Measurement And Localization Of Weak Signals Based On Continuous-Wave Radar Sensors

Continuous wave(CW)radar is a pivotal member of the radar family.With the rapid advancement of radar integration technology in the past two decades,miniaturized CW radar has unlocked a plethora of novel applications in emerging fields,including autonomous driving,smart healthcare,instrument measurement,and radio localization.These cutting-edge applications have subtly transformed people’s daily life and production processes.This dissertation delves into the challenges associated with microwave technology,such as feeble“Doppler echocardiography” signals,wideband passive intermodulation measurement,and moving target localization amidst potent indoor multipath interference conditions,using CW radar sensing technology.Through extensive theoretical,simulation,and experimental research,this dissertation has achieved pioneering and innovative results that carry significant implications for the field.The main innovative work of this dissertation includes:1.Research on the Doppler cardiogram measurement.During the early stages of Doppler cardiogram,there are still limitations in terms of low recognition accuracy and weak anti-noise performance.To address these challenges,this dissertation focuses on three key aspects of work.Firstly,a theoretical construction based on the Teichholz model of the electro-mechanical coupling mechanism was established to characterize the time-domain mapping between electrocardiography and mechanical displacement.Secondly,a V-band continuous-wave radar sensor was designed and implemented at a system level to enhance the ability to detect even the slightest movements at the micron scale.Finally,new algorithms were proposed for chord approximation,orthogonal calibration,and residual frequency estimation at an algorithmic level to achieve high levels of noise resistance and linearity in Doppler phase demodulation.The Experimental results from different subjects validated the significant improvement in measurement accuracy and robustness of human cardiac signal when using the proposed methods.2.Research on the testing of ultrawideband passive intermodulation.The current mainstream commercial passive intermodulation(PIM)analyzers are hindered by their narrowband nature,resulting in restricted narrowband measurements and challenges with high-resolution localization.To solve this problem,this dissertation presents a novel architecture for ultra-wideband PIM measurement,utilizing a continuous wave radar system with dual-carrier nulling.By leveraging theory of RF and baseband collaborative nulling,we constructed an RF-baseband nulling unit and developed a highly integrated prototype.Through simulation and experimental measurements,we demonstrate that the proposed architecture effectively performs PIM measurement across a continuous wide frequency spectrum ranging from 0.7-2.4 GHz,surpassing the limitations of traditional PIM frameworks that are restricted to narrowband measurements.3.Research on the passive indoor localization utilizing human random body movement(RBM).The proposed method aims to overcome the fundamental technical challenges associated with passive indoor localization in multipath environments.It boasts exceptional robustness against strong multipath interference and offers flexible deployment options.To accomplish this,the method leverages the inherent,unconscious RBM to constructs a self-organizing localization framework,which is paired with a moving target localization algorithm.The effectiveness and accuracy of the proposed method are validated through simulations and human experiments conducted in authentic indoor environments.