scholarly journals Transmission-Type 2-Bit Programmable Metasurface for Single-Sensor and Single-Frequency Microwave Imaging

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Yun Bo Li ◽  
Lian Lin Li ◽  
Bai Bing Xu ◽  
Wei Wu ◽  
Rui Yuan Wu ◽  
...  
Keyword(s):  
Microwave Imaging ◽  
Single Frequency ◽  
Single Sensor

scholarly journals A Subspace Preconditioned LSQR Gauss-Newton Method with a Constrained Line Search Path Applied to 3D Biomedical Microwave Imaging

2015 ◽  
Vol 2015 ◽  
pp. 1-21
Author(s):  
Jürgen De Zaeytijd ◽  
Ann Franchois
Keyword(s):  
Complex Permittivity ◽  
Line Search ◽  
Synthetic Data ◽  
Iterative Solution ◽  
Initial Guess ◽  
Microwave Imaging ◽  
Single Frequency ◽  
Problem Solution ◽  
Source Position ◽  
Search Path

Three contributions that can improve the performance of a Newton-type iterative quantitative microwave imaging algorithm in a biomedical context are proposed. (i) To speed up the iterative forward problem solution, we extrapolate the initial guess of the field from a few field solutions corresponding to previous source positions for the same complex permittivity (i.e., “marching on in source position”) as well as from a Born-type approximation that is computed from a field solution corresponding to one previous complex permittivity profile for the same source position. (ii) The regularized Gauss-Newton update system can be ill-conditioned; hence we propose to employ a two-level preconditioned iterative solution method. We apply the subspace preconditioned LSQR algorithm from Jacobsen et al. (2003) and we employ a 3D cosine basis. (iii) We propose a new constrained line search path in the Gauss-Newton optimization, which incorporates in a smooth manner lower and upper bounds on the object permittivity, such that these bounds never can be violated along the search path. Single-frequency reconstructions from bipolarized synthetic data are shown for various three-dimensional numerical biological phantoms, including a realistic breast phantom from the University of Wisconsin-Madison (UWCEM) online repository.

scholarly journals Single-shot and single-sensor high/super-resolution microwave imaging based on metasurface

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Libo Wang ◽  
Lianlin Li ◽  
Yunbo Li ◽  
Hao Chi Zhang ◽  
Tie Jun Cui
Keyword(s):  
Super Resolution ◽  
Microwave Imaging ◽  
Single Shot ◽  
Single Sensor

scholarly journals Single-frequency microwave imaging with dynamic metasurface apertures

2017 ◽  
Vol 34 (8) ◽  
pp. 1713 ◽  
Author(s):  
Timothy Sleasman ◽  
Michael Boyarsky ◽  
Mohammadreza F. Imani ◽  
Thomas Fromenteze ◽  
Jonah N. Gollub ◽  
...  
Keyword(s):  
Microwave Imaging ◽  
Single Frequency

A new global Gross Primary Production (GPP) dataset based on microwave Vegetation Optical Depth Climate Archive (VODCA)

2020 ◽  
Author(s):  
Benjamin Wild ◽  
Irene Teubner ◽  
Leander Moesinger ◽  
Wouter Dorigo
Keyword(s):  
Carbon Source ◽  
Primary Production ◽  
Optical Depth ◽  
Carbon Sink ◽  
Gross Primary Production ◽  
Operation Time ◽  
Ecosystem Dynamics ◽  
Single Frequency ◽  
Model Input ◽  
Single Sensor

<p>Gross Primary Production (GPP) describes the uptake of C0<sub>2</sub> by plants through photosynthesis and is essential to monitor and analyze ecosystem dynamics. Teubner et al.<sup>1</sup> developed a carbon sink-driven approach to estimate GPP on a global scale using Vegetation Optical Depth (VOD), derived from active and passive microwave observations. This allows to analyze GPP variability, complementing existing optical GPP products which are more affected by weather conditions. The short operation time of the individual microwave sensors and the bias between them prohibit analyzing GPP variability. This issue can potentially be overcome by using the Vegetation Optical Depth Climate Archive (VODCA) developed by Moesinger et al.<sup>2</sup>, which merges multiple VOD products into a single data record. However, the use of a long-running VOD composite for estimating global GPP is challenging because the implications of the VOD aggregation process on the modelling of GPP are difficult to identify a priori.</p><p>Here, we present the results of applying the carbon sink-driven GPP estimation approach on the VODCA datasets. As model input for each pixel we used raw VOD from VODCA as well as changes in VOD and median VOD, the latter serves as proxy for vegetation cover. In order to analyze the performance of the carbon sink-driven approach when using VODCA as input, the model is cross-validated against single-sensor (AMSR-E) VOD estimates and commonly used carbon source-driven estimates (MODIS/FLUXCOM). We assessed the ability to model GPP based on single-frequency VODCA (C-, X- and Ku-band) as well as using multiple frequencies as model input.</p><p>Overall, the results show that single-band as well as multi-band VODCA performs slightly better in predicting GPP than single-sensor based VOD. Especially in the tropical regions multi-frequency VODCA GPP outperforms single-sensor based estimates. Compared to source-driven approaches, VOD based GPP estimates are higher than FLUXCOM and MODIS GPP. The spatial patterns, however, show good correspondence with the carbon source-driven GPP products, confirming that VODCA can be used to extend the GPP estimates to the past three decades.</p><p><sup>1</sup>Teubner, I., Forkel, M., Camps-Valls, G., Jung, M., Miralles, Diego, Tramontana, G., van der Schalie, R., Vreugdenhil, M., Moesinger, L., Dorigo, W.:A carbon sink-driven approach to estimate gross primary production from microwave satellite observations, 2019. Remote Sensing of Environment. 229. 100-113. 10.1016/j.rse.2019.04.022.</p><p><sup>2</sup>Moesinger, L., Dorigo, W., de Jeu, R., van der Schalie, R., Scanlon, T., Teubner, I., and Forkel, M.: The Global Long-term Microwave Vegetation Optical Depth Climate Archive VODCA, Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2019-42, in review, 2019.</p>

scholarly journals A Two-Stage Procedure for Microwave Imaging of a Buried Dielectric along with the Randomly Rough Surface above It

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Tolga Ulaş Gürbüz ◽  
Birol Aslanyürek
Keyword(s):  
Rough Surface ◽  
Reference Model ◽  
Property Values ◽  
Microwave Imaging ◽  
Single Frequency ◽  
Nonlinear Inversion ◽  
Source Inversion ◽  
Entire Region ◽  
Two Stage

A two-stage microwave imaging procedure based on the contrast source inversion (CSI) is proposed for the determination of a buried dielectric along with the rough surface above it. It was previously shown that, the CSI, is very effective for the determination of a dielectric buried under a known rough surface. However, for an unknown surface, the application of the CSI to the entire region containing both the object and the roughness will yield significantly inaccurate dielectric property values and, thus, determination of objects will be almost impossible especially when they are small in size or low in contrast. Thus, we propose to construct a reference model for the background without the object by preimaging the entire region in a frequency-hopping scheme and imposing the a priori known property values to the approximately determined morphology of the background. In the second stage, the CSI is performed at single frequency, assuming the constructed reference model as the background. In this case, by taking the advantage of nonlinear inversion and without a restrictive assumption about the characteristics of the rough surface, the proposed approach yields qualitatively satisfactory results even for multiple objects buried under a surface having a high frequency or large roughness.

scholarly journals Experimental Validation of a Microwave Imaging Method for Shallow Buried Target Detection by Under-Sampled Data and a Non-Coperative Source

2021 ◽  
Author(s):  
Adriana Brancaccio ◽  
Giovanni Leone ◽  
Rocco Pierri ◽  
Raffaele Solimene
Keyword(s):  
Spatial Data ◽  
Horn Antenna ◽  
Test Site ◽  
Microwave Imaging ◽  
Single Frequency ◽  
Reference Plane ◽  
Imaging Method ◽  
Sampled Data ◽  
Working Frequency ◽  
Soil Interface

In microwave imaging it is often of interest to inspect electrically large spatial regions. In these cases, data must be collected over a great deal of measurement points which entails long measurement time and/or costly, and often unfeasible, measurement configurations. In order to counteract such drawbacks, we have recently introduced a microwave imaging algorithm which looks for the scattering targets in terms of equivalent surface currents supported over a given reference plane. While this method is suited to detect shallowly buried targets, it allows to independently process each frequency data, hence the source and the receivers do not need to be synchronized. Moreover, spatial data can be reduced at large extent, without incurring in aliasing artefacts, by properly combining single-frequency reconstructions. In this paper, we validate such an approach by experimental measurements. In particular, the experimental test site consists of a sand box in open air where metallic plate targets are shallowly buried (few cm) under the air/soil interface. The investigated region is illuminated by a fixed transmitting horn antenna whereas the scattered field is collected over a planar measurement aperture at a fixed height from the air-sand interface. The transmitter and the receiver share only the working frequency information. Experimental results confirm the feasibility of the method.

scholarly journals Experimental Validation of a Microwave Imaging Method for Shallow Buried Target Detection by Under-Sampled Data and a Non-Cooperative Source

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5148
Author(s):  
Adriana Brancaccio ◽  
Giovanni Leone ◽  
Rocco Pierri ◽  
Raffaele Solimene
Keyword(s):  
Spatial Data ◽  
Horn Antenna ◽  
Test Site ◽  
Microwave Imaging ◽  
Single Frequency ◽  
Reference Plane ◽  
Imaging Method ◽  
Sampled Data ◽  
Working Frequency ◽  
Soil Interface

In microwave imaging, it is often of interest to inspect electrically large spatial regions. In these cases, data must be collected over a great deal of measurement points which entails long measurement time and/or costly, and often unfeasible, measurement configurations. In order to counteract such drawbacks, we have recently introduced a microwave imaging algorithm that looks for the scattering targets in terms of equivalent surface currents supported over a given reference plane. While this method is suited to detect shallowly buried targets, it allows one to independently process all frequency data, and hence the source and the receivers do not need to be synchronized. Moreover, spatial data can be reduced to a large extent, without any aliasing artifacts, by properly combining single-frequency reconstructions. In this paper, we validate such an approach by experimental measurements. In particular, the experimental test site consists of a sand box in open air where metallic plate targets are shallowly buried a (few cm) under the air/soil interface. The investigated region is illuminated by a fixed transmitting horn antenna, whereas the scattered field is collected over a planar measurement aperture at a fixed height from the air-sand interface. The transmitter and the receiver share only the working frequency information. Experimental results confirm the feasibility of the method.

scholarly journals Methods to homogenize ECC ozonesonde measurements across changes in sensing solution concentration or ozonesonde manufacturer

2017 ◽  
Author(s):  
Terry Deshler ◽  
Rene Stübi ◽  
Francis J. Schmidlin ◽  
Jennifer L. Mercer ◽  
Herman G. J. Smit ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Electrochemical Cell ◽  
Solution Concentration ◽  
Solution Composition ◽  
Single Sensor ◽  
The One ◽  
Simple Ratio ◽  
Comparison Data

Abstract. From the mid 1990s to the late 2000s the consistency of electrochemical cell ozonesonde long term records has been compromised by differences in manufacturers, Science Pump and ENSCI, and differences in recommended sensor solution concentrations, 1.0 % potassium iodide (KI) and the one half dilution 0.5 %. To investigate these differences a number of organizations independently undertook comparisons of the various ozonesonde types and solution concentrations, resulting in 197 ozonesonde comparison profiles. The goal is to derive transfer functions to allow measurements outside of standard recommendations, for sensor composition and ozonesonde type, to be converted to a standard measurement and thus homogenize the data to the expected accuracy of 5 % (10 %) in the stratosphere (troposphere). Subsets of these data have been analyzed previously and intermediate transfer functions derived. Here all the comparison data are analyzed to compare: 1) differences in sensor solution composition for a single ozonesonde type, 2) differences in ozonesonde type for a single sensor solution composition and 3) the manufacturer’s recommendations of 1.0 % KI solution for Science Pump and 0.5 % KI for ENSCI. From the recommendations it is clear that ENSCI ozonesondes and 1.0 % KI solution result in higher amounts of ozone sensed. The results indicate that differences in solution composition and in ozonesonde type display little pressure dependence at pressures ≥ 30 hPa and thus the transfer function can be characterized as a simple ratio of the less sensitive to the more sensitive method. This ratio is 0.96 for both solution concentration and ozonesonde type. The ratios differ at pressures

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