RF Oscillator and Power Amplifier Feedback for Harmonic Suppression
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Solution Overview
Problem
Conventional RF transmitter circuits suffer from efficiency losses due to harmonic distortion and injection pulling, which are exacerbated by the coupling between digitally controlled oscillators (DCOs) and digital power amplifiers (DPAs).
Innovation Solution
The proposed solution involves a RF circuit design that includes a power amplifier with a feedback capacitor and a matching network transformer operating in an inverting configuration. This configuration enhances feedback coupling to suppress harmonic distortion, thereby mitigating injection pulling at the oscillator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a digital power amplifier (DPA) is used to reduce supply voltage and power, then power consumption is reduced, but harmonic distortion occurs at frequencies similar to the DCO operating frequency causing injection pulling
Solution Approach 1:
The patent introduces a feedback path that captures the harmful harmonic distortion generated by the DPA and feeds it back through a feedback capacitor to cancel the distortion at the DCO input. This converts the harmful harmonic distortion into a beneficial cancellation signal, allowing the DPA to operate at low voltage while maintaining spectral purity.
Solution Approach 2:
The patent implements a feedback mechanism where a portion of the DPA output is fed back to the DCO through a feedback capacitor. This feedback path allows the system to detect and counteract harmonic distortion in real-time, enabling the DPA to operate efficiently without causing injection pulling to the DCO.
2Loss of energy
If the DPA operates at low supply voltage to improve efficiency, then power efficiency is improved, but harmonic distortion suppression becomes more difficult
Solution Approach 1:
The feedback mechanism continuously monitors the DPA output and adjusts the cancellation signal accordingly, ensuring harmonic distortion suppression remains effective even as operating conditions change with varying supply voltage and process variations.
Solution Approach 2:
The feedback capacitor value and feedback path impedance are designed to optimize harmonic cancellation across different operating conditions. The system naturally adapts to parameter changes in the DPA by maintaining the feedback relationship, ensuring consistent distortion suppression despite voltage variations.
3Device complexity
If conventional transmitter circuits are used, then implementation is simpler, but efficiency is reduced due to injection pulling and harmonic distortion
Solution Approach 1:
The feedback path is integrated into the existing DPA and DCO structure, merging the harmonic cancellation function with the power amplification and oscillation circuits. This approach adds minimal external components while significantly improving transmitter efficiency by eliminating injection pulling.
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 effectively reduces or eliminates injection pulling, allowing the circuit to operate efficiently at low supply voltage and withstand process variations, while also saving circuit area and simplifying implementation.
Implementation Method 1
The capacitor is electrically coupled between a primary winding and a secondary winding of the matching network transformer. Serving as a feedback capacitor, the capacitor can enhance a feedback coupling from the secondary winding to the primary winding at a harmonic
Implementation Method 2
matching network transformer operating in an inverting configuration
Data Source
AI summary
Systems and methods for suppressing and mitigating harmonic distortion in a circuit are disclosed. In one example, a disclosed circuit includes a radio frequency (RF) oscillator and a power amplifier. The RF oscillator is configured to generate an RF signal. The power amplifier is configured to generate an amplified RF signal based on the RF signal. The power amplifier includes a transformer including a primary winding and a secondary winding, and a feedback capacitor electrically coupled to the primary winding and the secondary winding.