A W-band multiple-input multiple-output (MIMO) radar imaging system has been proposed. The 4 × 4 radar system that forms a 2-D virtual array operates at a center frequency of 94 GHz and bandwidth of 1 GHz with frequency-modulated continuous wave. A hybrid scheme comprising time- and frequency-division multiplexing is introduced for establishing orthogonal waveforms, where the transmit channels perform alternate transmission in pairs. The proposed scheme can efficiently extend the number of MIMO channels utilizing the existing hardware with simultaneous transmission. The design, implementation, measurements, and imaging results of the proposed radar system have been presented. The imaging performance was tested through outdoor experiments. The high-resolution performance was shown with images generated using a synthetic aperture radar. The impulse responses of all channels were measured, and the resolution was confirmed to be 0.15 m in all the channels. In addition, a human and a car at 100-m range were imaged using the proposed radar system. The polarimetric and interferometric capabilities were tested for multimode imaging with the MIMO configuration. Overall, the measurements and experimental results verified the feasibility of the proposed MIMO radar with hybrid scheme as a high-resolution multimode imaging system.
Circulating cell-free DNA (cfDNA) has great potential in clinical oncology. The prognostic and predictive values of cfDNA in non-small cell lung cancer (NSCLC) have been reported, with epidermal growth factor receptor (EGFR), KRAS, and BRAF mutations in tumor-derived cfDNAs acting as biomarkers during the early stages of tumor progression and recurrence. However, extremely low tumor-derived DNA rates hinder cfDNA application. We developed an ultra-high-sensitivity lung version 1 (ULV1) panel targeting BRAF, KRAS, and EGFR hotspot mutations using small amounts of cfDNA, allowing for semi-quantitative analysis with excellent limit-of-detection (0.05%).
This paper presents a radar laboratory course and an educational radar kit developed for the course. This course aims toprovide hands-on experience on pulse-Doppler radar (PDR) signal processing algorithms using modern methods andtools. Experiments and project-based learning (PBL) is introduced to the pedagogical methodology of this course. Thecourse is constructed by considering various backgrounds and levels of the students. The student learning consists of threeelements: theoretical knowledge, experiments, and proposal writing on their own research topic. The objective ofconvergence education is reflected on how the students are provided the opportunity to apply their knowledge andexpertise in radar system obtained through this course to their own research areas. For an efficient application of the PBL, asuitable educational kit is designed and implemented. The kit is developed as an open software and hardware platform forfacilitating the experimental studies of modern radar technologies for students. The kit, a low-cost multifunctional short-range PDR, is a relatively simple platform for beginners. The suggested hardware design is based on a single-chip software-defined radio (SDR) with an inexpensive system-on-chip (SoC). As the experimental prototype is based on commerciallyavailable evaluation modules, it is easy to assemble and use, and no special skills or equipment are required. The proposedsystem enables students to study modern signal processing techniques. The applied pedagogical methodology, coursedescription, experimental kit, projects descriptions, and assessments are discussed.
Synthetic aperture radar (SAR) is a powerful remote sensing technique providing high-resolution images of Earth’s sur-face. The pulsed operation of SAR may cause nadir echoes in SAR images which significantly affect the image quality. The selection of pulse repetition frequency (PRF) in the design of conventional spaceborne SAR systems is constrained to avoid the nadir interference. As this leads to the limitation of SAR performances such as the swath width and the ambiguities, a novel concept for nadir echo suppression using waveform encoding and dual-focus post-processing has been proposed to alleviate the constraint in PRF selection. This technique improves the image quality and the flexibility of SAR system design. This work analyses this concept with more realistic simulation and validates it with a TerraSAR-X experiment.
Computer simulations were conducted to demonstrate the generation of microwave-induced thermoacoustic signal. The simulations began with modelling an object with a biological tissue characteristic and irradiating it with a microwave pulse. The time-varying heating function data at every particular point on the illuminated object were obtained from absorbed electric field data from the simulation result. The thermoacoustic signal received at a point transducer at a particular distance from the object was generated by applying heating function data to the thermoacoustic equation. These simulations can be used as a foundation for understanding how thermoacoustic signal is generated and can be applied as a basis for thermoacoustic imaging simulations and experiments in future research.
Synthetic aperture radar (SAR) is a remote sensing technique capable of acquiring high-resolution images of Earth's surface independent of sunlight illumination and weather conditions. In conventional spaceborne SAR, nadir echo may significantly affect the SAR image quality, if the pulse repetition frequency (PRF) is not properly selected. Waveform-encoded SAR has been introduced to alleviate the constraint in PRF selection by varying the transmitted waveform from pulse to pulse and suppressing the nadir echo within the processing. In particular, cyclically-shifted chirps can be used. This work tackles the issue of reducing the number of required distinct waveforms to reduce system complexity and make the concept viable for implementation. A technique to generate a waveform sequence characterized by a reduced number of distinct waveforms is proposed based on the Eulerian circuit. The nadir echo suppression performance is assessed through simulations using real TerraSAR-X data and a realistic nadir echo model.
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