- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Chip-Scale Molecular Clock
摘要： An ultra-stable time-keeping device is presented, which locks its output clock frequency to the rotational-mode transition of polar gaseous molecules. Based on a high-precision spectrometer in the sub-terahertz (THz) range, our new clocking scheme realizes not only fully electronic operation but also implementations using mainstream CMOS technology. Meanwhile, the small wavelength of probing wave and high absorption intensity of our adopted molecules (carbonyl sulfide, 16O12C32S) also enable miniaturization of the gas cell. All these result in an 'atomic-clock-grade' frequency reference with small size, power, and cost. This paper provides the architectural and chip-design details of the first proof-of-concept molecular clock using a 65-nm CMOS bulk technology. Using a 231.061-GHz phase-locked loop (PLL) with frequency-shift keying (FSK) modulation and a sub-THz FET detector with integrated lock-in function, the chip probes the accurate transition frequency of carbonyl sulfide (OCS) gas inside a single-mode waveguide, and accordingly adjusts the 80-MHz output of a crystal oscillator. The clock consumes only 66 mW of dc power and has a measured Allan deviation of 3.8 × 10^{-10} at an averaging time of τ = 1000 s.
关键词： CMOS,molecular clock,rotational spectroscopy,Allan deviation,GPS,carbonyl sulfide (OCS),frequency stability,navigation
更新于2025-09-23 15:23:52
-
Hybrid Camera Array-Based UAV Auto-Landing on Moving UGV in GPS-Denied Environment
摘要： With the rapid development of Unmanned Aerial Vehicle (UAV) systems, the autonomous landing of a UAV on a moving Unmanned Ground Vehicle (UGV) has received extensive attention as a key technology. At present, this technology is confronted with such problems as operating in GPS-denied environments, a low accuracy of target location, the poor precision of the relative motion estimation, delayed control responses, slow processing speeds, and poor stability. To address these issues, we present a hybrid camera array-based autonomous landing UAV that can land on a moving UGV in a GPS-denied environment. We first built a UAV autonomous landing system with a hybrid camera array comprising a fisheye lens camera and a stereo camera. Then, we integrated a wide Field of View (FOV) and depth imaging for locating the UGV accurately. In addition, we employed a state estimation algorithm based on motion compensation for establishing the motion state of the ground moving UGV, including its actual motion direction and speed. Thereafter, according to the characteristics of the designed system, we derived a nonlinear controller based on the UGV motion state to ensure that the UGV and UAV maintain the same motion state, which allows autonomous landing. Finally, to evaluate the performance of the proposed system, we carried out a large number of simulations in AirSim and conducted real-world experiments. Through the qualitative and quantitative analyses of the experimental results, as well as the analysis of the time performance, we verified that the autonomous landing performance of the system in the GPS-denied environment is effective and robust.
关键词： GPS-denied environment,moving UGV,UAV autonomous landing,hybrid camera array,motion compensation
更新于2025-09-23 15:23:52
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Validation of SAR Iceberg Detection with Ground-Based Radar and GPS Measurements
摘要： Calving of icebergs at the tidewater glacier fronts is a component of the mass loss in Polar regions. Studying the regional distribution of icebergs, their volume, motion, and interaction with the environment is of interest. Here, we present the results from a fieldwork campaign conducted in Kongsfjorden, Svalbard in April 2016, where both satellite and ground-based remote sensing instruments were used to observe dynamics of sea ice, icebergs, and growlers. We used a ground-based radar system, imaging the study area every second minute during five days. During the same observation period, we collected four RADARSAT-2 (RS-2) quad-pol images, that are used for automatic detection of icebergs. In addition, the fieldwork team collected GPS positions of some drifting and grounded icebergs in the fjord to be used as ground-truth data. The comparison and combination of satellite, ground-based radar, and in-situ data contribute to cross-validate the results.
关键词： synthetic aperture radar,ground-based radar,polarimetry,GPS mapping,Iceberg,detection,sea ice
更新于2025-09-23 15:22:29
-
[IEEE 2018 International Conference on Advanced Technologies for Communications (ATC) - Ho Chi Minh City, Vietnam (2018.10.18-2018.10.20)] 2018 International Conference on Advanced Technologies for Communications (ATC) - Compact Diversity Multi-band Antennas Using for Low Power Communication Standards
摘要： In this paper, two PIFA multi-band antennas are presented. They are placed at two opposite sides of FR4 PCB. First antenna operates at the frequencies of 0.868 MHz, 1.57 GHz and 2.4 GHz, meanwhile another has the resonant frequencies of 1.57 GHz and 2.4 GHz. The obtained bandwidths cover BLE, GPS and LoRa that are the low power wireless communication standard. Thanks to these specifications, the proposed antenna can be used for the small tracking devices. With the dimension of 0.04λ x 0.07λ (λ is the wavelength at frequency of 0.868 MHz), the antennas provide the radiation efficiency higher than -5 dB for using in LoRa, GPS and BLE. The proposed antennas are simulated and optimized by using HFSS software.
关键词： tracker,LoRa,IoT,multi-band antenna,BLE,GPS
更新于2025-09-23 15:22:29
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A GPS-Reflectometry Simulator for Target Detection Over Oceans
摘要： The development and implementation of a GPS-Reflectometry (GPS-R) simulator for the ocean target detection application is proposed, with the objective of assessing and characterizing the capability of GPS-R as a new method for sea surface target detection. The novel idea is to use a backscattering configuration to enhance the electromagnetic return from the target compared to the surrounding ocean. Hence the backscattering simulator simulates images of GPS echoes from one or more targets embedded in an ocean clutter, and its outputs will be analysed as a function of hardware parameters, geometry, and signal processing approaches to determine the target detectability. Some preliminary results related to the backscattering simulations from both ocean and target will be presented.
关键词： target detection,GPS-Reflectometry,backscattering
更新于2025-09-23 15:21:21
-
An introduction to the FY3 GNOS instrument and mountain-top tests
摘要： The FY3 (Feng-Yun-3) GNOS (GNSS Occultation Sounder) mission is a GNSS (Global Navigation Satellite System) radio occultation mission of China for remote sensing of Earth’s neutral atmosphere and the ionosphere. GNOS will use both the global positioning system (GPS) and the Beidou navigation satellite systems on the China Feng-Yun-3 (FY3) series satellites. The ?rst FY3-C was launched at 03:07 UTC on 23 September 2013. GNOS was developed by the Center for Space Science and Applied Research, Chinese Academy of Sciences (CSSAR). It will provide vertical pro?les of atmospheric temperature, pressure, and humidity, as well as ionospheric electron density pro?les on a global basis. These data will be used for numerical weather prediction, climate research, and ionospheric research and space weather. This paper describes the FY3 GNOS mission and the GNOS instrument characteristics. It presents simulation results of the number and distribution of GNOS occultation events with the regional Beidou constellation and the full GPS constellation, under the limitation of the GNOS instrument occultation channel number. This paper presents the instrument performance as derived from analysis of measurement data in laboratory and mountain-based occultation validation experiments at Mt. Wuling in Hebei Province. The mountain-based GNSS occultation validation tests show that GNOS can acquire or track low-elevation radio signal for rising or setting occultation events. The refractivity pro?les of GNOS obtained during the mountain-based experiment were compared with those from radiosondes. The results show that the refractivity pro?les obtained by GNOS are consistent with those from the radiosonde. The rms of the differences between the GNOS and radiosonde refractivities is less than 3 %.
关键词： GNSS Occultation Sounder,FY3 GNOS,Beidou,atmospheric remote sensing,ionospheric research,GPS
更新于2025-09-23 15:21:01
-
Monitoring of Sheep Migration in Arid Region of Rajasthan, India Using EO Data
摘要： The annual aggregate spatially normal rainfall is extremely variable and most erratic in the western arid region of Rajasthan state. As a result, it frequently experiences spells of drought. Surface water resources are also meagre and distributed unevenly. Drought is a multi-dimensional phenomenon and its direct impacts include like withering of crops, drying of watering points, reduction in fodder for livestock, etc. Such crisis eventually compels Rebari pastoralists to migrate to other places and regions as a coping mechanism against the scarcity of fodder and water in the arid zone of Rajasthan. The scarcity of fodder at any time is a function of stocking rate and carrying capacity of the system at that time, which is affected mainly by the amount of precipitation and livestock population. This has been covered through analysing migration routes and determinants by using the data collected from the ATS plus GPS Collars. It has been found that biomass density changed following grazing across gradients and ground cover. Also, normalized difference vegetation index (NDVI) was 5-10% lower inside the grazing area than outside the grazing area.
关键词： Grazing lands,NDVI,Land degradation,ATS plus global positioning system (GPS) collars,Migration,Small ruminants
更新于2025-09-23 15:21:01
-
Combining Meteosat-10 satellite image data with GPS tropospheric path delays to estimate regional integrated water vapor (IWV) distribution
摘要： Using GPS satellites signals, we can study different processes and coupling mechanisms that can help us understand the physical conditions in the lower atmosphere, which might lead or act as proxies for severe weather events such as extreme storms and flooding. GPS signals received by ground stations are multi-purpose and can also provide estimates of tropospheric zenith delays, which can be converted into accurate integrated water vapor (IWV) observations using collocated pressure and temperature measurements on the ground. Here, we present for the first time the use of Israel’s dense regional GPS network for extracting tropospheric zenith path delays combined with near-real-time Meteosat-10 water vapor (WV) and surface temperature pixel intensity values (7.3 and 10.8 μm channels, respectively) in order to assess whether it is possible to obtain absolute IWV (kg m?2) distribution. The results show good agreement between the absolute values obtained from our triangulation strategy based solely on GPS zenith total delays (ZTD) and Meteosat-10 surface temperature data compared with available radiosonde IWV absolute values. The presented strategy can provide high temporal and special IWV resolution, which is needed as part of the accurate and comprehensive observation data integrated in modern data assimilation systems and is required for increasing the accuracy of regional numerical weather prediction systems forecast.
关键词： GPS,numerical weather prediction,integrated water vapor,tropospheric zenith delays,Meteosat-10
更新于2025-09-23 15:19:57
-
[IEEE 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Erlagol (Altai Republic), Russia (2018.6.29-2018.7.3)] 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - An Interface Model of the Interconnection Between Integrated Circuit Chip Die and Printed Circuit Board
摘要： This work represents results obtained during research of high frequency IC packaging. The interface between IC die and PCB is described and its inner structure is developed: contact pads on IC die, bondwires and chip outputs. As an example of method developed the interface effects into device development and characteristics are shown for the LNA module as a part of the GPS receiver test chip.
关键词： LNA,Low noise amplifier,GPS,CMOS,chip packaging,Noise Figure
更新于2025-09-19 17:15:36
-
Fuzzy Logic Vehicle Positioning System Based on Chromaticity and Frequency Components of LED Illumination
摘要： Given their wide applicability, vehicle positioning systems are being actively studied currently. As the conventional global positioning system (GPS) cannot determine the vehicle position inside tunnels and other GPS-shaded areas, we propose to improve vehicle positioning using a fuzzy logic system that can retrieve the position of a moving vehicle in such areas. The proposed system analyzes the chromaticity and frequency components of active LED illumination, which is being commonly installed at locations like inside tunnels. We verify the system performance in a test environment that resembles a tunnel. As the proposed method uses the chromaticity and frequency of LED lights for vehicle positioning, it is suitable for areas where GPS reception is poor or unavailable.
关键词： GPS-shaded areas,Chromaticity,vehicle positioning system
更新于2025-09-19 17:13:59