Push-Pull RF Power Amplifier Feedback for Higher Gain Margin
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Solution Overview
Problem
Existing push-pull radio frequency power amplifiers face limitations in gain margin due to the upper limit of single-stage transistor gain, especially in sub 6 GHz and millimeter wave bands, and adding drive amplifiers increases design complexity.
Innovation Solution
A push-pull radio frequency power amplifier with a coupling feedback circuit connected to the drive and power output stages, providing positive feedback to improve signal strength without increasing drive stages, using transformers and feedback devices like capacitors to enhance gain and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If drive amplifiers are added to increase gain margin, then gain and output power are improved, but design complexity increases
Solution Approach 1:
The patent applies feedback by extracting a portion of the output signal through a feedback network (including capacitors C18, C19 and inductors L8, L9) and feeding it back to the input stage. This feedback mechanism provides additional gain and output power without requiring additional drive amplifier stages, thereby avoiding increased design complexity while still achieving the desired power and gain improvement
2Power
If drive amplifiers are added to increase gain margin, then gain is improved, but design complexity increases
Solution Approach 1:
The feedback network extracts output signal and feeds it back to enhance gain in the input stage, achieving the required gain margin without adding more amplifier stages. This resolves the contradiction by providing gain improvement through signal recycling rather than through additional complex stages
3Power
If the number of drive stages is increased to overcome single-stage gain limits, then gain margin is improved, but device complexity increases
Solution Approach 1:
The patent uses a feedback network that taps into the output signal and feeds it back to the input stage, effectively increasing the gain margin without requiring additional drive stages. This approach maintains device simplicity while achieving the necessary gain margin improvement by utilizing the existing stages more efficiently through feedback
4Power
If positive feedback is applied to improve signal strength, then gain and output power are improved, but circuit stability may deteriorate
Solution Approach 1:
The patent implements a carefully designed feedback network with specific components (capacitors C18, C19 and inductors L8, L9) that provides positive feedback to enhance signal strength while maintaining circuit stability. The feedback network is designed to control the feedback amount and frequency characteristics, ensuring that signal strength is improved without causing instability or oscillation
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 improves gain and output power across a wider frequency band, reducing design complexity by optimizing signal superposition and maintaining gain without additional stages.
Implementation Method 1
the coupling feedback circuit includes the secondary coil led out from the base of the first transistor Q1... the primary coil of the first transformer T1 is coupled with the secondary coil led out from the base of the first transistor Q1 to form a second transformer T2
Implementation Method 2
the primary coil of the first transformer T1 is coupled with the secondary coil led out from the base of the first transistor Q1 to form a second transformer T2
Implementation Method 3
one end of the feedback device is configured to receive the alternating voltage, and the other end of the feedback device is connected with the input end of the first transistor Q1... the feedback device is any of the following: a coupling feedback capacitor
Data Source
AI summary
A push-pull radio frequency power amplifier includes a coupling feedback circuit, a drive stage circuit and a power output stage circuit, in which the coupling feedback circuit is connected with the drive stage circuit and/or the power output stage circuit; the coupling feedback circuit is configured to generate an alternating voltage at an input end of a first transistor and/or an input end of a push-pull transistor; when the alternating voltage and a voltage at the input end are in a same direction, a positive feedback of an input signal at the input end is achieved; and the first transistor represents a transistor in the drive stage circuit and the push-pull transistor represents a second transistor and a third transistor that form a push-pull structure in the power output stage circuit.