Voltage Boost Follower for OFDM Power Amplifier Peak Linearity
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Solution Overview
Problem
Integrated power amplifiers for OFDM signals face inefficiencies and increased complexity due to high peak-to-average power ratios, leading to high power consumption and distortion, particularly in WLAN systems, where supporting peak amplitudes requires complex and costly designs that are difficult to integrate within a single circuit.
Innovation Solution
A circuit with a charge storage component, amplifier voltage supply port, and a detector that switches between a standard voltage mode and a boosted voltage mode based on the detected amplitude of the RF signal, providing a boost voltage only during peak pulses to maintain linearity and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power amplifier is designed to support peak amplitude, then linearity is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The power amplifier transitions from a static design supporting peak amplitude continuously to a dynamic design where the supply voltage is adjusted in real-time based on the instantaneous signal amplitude. This allows the amplifier to operate efficiently at lower voltages during average conditions while maintaining linearity during peak excursions through voltage boosting.
Solution Approach 2:
The supply voltage parameter is changed dynamically rather than maintained at a constant high level. By modulating the supply voltage to match the signal envelope, the amplifier achieves peak performance only when needed, reducing overall power consumption while maintaining linearity during critical peak periods.
2Use of energy by moving object
If a DC-to-DC converter is used to vary supply voltage, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The complex DC-to-DC converter is extracted and replaced with a simpler voltage boosting mechanism that uses a capacitor and switching circuitry. This extraction removes the problematic complexity while retaining the essential function of dynamic voltage adjustment for power savings.
Solution Approach 2:
A capacitor is introduced as an intermediary energy storage element that enables voltage boosting without requiring a full DC-to-DC converter. The capacitor acts as a temporary energy reservoir that can be rapidly charged and discharged to provide the necessary voltage excursions, simplifying the power supply architecture.
3Loss of energy
If envelope tracking power supply is used, then efficiency is improved, but device complexity increases
Solution Approach 1:
The complex envelope tracking power supply is extracted and replaced with a simplified voltage follower circuit using a buffer amplifier. This extraction maintains the efficiency benefits of envelope tracking by dynamically matching the supply voltage to the signal envelope while removing the excessive complexity of prior art implementations.
Solution Approach 2:
The voltage follower circuit automatically adjusts the supply voltage to match the signal envelope without requiring complex external control circuitry. The buffer amplifier inherently provides the necessary voltage tracking by following the detector output, enabling self-service operation that improves efficiency while minimizing added complexity.
4Ease of manufacture
If inductor and PA are integrated on same substrate, then ease of manufacture is improved, but device complexity increases
Solution Approach 1:
The inductor is extracted from the integrated circuit substrate and implemented as an external discrete component. This extraction eliminates the manufacturing difficulties and complexity associated with integrating high-Q inductors on standard semiconductor substrates, while maintaining the power amplifier's performance requirements through the use of external filtering and impedance matching networks.
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 solution enhances the power output and efficiency of the power amplifier while reducing power supply complexity, enabling longer battery life and improved data transmission range without the need for a second voltage supply, facilitating integration within a single integrated circuit.
Implementation Method 1
a charge storage component; in the second mode of operation the at least a switch for providing a boost voltage at the amplifier voltage supply port in excess of the first voltage, the boost voltage resulting from a cooperation of the charge storage component and the first voltage
Data Source
AI summary
A collector boost circuit is disclosed for providing a first voltage in a first mode of operation to a power amplifier, and another voltage in a second mode of operation to the power amplifier. The collector boost circuit uses an indicator signal derived by an RF detector to switch between the first and the second mode of operation. The another voltage is a boosted voltage greater than the first voltage and is provided when required during peak excursions to prevent amplifier clipping through a boost capacitor. The another voltage is continuous and varies in accordance with the detected peak signal amplitude.