Receiver IMD Detection and Digital Cancellation for Signal Quality
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Solution Overview
Problem
Current wireless communication systems face challenges in mitigating intermodulation distortion (IMD) caused by non-linearity in receivers, which degrades performance and increases bit error rates due to mixing of transmit leakage signals with jammers, resulting in additional noise within the desired signal bandwidth.
Innovation Solution
A digital approach to detect and mitigate IMD by generating and correlating digital second-order (IM2) and third-order (IM3) intermodulation distortion, allowing for adjustment of circuit blocks and cancellation of conditioned IMD from the input signal, thereby reducing the levels of IMD within acceptable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital signal processing techniques are used to detect and mitigate intermodulation distortion, then receiver performance is improved by reducing noise and bit error rates, but device complexity increases due to additional digital processing circuitry
Solution Approach 1:
The patent creates a digital model (copy) of the expected intermodulation distortion based on the known transmit signal and channel characteristics. This digital replica is then correlated with the actual received signal to detect and mitigate IMD, avoiding the need for complex analog filtering while maintaining receiver performance through digital signal processing
Solution Approach 2:
The patent replaces potential analog/physical approaches to IMD mitigation with digital signal processing techniques. By using digital correlation and processing methods, the system achieves IMD reduction without requiring complex analog circuit modifications, thereby improving reliability while controlling device complexity through software-based solutions
2Ease of manufacture
If on-the-fly calibration of analog circuit blocks is performed, then manufacturing costs and power consumption are reduced, but measurement precision requirements increase to accurately detect intermodulation distortion
Solution Approach 1:
The patent performs calibration of analog circuit blocks during the manufacturing process itself, rather than requiring post-manufacturing adjustments. By incorporating calibration measurements into the manufacturing workflow, the system achieves accurate characterization of circuit blocks (improving measurement precision) while simultaneously reducing additional manufacturing steps and costs
Solution Approach 2:
The system uses its own transmit signal and received signal to self-calibrate and characterize its analog circuit blocks. By leveraging the existing signal paths and components, the calibration process requires no external test equipment or additional measurement infrastructure, thereby achieving high measurement precision without increasing manufacturing complexity or cost
Data Source
AI summary
Techniques for detecting and mitigating intermodulation distortion (IMD) are described. A device (e.g., a cellular phone) obtains digital intermodulation distortion and digitally determines intermodulation distortion in an input signal based on the digital intermodulation distortion. The device may correlate the digital intermodulation distortion with the input signal and determine intermodulation distortion in the input signal based on correlation results. The device may adjust the operation of one or more circuit blocks (e.g., a mixer, an LNA, etc.) in a receiver based on the detected intermodulation distortion in the input signal. Alternatively or additionally, the device may condition the digital intermodulation distortion to obtain conditioned intermodulation distortion matching intermodulation distortion in the input signal and may then subtract the conditioned intermodulation distortion from the input signal.