, filters, and signal processing stages that mediate between the TX LO leakage signal and the measurement circuitry, transforming the difficult-to-measure LO leakage into an easier-to-measure DC component while isolating it from corrupting influences
2Ease of operation
If non-linear mixers are used for signal conversion, then conversion capability is achieved, but measurement precision is degraded due to LO harmonics
Solution Approach 1:
The patent extracts and removes LO harmonics generated by non-linear mixers from the measurement path using selective filtering and additional mixing stages that downconvert harmonic components to frequencies where they can be effectively filtered out, preserving the accuracy of LO leakage measurement
Solution Approach 2:
The patent changes the frequency parameters of LO harmonic components through mixing and filtering operations, transforming them from interfering signals at the LO frequency to measurable DC or low-frequency components that can be separated from the target measurement signal
3Ease of operation
If phase differences exist between received signal and receiver LO, then signal reception is enabled, but measurement precision is degraded due to coupling between in-phase and quadrature components
Solution Approach 1:
The patent introduces phase correction circuitry and signal processing stages that act as intermediaries to compensate for phase differences between the received signal and receiver LO, decoupling the in-phase and quadrature components so that DC offset measurements remain accurate despite phase mismatches
Data Source
AI summary
A method and apparatus for estimating and compensating TX LO leakage using circuitry on a loopback path connecting the transmitter and receiver are provided. The TX LO leakage may be estimated by measuring the DC signal on the receiver, measuring the phase difference between the received LO signal and the receiver LO signal, and filtering LO harmonics that may arise from the use of non-linear mixers. The DC signal on the receiver may be measured by opening and closing the loopback path, or changing the gain of the loopback path, or flipping the phase of looped back TX signal. The method may be used in an initialization or tracking calibration scheme.