RF Power Amplifier Duty Cycle Control for Wide Dynamic Range
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Solution Overview
Problem
Nonlinear class power amplifiers in wireless communication devices achieve maximum power efficiency at maximum output power but efficiency degrades at lower output power, leading to a narrow dynamic range in terms of linearity and efficiency, which is a challenge for battery-operated devices with limited power budgets.
Innovation Solution
Implementing a duty cycle controller that adjusts the duty cycle of frequency-modulated signals based on target output power to reduce power consumption without sacrificing efficiency, using a programmable delay line and combinational logic to control the duty cycle of RF signals before amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nonlinear class power amplifiers are used to achieve better power efficiency, then power efficiency is improved, but the dynamic range in terms of linearity and efficiency becomes narrow
Solution Approach 1:
The patent applies dynamics by making the duty cycle adjustable and variable rather than fixed. The duty cycle controller dynamically adjusts the duty cycle of the constant-envelope FM signal based on the desired output power level, allowing the power amplifier to adapt to different operating conditions while maintaining high efficiency. This resolves the contradiction by enabling the amplifier to operate efficiently across a wide dynamic range through real-time parameter adjustment.
Solution Approach 2:
The patent changes the duty cycle parameter of the input signal to control the output power level. By varying the duty cycle (the proportion of time the signal is active within each period), the system can adjust the average output power while keeping the peak power and efficiency characteristics of the nonlinear amplifier. This parameter change enables wide dynamic range operation without sacrificing the power efficiency benefits of nonlinear class amplifiers.
2Power
If nonlinear class power amplifiers operate at lower output power, then output power is reduced, but power efficiency degrades
Solution Approach 1:
The patent uses periodic action by employing a constant-envelope frequency-modulated signal with a controllable duty cycle. The signal operates in periodic pulses, and by adjusting the duty cycle (the fraction of each period where the signal is active), the system can reduce average output power while maintaining the same peak power and efficiency characteristics. This periodic approach with variable duty cycle allows efficient operation across different power levels.
Solution Approach 2:
The patent applies partial action by using a duty cycle less than 100% to achieve the desired output power level. Instead of continuously driving the amplifier at full power and using attenuation, the system applies the full-power signal only for a partial duration (the duty cycle portion), achieving both power reduction and efficiency maintenance. This partial action approach keeps the amplifier operating in its efficient nonlinear region.
Data Source
AI summary
This disclosure provides methods, devices, and systems for wireless communications. The present implementations more specifically relate to reducing the power consumption of radio frequency (RF) power amplifiers without sacrificing power efficiency. In some aspects, an RF transmitter may include a modulator, a power amplifier, and a duty cycle controller coupled between the modulator and the power amplifier. The modulator is configured to modulate data onto a carrier signal according to a frequency modulation (FM) scheme. The duty cycle controller is configured to adjust a duty cycle of the FM signal based on a target output power associated with the power amplifier. In some implementations, the duty cycle controller may reduce the duty cycle of the FM signal so that the adjusted duty cycle causes the power amplifier to operate at the target output power. The power amplifier amplifies the adjusted FM signal for transmission over a wireless communication channel.