The Effect of Antenna Incident Field Distribution on Microwave Tomography Reconstruction

Bayat, Nozhan; Mojabi, Puyan

doi:10.2528/pier14021905

Cited by 10 publications

(4 citation statements)

References 24 publications

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“…However, it is beneficial for near-field MWI to investigate antennas which are specifically designed to achieve desired NF distributions: in NF MWI, it is the incident NF of the antenna, not its FF pattern, that interrogates the OI. As a follow-up to our previous work where we have discussed that the choice of the incident field distribution can affect the achievable reconstruction [ 27 , 33 ], we now discuss and demonstrate that a focused incident NF can be used advantageously in NF MWI to suppress undesired scattering events. The idea behind this paper is therefore simple: making sure that the spotlight of the antenna is on the OI, and not on the undesired scatterers.…”

Section: Introductionmentioning

confidence: 81%

On the Use of Focused Incident Near-Field Beams in Microwave Imaging

Bayat¹,

Mojabi²

2018

Sensors

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We consider the use of focused incident near-field (NF) beams to interrogate the object of interest (OI) in NF microwave imaging (MWI). To this end, we first discuss how focused NF beams can be advantageously utilized to suppress scattering effects from the neighbouring objects whose unknown dielectric properties are not of interest (i.e., undesired scatterers). We then discuss how this approach can also be helpful in reducing the required measured data points to perform imaging. Driven by the relation between the electromagnetic inverse source and inverse scattering problems, our approach emphasizes the importance of tailoring the induced contrast sources in the imaging domain through the utilized incident NF beams. To demonstrate this idea, we consider two recently-proposed NF beams, and simulate them for imaging applications. The first one is a subwavelength focused NF beam generated by a passive NF plate, and the other is a Bessel beam generated by a leaky radial waveguide. Simple imaging examples are considered to explore the potential advantages of this approach, in particular, toward mainly seeing the object of interest, and not the unknown undesired scatterers. The scope of this paper is limited to homogeneous dielectric objects for which the induced total field distributions in the interrogated objects are similar to the incident field distributions (e.g., those that satisfy the Born approximation). Simple inversion results for focused and non-focused beams are presented accompanied by discussions comparing the achieved reconstructed values.

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Section: Introductionmentioning

confidence: 81%

On the Use of Focused Incident Near-Field Beams in Microwave Imaging

Bayat¹,

Mojabi²

2018

Sensors

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“…Many research papers tackle the problem of accurate antenna modelling [9], [19]- [22], promising better imaging with more accurate models. Antenna array design is the subject of many works [5], [8], [11], [15], [23]- [25], just to name some.…”

Section: Introductionmentioning

confidence: 99%

“…A disadvantage of such antennas is their omnidirectional radiation pattern in the imaging plane, which increases mutual coupling. This degrades measured field signal fidelity [27] and degradates overall imaging quality [22].…”

Section: Introductionmentioning

confidence: 99%

Design and Modelling of an Enclosed Array of Square Spiral Antennas for Microwave Tomography

Subotic¹,

Pjevalica²,

Palfi³

2017

ElAEE

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Microwave tomography is a microwave imaging method in which the resolution is not limited by wavelength, but rather by measurement noise and modelling errors. Inversion algorithm is used for obtaining an image from the measured scattered waves. Performance improvement of the inversion algorithm is introduced by approximately modelled antennas as a point, line or plane source. Such modelling of antennas introduces modelling errors. Antenna array in the unshielded measurement chamber will pick up external interference, as well as backscattering of array's own radiation. Multipath occurring in measurement chamber has a large impact on the measurement performance. The wave propagated through the air and reflected from the chamber walls could mask a weaker wave scattered by the object under imaging. Also, a larger number of the antennas improves inversion and gives a more accurate image. This paper proposes a novel design of enclosed measurement antenna array for microwave tomography. To obtain an accurate and efficient antenna model in 3D FDTD, a square spiral wire antenna is used in this design. A metal shield protects the process of measurement from external interference and backscattering. Between the antenna array and the metal shield an absorption wall is introduced, which decreases multipath and partially prevents signal masking. Square spiral wire antennas are overlapped and packed, giving a larger number of antennas in the same space. Enclosed antenna array is modelled in 3D FDTD. Proposed antenna array is compared with solutions found in literature. Comparison is done using metrics relevant for antenna array measurement in microwave tomography.

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“…The scheme is applicable to microwave tomography of tissue samples. It has been of great interest in tomography of human breast to identify malignant tumours [8][9][10][11][12][13][14]. The high contrast between healthy and cancerous breast tissue provides opportunities for clearly identifying malignancies within breast tissue.…”

Section: Introductionmentioning

confidence: 99%

Improved Backpropagation Algorithms by Exploiting Data Redundancy in Limited-Angle Diffraction Tomography

Paladhi

Sinha²,

Tayebi

et al. 2016

PIER B

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Filtered backpropagation (FBPP) is a well-known technique used in Diffraction Tomography (DT). For accurate reconstruction of a complex-valued image using FBPP, full 360 • angular coverage is necessary. However, it has been shown that by exploiting inherent redundancies in the projection data, accurate reconstruction is possible with 270 • coverage. This is called the minimal-scan angle range. This is done by applying weighting functions (or filters) on projection data of the object to eliminate the redundancies. There could be many general weight functions. These are all equivalent at 270 • coverage but would perform differently at lower angular coverages and in presence of noise. This paper presents a generalized mathematical framework to generate weight functions for exploiting data redundancy. Further, a comparative analysis of different filters when angular coverage is lower than minimal-scan angle of 270 • is presented. Simulation studies have been done to find optimum weight filters for sub-minimal angular coverage. The optimum weights generate images comparable to a full 360 • coverage FBPP reconstruction. Performance of the filters in the presence of noise is also analyzed. These fast and deterministic algorithms are capable of correctly reconstructing complex valued images even at angular coverage of 200 • while still under the FBPP regime.

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The Effect of Antenna Incident Field Distribution on Microwave Tomography Reconstruction

Cited by 10 publications

References 24 publications

On the Use of Focused Incident Near-Field Beams in Microwave Imaging

On the Use of Focused Incident Near-Field Beams in Microwave Imaging

Design and Modelling of an Enclosed Array of Square Spiral Antennas for Microwave Tomography

Improved Backpropagation Algorithms by Exploiting Data Redundancy in Limited-Angle Diffraction Tomography

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