Power Amplifier Input Signal Coupling via Dynamic Biasing
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Solution Overview
Problem
Existing power amplifier systems face challenges in efficiently coupling input signals between stages, particularly due to signal attenuation and the need for impedance matching, which can lead to memory effects and reduced error vector magnitude (EVM) in transmitters.
Innovation Solution
The implementation of a dynamic biasing scheme using a common signal path for both the power amplifier signal and the bias voltage, facilitated by a CMFB amplifier and envelope detection circuitry, reduces memory effects and optimizes semiconductor die area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common signal path is used for both power amplifier signal and bias voltage, then memory effects are reduced and EVM is improved, but the semiconductor die area is minimized
Solution Approach 1:
The patent combines the power amplifier signal path and the bias voltage path into a single common signal path. The bias voltage is coupled to the power amplifier input through the same path that carries the RF signal, eliminating the need for separate biasing circuitry and reducing die area while maintaining signal integrity and reducing memory effects.
Solution Approach 2:
The common signal path serves multiple functions simultaneously: it transports the RF power amplifier input signal and also delivers the dynamic bias voltage to the power amplifier. This multi-functional approach replaces what would traditionally require separate dedicated paths, reducing overall circuit complexity and area.
2Reliability
If dynamic biasing is implemented to reduce memory effects, then EVM performance is improved, but additional circuit components increase die area
Solution Approach 1:
The system uses the power amplifier's own input signal path to deliver the bias voltage, rather than requiring external or separate biasing circuitry. The bias voltage is generated and coupled through existing signal routing infrastructure, allowing the system to provide dynamic biasing functionality using its own resources without adding significant area.
Solution Approach 2:
The patent introduces a bias coupling mechanism that acts as an intermediary to inject the dynamic bias voltage into the existing power amplifier input path. This intermediary approach allows biasing functionality to be added without creating completely separate signal paths, minimizing area overhead while achieving the desired EVM improvement.
Data Source
AI summary
Methods, systems, and apparatus are disclosed for coupling a power amplifier input signal. An example system a first amplifier including a signal input, a feedback input, and a differential output that includes a first output and a second output, a first resistor including a first resistor terminal and a second resistor terminal, wherein the first resistor terminal is coupled to the first output, a second resistor including a third resistor terminal and a fourth resistor terminal, wherein the third resistor terminal is coupled to the second resistor terminal at an output common mode node and the fourth resistor terminal coupled to the second output, and a second amplifier including a first input and a third output, wherein the first input is coupled to the second resistor terminal and third resistor terminal, and the third output is coupled to the feedback input of the first amplifier.