Radar Sensor Mixer Interference Compensation
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Solution Overview
Problem
Radar sensors, particularly in automotive applications, face efficiency issues due to saturation from strong and close-by reflections, leading to mixer overload and reduced performance, which is not effectively addressed in current bistatic designs or lower transmission power solutions at 77 GHz frequencies.
Innovation Solution
An adjustable reflection point at the reference input of the mixer allows for phase and amplitude adjustment of interference signals, enabling destructive interference and suppression of saturation, using laser-trimmable detour lines and stubs to optimize interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If active mixers are used to achieve conversion gain, then mixer efficiency is improved, but the mixer becomes prone to clipping and saturation when input signals are high
Solution Approach 1:
The patent applies preliminary anti-action by introducing a compensation signal that anticipates and counteracts the saturation effect before it occurs. The compensation signal is generated based on the transmitted signal and injected into the mixer input to preemptively neutralize the saturation-causing reflected signals, allowing the active mixer to operate linearly even in the presence of strong reflections.
Solution Approach 2:
The patent uses an intermediary compensation signal as a mediator between the transmitted signal and the mixer operation. This compensation signal acts as a buffer that absorbs the saturation effect by being combined with the received signal before the mixer, thereby protecting the active mixer from direct exposure to high-power reflected signals that would cause clipping.
2Reliability
If transmission power is reduced to avoid mixer saturation, then mixer overload is reduced, but the detection range is decreased
Solution Approach 1:
Instead of reducing transmission power preemptively, the patent applies preliminary anti-action by generating a compensation signal based on the actual transmitted signal. This allows the system to maintain high transmission power for extended detection range while the compensation signal counteracts the saturation effect in real-time, preventing mixer overload without sacrificing range.
Solution Approach 2:
The patent changes the parameter of the received signal by adding a compensation signal with specific amplitude and phase characteristics. This parameter modification (signal addition) transforms the saturation-prone high-power signal into a linear-range signal for the mixer, enabling high transmission power operation without overload.
3Reliability
If a transmit/receive switch is added to protect the receiver, then mixer saturation is prevented, but device complexity increases
Solution Approach 1:
The patent merges the saturation protection function with the existing signal processing path by combining the compensation signal generation and injection into the existing mixer input stage. This eliminates the need for separate protective components like transmit/receive switches, maintaining receiver protection while avoiding additional system complexity.
Solution Approach 2:
The system performs self-service by generating its own compensation signal internally using the transmitted signal as a reference. This self-generated compensation mechanism provides automatic protection against saturation without requiring external protective devices, thereby maintaining simplicity while ensuring reliability.
4Loss of information
If DC coupling is used at the mixer output, then DC offset information is preserved, but the mixer remains susceptible to clipping from high input signals
Solution Approach 1:
The patent applies preliminary anti-action by preventing the clipping condition before it occurs at the mixer input. The compensation signal is injected upstream to ensure the mixer operates in its linear region, thereby preserving both DC offset information and preventing clipping simultaneously. The DC coupling can then maintain DC offset without the risk of clipping-induced distortion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses mixer saturation, enhancing radar sensor efficiency and performance by minimizing DC offset and clipping, while maintaining high transmission power and range, suitable for both monostatic and bistatic radar systems.
Implementation Method 1
the phase and the amplitude of at least one of these signals can now be adjusted in such a way that destructive interference occurs and the resulting interference signal is thus suppressed
Data Source
Figure 1~2
Figure 3~4
AI summary
Radar sensor having a mixer (12) for mixing a received signal with a reference signal, and having a device for compensating for interference signals (SE) which would overdrive the mixer, characterized in that the device for compensating for the interference signals has an adjustable reflection point (22) at the reference input (18) of the mixer (12).