Complex-Valued Baseband Signal Dynamic Range Reduction
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Solution Overview
Problem
High peak-to-average power ratio (PAPR) in digital baseband signals, particularly in orthogonal frequency-division multiplexing (OFDM), leads to inefficient power-amplifier operation and increased dynamic range, complicating transmit-signal-processing stages.
Innovation Solution
The method involves mixing a complex-valued digital baseband signal to an intermediate frequency, extracting real components, clipping the intermediate-frequency real-valued signal, and down-converting it, thereby reducing the number of multiplications required for PAPR reduction by operating on real-valued signals instead of complex-valued signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If clipping and filtering is applied to complex-valued QAM baseband signals, then PAPR is reduced, but the number of multiplications increases significantly
Solution Approach 1:
The patent extracts only the real components of the complex-valued QAM signal after mixing to intermediate frequency, discarding the imaginary components. This extraction transforms the problem from processing complex-valued signals requiring multiple multiplications to processing real-valued signals requiring fewer operations, thereby reducing computational complexity while maintaining PAPR reduction effectiveness
Solution Approach 2:
Instead of directly clipping the complex-valued baseband signal as in conventional approaches, the patent inverts the conventional sequence by first mixing to intermediate frequency and then extracting real components before clipping. This inversion of the processing sequence enables the use of simpler real-valued clipping operations rather than complex-valued operations
2Object-generated harmful factors
If conventional clipping is applied to complex-valued signals, then dynamic range is reduced, but the number of multiplications increases
Solution Approach 1:
The patent extracts only the real components of the complex-valued signal at intermediate frequency, transforming the clipping operation from complex-valued (requiring multiple multiplications per sample) to real-valued (requiring fewer multiplications). This extraction reduces computational energy consumption while achieving the same dynamic range reduction goal
Solution Approach 2:
The patent changes the parameter domain from complex-valued to real-valued by mixing to intermediate frequency and extracting real components. This parameter transformation reduces the computational burden of clipping operations, decreasing the number of multiplications required per signal sample while maintaining the dynamic range reduction effect
Data Source
AI summary
To reduce the peak-to-average power ratio (PAPR) of a complex-valued digital baseband signal, the signal is mixed to an intermediate frequency and its real components extracted, to generate an intermediate-frequency real-valued digital signal. The intermediate frequency is one-quarter of a sampling rate of the complex-valued digital baseband signal. The intermediate-frequency real-valued digital signal is clipped and down-converted by one-quarter of the sampling rate.