Fast RF Receiver DC Offset Correction via Lookup Table
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Solution Overview
Problem
RF communications systems face challenges in quickly correcting direct current (DC) offsets in down conversion circuitry, especially when receiving RF signals continuously, as there is insufficient time for traditional DC offset correction methods.
Innovation Solution
The implementation of a fast DC correction method in down conversion circuitry that includes a DC correction amplifier downstream of the post mixer amplifier, which determines and applies DC corrections based on the gain of the post mixer amplifier during a calibration mode, allowing for real-time correction in a feed-forward manner during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DC offset correction methods are used, then DC offset correction can be performed accurately, but there is insufficient time to perform correction when receiving RF signals continuously
Solution Approach 1:
The system performs DC offset correction in advance by measuring and storing correction values in a lookup table during periods when no RF signals are being received. During normal operation, the pre-calculated correction values are retrieved and applied immediately, eliminating the need for time-consuming real-time correction calculations.
Solution Approach 2:
The patent implements a calibration mode that executes before normal signal reception to determine and store DC offset correction values for multiple gain levels. This preliminary calibration allows the system to quickly apply corrections during operation without interrupting signal reception or losing valuable time.
2Reliability
If DC offset correction is performed in real-time during signal reception, then system performance is maintained, but there is insufficient time available for correction
Solution Approach 1:
The system maintains reliability by performing all time-consuming DC offset correction calculations in advance during calibration mode, storing the results for immediate retrieval. During normal operation, only simple lookup and application of pre-calculated values is needed, ensuring system performance is maintained without sacrificing correction time.
Solution Approach 2:
The patent replaces complex real-time DC offset correction calculations with a simplified lookup table approach. Instead of performing mechanical computation during signal reception, the system uses pre-computed correction values stored in memory, substituting complex real-time processing with fast memory retrieval operations.
3Productivity
If DC offset correction is performed quickly, then real-time correction during signal reception is enabled, but correction accuracy may be compromised
Solution Approach 1:
The system achieves both high speed and high accuracy by performing comprehensive DC offset correction measurements in advance during calibration mode, storing accurate correction values in a lookup table. During normal operation, the pre-measured accurate correction values are retrieved and applied instantly, maintaining both correction accuracy and real-time performance.
Data Source
AI summary
The present disclosure relates to down conversion circuitry that uses a fast DC correction method to correct for a DC offset of an RF mixer and a post mixer amplifier. The down conversion circuitry may include a DC correction amplifier downstream of the post mixer amplifier to apply a DC correction, which is based on a gain of the post mixer amplifier. During a calibration mode, the DC offset of the RF mixer and the post mixer amplifier are determined at multiple gain levels of the post mixer amplifier. The DC correction needed at multiple gain levels of the post mixer amplifier is then determined based on the determined DC offset. During a normal operation mode, a desired gain of the post mixer amplifier is selected and a determined DC correction that correlates with the desired gain is provided.