Windowed FIR Crest Factor Reduction for Broadband Transmitters
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Solution Overview
Problem
High crest factors in communication signals can distort the linearity of power amplifiers in transmitters, leading to inefficiencies and potential non-compliance with emission masks due to increased out-of-band signal levels, which existing multi-stage and window-based crest factor reduction algorithms may not adequately address, especially for broadband signals with stringent delay requirements.
Innovation Solution
A wireless communication system employing a windowing signal generator with a finite impulse response (FIR) filter using canonic signed digit (CSD) arithmetic and a folding structure to reduce crest factors, which includes a clipping signal generator and multipliers with windowing function coefficients, and utilizes feedback signals to minimize delay and implementation complexity, enabling efficient processing of broadband signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multi-stage crest factor reduction algorithms are used, then crest factor is reduced, but implementation complexity increases
Solution Approach 1:
The FIR filter is divided into multiple parallel sub-filters, each processing a portion of the input signal. This segmentation allows the crest factor reduction to be achieved through parallel processing of simpler filter stages rather than a single complex sequential algorithm, thereby reducing overall implementation complexity while maintaining effectiveness.
Solution Approach 2:
Multiple parallel FIR filter paths are merged into a single output signal. By combining the results from several simplified parallel filter stages, the system achieves crest factor reduction with reduced complexity compared to implementing a single multi-stage algorithm sequentially.
2Object-affected harmful factors
If conventional FIR filter structures are used, then crest factor reduction is achieved, but processing speed decreases due to delay requirements
Solution Approach 1:
The filter structure is segmented into parallel paths that can be processed simultaneously. This parallel segmentation eliminates the sequential delay inherent in conventional single-path FIR filters, enabling high-speed processing of broadband signals while maintaining the crest factor reduction function.
Solution Approach 2:
The parallel filter structure enables periodic processing of signal segments through multiple paths. By distributing the processing load across parallel periodic operations rather than sequential delays, the system achieves both crest factor reduction and high processing speed suitable for broadband applications.
3Object-generated harmful factors
If windowing methods with FIR filters are used, then out-of-band signal levels are reduced, but device complexity increases
Solution Approach 1:
The windowing function is implemented through segmented parallel FIR filter paths rather than a single complex filter. This segmentation reduces the complexity of individual filter stages while collectively achieving the desired out-of-band signal level reduction through the combined effect of multiple parallel paths.
Solution Approach 2:
The parallel FIR filter structure serves multiple functions simultaneously: it performs crest factor reduction, out-of-band signal level control, and high-speed processing. By designing a single multi-functional parallel filter system rather than separate dedicated circuits for each function, device complexity is reduced while achieving all required performance goals.
Data Source
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AI summary
The present disclosure describes methods, systems, and computer program products for a reducing crest factors. An input signal is received. The input signal includes a clipping signal that reduces a peak amplitude of a source signal based on a predetermined clipping level. The input signal is transposed to a plurality of transposed signals using a plurality of multipliers. A feedback signal is generated based on the plurality of transposed signals using a first plurality of delay taps. A windowing signal is generated based on the feedback signal. The windowing signal is used to reduce a crest factor of the source signal.