Low-IF Receiver Image Cancellation for I-Q Imbalance Blocking
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Solution Overview
Problem
Low intermediate frequency (IF) receivers face signal distortions due to I-Q imbalance, which leads to unwanted signal blocking and reduced signal-to-noise and distortion ratio (SNDR), making it difficult to filter out image signals at the +IF location without impacting the desired signal.
Innovation Solution
Implementing a digital correction system that includes a corrector and a corrector controller to selectively enable and disable the correction of image signals based on power measurements at specific frequency ranges, using a trainer to generate cancellation signals and reduce distortions caused by I-Q imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital correction is continuously applied to cancel image signals, then signal distortions are reduced and SNDR is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent implements dynamic correction by using a detector to monitor blocking signals and a controller to selectively enable or disable the corrector based on detected conditions. The correction system transitions from static continuous operation to dynamic conditional operation, reducing complexity and power consumption when correction is not needed while maintaining reliability when blocking signals are present
Solution Approach 2:
The system uses the detector to automatically identify when blocking signals are present and triggers the controller to enable correction only in those conditions. The system serves itself by monitoring its own operational state and adjusting correction application accordingly, eliminating the need for continuous complex processing
2Object-affected harmful factors
If filtering is applied to remove image signals at +IF location, then blocking signal interference is reduced, but the desired signal is also negatively impacted
Solution Approach 1:
Instead of filtering out the image signal directly (which would also remove the desired signal), the system uses the detected blocking signal characteristics to generate a cancellation signal that specifically targets and cancels only the harmful image component. The harmful blocking signal is converted into a beneficial cancellation reference that eliminates interference while preserving the desired signal
Solution Approach 2:
The patent introduces a cancellation signal as an intermediary element that mediates between the blocking signal and the desired signal. This cancellation signal acts as a bridge that selectively neutralizes the harmful image component without affecting the desired signal, avoiding the direct filtering approach that would harm both signals
3Reliability
If I-Q imbalance correction is applied, then signal distortions are reduced, but device complexity and processing overhead increase
Solution Approach 1:
The system performs correction processing periodically or conditionally based on blocking signal detection rather than continuously. The controller enables correction only when blocking signals are detected, creating a periodic or event-driven correction pattern that reduces processing overhead and device complexity while maintaining signal quality when needed
Solution Approach 2:
The patent applies partial correction by using a detector and controller to determine when full correction is necessary. Instead of applying complete correction processing continuously, the system applies correction partially or fully only when blocking signals are present, reducing overall processing complexity while maintaining adequate signal quality
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
The solution effectively reduces signal distortions and increases the SNDR by partially canceling image signals at the IF frequency, improving the performance of low IF receivers in various RF applications.
Implementation Method 1
A heterodyne receiver uses frequency mixing to convert the received signals into a new frequency range for processing. In general, a low intermediate frequency (IF) receiver is a type of heterodyne receiver that mixes the received signals to a non-zero low intermediate frequency (IF).
Data Source
AI summary
The embodiments described herein provide systems and methods for digital correction in low intermediate frequency (IF) receivers. Specifically, the embodiments described herein use digital correction techniques that can correct for signal distortions in low IF receivers caused by I-Q imbalance, including both I-Q magnitude imbalance and I-Q phase imbalance. In general, the embodiments described herein are implemented to at least partially cancel an image of a blocking signal in the complex digital signal. Such a cancellation can be implemented to at least partially cancel an image of blocking signal where that image occurs at or near the intermediate frequency. In one embodiment, a corrector is implemented in a low RF receiver and is configured to receive a complex digital signal that includes an image of a blocking signal. Such a low RF receiver can further include a corrector controller to selectively enable the corrector.