Three-Level Class-D RF Amplifier for Harmonic Suppression
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Solution Overview
Problem
Polar modulation transmitter circuits face issues with energy loss and interference due to signal harmonics, particularly when using switching power amplifiers, which introduce harmonics that can interfere with other communication frequencies.
Innovation Solution
A harmonic suppression circuit is used in conjunction with class-D switching amplifiers to modify the polar modulated data signal by introducing a middle signal level with a time duration based on a selected harmonic, effectively suppressing the harmonic through a three-level switching amplifier configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If switching power amplifiers are used to amplify polar modulated signals, then power efficiency is improved, but harmonics are introduced that cause interference with other communication frequencies
Solution Approach 1:
The patent converts the harmful harmonic effects into beneficial outcomes by using the same switching amplifiers to generate cancellation signals. The harmonics produced by the amplifiers are deliberately utilized to create opposing signals that cancel unwanted frequency components, transforming the harmful interference into a useful cancellation mechanism that improves spectral purity while maintaining high power efficiency
Solution Approach 2:
The patent applies preliminary anti-action by pre-generating cancellation signals that are designed to counteract the harmonics before they cause interference. The system predicts the harmonic content based on the switching amplifier operation and generates opposing signals in advance, ensuring that the harmful frequency components are neutralized before they can interfere with other communications
2Object-generated harmful factors
If additional filter circuits are used to suppress harmonics, then interference is reduced, but device complexity and cost increase
Solution Approach 1:
The patent merges the harmonic suppression function with the existing power amplification circuitry by using the same switching amplifiers to generate both the amplified signal and the cancellation signals. This integration eliminates the need for separate filter circuits, reducing device complexity and cost while maintaining effective harmonic suppression
Solution Approach 2:
The system performs self-service by using its own internal resources (the switching amplifiers) to generate the cancellation signals needed for harmonic suppression. Rather than requiring external filter circuits, the amplifiers themselves produce the opposing signals, making the system self-sufficient and reducing overall circuit complexity
Data Source
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AI summary
Configurable suppression of harmonics in a radio frequency (RF) transmitter circuit having two class-D switching amplifiers that produce a differential output signal having introduced harmonics is contemplated. A selected harmonic is used to determine a time duration. A harmonic suppression circuit modifies a radio frequency polar modulated data signal that is encoded using an amplitude component and a phase component. The modification is responsive to the determined time duration. The switching power amplifiers amplify the modified polar modulated data signal to produce an amplified signal. The amplified signal includes three signal levels, a high signal level, a middle signal level and a low signal level. The timing of transitions between the high and low signal levels represents the phase component, and the transitions include the middle signal level for the time duration, thereby suppressing the selected harmonic.