RF Power Amplifier Stage Bias Shaping for Low- and Mid-Power PAE
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Solution Overview
Problem
RF power amplifier circuits with multiple stages experience a drop in Power Added Efficiency (PAE) in low and middle power modes due to increased signal loss from impedance mismatch, leading to a decrease in output power and efficiency.
Innovation Solution
The RF power amplifier circuit employs a controller to continuously adjust the quiescent currents and gains of previous- and next-stage amplifiers in response to a power control voltage, with the next-stage amplifier's quiescent current and gain changes following a continuous function higher than the previous-stage amplifier's by at least one degree, optimizing device sizes and minimizing signal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the quiescent current of the final stage amplifier is reduced to improve power efficiency in low power mode, then power efficiency increases, but the signal loss from impedance mismatch increases causing PAE to drop
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the quiescent current of the final stage amplifier based on the operating power level. In low power mode, the quiescent current is reduced to improve power efficiency, while in high power mode, it is increased to maintain low impedance and reduce signal loss. This continuous parameter adjustment resolves the contradiction between power efficiency and signal loss.
Solution Approach 2:
The patent implements dynamics by making the quiescent current of the final stage amplifier variable rather than fixed. The bias control circuit continuously adjusts the quiescent current according to the operating conditions, enabling the amplifier to adapt its characteristics dynamically. This dynamic adjustment allows the system to optimize both power efficiency and signal loss performance across different operating ranges.
2Loss of energy
If the device size of the final stage amplifier is increased to reduce impedance and signal loss, then signal loss decreases, but power efficiency drops in low and middle power modes
Solution Approach 1:
Instead of using a fixed large device size, the patent changes the operating parameter (quiescent current) of the final stage amplifier dynamically. By adjusting the quiescent current based on the operating power level, the system achieves low impedance and reduced signal loss in high power mode while maintaining power efficiency in low and middle power modes. This parameter-based approach avoids the need for oversized devices that would waste power.
3Loss of energy
If the quiescent current is adjusted to maintain low impedance in high power mode, then signal loss is reduced, but power efficiency decreases due to increased current consumption
Solution Approach 1:
The patent applies dynamics by making the quiescent current adjustable rather than fixed. The bias control circuit dynamically adjusts the quiescent current based on the operating power level: increasing it in high power mode to maintain low impedance and reduce signal loss, and decreasing it in low power mode to improve power efficiency. This dynamic adjustment resolves the contradiction between signal loss and current consumption.
Data Source
AI summary
The RF power amplifier circuit including multiple amplification stages has a previous-stage amplifier, a next-stage amplifier and a controller. The previous-stage amplifier responds to an RF transmission input signal. The next-stage amplifier responds to an amplification signal output by the previous-stage amplifier. In response to an output-power-control voltage, the controller controls the former- and next-stage amplifiers in quiescent current and gain. In response to the output-power-control voltage, the quiescent current and gain of the previous-stage amplifier are continuously changed according to a first continuous function, whereas those of the next-stage amplifier are continuously changed according to a second continuous function. The second continuous function is higher than the first continuous function by at least one in degree. The RF power amplifier circuit brings about the effect that the drop of the power added efficiency in low and middle power modes is relieved.