Feedback-Stabilized Electronic Mixer With RC Pole Shifting
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Solution Overview
Problem
Frequency mixers in telecommunications and audio devices face challenges in efficiently mixing signals and stabilizing output currents due to process variations and linearity requirements, particularly in down-converting television signals across different frequency bands.
Innovation Solution
An electronic mixer with an input stage for amplifying signals, a switching stage that mixes amplified inputs with a local oscillator signal, and an output stage coupled with a feedback stage to stabilize current through a comparator and adjust bias signals, utilizing switchable transistors and RC circuits to control pole movement and reduce linearity demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mixing circuits are used, then signal mixing function is achieved, but linearity is poor and current consumption is high
Solution Approach 1:
The patent employs dynamic switching of transistors in the mixing stage based on the local oscillator signal, allowing the circuit to operate in different states (active/off) rather than continuous conduction. This dynamic operation reduces average current consumption while maintaining mixing functionality and improving linearity through controlled switching behavior.
Solution Approach 2:
The patent changes the operating parameters of the mixing circuit by using switchable transistors that alter the circuit's electrical characteristics dynamically. By switching between different transistor states and configurations, the circuit achieves better linearity and controlled current consumption compared to conventional static mixing circuits.
2Reliability
If process variations are present, then manufacturing tolerances increase, but output current stability deteriorates
Solution Approach 1:
The patent incorporates a feedback mechanism where the current through the switching stage is sensed and used to control the switching behavior. This feedback loop compensates for process variations by adjusting the switching parameters dynamically, ensuring stable output current despite manufacturing tolerances and process variations.
Solution Approach 2:
The mixing circuit automatically adjusts its own operating characteristics through the feedback-controlled switching mechanism. The circuit self-regulates the current through the switching stage by comparing it with a reference and adjusting the switching duty cycle or timing, eliminating the need for external calibration and maintaining stability against process variations.
3Productivity
If switching transistors are used for mixing, then signal mixing is achieved, but pole positioning in output signals becomes problematic
Solution Approach 1:
The patent introduces an RC circuit as an intermediary element connected to the output of the switching stage. This RC circuit acts as a pole-positioning network that shapes the output signal's frequency response by introducing a controlled pole at a specific location. The RC time constant determines the pole position, providing simple yet effective control over the output characteristics without complicating the core switching mixing mechanism.
Data Source
AI summary
The present invention discloses a mixer comprising with an input stage (100) for receiving and amplifying input signals (VINP, VINN) and an output stage (300) for outputting output signals (Voutp, Voutn). A switching stage (200) is coupled between the input stage (100) and the output stage (300), the switching stage (200) mixing the amplified input signals with a local oscillator signal (vlop, vlon) to produce the output signals (Voutp, Voutn) at the output stage (300). An RC circuit (cop, rop; con, ron) is connected to the output stage (300) and adapted to move the pole of the output signals.