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This paper proposes a compact three-mode base station capable of performing radar sensing, communication, and wireless power transfer (WPT) in collaboration with indoor sensor networks. With regard to the wireless sensor node, the base station transmits two-tone signals in the downlink to support its operation and provides two-way communication. The sensor node sends uplink information through backscattering using the third order intermodulation (IM3) product of the rectification. In the radar mode, a single-tone continuous wave (CW) is used to monitor if there is a moving target in the static environment. If a speed is detected, the transmit signal to the node is stopped, while the single-tone CW excitation will continue until the speed of the target is zero, and then the base station transmits a stepped frequency continuous wave (SFCW) signal to measure the distance of the target. The repeat between the two radar waveforms continues until the target is undetectable within the detection range. The software defined radio PlutoSDR is adopted as the base station. The system can wirelessly supply power and bi-directionally communicate with a CO 2 sensor node 2 m away. It gives a range resolution of 2.5 cm and a minimum detectable speed of 0.25 m/s in the radar mode. [ABSTRACT FROM AUTHOR]

To date, 3-D radar imaging of moving objects in a multipath coordinate space close to antennas remains a technical challenge. In this work, we demonstrate the implementation of such 3-D motion imaging based on a continuous-wave, multiple-input multiple-output (MIMO) Doppler radar sensor (DRS). Working with a time-division-multiplex (TDM) scheme, this portable, cost-effective DRS is a bistatic system with one transmitting and one receiving channels, and a radio frequency (RF) switch in each channel toggling between two antennas. Assisted by algorithms specifically derived for the TDM-MIMO architecture, highly sensitive 3-D imaging performed in a multipath indoor environment was experimentally implemented. Numerical simulations and experimental demonstrations verified the effectiveness and accuracy of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a printed circuit board realization of a $K$ -band portable frequency-modulated continuous-wave radar transceiver with beamforming array for short-range localization. The transmitter channel of the proposed radar consists of a free-running voltage-controlled oscillator (VCO) and a single patch antenna. A linear frequency-modulated chirp signal is generated by the VCO, which is controlled by an analog “sawtooth” voltage generator. The receiver channel has a four-element linear beamforming array, a six-port circuit, and a baseband circuit. The beam of the array can be continuously steered in a range of ±45° on the $H$ -plane through an array of vector controllers. Each vector controller is capable of simultaneously controlling the phase and the amplitude of the corresponding array element. The design principle of the binary-phase-shift attenuator, the vector controller, and the radar system are discussed. Calibration method of the array is introduced to minimize the errors caused by component variation and fabrication. The radiation patterns of the array with phase-only beam steering and phase-amplitude beamforming are measured and compared, demonstrating the advantage of the beamforming design. System-level experiments showed that the proposed solution is suitable for short-range localization. In addition, experiments with a human subject revealed the capability of the proposed radar system to discriminate a human target from other objects based on the vital-Doppler effect. [ABSTRACT FROM AUTHOR]

Wireless localization has become a hot topic in the area of microwave engineering. In this paper, we propose a new approach for short-range wireless localization based on meta-aperture and compressed sensing (CS). Utilizing the plasmonic dispersion of a magnetically uniaxial metamaterial, a pushpin-shaped autocorrelation characteristic of the localization system can be obtained to ensure high localization precision. Compared with existing realizations based on traveling wave excited, randomly arranged subwavelength resonant elements, our method uses a homogeneous aperture for the generation of randomized illumination. Based on the CS, localization can be obtained with much less data and much faster data processing than conventional methods. Simulation and experimental investigation are conducted, and the results demonstrate the effectiveness of the proposed approach. With the simple implementation for fast localization, our method has promising potential in practical applications. [ABSTRACT FROM PUBLISHER]

This paper reviews recent progress of portable short-range noncontact microwave radar systems for motion detection, positioning, and imaging applications. With the continuous advancements of modern semiconductor technologies and embedded computing, many functionalities that could only be achieved by bulky radar systems in the past are now integrated into portable devices with integrated circuit chips and printed circuits boards. These portable solutions are able to provide high motion detection sensitivity, excellent signal-to-noise ratio, and satisfactory range detection capability. Assisted by on-board signal processing algorithms, they can play important roles in various areas, such as health and elderly care, veterinary monitoring, human-computer interaction, structural monitoring, indoor tracking, and wind engineering. This paper reviews some system architectures and practical implementations for typical wireless sensing applications. It also discusses potential future developments for the next-generation portable smart radar systems. [ABSTRACT FROM AUTHOR]

Recently, progresses have been made in hand gesture recognition based on Doppler radar sensors. However, it remains a technical challenge to avoid the interfering human motions. An example is detecting hand gestures in the presence of random body movements. In this paper, we propose a solution based on a Single-input Multiple-output frontend and a blind motion separation algorithm. Assisted by an additional receiving channel, Doppler signals caused by different motions can be separated by extending the algorithm originally developed for separating human voices. The experimental separation of hand gestures from interfering movements verified the effectiveness of this approach. The proposed solution can be potentially used in novel applications such as human gait and gesture recognitions. [ABSTRACT FROM AUTHOR]

Flicker noise and dc offset have strong impacts on the performance of zero-IF receivers. In this paper, we propose a generalized approach to eliminate such impacts on zero-IF architecture pulse compression radars (PCRs). The conventional low-pass filter in a zero-IF receiver is replaced with a predefined filter (PDF) to filter out the dc and low-frequency components from the demodulated radar signal. Simulation and experimental results demonstrate that, based on the prior knowledge of the radar signal and the PDF, the performance degradation, due to the complete filtering of the low-frequency components, can be recovered through a newly deduced compensation equation. Our approach can be widely used in the implementation of highly integrated high-performance PCR systems in the future. [ABSTRACT FROM AUTHOR]

Utilizing microwave continuous-wave Doppler radars to wirelessly detect mechanical vibrations have been attracting more and more interests in recent years. In this paper, aiming to solve the null point and nonlinear issues in small-angle approximation-based Doppler radar sensors and eliminate the codomain restriction in the arctangent demodulation approach, we propose and investigate an extended differentiate and cross-multiply (DACM) algorithm. With an additional accumulator, the noise performance of the original DACM algorithm is improved. Moreover, the amplitude information of the vibration can be directly retrieved from accumulation without involving any distance-dependent issue. Experimental validations show that the proposed algorithm can fully recover the vibration patterns with the measured noncalibrated amplitude agreeing well with the known precalibrated data. Application examples of mechanical fault detection and human vital sign detection are demonstrated, showing a wide range of potential applications of this algorithm. [ABSTRACT FROM PUBLISHER]

Doppler radar has been used for small-scale displacement detection, e.g. respiration and heartbeat. The motion amplitude is less than half a carrier wavelength. In this letter, a novel Doppler radar technique is presented for accurate tracking of large-scale displacement of several carrier wavelengths, e.g., the water level variation. The DC-coupled architecture is used to ensure precise measurement of slow motions even with stationary moment. A novel signal processing approach is proposed to increase the demodulation linearity to deal with inconstant signal amplitude, dynamic dc offset and phase ambiguity in large-scale displacement tracking. Experiments have been carried out in the outdoor environment to monitor the relative water level position in a rain barrel when the water was pumped in or drained out. It is shown that the proposed technique can accurately gauge the relative water level variation of 3.5 wavelengths with mm accuracy. [ABSTRACT FROM PUBLISHER]