Automotive Radar Voltage Gain Amplifier for DC Offset Cancellation
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Solution Overview
Problem
Automotive radar systems face challenges in maintaining linearity, reducing noise, and canceling DC offset while ensuring full output swing matching the ADC range, particularly in high gain operations and fluctuating input common mode voltages.
Innovation Solution
A voltage gain amplifier design that increases transconductance of differential amplifier transistors by sourcing more current than sinking, while maintaining constant voltage across transistors and adjusting current sources based on differential output voltages to cancel DC offset and maintain linearity, using a differential amplifier configuration with current sourcing and sinking circuits and an output amplification circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current is increased to increase transconductance of differential amplifier transistors, then linearity and operating margin are improved, but common mode voltage fluctuation causes instability
Solution Approach 1:
The patent employs feedback mechanisms where the differential output voltages are fed back to control the current sources. Specifically, the control signals for current sources are generated from the differential output voltages after amplification, creating a closed-loop system that automatically adjusts current to maintain constant voltage across transistors despite common mode voltage fluctuations.
Solution Approach 2:
The patent dynamically changes the current parameter in response to voltage conditions. By increasing the current sourced to transistors in equal magnitude to the increase in current sunk, the transconductance is increased without increasing common mode voltage, thereby maintaining stability while improving linearity.
2Reliability
If current sources are adjusted to maintain constant voltage across transistors, then operating margin is improved, but device complexity increases
Solution Approach 1:
The differential output voltages serve multiple functions: they are the amplified output signals and simultaneously serve as control signals for the current sources. This multi-functionality reduces the need for separate control circuits, thereby limiting the increase in device complexity while achieving constant voltage maintenance across transistors.
3Measurement precision
If DC offset is canceled by adjusting current sources, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs DC offset cancelation through self-adjustment using the differential output voltages to control the current sources. The calibration process utilizes the existing differential output signals without requiring external calibration equipment or complex additional circuits, allowing the system to self-correct DC offset while minimizing complexity increase.
Data Source
AI summary
Disclosed herein is a method including sinking current from a pair of input transistors of a differential amplifier while sourcing more current to the pair of input transistors than is sunk. The method further includes generating a pair of input differential signals using a pair of input voltage regulators, and amplifying a difference between the pair of input differential signals to produce a pair of differential output voltages, using the differential amplifier. The method also includes amplifying the pair of differential output voltages using at least one voltage gain amplifier, and generating control signals for current sources that source the current to the pair of input transistors of the differential amplifier, from the pair of differential output voltages after at least amplification.