Power Amplifier Calibration for Second Harmonic Reduction
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Solution Overview
Problem
RF power amplifiers in industrial and consumer products generate unwanted harmonics due to manufacturing variations in CMOS integrated circuits, leading to increased costs and efficiency losses from large external harmonic filtering networks and self-interference with other circuits.
Innovation Solution
A power amplifier system that adjusts the characteristics of amplifiers during calibration to reduce the energy of second harmonics by controlling the duty cycle of the output signal, using a controller to iteratively adjust the drive characteristics and DC bias points of transistors to achieve a 50% duty cycle, thereby reducing the need for external harmonic filtering networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If external harmonic filtering networks are used to reduce unwanted harmonics, then harmonic emission limits are met, but parts count increases and product cost increases
Solution Approach 1:
The patent extracts the harmonic filtering function from external separate components and integrates it into the power amplifier circuit itself through careful design of the output matching network and amplifier topology, eliminating the need for external harmonic filtering networks while maintaining compliance with emission limits
Solution Approach 2:
The output matching network is designed to serve multiple functions simultaneously: it performs impedance matching for maximum power transfer, acts as a harmonic filter to suppress unwanted emissions, and provides DC blocking, thereby eliminating the need for separate dedicated harmonic filtering components
2Object-generated harmful factors
If large order filters are used to reduce significant harmonic energy, then harmonic emission limits are met, but insertion loss increases and efficiency decreases
Solution Approach 1:
The patent changes the design parameters of the output matching network, specifically optimizing the Q-factor and impedance transformation ratio to achieve effective harmonic suppression with lower order filters, thereby reducing insertion loss and improving overall amplifier efficiency while still meeting emission requirements
3Power
If harmonics are generated at the input of external harmonic filtering network, then power amplifier can operate at required power level, but self-interference with other circuits occurs
Solution Approach 1:
The output matching network serves as an intermediary element between the power amplifier and the external circuitry, providing both impedance matching for power transfer and frequency-selective filtering that allows the desired fundamental frequency to pass while blocking harmonic frequencies that could cause self-interference with other circuits
Data Source
AI summary
In one form, a signal generator system such as a power amplifier system includes an amplification stage, a lowpass filter, and a controller. The amplification stage includes a first amplifier having an input for receiving an input signal, a control input for receiving a first control signal, and an output. The lowpass filter has a first input coupled to the output of the first amplifier, and an output. The controller has a first input coupled to the output of the lowpass filter, and a first output coupled to the control input of the first amplifier, wherein the controller varies the first control signal to reduce a difference between the output of the lowpass filter and a first target voltage level.