Automotive Radar Receiver Circuit Flicker Noise Reduction
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Solution Overview
Problem
Automotive radar systems face challenges in achieving low noise figures at short distances due to flicker noise, which affects detection capability, despite advancements in CMOS technology that increase bandwidth and detection range, leading to higher noise figures at low frequencies.
Innovation Solution
A radar unit with a controller that switches between complex and real receiver modes, adjusting high-pass filter capacitance and resistance to reduce flicker noise at lower frequencies while maintaining performance at higher frequencies, allowing for both long-range and short-range radar applications with minimal impact on area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CMOS technology is used to increase bandwidth and detection range, then long-range detection capability is improved, but noise figure at low frequencies increases due to flicker noise
Solution Approach 1:
The receiver circuit dynamically switches between complex mode and real mode based on detection range requirements. For short-range detection, the circuit operates in real mode with adjusted high-pass filter parameters to minimize flicker noise. For long-range detection, it switches to complex mode to maximize bandwidth and detection range. This dynamic adaptation resolves the contradiction by optimizing noise performance for each operating condition.
Solution Approach 2:
The high-pass filter parameters (capacitance and resistance) are changed based on the operating mode. In real mode for short-range detection, the capacitance is doubled and resistance is halved to push the noise corner frequency higher, thereby reducing flicker noise impact. This parameter adjustment allows the system to maintain low noise figure at low frequencies while preserving long-range capability when needed.
2Length of stationary object
If complex receiver mode is used for long-range radar, then detection range is extended, but noise figure at low frequencies increases
Solution Approach 1:
The system dynamically selects between complex and real receiver modes based on the required detection range. The controller determines the appropriate mode and configures the receiver circuit accordingly, switching from complex mode (which extends detection range but increases low-frequency noise) to real mode (which reduces noise figure for short-range detection). This dynamic selection resolves the contradiction by matching the receiver mode to the operational requirements.
Solution Approach 2:
The receiver circuit parameters are changed between operating modes. In real mode, the high-pass filter capacitance is doubled and resistance is halved compared to complex mode, which shifts the noise characteristics and reduces flicker noise impact at low frequencies. This parameter transformation allows the system to achieve low noise figure when operating in real mode while maintaining the ability to switch to complex mode for extended range when needed.
3Object-affected harmful factors
If real receiver mode is used for short-range radar, then noise figure is reduced, but detection capability at long range is compromised
Solution Approach 1:
The receiver circuit operates in real mode for short-range detection where low noise figure is critical, and switches to complex mode for long-range detection where extended detection capability is required. The controller dynamically adjusts the operating mode based on target distance and detection requirements, ensuring optimal performance for each scenario without permanent compromise.
Solution Approach 2:
The receiver circuit is designed to perform multiple functions by supporting both complex and real operating modes within the same hardware architecture. The circuit can adapt its configuration to serve different detection needs - using real mode for short-range applications with low noise requirements and complex mode for long-range applications with extended detection requirements - making the system universal rather than specialized for a single function.
4Object-affected harmful factors
If high-pass filter capacitance is increased and resistance decreased in real mode, then flicker noise is reduced, but circuit area may increase
Solution Approach 1:
The high-pass filter capacitance for the real mode is created by combining (adding) the capacitances from both the I-channel and Q-channel filters. This merging approach allows the system to achieve doubled effective capacitance for noise reduction without adding entirely new capacitor components, thereby minimizing the increase in circuit area while still achieving the desired noise performance improvement.
Data Source
AI summary
In accordance with a first aspect of the present disclosure, a radar unit is provided, comprising: a receiver circuit configured to receive a radar signal; a controller configured to control said receiver circuit, wherein said controller is configured to cause said receiver circuit to operate either in a complex receiver mode or in a real receiver mode. In accordance with a second aspect of the present disclosure, a method of operating a radar unit is conceived, comprising: receiving, by a receiver circuit comprised in the radar unit, a radar signal; controlling, by a controller comprised in said radar unit, said receiver circuit, wherein said controller causes said receiver circuit to operate either in a complex receiver mode or in a real receiver mode.