Tracker Circuit Shunt Filtering for TDD PA Distortion Control
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Solution Overview
Problem
Existing power amplifier circuits using discrete voltages for envelope tracking modes, such as digital ET mode, result in increased distortion and spurious emissions, particularly in time division duplex (TDD) bands, leading to degradation of adjacent channel power ratio and spurious emissions.
Innovation Solution
A tracker circuit with an output switching circuit, a first voltage supply path, and a filter circuit is used to selectively output discrete voltages to a power amplifier, with the filter circuit connected in shunt with the voltage supply path, and controlled based on channel bandwidth to reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If discrete voltages are supplied to power amplifier for envelope tracking, then power-added efficiency is improved, but signal distortion and spurious emissions increase
Solution Approach 1:
A filter circuit is introduced as an intermediary component between the voltage supply path and ground to suppress spurious emissions and distortion while maintaining the discrete voltage supply for envelope tracking. The filter acts as a mediator that allows the efficiency benefits to continue while removing the harmful spectral components.
Solution Approach 2:
The patent adjusts the connection configuration of the filter circuit (connected to ground rather than in series) and selectively connects/disconnects the filter based on channel bandwidth parameters. This parameter-based approach allows optimization of both efficiency and signal quality under different operating conditions.
2Object-generated harmful factors
If filter circuit is connected in series with voltage supply path, then spurious emissions are reduced, but voltage supply responsiveness deteriorates
Solution Approach 1:
Instead of connecting the filter circuit in series with the voltage supply path (which would slow down voltage transitions), the patent inverts the approach by connecting the filter circuit in parallel to ground. This allows the filter to suppress spurious emissions without impeding the speed of voltage supply changes.
Solution Approach 2:
The patent dynamically changes the connection state of the filter circuit based on channel bandwidth parameters, disconnecting it when wide bandwidth is required to maintain voltage supply responsiveness, and connecting it when narrow bandwidth allows for spurious emission suppression.
3Object-generated harmful factors
If filter circuit is always connected to voltage supply path, then distortion is reduced, but device complexity and power loss increase
Solution Approach 1:
The filter circuit's connection state is made dynamic rather than static, allowing it to be selectively connected or disconnected based on operating conditions such as channel bandwidth. This dynamic approach reduces unnecessary power loss and simplifies the effective circuit configuration when the filter is not needed.
Solution Approach 2:
The control mechanism for the filter circuit serves multiple functions: it manages distortion reduction, optimizes power efficiency, and adapts to different channel bandwidth conditions. This multi-functionality reduces overall system complexity by consolidating control logic.
Data Source
AI summary
Some exemplary aspects of the disclosure provide a tracker circuit that includes an output switching circuit, a first voltage supply path and a filter circuit. The output switching circuit is configured to selectively output at least one of a plurality of discrete voltages. The first voltage supply path is configured to connect the output switching circuit and a first power amplifier to provide the at least one of the plurality of discrete voltages to the first power amplifier. The filter circuit is configured to be connected in shunt with the first voltage supply path, the first power amplifier is configured to amplify a first radio frequency signal of a first band with time division duplex being applied.