Interleaving Multiplexer Spur Correction for FDAC/2 Errors
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Solution Overview
Problem
In 4.5G and 5G wireless systems, dual band transmit chains configured in an interleaving-by-two mode introduce errors due to differences in signal magnitudes and parasitic capacitance, leading to FDAC/2 spurs that degrade the spurious-free dynamic range.
Innovation Solution
A spur correction system comprising a spur sense chain, a correction controller, and a Q path corrector estimates and corrects for I-phase and Q-phase errors by injecting correction signals and selectively connecting capacitors within the interleaving multiplexer, thereby compensating for signal magnitude differences and capacitance mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an interleaving-by-two configuration is used to reduce power consumption and switching errors, then power consumption and switching errors are reduced, but FDAC/2 spurs are introduced that degrade the spurious-free dynamic range
Solution Approach 1:
The patent introduces a spur correction system comprising a spur sense chain, correction controller, and Q path corrector as intermediary components. The spur sense chain detects FDAC/2 spurs, the correction controller processes the detected spur information, and the Q path corrector applies correction signals to cancel the spurs. This intermediary correction system allows the interleaved transmit chain to maintain both low power consumption and reduced spurious emissions.
Solution Approach 2:
The patent implements a feedback mechanism where the spur sense chain continuously monitors the output for FDAC/2 spurs, feeds this information back to the correction controller, which then adjusts the Q path correction signals accordingly. This closed-loop feedback system dynamically compensates for spurs while maintaining the energy-efficient interleaved operation.
2Reliability
If an interleaving-by-two configuration is used to reduce the number of switching errors, then switching errors are reduced, but FDAC/2 spurs are introduced that degrade the spurious-free dynamic range
Solution Approach 1:
The spur correction system acts as an intermediary that preserves the benefits of interleaved operation (reduced switching errors) while eliminating the harmful effect (FDAC/2 spurs). The Q path corrector with its array of capacitors and switches provides fine-grained control to cancel spurs without disrupting the reliable switching operation of the main transmit chain.
Solution Approach 2:
The patent changes the electrical parameters (capacitance values) in the Q path corrector to compensate for spurs. By adjusting the capacitance values in the array of capacitors controlled by the correction controller, the system modifies the signal parameters to cancel out FDAC/2 spurs while maintaining reliable switching operation.
3Measurement precision
If correction signals are injected to compensate for I-phase errors, then I-phase error is reduced, but system complexity increases
Solution Approach 1:
The patent merges the I-phase correction and Q-phase correction functions into a unified spur correction system. The correction controller integrates both correction paths and coordinates their operation, reducing overall system complexity compared to having separate independent correction systems for each phase.
Solution Approach 2:
The correction controller serves multiple functions: it receives spur detection data from the spur sense chain, processes both I-phase and Q-phase correction requirements, coordinates the Q path corrector, and manages the overall correction operation. This multi-functional design reduces the need for separate dedicated circuits for each correction function.
4Measurement precision
If an array of capacitors is used in the Q path corrector to compensate for Q-phase errors, then Q-phase error is reduced, but device complexity increases
Solution Approach 1:
The Q path corrector uses an array of discrete capacitors that can be individually switched, segmenting the total capacitance into manageable units. This segmentation allows precise control of Q-phase correction while keeping each individual capacitor component simple and standardized, reducing overall device complexity compared to using a single large variable capacitor.
Solution Approach 2:
The array of capacitors in the Q path corrector is dynamically controlled by the correction controller, which switches capacitors in and out of the circuit based on the detected Q-phase error magnitude and direction. This dynamic reconfiguration allows the system to achieve high precision correction while maintaining a relatively simple fixed-capacitor architecture rather than requiring complex continuous adjustment mechanisms.
Data Source
AI summary
A spur correction system for a transmit chain having an interleaving multiplexer. In some embodiments, the spur correction system includes a spur sense chain, a correction controller, and a Q path corrector. The interleaving multiplexer combines signals from multiple bands in response to a clock signal. The spur sense chain estimates an error that is in phase with the clock signal (an I-phase error) and an error that is a derivative of the clock signal (a Q-phase error). The correction controller compensates for the estimated I-phase error by injecting an I-phase correction signal into the transmit chain. The Q path corrector compensates for the estimated Q-phase error by selectively connecting one or more capacitors within the interleaving multiplexer.