DC Offset Correction via Configurable Feedback Loops
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Solution Overview
Problem
Wireless communication receivers, particularly Direct Conversion Receivers, face challenges with DC offset errors due to local oscillator leakage, which existing technologies have not effectively addressed during the 'training time' when baseband signals should have no DC content.
Innovation Solution
A DC offset correction system utilizing multiple configurable feedback loops, including a DC notch filter transfer function, is activated during training time to remove DC offsets from baseband receive signals without interfering with frequency content above the cut-off, and transitions to a hold mode to maintain constant correction before the end of training time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a DC offset correction system is implemented in Direct Conversion Receivers, then DC offset errors caused by LO leakage are reduced, but the system complexity increases due to additional correction circuits
Solution Approach 1:
The DC offset correction system is divided into multiple independent feedback loops (first feedback loop for I channel, second feedback loop for Q channel). Each loop processes one component separately, allowing the complex correction task to be segmented into manageable parts that can be implemented and controlled independently, thus managing system complexity while achieving comprehensive DC offset correction.
Solution Approach 2:
The patent employs feedback mechanisms where the corrected baseband signal is fed back through multiple loops to continuously adjust and eliminate DC offset. The feedback loops monitor the DC component levels and dynamically adjust correction parameters, creating a self-regulating system that maintains accuracy without requiring complex manual calibration circuits.
2Measurement precision
If multiple configurable feedback loops are activated during training time, then DC offset removal accuracy is improved, but the processing time and computational load increase
Solution Approach 1:
The feedback loops are configured to be dynamically activated only during training time when DC offset correction is most critical, and can be deactivated or put in hold mode during normal operation. This dynamic control allows the system to achieve high correction accuracy when needed while minimizing processing time and computational load during other operational phases.
Solution Approach 2:
The system performs DC offset correction during training time before actual data reception begins. By addressing the DC offset issue in advance during the preamble/header portion of the signal, the correction is established beforehand, allowing faster processing during the subsequent data transmission phase without compromising accuracy.
3Object-affected harmful factors
If a DC notch filter transfer function is used, then DC offset correction effectiveness is improved, but the cut-off frequency may interfere with low-frequency signal components
Solution Approach 1:
The DC notch filter is designed with a very narrow stopband centered precisely at DC (0 Hz), providing high attenuation only at the DC frequency while maintaining passband characteristics for all other frequencies. This localized filtering approach ensures that low-frequency signal components above DC are preserved, achieving effective DC offset removal without sacrificing useful signal information.
Data Source
AI summary
The present invention provides a DC offset correction system for a wireless communication device that removes a DC offset from a baseband receive signal during “training time” when the baseband receive signal should ideally have no DC content. In general, the DC offset correction system includes multiple configurable feedback loops that operate to remove or cancel the DC offset from the baseband receive signal. One or more of the multiple configurable feedback loops is activated for a period of time during operation when it is known that the received signal should ideally contain no DC content. This training time varies depending on the particular communication standard being used by the wireless communication device. For example, the training time may be during reception of the preamble and header of an IEEE 802.11 packet.