Doherty Auxiliary Path Biasing for Low-Power Efficiency
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Solution Overview
Problem
Existing Doherty power amplifiers face inefficiencies due to constant power consumption in components preceding the auxiliary amplifier, especially at low output power levels, which is exacerbated at high frequencies in systems with multiple antennas.
Innovation Solution
Implementing envelope-controlled biasing to deactivate components in the auxiliary path of the Doherty power amplifier when the envelope of the input signal falls below a threshold, using a comparator and bias current controller to adjust bias levels based on the envelope signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If components in the auxiliary path are kept active to maintain signal processing capability, then the transmitter can respond quickly to signal demands, but power consumption remains high especially at low output power levels
Solution Approach 1:
The bias current supplied to components in the auxiliary path is made dynamic rather than static. The bias current controller adjusts the bias level based on the envelope signal amplitude, allowing components to operate at optimal current levels that adapt to the instantaneous signal conditions, thereby reducing power consumption during low-signal periods while maintaining readiness.
Solution Approach 2:
The patent changes the operating parameter (bias current) of components in the auxiliary path based on the envelope signal. By varying the bias current according to signal amplitude thresholds, the system achieves variable power consumption that matches the actual processing needs, resolving the contradiction between maintaining responsiveness and reducing energy use.
2Loss of energy
If envelope-controlled biasing is implemented to reduce power consumption in auxiliary path components, then overall transmitter efficiency improves, but system complexity increases due to additional control circuitry
Solution Approach 1:
The bias current controller serves multiple functions: it monitors the envelope signal, determines when threshold conditions are met, and adjusts the bias current accordingly. This multi-functional approach consolidates what could be separate complex circuits into a single integrated controller, improving efficiency while minimizing the increase in overall system complexity.
Solution Approach 2:
The patent introduces a bias current controller as an intermediary element that mediates between the envelope signal detector and the auxiliary path components. This intermediary simplifies the control architecture by providing a single point of control that manages power distribution to multiple components based on a unified decision logic, rather than requiring independent control circuits for each component.
3Use of energy by moving object
If the auxiliary amplifier and its preceding components are deactivated at low power levels, then power consumption is reduced, but the phase shift and signal processing continuity may be affected
Solution Approach 1:
The system employs periodic or threshold-based activation rather than continuous operation. The auxiliary path components are activated only when the envelope signal exceeds predetermined thresholds, creating a periodic pattern of operation that reduces average power consumption while ensuring the system is ready to process signals whenever needed, thus maintaining processing continuity.
Solution Approach 2:
The bias current controller prepares the auxiliary path components by gradually adjusting the bias current before full activation is needed. This preliminary action ensures that when the envelope signal crosses the threshold, the components are already partially prepared and can transition smoothly into full operation, maintaining signal processing continuity without abrupt changes that would disrupt the phase relationship.
Data Source
AI summary
A transmitter and Doherty power amplifier configured for envelope-controlled biasing of an auxiliary transmitter of the Doherty power amplifier are disclosed. According to one aspect, a transmitter having a main amplifier in a main signal path and an auxiliary amplifier in an auxiliary signal path is provided. The auxiliary amplifier is configured to be activated only when an envelope of an input signal of the transmitter exceeds a power threshold. The transmitter also includes at least one component in the auxiliary signal path configured to be deactivated when the auxiliary amplifier is deactivated, the at least one component including at least one of a pre-power amplifier, a mixer and a local oscillator buffer.