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Zhaoyi Xu - IEEE Xplore Author Profile

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A phased array equipped with double phase shifters (DPS) can reduce interference and enable multi-target vital sign monitoring (VSM) based on a single receive antenna. The DPS-phased array can control both the magnitude and the phase of the signal transmitted by each antenna, allowing for flexibly creating a desired beampattern. We consider the DPS-phased array weight design problem, taking into a...Show More
Time-modulated arrays (TMA) transmitting orthogonal frequency division multiplexing (OFDM) waveforms achieve physical layer security by allowing the signal to reach the legitimate destination undistorted, while making the signal appear scrambled in all other directions. In this paper, we examine how secure the TMA OFDM system is, and show that it is actually possible for the eavesdropper to defy t...Show More
We consider an OFDM transmitter aided by an intelligent reflecting surface (IRS) and propose a novel approach to enhance waveform security by employing time modulation (TM) on the IRS side. By controlling the periodic TM pattern of the IRS elements, the system is designed to preserve communication information towards an authorized recipient and scramble the information in all other directions. Com...Show More
The efficacy of sensor arrays improves with more elements, yet increased number of elements leads to higher computational demands, cost and power consumption. Sparse arrays offer a cost-effective solution by utilizing only a subset of available elements. Each subset has a different effect on the performance properties of the array. This paper presents an unsupervised learning approach for sensor s...Show More
Dual-function radar-communication (DFRC) systems offer high spectral, hardware and power efficiency, as such are prime candidates for 6G wireless systems. DFRC systems use the same waveform for simultaneously probing the surroundings and communicating with other equipment. By exposing the communication information to potential targets, DFRC systems are vulnerable to eavesdropping. In this work, we...Show More
Recognizing the low-cost advantage of phased arrays, we investigate the improvement of the beamforming capability of a phased array via the use of double-phase shifters (DPS), i.e., each antenna is fed with the sum of the outputs of two phase shifters. The use of DPS allows for the manipulation of both the magnitude and phase of the signal transmitted by each antenna, thus enabling the formation o...Show More
A novel dual-function radar communication (DFRC) system is proposed, that achieves high communication rate, and can flexibly trade-off rate for improved sensing performance. The proposed system is a monostatic multiple-input multiple-output (MIMO) radar and transmits wideband, precoded, orthogonal frequency division multiplexing (OFDM) waveforms from its antennas. The system subcarriers are divide...Show More
The passive electronically scanned array (PESA) is widely used due to its simple structure and low cost. Its antenna weights have unit modulus and thus, only the weights phases can be controlled. PESA has limited degrees of freedom for beampattern design, where only the direction of the main beam can be controlled. In this paper we propose a novel way to improve the beamforming capability of PESA ...Show More
Dual function radar communication (DFRC) systems can achieve significant improvements in spectrum efficiency, system complexity and energy efficiency, and are attracting a lot of attention for next generation wireless system design. This paper considers DFRC systems using MIMO radar with a sparse transmit array, transmitting OFDM waveforms, and assigning shared and private subcarriers to active tr...Show More
We consider multi-input multi-output (MIMO) dual function radar communication (DFRC) systems, and design a transmit beamforming matrix that optimizes a weighted combination of the radar estimate Cramer-Rao bound (CRB) and the communication rate. A hybrid beamforming structure is considered, with fewer RF chains than antennas, to achieve the benefits of MIMO systems while maintaining low cost. Howe...Show More
Vital sign monitoring plays a critical role in tracking the physiological state of people and enabling various health-related applications (e.g., recommending a change of lifestyle, examining the risk of diseases). Traditional approaches rely on hospitalization or body-attached instruments, which are costly and intrusive. However, in recent years there is an emergence of contact-less vital sign mo...Show More
In this paper, we propose an energy-efficient radar beampattern design framework for Millimeter Wave (mmWave) massive multi-input multi-output (mMIMO) systems, equipped with a hybrid analog-digital (HAD) beamforming structure. Aiming to reduce the power consumption and hardware cost of the mMIMO system, we employ a learning approach to synthesize the probing beampattern based on a small number of ...Show More
A novel dual-function radar communication (DFRC) system is proposed, that achieves high target resolution and high communication rate. It consists of a multiple-input multiple-output (MIMO) radar, where only a small number of antennas are active in each channel use. The probing waveforms are orthogonal frequency division multiplexing (OFDM) type. The OFDM carriers are divided into two groups, one ...Show More