Outphasing Amplifier Branch Filtering for Lower Sideband Energy
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Solution Overview
Problem
Conventional amplifiers face inefficiency and signal distortion when amplifying RF signals with high input peak to average power ratio, as they must operate in the linear region to avoid saturation, leading to bandwidth expansion and increased power requirements.
Innovation Solution
An outphasing amplifier with a first and second branch, each processing phase modulated signals with constant amplitude envelopes, reduces energy in sidebands away from the central frequency while retaining phase information, using filtering and reconstructor circuitry to reassert phase information and reduce bandwidth requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional amplifiers operate in the linear region to avoid saturation, then signal distortion is reduced, but efficiency decreases significantly
Solution Approach 1:
The amplifier is divided into two separate amplification paths (in-phase and quadrature branches), each handling a phase-modulated signal with constant envelope. This segmentation allows each branch to operate independently in saturation mode while maintaining overall signal fidelity through coherent combination at the output.
Solution Approach 2:
The invention transforms the amplitude-modulated input signal into two phase-modulated signals with constant amplitude envelopes. By changing the modulation parameter from amplitude to phase, the signals can be amplified in saturation without distortion, as phase information is preserved even when amplitude is clipped.
2Use of energy by moving object
If outphasing amplifiers operate at saturation for maximum efficiency, then energy consumption is reduced, but bandwidth expands
Solution Approach 1:
The invention extracts and removes the amplitude information from the input signal, leaving only phase information to be transmitted. By taking out the amplitude component and representing the signal purely in phase domain with constant envelope, the bandwidth expansion problem is eliminated while maintaining saturation operation for efficiency.
3Use of energy by moving object
If outphasing amplifiers operate at saturation, then efficiency increases, but power requirements increase
Solution Approach 1:
By transforming the signal representation from amplitude-modulated to phase-modulated with constant envelope, the invention enables saturation operation where power is efficiently utilized. The constant amplitude allows the amplifier to operate continuously at maximum power transfer without wasting energy in linear region operation.
4Reliability
If conventional amplifiers are used for high peak-to-average power ratio signals, then signal fidelity is maintained, but efficiency drops below 50%
Solution Approach 1:
The invention changes the modulation parameter from amplitude to phase, creating constant envelope signals that can be amplified in saturation. This parameter transformation preserves phase information (maintaining signal fidelity) while enabling efficient saturation operation, achieving both goals simultaneously.
Data Source
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Figure 3A~3B
AI summary
An outphasing amplifier (100) having: a first branch (106) arranged to receive and process a first branch signal (S1), the first branch signal (S1) being phase modulated, with constant amplitude envelope; and a second branch (110) arranged to receive and process a second branch signal (S2), the second branch signal (S2) being phase modulated, with constant amplitude envelope, and at least a portion of the second branch signal anti-phase from the first branch signal (S1), wherein each branch (106, 110) includes: circuitry (400) arranged to process the signal (S1, S2) to reduce the energy in sidebands of the signal (S1, S2) away from the central frequency, while retaining the phase information in the signal (S1, S2); and an amplifier (108, 112) arranged to amplify the filtered and re-asserted branch signal (S1, S2).