Envelope Amplifier Current-Summing Circuit for Linear Efficiency
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Solution Overview
Problem
Existing envelope amplifiers for wireless communication face a trade-off between linearity and power efficiency due to the varying power supply voltage, leading to inefficiencies and frequency limitations, particularly in high data rate communication standards like WCDMA, HSUPA, WLAN, and LTE, where modulated signals with non-constant envelopes require high linearity and efficient power handling.
Innovation Solution
The proposed envelope amplifier configuration includes a first and second output section with proportional currents, a comparator unit for comparing current values, and an output unit that sums currents via an inductor to deliver a resulting sum current, allowing for simplified circuit design and reduced current consumption by eliminating the need for a rail-to-rail input stage and minimizing switching noise, thereby improving efficiency and frequency performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power supply voltage of the amplifier is varied in response to an envelope signal to improve power efficiency, then power efficiency is improved, but linearity deteriorates
Solution Approach 1:
The amplifier is divided into two independent amplification paths: a linear amplifier that maintains signal linearity and a switching amplifier that provides efficient power amplification. Each amplifier operates independently with its own feedback loop, allowing the linear amplifier to preserve signal fidelity while the switching amplifier handles power efficiency, thus resolving the trade-off between linearity and power efficiency.
Solution Approach 2:
The patent combines two different amplification techniques (linear amplification and switching amplification) into a single system. The output signals from both amplifiers are combined to deliver the final amplified output, leveraging the strengths of both approaches: linearity from the linear amplifier and efficiency from the switching amplifier.
2Use of energy by moving object
If a PWM type DC-DC convertor circuit is used as the envelope amplifier, then power efficiency is improved, but switching noise is generated and frequency limitations occur
Solution Approach 1:
The patent extracts the switching operation from the signal path by using a switching amplifier that operates independently from the linear amplifier. The switching amplifier handles power amplification separately, allowing the linear amplifier to process the signal without exposure to switching noise, thus eliminating the harmful effect while maintaining efficiency.
Solution Approach 2:
The patent introduces an intermediary structure where the switching amplifier operates as a separate entity with its own feedback loop. This intermediary configuration allows the switching amplifier to provide efficient power amplification without directly interfering with the signal processing in the linear amplifier, thereby reducing switching noise impact.
3Object-generated harmful factors
If the internal switching frequency is set at a lower value to reduce switching noise, then switching noise is reduced, but the cut-off frequency of the low-pass filter becomes low, imposing frequency limitations
Solution Approach 1:
The patent segments the amplification function into two independent paths, allowing each amplifier to operate at optimal frequencies. The linear amplifier can handle higher frequency signals without being constrained by switching frequency limitations, while the switching amplifier operates at lower frequencies for efficient power amplification, thus resolving the frequency response limitation.
4Object-generated harmful factors
If a resistor is connected between the linear amplifier and the output terminal to reduce switching noise, then switching noise is reduced, but the resistance value must be sufficiently low, which is difficult to implement with accurate values in CMOS circuits
Solution Approach 1:
The patent removes the need for a low-value resistor by extracting the switching noise path from the signal path. The switching amplifier operates independently with its own feedback loop, eliminating the requirement for a resistor to suppress switching noise, thus simplifying the circuit implementation and avoiding manufacturing difficulties associated with low-value resistors in CMOS circuits.
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
This configuration enhances the power efficiency and frequency handling capabilities of the envelope amplifier, allowing for higher circuit performance and reduced current consumption, while maintaining high linearity and efficient power supply management, even under varying load conditions.
Implementation Method 1
an output unit for summing a current via an inductor derived from a current, which is sustained or broken in response to compared result of the comparator unit, to a second current
Data Source
AI summary
An envelope amplifier includes an amplifier unit, a comparator unit and an output unit. The amplifier unit is made up of a first output section that outputs a first current in response to an amplitude of an input envelope signal, and a second output section. The second output section outputs a second current of a current value proportionate to a current value of the first current. Absolute value of the current value of the second current is greater than that of a current value of the first current. Comparator unit compares the current value of the first current. The output unit sums a current via an inductor derived from a current sustained or broken in response to a compared result of the comparator unit to the second current to deliver the resulting sum current at an output end. The first current is configured to be terminated without being delivered to the output unit (FIG. 1).