Two-Part Main SCPA Cells for Back-Off Efficiency
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Solution Overview
Problem
Existing high efficiency power amplifiers face challenges in maintaining efficiency at output power back-off for modulated signals like OFDM and constant envelope signals such as BLE, particularly due to increased capacitive losses in Doherty implementations.
Innovation Solution
A power amplifier design incorporating a main Switched Capacitor Power Amplifier (SCPA) with tri-state inverters and a peak SCPA, where each cell is split into two parts - a fixed inverter and a configurable tri-state inverter, allowing independent optimization of capacitive and resistive losses for peak and back-off conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a Doherty power amplifier implementation is used, then peak power efficiency is improved, but capacitive losses increase at output power back-off
Solution Approach 1:
Each SCPA cell is segmented into two independent inverter parts: a first inverter that handles capacitive switching functions and a second inverter that handles resistive loading functions. This segmentation allows each inverter to be optimized independently for its specific function, reducing overall capacitive losses during back-off operation while maintaining peak power efficiency.
Solution Approach 2:
The patent implements dynamic control of the two inverter parts through separate control signals. The first inverter can be dynamically adjusted to minimize capacitive switching losses at different power levels, while the second inverter maintains optimal resistive loading. This dynamic adjustment enables high efficiency across both peak and back-off power conditions.
2Loss of energy
If power amplifier sizing is optimized for peak power, then peak power efficiency is improved, but efficiency deteriorates at low power modes
Solution Approach 1:
The power amplifier is divided into two functional segments within each cell: inverters optimized for capacitive switching and inverters optimized for resistive loading. This allows the amplifier to adapt to different power modes by selectively controlling the operation of each segment, maintaining high efficiency across peak and low power conditions.
Solution Approach 2:
The patent changes operational parameters by applying different control signals to the two inverter parts based on the desired power mode. At peak power, both inverters operate together with parameters optimized for maximum output. At low power back-off, the control signals adjust the first inverter to minimize capacitive losses while the second inverter maintains optimal resistive loading, achieving high efficiency across all power modes.
Data Source
AI summary
A power amplifier includes a main switched capacitor power amplifier (SCPA) and a peak SCPA in parallel with the main SCPA. The main SCPA includes a plurality of first cells electrically coupled in parallel. Each first cell includes a first inverter, a tri-state second inverter in parallel with the first inverter, and a first capacitor electrically coupled in series with the first inverter and the second inverter. Each first cell also includes first control logic to apply a local oscillator (LO) signal to the first inverter or set the first inverter to a static logic state in response to a first control signal, and apply the LO signal to the second inverter or set the second inverter to a high-impedance state in response to a second control signal.