Adaptive Digital Predistortion With EBEE Filtering for Receiver Sensitivity
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Solution Overview
Problem
Traditional pre-distortion systems face challenges in decoupling receiver performance from transmitter performance, leading to increased noise and interference, which complicates baseband filter design and increases costs and power consumption.
Innovation Solution
The implementation of an adaptive digital pre-distortion method using an Effective Bandwidth Enhancement Equalizer (EBEE) filter and a pre-distorter, which allows for independent tuning of linear and nonlinear systems, decouples analog and digital front-ends, and adapts to system changes using algorithms like least squares to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional pre-distortion systems are used, then transmitter linearity is improved, but receiver sensitivity deteriorates due to increased noise and interference
Solution Approach 1:
The system segments the pre-distortion function into two independent parts: a digital pre-distorter for nonlinear correction and an EBEE filter for linear correction. This segmentation allows each component to be optimized independently, with the digital pre-distorter improving transmitter linearity while the EBEE filter protects receiver sensitivity by removing out-of-band emissions without requiring complex baseband filtering.
Solution Approach 2:
The EBEE filter acts as an intermediary between the digital pre-distorter and the baseband filter. It mediates the conflicting requirements by providing linear correction in the out-of-band region, thereby reducing noise and interference that would otherwise degrade receiver sensitivity while maintaining the effectiveness of digital pre-distortion for transmitter linearity.
2Reliability
If baseband filtering is strengthened to protect receiver sensitivity, then receiver sensitivity is improved, but pre-distortion effectiveness deteriorates
Solution Approach 1:
The EBEE filter performs preliminary linear correction of out-of-band emissions before the signal reaches the baseband filter. This preliminary action ensures that the baseband filter can operate with relaxed constraints, maintaining both receiver sensitivity and pre-distortion effectiveness without requiring aggressive filtering that would compromise the pre-distorted signal.
3Manufacturing precision
If complex baseband filtering is used to achieve good pre-distortion performance, then pre-distortion effectiveness is improved, but device complexity increases
Solution Approach 1:
The EBEE filter serves as an intermediary that handles the complex linear correction requirements in the out-of-band region, thereby simplifying the baseband filter design. This allows good pre-distortion performance to be achieved without requiring complex baseband filtering, as the EBEE filter absorbs the complexity of linear correction.
4Reliability
If aggressive baseband filtering is applied to reduce noise and interference, then receiver sensitivity is improved, but signal bandwidth is reduced
Solution Approach 1:
The filtering function is segmented into two stages: the EBEE filter handles out-of-band noise and interference reduction without affecting in-band signal bandwidth, while the baseband filter focuses on in-band signal processing. This segmentation allows aggressive noise filtering to improve receiver sensitivity without compromising the bandwidth of the desired signal.
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AI summary
A pre-distortion method. A signal to be transmitted Tx is pre-distorted to compensate for nonlinearities of a transmitter. The pre-distorted signal is filtered by an EBEE filter and a baseband filter. The EBEE filter has a filter characteristic of that cancels the baseband filter response over the range of frequencies from a first corner frequency of the baseband filter to a frequency of N*fB where N is a highest order of distortion component being cancelled and fB is the bandwidth of the original signal to be transmitted. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract.