Multi-Amplifier RF Transmission for Back-Off Power Efficiency
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Solution Overview
Problem
Transmission devices experience degraded signal-to-noise ratio due to quantization noise from delta-sigma modulation and suffer from low power efficiency, especially when amplifying signals with small amplitudes, as a result of fixed power loss and on/off switching in class D amplifiers.
Innovation Solution
A transmission device that generates pulse-modulated signals by varying pulse width or density based on the amplitude component, integrates these signals with phase components, and uses a power amplifying system with multiple amplifiers that adjust according to the amplitude level of the signal, ensuring high power efficiency even at large back-off operating regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sufficiently large back-off from saturation power is ensured to maintain high linearity, then the amplifier operates in a region with high linearity, but the average power efficiency of the amplifier decreases
Solution Approach 1:
The amplifier is divided into multiple amplifying means (first amplifier, second amplifier, third amplifier) with different operating characteristics. The first amplifier operates with high linearity at lower power levels, while the second and third amplifiers operate at higher power levels with different efficiency characteristics. This segmentation allows the system to maintain high linearity when needed while improving overall power efficiency through coordinated operation of multiple amplifiers.
2Use of energy by moving object
If class D amplifiers with on/off switching are used to improve power efficiency, then power efficiency is improved, but signal-to-noise ratio is degraded due to quantization noise from delta-sigma modulation
Solution Approach 1:
The invention combines multiple amplifying means with different operating characteristics to achieve both high power efficiency and high signal-to-noise ratio. The first amplifier provides high linearity for low-power signals, while the second and third amplifiers provide efficient high-power amplification. By merging these different amplification paths and coordinating their operation based on signal amplitude, the system achieves both high power efficiency and high signal-to-noise ratio without the quantization noise problems of pure class D amplifiers.
3Adaptability or versatility
If the number of amplifiers is increased to cover a wide dynamic range, then the operating region is expanded, but the device complexity increases
Solution Approach 1:
The invention dynamically controls the operation of multiple amplifiers based on the amplitude level of the input signal. The control unit determines which amplifiers should be active at any given time, allowing the system to adapt to different operating conditions. This dynamic control enables a wide operating dynamic range while managing device complexity through intelligent coordination rather than simply adding more amplifiers indiscriminately.
Data Source
AI summary
A transmission device includes a pulse modulated signal generator that generates a pulse-modulated signal by changing the width of a pulse or the density of a pulse according to the magnitude of the amplitude component of an input signal while discretely changing the pulse height according to the magnitude of the amplitude, a modulated-signal generator that generates a modulated signal by integrating the pulse-modulated signal and the phase component of the input signal, a power amplifier that includes at least as many amplifiers as the number of the discrete amplitude levels of the modulated signal, changes the number of amplifies that amplify the modulated signal on the basis of the value of the amplitude level of the modulated signal, combines outputs of the amplifiers, and outputs a combined output, and an output filter that eliminates a square-wave component from the output of the power amplifier.