Digital Beamforming with Low-Resolution DACs and Distortion Decorrelation
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Solution Overview
Problem
High-speed, high-resolution digital-to-analog converters (DACs) in large antenna array systems consume significant power and either result in high power consumption or limited spatial duplexing ability, while analog beam-forming methods lack amplitude control and require complex calibration.
Innovation Solution
An antenna arrangement using low-resolution DACs with a de-correlator and dithering units to reduce power consumption and improve spatial resolution, where each DAC has a resolution below the regulatory requirement, and the de-correlator reduces correlation between distortion components in the transmitted signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution DACs are used in each antenna branch, then the transmission signal quality meets regulatory requirements, but the power consumption increases significantly
Solution Approach 1:
The patent combines multiple low-resolution DACs (e.g., 4-bit DACs) to collectively perform the function of a single high-resolution DAC. By using N antenna branches each with low-resolution DACs, the system achieves the equivalent signal quality of a high-resolution DAC while reducing individual DAC power consumption. The combined output of multiple low-resolution converters provides the necessary resolution through spatial diversity.
Solution Approach 2:
The patent replaces expensive, high-power high-resolution DACs with cheaper, low-power low-resolution DACs. Each low-resolution DAC consumes significantly less power (e.g., 100x less for 4-bit vs 16-bit), and while individual DACs have lower resolution, their collective output through multiple antenna branches achieves the required signal quality, effectively using multiple inexpensive components to replace one expensive component.
2Use of energy by moving object
If analog beam-forming with phase-shifters is used, then power consumption is reduced, but amplitude control capability is lost and calibration complexity increases
Solution Approach 1:
The patent introduces digital signal processing as an intermediary between the baseband and RF stages. Instead of using analog phase-shifters that directly manipulate RF signals, the system uses digital beam-forming with low-resolution DACs that can be precisely controlled in the digital domain. This digital intermediary provides both amplitude and phase control capabilities while maintaining low power consumption, avoiding the limitations of purely analog approaches.
3Use of energy by moving object
If low-resolution DACs are used, then power consumption is reduced, but quantization errors and signal distortion increase
Solution Approach 1:
The patent converts the harmful quantization errors from low-resolution DACs into a manageable form by exploiting spatial diversity. Instead of trying to eliminate quantization errors in each individual DAC, the system allows them to exist but distributes them across multiple antenna branches. Through proper signal processing and combining at the receiver, these quantization errors become uncorrelated noise that can be averaged out, transforming a deterministic distortion problem into a stochastic noise problem that is easier to handle.
Solution Approach 2:
The patent segments the signal transmission function across multiple antenna branches, each with its own low-resolution DAC. Rather than using a single high-resolution DAC, the system divides the transmission task into N segments, each handled by a low-resolution DAC. This segmentation allows the system to benefit from the low power consumption of individual low-resolution DACs while the collective output of all segments provides the necessary overall signal quality through spatial diversity.
Data Source
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AI summary
An antenna arrangement configured for digital beam-forming of a transmit signal comprising; a number N>1 of digital to analog converters, DACs, each of the N DACs being arranged to receive one respective digital transmit signal component, and to convert and output an analog transmit signal component, each of the N DACs having a respective resolution below a resolution required to fulfill a regulatory radio requirement in an interchangeable antenna arrangement arranged for transmission by a single antenna element connected to a single DAC; and N antenna elements, each of the N antenna elements being configured to receive one respective analog transmit signal component and to transmit the analog transmit signal component as part of the digitally beam-formed transmit signal.