RF Differential Amplifier Feedback Topology for Stable Linearity
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Solution Overview
Problem
Conventional differential amplifying circuits fail to maintain high linearity, especially when amplifying radio-frequency signals with complex modulation methods, due to decreasing gains with increasing frequency.
Innovation Solution
A radio-frequency differential amplifying circuit design incorporating input and output baluns, first and second differential amplifying circuits, and first and second linear feedback circuits, which are connected in specific configurations to ensure consistent gain across operating frequency bands, thereby improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power amplifying elements are used in the differential amplifier, then the circuit structure is simple, but the gain decreases as frequency increases, resulting in poor linearity
Solution Approach 1:
The patent divides the single differential amplifier into two separate differential amplifying circuits (first and second differential amplifying circuits). Each circuit processes one phase of the differential signal independently with its own feedback path, allowing individual optimization of gain and linearity for each path, thereby improving overall linearity while managing complexity through modular design
Solution Approach 2:
The patent introduces first and second linear feedback circuits that feed back a portion of the output signal to the input of each differential amplifying circuit. This feedback mechanism linearizes the gain characteristic across the frequency band, compensating for the natural gain decrease at higher frequencies and maintaining consistent linearity throughout the operating range
2Reliability
If the differential amplifier uses fixed gain amplification, then the circuit is simple, but it cannot maintain consistent gain across different frequency bands, especially for complex modulation signals
Solution Approach 1:
The patent implements dynamic gain control through the feedback circuits that automatically adjust the effective gain of each differential amplifying circuit based on the input signal characteristics and frequency content. The feedback mechanism creates a self-regulating system that maintains consistent overall gain across varying frequency bands, adapting to complex modulation signals without requiring manual intervention or complex external control circuits
Data Source
AI summary
The radio-frequency differential circuit includes an input balun, an output balun, a first differential amplifying circuit, a second differential amplifying circuit, a first linear feedback circuit and a second linear feedback circuit; the first differential amplifying circuit is arranged between a first output end of the input balun and a first input end of the output balun; the second differential amplifying circuit is arranged between a second output end of the input balun and a second input end of the output balun; a first end of the first linear feedback circuit is connected with the input balun, a second end of the first linear feedback circuit is connected with the first differential amplifying circuit; a first end of the second linear feedback circuit is connected with the input balun, and a second end of the second linear feedback circuit is connected with the second differential amplifying circuit.