Active Bias Circuit With PTAT Feedback for PA Linearity Stability
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Solution Overview
Problem
Current bias circuits for power amplifiers in 3G/4G mobile phones fail to maintain stabilized bias states and linearity due to temperature fluctuations, leading to increased design complexity, power loss, and cost, and are not applicable to high-power output states.
Innovation Solution
An active bias circuit incorporating a PTAT current source circuit, reference voltage circuit, isolation voltage stabilizing circuit, and bias voltage circuit, along with a self-heating compensation mechanism, to generate a stabilized bias voltage and compensate for temperature-induced linearity deterioration, implemented using existing chip production processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex bias circuit structure is used to maintain stabilized bias state and linearity, then the power amplifier's linearity and stability are improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the bias circuit with the power amplifier chip to form an integrated structure, eliminating the need for separate bias circuit chips. The bias circuit shares the same substrate and manufacturing process as the power amplifier, reducing overall device complexity while maintaining stabilization functionality through integrated temperature sensing and feedback mechanisms
Solution Approach 2:
The bias circuit incorporates self-heating compensation capabilities where the power amplifier tube's own temperature changes are detected and compensated for in real-time. The circuit uses the power amplifier tube's temperature characteristics to automatically adjust bias voltages, enabling the system to self-regulate without external intervention and maintain stable operation under varying temperature conditions
2Reliability
If a complex bias circuit structure is used to maintain stabilized bias state and linearity, then the power amplifier's linearity and stability are improved, but the manufacturing cost increases
Solution Approach 1:
The patent integrates the bias circuit and power amplifier chip into a single unified device, allowing both components to be manufactured using the same semiconductor fabrication process. This integration eliminates the need for separate bias circuit chips and reduces assembly steps, directly lowering manufacturing costs while maintaining the temperature compensation functionality
Solution Approach 2:
The integrated chip structure allows the same manufacturing process and substrate to serve multiple functions - both power amplification and temperature compensation. The bias circuit reuses elements from the power amplifier structure itself, making the manufacturing process more efficient and reducing overall production costs while maintaining reliability
3Power
If high power output is achieved in 3G/4G communications, then the data transmission capability is improved, but the chip temperature rises causing bias state shifting and linearity deterioration
Solution Approach 1:
The patent implements a feedback mechanism where temperature sensors continuously monitor the chip temperature and feed this information back to the bias circuit. The bias circuit automatically adjusts bias voltages based on temperature feedback, compensating for temperature-induced shifts in real-time and maintaining stable operation even at high power output levels
Solution Approach 2:
The patent converts the harmful effect of temperature rise into a useful compensation mechanism. By deliberately designing the bias circuit to detect and respond to temperature changes, the system uses the temperature rise itself as a signal to trigger compensatory adjustments, transforming what would normally be a detrimental effect into a controlled parameter that maintains linearity and stability
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
The active bias circuit effectively suppresses bias state shifting and linearity deterioration caused by temperature changes, improving the power amplifier's linearity and stability while reducing design complexity and costs.
Implementation Method 1
an input end of the PTAT current source circuit is connected to a voltage source, and an output end is connected to the reference voltage circuit, to generate a current that is in proportion to the voltage source and a temperature
Implementation Method 2
the reference voltage circuit generates a reference voltage that is in proportion to the current and the temperature
Implementation Method 3
the isolation voltage stabilizing circuit isolates the reference voltage circuit from the bias voltage circuit, and supplies a stabilized voltage to the bias voltage circuit by using a negative feedback loop
Data Source
AI summary
An active bias circuit for a power amplifier and a mobile terminal are disclosed. The circuit includes a proportional to absolute temperature (PTAT) current source circuit, a reference voltage circuit, an isolation voltage stabilizing circuit, and a bias voltage circuit. An input end of the PTAT current source circuit is connected to a voltage source (Vbat), and an output end is connected to the reference voltage circuit. The reference voltage circuit generates a reference voltage that is in proportion to a current and a temperature. The isolation voltage stabilizing circuit isolates the reference voltage circuit from the bias voltage circuit, and supplies a stabilized voltage to the bias voltage circuit by using a negative feedback loop. The bias voltage circuit receives the voltage of the isolation voltage stabilizing circuit, and is also connected to the voltage source (Vbat).