Doherty Power Amplifier Bias Control for Fast Saturation Response
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Solution Overview
Problem
Existing Doherty amplifier technologies suffer from slow response times in detecting carrier amplifier saturation, leading to degradation in high-frequency output signal quality, especially when faced with instantaneous power increases.
Innovation Solution
A power amplification device with a drive-level detector circuit that quickly adjusts bias circuits for peak amplifiers based on the drive level of carrier amplifiers, using a splitter, carrier and peak amplifiers, bias circuits, and a coupler to maintain unsaturation of carrier amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional saturation detection circuits are used to control the peak amplifier bias, then the circuit can detect carrier amplifier saturation, but the response time is several tens of nanoseconds which is too slow for instantaneous power increases
Solution Approach 1:
The invention performs preliminary action by detecting the input signal level before the carrier amplifier actually saturates. The detector circuit monitors the input signal and predicts when saturation will occur, allowing the peak amplifier bias to be adjusted in advance. This prevents the several-tens-of-nanoseconds delay that occurs when waiting for saturation to actually happen and then detect it.
Solution Approach 2:
The invention applies dynamics by making the peak amplifier bias dynamically adjustable based on real-time input signal level detection. The bias circuit receives control signals that continuously adjust the peak amplifier operating point according to the instantaneous input power level, enabling fast response to power increases without the fixed delay of conventional saturation detection.
2Ease of operation
If the peak amplifier bias is controlled based on input signal level using conventional bias circuits, then the bias can be adjusted, but the response time is slow and degradation in output signal quality occurs
Solution Approach 1:
The invention implements feedback by creating a closed-loop control system where the detector circuit continuously monitors the input signal level and feeds this information back to the bias circuit. The bias circuit then adjusts the peak amplifier bias accordingly, and this adjusted bias affects the overall amplifier output, which in turn influences future detection. This feedback mechanism ensures fast response and maintains output signal quality by continuously adapting to input conditions.
3Loss of energy
If the carrier amplifier operates at saturation to achieve high efficiency, then power efficiency is improved, but the response to instantaneous power increases is delayed causing signal quality degradation
Solution Approach 1:
The invention applies partial or excessive action by having the peak amplifier provide additional amplification beyond what the carrier amplifier alone can deliver. When the input signal level increases, the peak amplifier is activated with appropriate bias to supplement the carrier amplifier output, preventing carrier amplifier saturation while maintaining high overall efficiency. This excessive action ensures that the carrier amplifier operates in its optimal efficiency region even during power increases.
Data Source
AI summary
A power amplification device includes a substrate, an integrated circuit, a splitter, a carrier amplifier, a peak amplifier, a first bias circuit that provides bias to the carrier amplifier, a second bias circuit that provides bias to the peak amplifier, a drive-level detector circuit that outputs a signal indicating a drive level of the carrier amplifier, based on a high-frequency signal outputted by the carrier amplifier, a detector circuit that outputs a control signal to control the second bias circuit, based on an inputted high-frequency signal and the signal indicating the drive level of the carrier amplifier, and a coupler. The detector circuit varies a threshold for the control signal. The integrated circuit includes the splitter, the carrier amplifier, the peak amplifier, the first bias circuit, the second bias circuit, the drive-level detector circuit, and the detector circuit.