Active Mixer Twin Feedback Bias for Better Linearity
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Solution Overview
Problem
Conventional mixers suffer from poor linearity, compromised conversion gain, and increased noise due to complex bias circuit structures, which affect overall communication system performance.
Innovation Solution
An active mixer with a self-adaptive dual feedback bias structure, comprising a power supply, RF input match/drive unit, local oscillator input match/drive unit, mixer core unit, and self-adaptive twin bias circuit, which uses two linear bias circuits connected in parallel to provide a stable bias for improved linearity without affecting other characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bias circuit is used in the mixer, then the mixer can operate, but the linearity becomes poor when input signal is increased
Solution Approach 1:
The patent implements a feedback bias circuit that automatically adjusts the bias current based on the input signal level. When the input signal increases, the feedback mechanism detects this change and adjusts the bias accordingly to maintain optimal linearity. This resolves the contradiction by dynamically adapting the bias circuit to signal conditions rather than using a fixed conventional bias structure.
Solution Approach 2:
The bias circuit transitions from a static conventional design to a dynamic self-adjusting system. The bias current is no longer fixed but varies automatically with input signal conditions, enabling the mixer to maintain poor linearity performance across different signal levels without requiring complex manual adjustment mechanisms.
2Reliability
If digital control circuit structures are added to improve linearity, then the linearity of mixer is increased, but the conversion gain is decreased and signal-to-noise rate is increased
Solution Approach 1:
The feedback bias circuit is designed to be self-regulating, automatically adjusting the bias current without requiring external digital control circuits. This self-service mechanism improves linearity through analog feedback rather than digital intervention, thereby avoiding the conversion gain degradation and noise increase that would result from adding complex digital control structures.
Solution Approach 2:
The patent replaces potential digital control mechanisms with an analog feedback-based bias adjustment system. By using continuous analog feedback to control the bias current, the system achieves improved linearity without the discrete, noisy nature of digital control circuits, thus preserving conversion gain and signal-to-noise ratio.
3Reliability
If multiple bias power units are added to improve linearity, then the linearity of mixer is increased, but current consumption increases and overall performance is affected
Solution Approach 1:
The patent merges the bias control function into a unified feedback mechanism that simultaneously manages multiple bias currents. Rather than adding separate bias power units, the feedback circuit integrates control of various bias elements, achieving improved linearity while avoiding the increased current consumption that would result from multiple independent bias sources.
Solution Approach 2:
The feedback bias circuit dynamically changes bias current parameters based on input signal conditions. By adjusting the magnitude and distribution of bias currents in response to signal levels, the system optimizes linearity without requiring permanently elevated bias currents that would increase overall power consumption.
Data Source
AI summary
An active mixer with self-adaptive bias feedback is described and resolves a poor linearity, inconvenient design of a bias circuit, and other defects of a conventional mixer. The dual self-feedback bias structure according to this invention is used. The active mixer with self-adaptive bias feedback has a power supply, an RF input match/drive unit, a local oscillator input match/drive unit, a mixer core unit, a self-adaptive twin bias circuit and an IF output match/buffer unit. This invention improves the linearity of a conventional mixer and does not affect other characteristics. There are fewer components in this invention; an area of the mixer is thus smaller. Further, this invention may improve temperature response, increase yield factor, and lower unit cost. The dual self-feedback bias structure is designed for further application to other semiconductor manufacturing processes, components, and microwave products.