Multi-Transceiver DPD Alignment for Wideband RF Signal Linearity
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Solution Overview
Problem
Current transmitters with integrated DPD cores in Field Programmable Gate Arrays (FPGAs) are unable to meet the high bandwidth needs of 3GPP 5G technology standards, particularly in supporting wide frequency bands like 3GPP B42 and B43 in Europe and the Citizens Broadband Radio Service (CBRS) C-band in the United States, due to inefficiencies in implementing Digital Pre-distortion (DPD) for linear operation.
Innovation Solution
A multi-transceiver radio frequency (RF) signal processing system with a controller, DPD core, and transceiver paths that process adjacent frequency blocks in parallel, applying digital pre-distortion to minimize distortion across a wide contiguous spectrum, and employs phase and amplitude calibration to align transceiver paths, using flexible bandwidth settings and in-field calibration techniques to mitigate misalignments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single transceiver path with integrated DPD core in FPGA is used, then device complexity is reduced, but bandwidth capability is insufficient to support wide frequency bands like 3GPP B42/B43 and CBRS C-band
Solution Approach 1:
The system divides the wide frequency band into multiple adjacent frequency blocks, with each block processed by a separate transceiver path. This segmentation allows the system to support wide bandwidth (3GPP B42/B43, CBRS C-band) by distributing the processing across multiple parallel paths, each handling a portion of the total bandwidth.
Solution Approach 2:
Multiple transceiver paths are combined through a hybrid circuit to operate as a unified wideband system. The individual paths process adjacent frequency blocks in parallel, and their outputs are merged to achieve the desired wideband capability while maintaining manageable complexity in each individual path.
2Adaptability or versatility
If multiple transceiver paths are used to increase bandwidth, then bandwidth capability is improved, but phase and amplitude misalignment at border frequencies causes signal degradation
Solution Approach 1:
The system implements in-field calibration that measures actual phase and amplitude characteristics of each transceiver path and uses this feedback to compute correction coefficients. These coefficients are applied to pre-distort the signals, compensating for the measured misalignments at border frequencies and maintaining signal quality across the wideband operation.
Solution Approach 2:
The system dynamically adjusts phase and amplitude parameters of each transceiver path through calibration procedures. By measuring the actual performance parameters and modifying them through correction coefficients, the system optimizes the operation of multiple transceiver paths to work coherently across adjacent frequency blocks.
3Manufacturing precision
If Digital Pre-distortion is applied to linearize transmitter operation, then signal linearity is improved, but implementation in current FPGAs is unable to fulfill high bandwidth needs
Solution Approach 1:
The DPD function is segmented and distributed across multiple transceiver paths, with each path applying DPD to its assigned frequency block. This allows the overall system to achieve wideband DPD capability by combining the narrowband DPD performance of individual paths, overcoming the bandwidth limitations of current FPGA implementations.
Data Source
AI summary
One embodiment is directed to a multi-transceiver radio frequency (RF) signal processing system. The system comprises at least one processor configured to execute signal processing for multiple transceiver paths and to implement a digital pre-distortion (DPD) core, and a plurality of transceiver paths coupled to the at least one processor. The transceiver paths comprise at least a first transceiver path for a first frequency block and a second transceiver path for a second frequency block. The signal processing outputs a first digital signal corresponding to the first frequency block to the first transceiver path for wireless transmission and a second digital signal corresponding to the second frequency block to the second transceiver path for wireless transmission. The DPD core applies a distortion to the first digital signal and the second digital signal that covers the first and second frequency blocks.