Multilevel RF Amplifier Bias Modulation for Spectral Suppression
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Solution Overview
Problem
Achieving high efficiency and linearity in radio-frequency (RF) amplifier systems is challenging, particularly in improving efficiency and reducing noise, especially in multilevel RF amplifier systems where discrete bias states and rapid signal amplitude variations complicate the suppression of undesired spectral components.
Innovation Solution
The system modulates power supply signals to RF amplifiers using multiple modulators and a delay circuit to combine and shape the power supply voltages, reducing high-frequency components and improving linearity by introducing a time delay to suppress unwanted signal components, thereby enhancing the quality of the RF output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If supply modulation is used to improve efficiency by dynamically adjusting power supply voltage, then efficiency is improved, but undesired spectral components and noise are introduced
Solution Approach 1:
The patent converts the harmful high-frequency spectral components generated by supply modulation into beneficial effects by using multiple modulators with delayed transitions to create frequency nulls through destructive interference, thereby eliminating the undesired components while maintaining efficiency improvements
Solution Approach 2:
The patent introduces multiple modulators as intermediary elements between the power supply and the RF amplifier, where these modulators work together with specific timing relationships to filter out undesired spectral components while allowing the efficiency benefits of supply modulation to pass through
2Use of energy by moving object
If discrete bias states are used to improve efficiency, then efficiency is improved, but linearity deteriorates
Solution Approach 1:
The patent uses periodic switching among multiple discrete bias states in a controlled sequence, where the transitions are timed to create constructive and destructive interference patterns that maintain linearity while achieving efficiency improvements through the discrete states
3Speed
If rapid voltage transitions are used to track RF signal variations, then efficiency is improved through better tracking, but high-frequency spectral components increase
Solution Approach 1:
The patent applies preliminary filtering through multiple modulators with predetermined time delays before the voltage transitions reach the RF amplifier, preparing the signal by eliminating harmful high-frequency components in advance while preserving the rapid tracking capability
Solution Approach 2:
The patent converts the harmful high-frequency transitions into beneficial frequency nulls by using the delayed transitions from multiple modulators to create destructive interference at specific frequencies, thereby eliminating the harmful components while maintaining fast tracking
Data Source
AI summary
Described is a system for modulating power to one or more radio frequency (RF) amplifiers to suppress undesired output signal components, improve linearity and reduce noise. The described systems and techniques enable shaping of spectral components introduced via an amplifier bias voltage owing to transitions among bias discrete states. The systems and techniques facilitate operation of multilevel, RF amplifiers under a wider range of operating conditions. In embodiments, the system includes modulators coupled to a supply terminal port of each of the one or more amplifiers to modulate the voltage levels supplied to the one or more amplifiers. The outputs of the modulators may be combined to provide a combined signal coupled to the amplifiers. A delay circuit delays switching of at least one of the power modulators relative to other modulator, by a variable time delay. This results in suppression of undesired output signal components of the amplifier output.