Pulse Position Transmitter Subranging for Efficient OFDM Power Amplification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Orthogonal frequency division multiplexing (OFDM) transmitters face efficiency issues due to high peak-to-average power ratios and require power control, which affects reliability and battery life in mobile devices, and conventional radio transmitters are not compatible with scaled CMOS processes.
Innovation Solution
A digital integrated transmitter using subranging for pulse-position and pulse-width modulation, which decomposes the RF signal into phase-modulated components to drive multiple power amplifiers efficiently, optimizing power usage and compatibility with CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear amplifiers are used for OFDM transmitters to maintain amplitude and phase information, then modulation quality is preserved, but power efficiency deteriorates due to lower efficiency in the power amplifier
Solution Approach 1:
The transmitter is divided into multiple parallel paths (in-phase path and quadrature path), each handling specific signal components. This segmentation allows independent optimization of each path, enabling the use of switching power amplifiers in each path while maintaining overall modulation quality through coherent combination of the paths.
2Use of energy by moving object
If switching power amplifiers are used to achieve higher efficiency, then power efficiency improves, but compatibility with OFDM systems deteriorates as application to OFDM is not straightforward
Solution Approach 1:
The OFDM signal is segmented into in-phase and quadrature components that can be independently processed by switching power amplifiers. Each path uses pulse-position and pulse-width modulation to encode signal information in a manner compatible with switching amplifier operation, resolving the compatibility issue.
Solution Approach 2:
The patent replaces traditional linear analog power amplification with digital pulse modulation techniques combined with switching power amplifiers. This substitution transitions from continuous linear amplification to discrete switching operation, enabling higher efficiency while maintaining OFDM compatibility through digital signal processing.
3Duration of action of moving object
If power control is applied to mobile units to reduce transmit power, then battery life improves, but reliability deteriorates due to thermal issues and lower average efficiency
Solution Approach 1:
The patent changes the operational parameters of the power amplifier by using pulse-position and pulse-width modulation to maintain optimal efficiency across varying power levels. This allows the system to operate switching power amplifiers in their efficient region even at reduced power levels, maintaining reliability while extending battery life.
4Ease of manufacture
If conventional analog circuits are used in radio transmitters, then implementation is straightforward, but compatibility with scaled CMOS processes deteriorates and die area increases due to inductor requirements
Solution Approach 1:
The patent replaces analog circuits with digital logic circuits implemented in CMOS. The use of digital pulse modulation and logic-based signal processing eliminates the need for large inductors and analog components, enabling compact integration in scaled CMOS processes while maintaining transmitter functionality.
Data Source
AI summary
Briefly, in accordance with one or more embodiments, in a pulse position and pulse position modulation out-phasing transmitter, the range of the phase angle, theta, may be divided into more than one range to drive a first power amplifier with a first range of theta, and to drive a second power amplifier with a second range of theta. In one or more embodiments, a main power amplifier is driven with a first phase range having a higher probability density function, and an overload power amplifier is driven with a first phase range having a lower probability density function. In one or more embodiments, a full adder may be used to combine the two phases wherein the sum signal is used to drive the main power amplifier, and the carry signal is used to drive the overload power amplifier.