In this paper, a novel wideband patch antenna array with improved isolation and corrected radiation patterns is proposed in integrated sensing and communication (ISAC) at the X band. The relationship between the self-interference signal and emission waveform of ISAC is firstly analyzed to draw a conclusion that the signal-to-noise ratio (SNR) is directly proportional to the degree of self-interference suppression when the emission waveform is determined across a wide bandwidth. Then, a wideband aperture-coupled patch antenna array with the dual-decoupling technique is introduced to improve the isolation from 8 dB to more than 23 dB within a large bandwidth better than 12.7%. To prove the feasibility of the proposed wideband decoupling scheme, the prototype is also fabricated, and measured. The measured results show good agreement with the simulation data, demonstrating the feasibility of the proposed antenna in broadband ISAC applications. © 2024 IEEE.

A new receiver (Rx) reconfigurable method is proposed to enhance the target signal. After theoretical derivation and experimental verification, the proposed method solves the problem of poor signal-to-signal ratio (SNR) when using 60GHz MIMO FMCW radar for indoor positioning. The proposed method combines multiple original Rx channel data to form a new data channel, forming a new virtual antenna array. This method improves the SNR of the echo signal without affecting the estimation of the target angle. In the scenarios where the human body is standing or sitting, the SNR is improved by more than 28dB. The new data matrix is used to resolve the angle. Due to the improved target strength, the angle resolution accuracy is also improved compared with the traditional single Rx channel © 2023 IEEE.

In this work, a K-band 24-GHz ac-coupled Doppler radar sensor was designed to measure the Doppler Cardiogram (DCG) in the presence of human respiration. The AC coupling architecture avoids dc-tuning and has simple hardware implementation. In addition, a novel DCG extraction algorithm was proposed to extract the accurate DCG from the Doppler radar signals scattered by the skin of the chest wall with no need for subject holding his/her breath. A PPG sensor was simultaneously employed as the reference. Experimental results show that the DCG obtained in this work is aligned well with the cardiac activities recorded by PPG. It also has many characteristic points which contain the velocity and strength information of the heart, which is highly desirable for long-term personal daily healthcare. © 2022 IEEE.

The accuracy of motion sensing with a Continuous-Wave (CW) radar is subject to noises. The low intermediate-frequency (IF) CW radar tackles the impact of the flicker noise. However, it still suffers from other noise components which mainly include the Additive White Noise (AWN) in short-range sensing. This paper proposes a novel Noise-Immune Motion Sensing (NIMS) technique for accurate displacement motion sensing against the AWN in low-IF CW radars. It works by dividing the IF signals sequentially into segments, extracting phases from the spectra of the sequential segments, and combing the phases to reconstruct the phase evolution for the target displacement motion. The theory and working principle are presented. Simulation and experimental results show that the Signal-to-Noise Ratio (SNR) is improved for about 20.1 dB with the proposed technique and the mechanical displacement motion is accurately obtained with the root-mean-square-error (RMSE) decreased by 99.2%. © 2022 IEEE.

A novel in-vehicle occupant detection technique with a 60 GHz frequency modulated continuous wave (FMCW) radar is presented. The 2D imaging is obtained by digital beamforming (DBF) based on the virtual array of the multiple input multiple output (MIMO) architecture. A logistic regression presence-absence detection method is proposed to provide information about the number of the passengers as well as their location. The feature matrix is extracted from the 2D imaging and multiplied by the weight vector to obtain the occupants' presence-absence probability. A series of experiments are carried out in real in-vehicle environments to validate the proposed technique. The experimental results show that the proposed technique can well detect the number and location of the occupants. © 2022 IEEE.

This paper characterizes the impact of the frequency ramp nonlinearity (FRN) on the range resolution and accuracy in linear-frequency-modulated continuous-wave (LFMCW) radars. A nonlinearity index that adapts to different types of FRN is proposed for rigid analysis. Based on the theoretical analysis and experimental evaluations, a new range-dependent resolution model and a new range-dependent accuracy model are proposed for the LFMCW radars under the influence of different types of FRN. Moreover, a novel design methodology is also proposed which might guide the design of LFMCW radars under the influence of the FRN. Both simulations and experiments are performed to validate the proposed theory and methodology. © 2022 IEEE.

In this paper, a dual circularly polarized simultaneous transmit and receive common aperture antenna array for integrated sensing and communication (ISAC) is designed, manufactured and measured. The simulation and measured results demonstrate that the proposed antenna array possesses a 67 dB TX/RX isolation and better than 1.4 dB axial ratios in band. Experiments in a wireless communication system and a radar sensing system are also carried out, which prove the feasibility of design methodology and practicality in ISAC. © 2022 IEEE.