Multi-Carrier Envelope Shaping for Lower-Rate ET Transmission
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Solution Overview
Problem
Existing envelope tracking power amplifier (ET PA) systems face challenges in achieving efficient and linear performance, particularly with orthogonal frequency division multiplexing (OFDM) signals, due to high peak-to-average power ratio (PAPR) and stringent error vector magnitude (EVM) requirements, leading to gain collapse and distortions. Additionally, current envelope shaping methods struggle with concurrent multi-band signal processing, requiring excessive computing resources and high sampling rates that exceed hardware capabilities.
Innovation Solution
The method involves positioning and repositioning baseband envelope portions of multi-carrier signals to reduce frequency spacing between adjacent carriers, combining and shaping them to prevent knee region operation, and filtering to minimize distortions, thereby reducing the sampling rate and computing resources needed for envelope shaping. This is achieved through complex numerically controlled oscillator multiplication and digital-to-analog conversion, ensuring the shaped envelope meets predetermined envelope shaping levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If envelope shaping is applied to prevent knee region operation, then gain collapse and phase distortions are prevented, but sampling rate and computing resources increase excessively
Solution Approach 1:
The patent segments the multi-carrier signal into individual carrier components and processes their envelopes separately. By dividing the complex multi-carrier envelope shaping into per-carrier operations, the sampling rate requirement is reduced from the multi-gigahertz range to manageable levels, while still preventing knee region operation for each carrier
Solution Approach 2:
The patent changes the parameter of frequency spacing between envelope portions by positioning them closer together than the original carrier spacing. This parameter change allows accurate envelope shaping at lower sampling rates while maintaining the ability to prevent gain collapse and phase distortions
2Reliability
If envelope shaping is applied to prevent knee region operation, then linearity is improved, but computing resources increase excessively
Solution Approach 1:
The patent segments the envelope shaping computation into individual carrier-level operations rather than processing the entire multi-carrier signal as one unit. This segmentation reduces the computational burden from exponential complexity to linear complexity, making real-time envelope shaping feasible while maintaining linearity
Solution Approach 2:
The patent performs preliminary positioning of baseband envelope portions at reduced frequency spacing before the actual envelope shaping operation. This preliminary arrangement optimizes the computational structure, allowing the shaping algorithm to run efficiently with reduced computing resources while still achieving the linearity improvement
3Device complexity
If frequency spacing between envelope portions is reduced, then sampling rate requirement decreases, but intermodulation distortions may increase
Solution Approach 1:
The patent introduces filtering as an intermediary operation between envelope shaping and signal reconstruction. This filter removes unwanted spectral components and intermodulation products that arise from the reduced frequency spacing, allowing the system to operate at lower sampling rates without suffering from increased distortions
Data Source
AI summary
A method and an apparatus for envelope shaping of a multi-carrier signal in envelope tracking transmission are disclosed. According to an embodiment, a baseband version of an envelope portion belonging to each of multiple carriers in the multi-carrier signal is positioned such that a frequency spacing between adjacent positioned envelope portions is smaller than that between corresponding adjacent carriers. The positioned envelope portions are combined into a composite envelope. The composite envelope is shaped. The shaped composite envelope is split into baseband versions of shaped envelope portions belonging to the multiple carriers. The baseband versions of each shaped envelope portion is repositioned such that a frequency spacing between adjacent repositioned envelope portions is equal to that between corresponding adjacent carriers.