scholarly journals Imaging for Small UAV-Borne FMCW SAR

Sensors ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 87 ◽  
Author(s):  
Xianyang Hu ◽  
Changzheng Ma ◽  
Ruizhi Hu ◽  
Tat Yeo
Keyword(s):  
Continuous Wave ◽  
Target Identification ◽  
Low Cost ◽  
Real Data ◽  
Gradient Algorithm ◽  
Minimum Entropy ◽  
Phase Gradient ◽  
Minimization Technique ◽  
Range Cell Migration ◽  
Synthetic Aperture Radars

Unmanned aerial vehicle borne frequency modulated continuous wave synthetic aperture radars are attracting more and more attention due to their low cost and flexible operation capacity, including the ability to capture images at different elevation angles for precise target identification. However, small unmanned aerial vehicles suffer from large trajectory deviation and severe range-azimuth coupling due to their simple navigational control and susceptibility to air turbulence. In this paper, we utilize the squint minimization technique to reduce this coupling while simultaneously eliminating intra-pulse motion-induced effects with an additional spectrum scaling. After which, the modified range doppler algorithm is derived for second order range compression and block-wise range cell migration correction. Raw data-based motion compensation is carried out with a doppler tracker. Squinted azimuth dependent phase gradient algorithm is employed to deal with azimuth dependent parameters and inexact deramping, with minimum entropy-based autofocusing algorithms. Finally, azimuth nonlinear chirp scaling is used for azimuth compression. Simulation and real data experiment results presented verify the effectiveness of the above signal processing approach.

scholarly journals A Local Oscillator Phase Compensation Technique for Ultra-Wideband Stepped-Frequency Continuous Wave Radar Based on a Low-Cost Software-Defined Radio

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 780
Author(s):  
Kazunori Takahashi ◽  
Takashi Miwa
Keyword(s):  
Software Defined Radio ◽  
Initial Phase ◽  
Continuous Wave ◽  
Low Cost ◽  
Local Oscillator ◽  
The Other ◽  
Ultra Wideband ◽  
Single Frequency ◽  
Wave Radar ◽  
Stepped Frequency

The paper discusses a way to configure a stepped-frequency continuous wave (SFCW) radar using a low-cost software-defined radio (SDR). The most of high-end SDRs offer multiple transmitter (TX) and receiver (RX) channels, one of which can be used as the reference channel for compensating the initial phases of TX and RX local oscillator (LO) signals. It is same as how commercial vector network analyzers (VNAs) compensate for the LO initial phase. These SDRs can thus acquire phase-coherent in-phase and quadrature (I/Q) data without additional components and an SFCW radar can be easily configured. On the other hand, low-cost SDRs typically have only one transmitter and receiver. Therefore, the LO initial phase has to be compensated and the phases of the received I/Q signals have to be retrieved, preferably without employing an additional receiver and components to retain the system low-cost and simple. The present paper illustrates that the difference between the phases of TX and RX LO signals varies when the LO frequency is changed because of the timing of the commencement of the mixing. The paper then proposes a technique to compensate for the LO initial phases using the internal RF loopback of the transceiver chip and to reconstruct a pulse, which requires two streaming: one for the device under test (DUT) channel and the other for the internal RF loopback channel. The effect of the LO initial phase and the proposed method for the compensation are demonstrated by experiments at a single frequency and sweeping frequency, respectively. The results show that the proposed method can compensate for the LO initial phases and ultra-wideband (UWB) pulses can be reconstructed correctly from the data sampled by a low-cost SDR.

scholarly journals Stereoscopic PIV measurements using low-cost action cameras

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Theo Käufer ◽  
Jörg König ◽  
Christian Cierpka
Keyword(s):  
Continuous Wave ◽  
Low Cost ◽  
Frame Rate ◽  
Processing Scheme ◽  
Piv Measurements ◽  
Stereoscopic Piv ◽  
Cost Action ◽  
Image Velocimetry ◽  
Frequency Generator ◽  
Educational Applications

Abstract Recently, large progress was made in the development towards low-cost PIV (Particle Image Velocimetry) for industrial and educational applications. This paper presents the use of two low-cost action cameras for stereoscopic planar PIV. A continuous wave laser or alternatively an LED was used for illumination and pulsed by a frequency generator. A slight detuning of the light pulsation and camera frame rate minimizes systematic errors by the rolling shutter effect and allows for the synchronization of both cameras by postprocessing without the need of hardware synchronization. The setup was successfully qualified on a rotating particle pattern in a planar and stereoscopic configuration as well as on the jet of an aquarium pump. Since action cameras are intended to be used at outdoor activities, they are small, very robust and work autarkic. In conjunction with the synchronization and image pre-processing scheme presented herein, those cameras enable stereoscopic PIV in harsh environments and even on moving experiments. Graphic abstract

A HIGH-RESOLUTION 2D IMAGING LASER RADAR FOR OCCLUDED HARD TARGET VIEWING AND IDENTIFICATION

2008 ◽  
Vol 18 (02) ◽  
pp. 393-400 ◽  
Author(s):  
ROBERT J. GRASSO ◽  
JOHN C. WIKMAN ◽  
DAVID P. DROUIN ◽  
GEORGE F. DIPPEL ◽  
PAUL I. EGBERT
Keyword(s):  
High Resolution ◽  
Target Identification ◽  
Low Cost ◽  
System Size ◽  
Operating Conditions ◽  
Array Technology ◽  
Diode Pumped ◽  
Target Ranging ◽  
2D Imaging ◽  
Gated Imaging

BAE SYSTEMS has developed a Low Cost Targeting System (LCTS) consisting of a FLIR for target detection, laser-illuminated, gated imaging for target identification, laser rangefinder and designator, GPS positioning, and auto-tracking capability within a small compact system size. The system is based upon BAE Systems proven micro-bolometer passive LWIR camera coupled with Intevac's new EBAPS camera. A dual wavelength diode pumped laser provides eyesafe ranging and target illumination, as well as designation; a custom detector module senses the return pulse for target ranging and to set the range gates for the gated camera. Trials show that the current detectors offer complete extinction of signals outside of the gated range, thus, providing high resolution within the gated region. The images have shown high spatial resolution arising from the use of solid state focal plane array technology. Imagery has been collected in both the laboratory and the field to verify system performance during a variety of operating conditions.

scholarly journals Gold Nanorods for Light-Based Lung Cancer Theranostics

2018 ◽  
Vol 19 (11) ◽  
pp. 3318 ◽  
Author(s):  
Oscar Knights ◽  
James McLaughlan
Keyword(s):  
Gold Nanorods ◽  
Photothermal Therapy ◽  
Continuous Wave ◽  
Low Cost ◽  
Laser System ◽  
Controlled Synthesis ◽  
Surface Plasmon Resonances ◽  
Plasmon Resonances ◽  
Theranostic Applications ◽  
Cancer Theranostics

Gold nanorods (AuNRs) have the potential to be used in photoacoustic (PA) imaging and plasmonic photothermal therapy (PPTT) due to their unique optical properties, biocompatibility, controlled synthesis, and tuneable surface plasmon resonances (SPRs). Conventionally, continuous-wave (CW) lasers are used in PPTT partly due to their small size and low cost. However, if pulsed-wave (PW) lasers could be used to destroy tissue then combined theranostic applications, such as PA-guided PPTT, would be possible using the same laser system and AuNRs. In this study, we present the effects of AuNR size on PA response, PW-PPTT efficacy, and PA imaging in a tissue-mimicking phantom, as a necessary step in the development of AuNRs towards clinical use. At equivalent NP/mL, the PA signal intensity scaled with AuNR size, indicating that overall mass has an effect on PA response, and reinforcing the importance of efficient tumour targeting. Under PW illumination, all AuNRs showed toxicity at a laser fluence below the maximum permissible exposure to skin, with a maximum of 80% cell-death exhibited by the smallest AuNRs, strengthening the feasibility of PW-PPTT. The theranostic potential of PW lasers combined with AuNRs has been demonstrated for application in the lung.

scholarly journals CELLULAR NETWORK TRAFFIC PREDICTION USING EXPONENTIAL SMOOTHING METHODS

2018 ◽  
Author(s):  
Quang Thanh Tran ◽  
Li Jun Hao ◽  
Quang Khai Trinh
Keyword(s):  
Network Traffic ◽  
Cellular Network ◽  
Low Cost ◽  
Real Data ◽  
Exponential Smoothing ◽  
High Accuracy ◽  
Training Data ◽  
Traffic Prediction ◽  
Data Traffic ◽  
Smoothing Methods

Wireless traffic prediction plays an important role in network planning and management, especially for real-time decision making and short-term prediction. Systems require high accuracy, low cost, and low computational complexity prediction methods. Although exponential smoothing is an effective method, there is a lack of use with cellular networks and research on data traffic. The accuracy and suitability of this method need to be evaluated using several types of traffic. Thus, this study introduces the application of exponential smoothing as a method of adaptive forecasting of cellular network traffic for cases of voice (in Erlang) and data (in megabytes or gigabytes). Simple and Error, Trend, Seasonal (ETS) methods are used for exponential smoothing. By investigating the effect of their smoothing factors in describing cellular network traffic, the accuracy of forecast using each method is evaluated. This research comprises a comprehensive analysis approach using multiple case study comparisons to determine the best fit model. Different exponential smoothing models are evaluated for various traffic types in different time scales. The experiments are implemented on real data from a commercial cellular network, which is divided into a training data part for modeling and test data part for forecasting comparison. This study found that ETS framework is not suitable for hourly voice traffic, but it provides nearly the same results with Holt–Winter’s multiplicative seasonal (HWMS) in both cases of daily voice and data traffic. HWMS is presumably encompassed by ETC framework and shows good results in all cases of traffic. Therefore, HWMS is recommended for cellular network traffic prediction due to its simplicity and high accuracy.  

scholarly journals Vision-based SLAM system for MAVs in GPS-denied environments

2017 ◽  
Vol 9 (4) ◽  
pp. 283-296 ◽  
Author(s):  
Sarquis Urzua ◽  
Rodrigo Munguía ◽  
Antoni Grau
Keyword(s):  
Sensory Input ◽  
Low Cost ◽  
Real Data ◽  
Micro Aerial Vehicle ◽  
Localization And Mapping ◽  
Monocular Slam ◽  
Payload Capacity ◽  
The World ◽  
Aerial Vehicle ◽  
Metric Scale

Using a camera, a micro aerial vehicle (MAV) can perform visual-based navigation in periods or circumstances when GPS is not available, or when it is partially available. In this context, the monocular simultaneous localization and mapping (SLAM) methods represent an excellent alternative, due to several limitations regarding to the design of the platform, mobility and payload capacity that impose considerable restrictions on the available computational and sensing resources of the MAV. However, the use of monocular vision introduces some technical difficulties as the impossibility of directly recovering the metric scale of the world. In this work, a novel monocular SLAM system with application to MAVs is proposed. The sensory input is taken from a monocular downward facing camera, an ultrasonic range finder and a barometer. The proposed method is based on the theoretical findings obtained from an observability analysis. Experimental results with real data confirm those theoretical findings and show that the proposed method is capable of providing good results with low-cost hardware.

scholarly journals Phase gradient algorithm method for three-dimensional holographic ladar imaging

2016 ◽  
Vol 55 (17) ◽  
pp. 4611 ◽  
Author(s):  
Jason W. Stafford ◽  
Bradley D. Duncan ◽  
David J. Rabb
Keyword(s):  
Three Dimensional ◽  
Gradient Algorithm ◽  
Phase Gradient

scholarly journals Low Cost and Compact FMCW 24 GHz Radar Applications for Snowpack and Ice Thickness Measurements

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3909
Author(s):  
Patrick Pomerleau ◽  
Alain Royer ◽  
Alexandre Langlois ◽  
Patrick Cliche ◽  
Bruno Courtemanche ◽  
...  
Keyword(s):  
Snow Depth ◽  
Continuous Wave ◽  
Snow Water Equivalent ◽  
Low Cost ◽  
Ice Thickness ◽  
Lake Ice ◽  
Wide Range ◽  
Thickness Measurements ◽  
24 Ghz

Monitoring the evolution of snow on the ground and lake ice—two of the most important components of the changing northern environment—is essential. In this paper, we describe a lightweight, compact and autonomous 24 GHz frequency-modulated continuous-wave (FMCW) radar system for freshwater ice thickness and snow mass (snow water equivalent, SWE) measurements. Although FMCW radars have a long-established history, the novelty of this research lies in that we take advantage the availability of a new generation of low cost and low power requirement units that facilitates the monitoring of snow and ice at remote locations. Test performance (accuracy and limitations) is presented for five different applications, all using an automatic operating mode with improved signal processing: (1) In situ lake ice thickness measurements giving 2 cm accuracy up to ≈1 m ice thickness and a radar resolution of 4 cm; (2) remotely piloted aircraft-based lake ice thickness from low-altitude flight at 5 m; (3) in situ dry SWE measurements based on known snow depth, giving 13% accuracy (RMSE 20%) over boreal forest, subarctic taiga and Arctic tundra, with a measurement capability of up to 3 m in snowpack thickness; (4) continuous monitoring of surface snow density under particular Antarctic conditions; (5) continuous SWE monitoring through the winter with a synchronized and collocated snow depth sensor (ultrasonic or LiDAR sensor), giving 13.5% bias and 25 mm root mean square difference (RMSD) (10%) for dry snow. The need for detection processing for wet snow, which strongly absorbs radar signals, is discussed. An appendix provides 24 GHz simulated effective refractive index and penetration depth as a function of a wide range of density, temperature and wetness for ice and snow.

scholarly journals Low-Cost Ka-Band Cloud Radar System for Distributed Measurements within the Atmospheric Boundary Layer

2020 ◽  
Vol 12 (23) ◽  
pp. 3965
Author(s):  
Roberto Aguirre ◽  
Felipe Toledo ◽  
Rafael Rodríguez ◽  
Roberto Rondanelli ◽  
Nicolas Reyes ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Low Cost ◽  
Medium Size ◽  
Physical Parameters ◽  
Mountain Range ◽  
Ka Band ◽  
Range Resolution ◽  
Cloud Radar ◽  
Marine Stratus ◽  
Application Fields

Radars are used to retrieve physical parameters related to clouds and fog. With these measurements, models can be developed for several application fields such as climate, agriculture, aviation, energy, and astronomy. In Chile, coastal fog and low marine stratus intersect the coastal topography, forming a thick fog essential to sustain coastal ecosystems. This phenomenon motivates the development of cloud radars to boost scientific research. In this article, we present the design of a Ka-band cloud radar and the experiments that prove its operation. The radar uses a frequency-modulated continuous-wave with a carrier frequency of 38 GHz. By using a drone and a commercial Lidar, we were able to verify that the radar can measure reflectivities in the order of −60 dBZ at 500 m of distance, with a range resolution of 20 m. The lower needed range coverage imposed by our case of study enabled a significant reduction of the instrument cost compared to existent alternatives. The portability and low-cost of the designed instrument enable its implementation in a distributed manner along the coastal mountain range, as well as its use in medium-size aerial vehicles or balloons to study higher layers. The main features, limitations, and possible improvements to the current instrument are discussed.

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