Passive FET Multi-Phase Mixers With Pre-Discharge Bypass Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing passive mixer circuits in wireless communication systems face challenges with noise performance and linearity due to flicker noise and parasitic capacitance, leading to limitations in noise figure and third-order intercept point.
Innovation Solution
The implementation of a mixer circuit with switching transistors and bypass switches that discharge parasitic capacitances prior to activation, using a local oscillator providing phased LO signals with specific duty cycles to reduce noise and tilt in conversion gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching transistors are activated without discharging parasitic capacitances, then the mixer can operate continuously, but noise figure deteriorates and tilt in conversion gains increases
Solution Approach 1:
The bypass switches discharge parasitic capacitances of the switching transistors in an appropriate time slot prior to activation of the switching transistors. This preliminary action removes accumulated charge that would otherwise cause noise and gain tilt, improving noise performance without requiring fundamental circuit redesign
Solution Approach 2:
Bypass switches are introduced as intermediary elements between the switching transistors and ground. These bypass switches provide a controlled discharge path for parasitic capacitances, mediating between the need for continuous operation and the need to maintain low noise performance
2Object-affected harmful factors
If bypass switches are added to discharge parasitic capacitances, then noise response improves, but device complexity increases
Solution Approach 1:
Bypass switches are introduced as intermediary elements between the switching transistors and ground. These bypass switches provide a controlled discharge path for parasitic capacitances, mediating between the need for continuous operation and the need to maintain low noise performance
Solution Approach 2:
The circuit utilizes changes in the state parameters of the bypass switches (on/off states controlled by LO signals) to dynamically manage parasitic capacitance discharge. By changing the operational parameters of the bypass switches in synchronization with the switching transistors, the circuit achieves noise reduction through parameter control rather than structural overhaul
Data Source
AI summary
The noise response in a passive mixer circuit is improved by discharging the switching transistors in the mixer circuit in an appropriate time slot prior to activation. In addition to improving the noise response, tilt in conversion gains and linearity can be reduced. A passive mixer circuit includes bypass switches arranged in proximity to the switching transistors that make up the mixer core. These bypass switches, which are activated in intervals just prior to the active intervals of their neighboring switching transistors, discharge to ground accumulated charges on the switching transistors or on reactive components around switches.