RF Power Amplifier Closed-Loop Bias Control for Stable Output
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Solution Overview
Problem
Existing radio frequency power amplifiers face challenges in accurately controlling output power due to inefficiencies in power control methods, leading to unnecessary waste and instability at different power levels.
Innovation Solution
A radio frequency power amplifier is designed with a power amplifier circuit, output matching circuit, power detection circuit, and bias comparison circuit, forming a closed-loop system. The power detection circuit detects output power, generating an equivalent voltage that is adjusted and compared with a control voltage in the bias comparison circuit to provide stable bias and collector voltages for the power amplifier circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop control method is used to control input power, then output power can be controlled, but current has margin causing unnecessary waste
Solution Approach 1:
The patent implements a closed-loop feedback control system where the power detection circuit continuously monitors the output power and feeds back a detection voltage to the bias comparison circuit. The bias comparison circuit compares this feedback voltage with a reference voltage and adjusts the bias voltage accordingly, creating a feedback mechanism that precisely controls output power while optimizing current utilization and eliminating waste.
2Ease of operation
If open-loop control method is used with control voltage, then output power can be controlled, but control voltage cannot precisely control bias voltage
Solution Approach 1:
The patent transforms the open-loop control into a closed-loop system by introducing power detection circuit and bias comparison circuit. The power detection circuit converts output power into a detection voltage that is fed back to the bias comparison circuit, which then adjusts the bias voltage based on the feedback signal, ensuring precise control while maintaining operational simplicity.
Solution Approach 2:
The patent replaces direct voltage control with a feedback-based control mechanism. Instead of directly controlling bias voltage through control voltage, the system uses power detection and feedback comparison to indirectly and more precisely control the bias voltage, substituting a more complex control mechanism for a simpler but less precise direct control.
3Adaptability or versatility
If same bias voltage is used for power control, then output power can be achieved, but current margin causes waste at low power levels
Solution Approach 1:
The patent implements dynamic bias voltage adjustment where the bias voltage is no longer fixed but varies dynamically based on the required output power level. The bias comparison circuit continuously adjusts the bias voltage according to the feedback from power detection, enabling the system to adapt to different power levels and optimize current usage at each operating point.
Solution Approach 2:
The patent changes the bias voltage parameter dynamically based on output power requirements. Instead of using a fixed bias voltage, the system adjusts the bias voltage parameter according to the detected output power level, allowing optimal current utilization across different power operating points and eliminating waste at low power levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the radio frequency power amplifier to maintain stable gain and output power across different power levels, reducing waste and improving control precision.
Implementation Method 1
an output power on the main signal path is detected by the power detection circuit, and an equivalent voltage proportional to the output power is obtained
Implementation Method 2
Each branch equivalent voltage is separately compared with a control voltage pre-inputted to the bias comparison circuit, and a bias voltage and/or a collector voltage are continuously provided to the power amplifier circuit, until the control voltage corresponds to an output power level of the radio frequency power amplifier
Data Source
AI summary
A radio frequency power amplifier, a chip, and a communication terminal. The radio frequency power amplifier comprises a power amplifier circuit (5), an output matching circuit (2), a power detection circuit (3), and a bias comparison circuit (4). The output power on a main signal path is measured by the power detection circuit (3), and an equivalent voltage proportional to the output power is obtained and input to the bias comparison circuit (4); the equivalent voltage value is adjusted by means of the bias comparison circuit (4) and compared with a control voltage (1) to provide a bias voltage and/or collector voltage for the power amplifier circuit (5), thereby forming a closed-loop circuit, such that the radio frequency power amplifier can work in a stable state when gains and output power are in different power levels.