RF DAC Interleaving Correction for Gain and Timing Mismatch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed radio-frequency (RF) digital-to-analog converters (DACs) in 5G wireless base stations face power consumption challenges and generate interleaving images due to gain and timing mismatches between DACs, leading to significant harmonic distortion and adjacent-channel power ratio (ACPR) issues.
Innovation Solution
The implementation of an interleaving DAC system with independently adjustable bias voltages and clock edge timing correction mechanisms, including analog and digital pre-cancelation techniques, to reduce interleaving image magnitude by addressing gain and timing mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If interleaving DACs are used to achieve high-speed conversion, then the sampling rate is improved, but gain and timing mismatches between DACs cause interleaving images and harmonic distortion
Solution Approach 1:
The patent applies preliminary action by measuring and storing gain and timing mismatch parameters before actual signal conversion, then using these pre-measured parameters to configure correction coefficients that compensate for mismatches during operation. This allows the system to address manufacturing precision issues proactively rather than reactively.
Solution Approach 2:
The patent changes parameters by dynamically adjusting digital correction coefficients based on measured mismatch characteristics. The system measures actual gain and timing deviations and modifies the digital signal parameters accordingly to cancel out the interleaving images caused by hardware mismatches.
2Manufacturing precision
If analog correction circuits are added to correct mismatches, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex analog correction circuits with a digital signal processing approach. Instead of using additional analog components to physically correct mismatches, the system uses digital algorithms to calculate and apply correction coefficients, substituting mechanical/analog correction with computational methods.
Solution Approach 2:
The patent creates a digital model or copy of the mismatch characteristics by measuring the actual gain and timing deviations. This digital representation of the error is then used to generate correction coefficients, allowing the system to work with a replicated version of the problem rather than directly manipulating the physical analog signals.
3Manufacturing precision
If digital correction is applied to reduce interleaving images, then manufacturing precision is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent performs the computationally intensive measurement and coefficient calculation in advance, before real-time signal processing begins. By pre-determining the correction parameters offline or during initialization, the system avoids time-consuming computations during actual operation, thus minimizing processing time loss.
Solution Approach 2:
The patent implements a two-stage correction approach where a first-order correction is applied to eliminate the most significant interleaving image components, and optional second-order correction addresses remaining smaller errors. This partial correction strategy achieves sufficient precision without requiring full complex correction for all possible error sources.
Data Source
AI summary
Analog gain correction circuitry and analog switching clock edge timing correction circuitry can provide coarse correction of interleaving errors in radio-frequency digital-to-analog converters (RF DACs), such as may be used in 5G wireless base stations. The analog correction can be supplemented by digital circuitry configured to “pre-cancel” an interleaving image by adding to a digital DAC input signal a signal equal and opposite to an interleaving image created by the interleaving DAC, such that the interleaving image is effectively mitigated. Error correction control parameters can be periodically adjusted for changes in temperature by a controller coupled to an on-chip temperature sensor. A model useful for understanding the sources of error in interleaving DACs is also described.