Combination Modulator Switching Between Quadrature and Polar Domains
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing communications transmitters face limitations in spectral efficiency and energy efficiency due to the tradeoff between linearity and power consumption, particularly in quadrature-modulator-based transmitters, and bandwidth expansion issues in polar modulation transmitters, especially at low output power levels and with modulation schemes that produce signals with low amplitude magnitudes.
Innovation Solution
A communications transmitter design that combines quadrature and polar modulation domains, allowing the baseband processor to generate appropriate signals for the output power level and modulation scheme, enabling the amplifier to operate in linear, envelope tracking, or switch modes, thereby optimizing energy efficiency and avoiding bandwidth expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quadrature-modulator-based transmitters use linear power amplifiers to avoid signal distortion, then linearity is improved, but energy efficiency deteriorates
Solution Approach 1:
The transmitter dynamically switches between quadrature modulation and polar modulation modes based on operating conditions. The modulator type is changed adaptively to optimize performance, allowing the system to use linear amplifiers only when necessary for signal integrity while using efficient nonlinear amplifiers under normal conditions.
Solution Approach 2:
The system changes the modulation domain parameter from rectangular (quadrature) to polar coordinates. This parameter transformation allows the signal to be represented in a form that is compatible with nonlinear power amplifiers, enabling efficient operation without signal distortion through the use of envelope tracking and peak clipping techniques.
2Use of energy by moving object
If polar modulation transmitters use switch-mode power amplifiers to improve energy efficiency, then energy efficiency is improved, but bandwidth expansion occurs
Solution Approach 1:
The system dynamically selects between quadrature and polar modulation based on the specific operating scenario. When bandwidth expansion is problematic, the system switches to quadrature modulation with linear amplification. When energy efficiency is the priority and bandwidth is sufficient, it uses polar modulation with switch-mode amplifiers.
Solution Approach 2:
The modulation function is segmented into two distinct domains (quadrature and polar), each optimized for specific operating conditions. The system divides the operational space and applies the appropriate modulation type for each segment, rather than using a single modulation scheme for all conditions.
3Use of energy by moving object
If polar modulation is used for modulation schemes with trajectories passing through the origin, then energy efficiency is improved, but abrupt phase changes cause bandwidth expansion
Solution Approach 1:
The system dynamically determines the appropriate modulation domain based on the signal trajectory characteristics. When the signal trajectory passes through or near the origin (indicating potential abrupt phase changes), the system switches to quadrature modulation to avoid the bandwidth expansion problem, while maintaining energy efficiency through other means.
Solution Approach 2:
The system uses feedback about the signal characteristics (trajectory in the complex plane) to determine the optimal modulation mode. By monitoring whether the signal passes through the origin, the system adapts its modulation approach to prevent problematic phase transitions while maintaining overall performance.
Data Source
AI summary
A communications transmitter includes a combination modulator and a baseband processor configured to generate amplitude, angle, in-phase and quadrature signals. The combination modulator is configured to modulate in the quadrature domain or the polar domain, depending on an output power level of the transmitter and/or the type of modulation scheme being used. When configured to modulate in the quadrature domain, the baseband processor is configured to generate time-varying in-phase and quadrature modulating signals and time-invariant amplitude and angle signals for the combination modulator. When configured to modulate in the polar domain, the baseband processor is configured to generate time-varying amplitude and angle modulating signals and time-invariant in-phase and quadrature signals for the combination modulator. In another embodiment of the invention, the communications transmitter is configurable to operate in three different operational modes: linear, envelope tracking and switch modes. Which operational mode the communications transmitter is configured to transmit depends on the type of modulation scheme being used and/or the transmitter output power level.