Cascaded Phase Modulation Transmitter for Efficient OFDM Power Amplification
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Solution Overview
Problem
OFDM transmitters face inefficiencies due to high peak-to-average power ratios and require linear amplifiers, which reduce power efficiency, and conventional radio transmitters are sensitive to process, voltage, and temperature variations, making them unsuitable for mobile and handheld applications.
Innovation Solution
A cascaded phase pulse position and pulse width modulation based digital transmitter architecture is employed, using parallel-path phase decomposition and closed-loop power control to achieve efficient amplification and transmission of OFDM signals, incorporating switched power amplifiers and digital calibration to maintain efficiency and compatibility with CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear amplifiers are used to maintain amplitude and phase information in OFDM signals, then signal fidelity is improved, but power efficiency deteriorates
Solution Approach 1:
The signal is decomposed into multiple constant-envelope sub-signals through phase decomposition, each of which can be amplified efficiently by switching amplifiers. The segmented sub-signals are then recombined to reconstruct the original OFDM signal, achieving both high power efficiency and signal fidelity.
Solution Approach 2:
A digital signal processing intermediary is introduced that performs phase decomposition and reconstruction operations. This intermediary transforms the amplitude-and-phase-modulated OFDM signal into constant-envelope sub-signals suitable for efficient switching amplifier operation, while preserving the original signal information.
2Use of energy by moving object
If switching power amplifiers are used to achieve higher efficiency, then power efficiency is improved, but compatibility with OFDM systems deteriorates
Solution Approach 1:
The invention changes the parameter domain by transforming the amplitude-and-phase-modulated OFDM signal into constant-envelope sub-signals through phase decomposition. This parameter transformation enables the use of switching power amplifiers while maintaining OFDM system compatibility, as the sub-signals are specifically designed to be compatible with efficient amplification techniques.
3Productivity
If conventional analog circuits are used in radio transmitters, then signal processing capability is improved, but sensitivity to process, voltage and temperature variations worsens
Solution Approach 1:
Analog circuits are replaced with digital signal processing circuits that perform phase decomposition and reconstruction. Digital circuits are inherently more resistant to process, voltage, and temperature variations, while maintaining the necessary signal processing capability through computational algorithms.
4Productivity
If inductors are used in conventional radio transmitters, then signal tuning capability is improved, but die area occupation worsens
Solution Approach 1:
Inductor-based analog tuning circuits are replaced with digital signal processing approaches that achieve signal tuning through computational methods. This substitution eliminates the need for large inductors, significantly reducing the die area while maintaining tuning capability through digital algorithms.
Data Source
AI summary
Briefly, in accordance with one or more embodiments, a digital transmitter may comprise two or more phase modulators in a cascaded arrangement. The phase modulators may modulate a local oscillator signal using control signals derived from the quadrature baseband data to be transmitted. A closed loop power control feedback arrangement may be used to compare the output power of the transmitter with a desired output signal, and make corrections to the output signal by modifying at least one of the control signals provided to the cascaded phase modulators.