Programmable Power Amplifier Feedback for Precise RF Power Steps
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Solution Overview
Problem
Existing RF power amplifiers are sensitive to temperature, manufacturing process tolerances, and power supply voltage variations, making precise linear power control and output power steps of 0.5 dB or smaller difficult to achieve.
Innovation Solution
A programmable power amplifier with a power amplifier core transistor circuit, a switch, and a feedback circuit comprising a digital-to-analog converter and an operational amplifier, allowing for precise control of current flow and output power, with optional waveform shaping and independence from power supply voltage until a set brown out level, using a digital-to-analog converter with programmable resistance and an inductor connected to an RF matching network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional power amplifier control techniques are used, then the amplifier can operate with simple control circuitry, but the output power control precision deteriorates and temperature stability is poor
Solution Approach 1:
The patent implements a feedback circuit that includes an operational amplifier and a digital-to-analog converter with programmable resistance. The feedback circuit receives a portion of the output signal and adjusts the control signal to the power amplifier core transistor based on the actual output, enabling precise closed-loop power control. This feedback mechanism directly resolves the contradiction by providing high precision output power control through systematic measurement and correction.
Solution Approach 2:
The patent employs a digital-to-analog converter with programmable resistance value that can be adjusted to change the transfer function of the feedback circuit. By programmably changing the resistance parameter, the system achieves precise control over output power levels and temperature compensation without requiring complex hardware reconfiguration, thus improving precision while managing complexity.
2Stability of the object's composition
If conventional power amplifier control techniques are used, then the amplifier structure remains simple, but temperature stability and manufacturing tolerance sensitivity worsen
Solution Approach 1:
The feedback circuit continuously monitors the output and adjusts the control signal to compensate for temperature drift and manufacturing variations. The operational amplifier compares the actual output with the desired output and generates corrective signals, enabling the system to maintain stability despite environmental changes and component tolerances.
Solution Approach 2:
The patent incorporates a programmable resistance in the digital-to-analog converter that can be pre-adjusted to compensate for known manufacturing tolerances and temperature coefficients. This allows the system to be calibrated beforehand to counteract expected variations, providing temperature stability and compensation for manufacturing tolerances before they become problematic.
3Manufacturing precision
If conventional power control methods are used, then the control implementation is straightforward, but achieving linear power control with 0.5 dB or smaller steps becomes difficult
Solution Approach 1:
The feedback circuit enables precise linear power control by continuously measuring the actual output power and adjusting the control signal accordingly. The operational amplifier provides high-gain error correction that ensures linear relationship between control input and output power, achieving 0.5 dB or smaller precision steps through systematic feedback control rather than relying on component precision alone.
Solution Approach 2:
The programmable resistance in the digital-to-analog converter allows for fine adjustment of the feedback transfer function, enabling precise control over the power steps. By programmably changing the resistance value, the system can achieve 0.5 dB or smaller power steps with linear control characteristics, as the digital control word directly translates to precise analog control voltage through the programmable DAC.
4Reliability
If output power control is implemented through gate or base drive control, then the control mechanism is simple, but sensitivity to power supply voltage variations increases
Solution Approach 1:
The feedback circuit decouples the output power control from power supply voltage variations by measuring the actual output and adjusting the control signal independently of supply fluctuations. The operational amplifier provides error correction that compensates for power supply variations, making the output power reliable and insensitive to supply voltage changes while managing the added circuit complexity through efficient feedback topology.
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
The solution provides high accuracy in output power control with programmable step sizes less than 0.5 dB, temperature stability tied to bandgap voltage stability, and flexibility to meet governmental bandwidth requirements, ensuring consistent performance across operational temperature ranges.
Implementation Method 1
a feedback circuit of the power amplifier core transistor circuit, the feedback circuit comprising a digital-to-analog converter and an operational amplifier
Implementation Method 2
an operational amplifier having a first input node configured to receive a first reference signal; a second input node connected to the digital-to-analog converter; and an output node for outputting an operational amplifier output signal
Implementation Method 3
by attaching the output of the power amplifier to an inductor that is also connected to a power supply and to an RF matching network, the current output from the amplifier generates a voltage across the inductor and thus RF power
Data Source
AI summary
The present invention concerns a programmable power amplifier comprising:an amplifier core transistor circuit connected to an amplifier output node; a switch connected to the amplifier core transistor circuit, the switch being configured to switch on and off the amplifier core transistor circuit; and a feedback circuit of the amplifier core transistor circuit. The feedback circuit comprises a digital-to-analog converter and an operational amplifier having a first input node configured to receive a first reference signal; a second input node connected to the digital-to-analog converter; and an output node for outputting an operational amplifier output signal and connected to the amplifier core transistor circuit for controlling the amount of current flowing in the amplifier core transistor circuit. The digital-to-analog converter has a programmable resistance value for controlling the resistance of the digital-to-analog converter to thereby adjust a digital-to-analog converter output signal fed to the second input node of the operational amplifier for controlling an amplifier output signal at the amplifier output node.