CE-OFDM Demodulation Correction After Frequency Domain Equalization
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Solution Overview
Problem
Mobile communications devices using Class C or E power amplifiers for OFDM signals face distortion issues due to non-linearity, which decreases battery life despite their efficiency, and CE-OFDM devices with FDEs introduce additional distortion.
Innovation Solution
A portable communications device employing a receiver with a frequency domain equalizer, a non-linear function block, and a demodulation correction block using look-up tables or a test CE-OFDM frame to correct distortions introduced by FDE and other components, along with a forward error correction block for improved signal processing and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Class C or E power amplifiers are used for OFDM signals, then power efficiency is improved, but signal distortion increases due to non-linearity
Solution Approach 1:
The patent applies preliminary action by encoding the OFDM signal with constant envelope modulation before amplification. This pre-processing step ensures that the signal maintains a constant amplitude envelope, making it compatible with non-linear Class C or E amplifiers without introducing excessive distortion. The constant envelope encoding is performed before the power amplifier stage, allowing efficient amplification while preserving signal integrity.
2Reliability
If frequency domain equalizer (FDE) is used in CE-OFDM devices, then channel equalization is achieved, but additional distortion is introduced into the received signal
Solution Approach 1:
The patent implements feedback by using the received signal itself to characterize and correct the distortion introduced by the FDE and other receiver components. The system captures the output of the FDE, analyzes its distortion characteristics, and uses this information to create correction factors that are applied back to the signal processing chain, thereby compensating for the harmful effects of the equalizer.
3Object-generated harmful factors
If iterative demodulation between pre and post demodulation equalizers is implemented, then distortion correction is improved, but device complexity increases
Solution Approach 1:
The patent extracts and isolates the distortion characteristics introduced by the FDE and other receiver components into a separate characterization model. Instead of implementing complex iterative demodulation between multiple equalizers, the system extracts the distortion profile from the received signal and uses this extracted information to correct the signal through a simplified processing path, thereby reducing overall device complexity while maintaining effective distortion correction.
Data Source
AI summary
A portable communications device communicates based upon constant envelope orthogonal frequency-division multiplexing (CE-OFDM). The portable communications device may include an antenna for receiving a CE-OFDM signal, and a receiver coupled to the antenna. The receiver may include a frequency domain equalizer (FDE) operating based upon a channel estimate of the received CE-OFDM signal, a non-linear function block coupled to and downstream from the FDE, and a demodulation correction block coupled to and downstream from the non-linear function block for correcting an output of the non-linear function block.