Radar ADC Thresholding for Weak Echo Detection Under Leakage
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Solution Overview
Problem
Biometric sensing radars face challenges in accurately detecting weak target signals due to interference from strong leakage signals and thermal noise, which can cause ADC saturation or clipping, compromising the extraction of vital signs-related information.
Innovation Solution
The ADC threshold adjustments and processor configurations allow for improved sensitivity by positioning thresholds to be tripped by thermal noise, enabling the ADC to discern weak target signals more effectively, including mid-tread and on-tread threshold settings, dynamic threshold adjustments, and filtering out quantization noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ADC uses conventional threshold settings, then it can handle strong leakage signals, but it fails to detect weak target signals due to saturation and clipping
Solution Approach 1:
The patent implements dynamic threshold adjustment where the ADC thresholds are changed based on the signal environment. During periods when leakage is present, thresholds are adjusted to prevent saturation, and during periods when leakage is absent, thresholds are lowered to improve sensitivity for detecting weak target signals. This dynamic adaptation resolves the contradiction between handling strong leakage and detecting weak signals.
Solution Approach 2:
The system uses periodic pulse transmission with alternating active and inactive periods. During inactive periods, the ADC can use lower thresholds to detect weak signals without interference from strong leakage. This periodic switching between different operational states allows the system to achieve both high sensitivity during signal detection and protection from saturation during transmission.
2Measurement precision
If the ADC thresholds are lowered to detect weak signals, then detection sensitivity improves, but the ADC becomes more susceptible to saturation from strong leakage
Solution Approach 1:
The patent employs dynamic threshold adjustment where the ADC thresholds are adaptively changed based on the presence and strength of leakage signals. When strong leakage is detected, thresholds are raised to prevent saturation, ensuring reliability. When leakage is weak or absent, thresholds are lowered to improve detection sensitivity for weak target signals, thus resolving the contradiction between sensitivity and reliability.
Solution Approach 2:
The system performs preliminary detection of leakage signal strength before setting the ADC thresholds. By assessing the environment first and then adjusting thresholds accordingly, the system prevents saturation before it occurs while maintaining optimal sensitivity for signal detection, thereby resolving the contradiction between weak signal detection and saturation resistance.
3Measurement precision
If the ADC sampling rate is increased to capture weak signals, then detection capability improves, but the impact of thermal noise and leakage increases
Solution Approach 1:
The patent extracts and removes the leakage signal component from the received signal before ADC conversion. By separating and eliminating the harmful leakage and thermal noise components, the system can then use appropriate sampling rates to detect weak target signals without being overwhelmed by noise, thus resolving the contradiction between capture accuracy and noise interference.
Solution Approach 2:
The system introduces an intermediary signal processing stage between the receiver and ADC that filters out thermal noise and leakage components. This intermediary filtering process allows the ADC to operate at optimal sampling rates for detecting weak signals without the detrimental effects of amplified thermal noise and leakage that would occur with direct high-rate sampling.
Data Source
AI summary
A sensing radar includes a transmitter configured to transmit bursts of pulses, a receiver configured to receive a signal comprising an echo from the bursts of pulses and a leakage of the bursts of pulses from the transmitter to the receiver; an analog-to-digital converter (ADC) coupled to the receiver, and a processor coupled to the ADC. At least one of thresholds of the ADC is configured such that the ADC has a chance of at least 5% to be tripped by thermal noise at an input of the ADC regardless of an amplitude of the signal. The processor is configured to process an output of the ADC at intervals of the bursts of pulses and ignore durations of transmitting the bursts of pulses to retrieve the echo from the signal.