Passive millimeter-wave camera with interferometric processing

Nohmi, Hitoshi; Ohnishi, Seiki; Kujubu, Osamu

doi:10.1117/12.666550

Cited by 5 publications

(3 citation statements)

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“…However, rather than performing traditional radar detection and estimation algorithms, in this imaging system the uncorrelated nature of multiple WiFi signals transmitted from spatially diverse locations enables the use of Fourier-domain spatial sampling to create images. While earlier works on passive imaging systems used sparse arrays [22], [23], such passive systems measure the extremely low-power thermally-generated electromagnetic radiation in the microwave and millimeter-wave bands. To capture this radiation, the receivers must be implemented with very wide bandwidths, in the range of 100s or 1000s of MHz, and very high gains, often exceeding 100 dB, combined with integration times on the order of a few milliseconds to seconds.…”

Section: The Main Drawback Of Compressive Imagers Is Their Heavymentioning

confidence: 99%

Imaging With WiFi

2019

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A new method of creating microwave imagery by capturing the signals emitted by a small set of wireless WiFi transmitters is presented. The imaging technique leverages the fact that the signals emitted by separate WiFi transmitters are sufficiently statistically independent to create a radiation pattern that is spatially incoherent, enabling the use of spatial frequency sampling using a small set of receiving antennas in a sparse array. In contrast to traditional microwave imaging, this method requires no mechanical or electrical beam scanning and no coordination between transmitters and receivers. Furthermore, the WiFi imaging system requires far less receiver gain than passive microwave imagers and significantly less bandwidth. We experimentally demonstrate the 2-D image reconstruction of reflecting metal spheres and an X-shaped reflecting target using three transmitters emitting independent 16-level quadrature amplitude modulated signals at 5.5 GHz matching commercial WiFi protocols 802.11n/ac.

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Section: The Main Drawback Of Compressive Imagers Is Their Heavymentioning

confidence: 99%

Imaging With WiFi

2019

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“…Partial coherence refers that electromagnetic wave radiation from a point source is coherent to itself, but irrelevant with the others, this characteristic is used to calculate mutual intensity in (1). MMW-SAR technology can use phase information to get target azimuth with self-coherence, so also called interference synthetic aperture [9], thus make it have the capability of range resolution in near range.…”

Section: Introductionmentioning

confidence: 99%

“…1. In recent years, near range MMW-SAR passive imaging technology has been developed, and imaging prototypes have been reported by Japanese NEC Corp. [9] and Australian ICT center of CSIRO [10]. Also, there is similar research on Terahertz in NJIT of USA [11].…”

Section: Introductionmentioning

confidence: 99%

Near range MMW synthetic aperture radiometer 3D passive imaging

Ben-qing

Qian

2008

2008 8th International Symposium on Antennas, Propagation and EM Theory

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Millimeter wave synthetic aperture radiometer (MMW-SAR) technology can use phase information of electromagnetic wave radiating from target, and will be real-time imaging with less receiver elements. However MMW-SAR is limited to 2D imaging due to passive regime nowadays, lack of range information of target, which is very unfavorable for target detection and identification, thus this paper presents novel principle and algorithm for MMW-SAR 3D passive imaging under near range conditions. In near range, it is spherical wave radiation and wave front curvature of spherical wave is inversely proportional to propagation distance, synthetic aperture technology can get the curvature of the wave front. Thus there is quadratic phase factor in imaging formula primarily. Regarding the factor as LFM, the 3D imaging algorithm calculates the slope of LFM so as to get wave front curvature, then calculated range distribution. MMW-SAR 3D passive imaging can get both range distribution and brightness temperature distribution, which could effectively overcome fuzzy problem caused by defocus. Index Items-Millimeter wave radiometer; synthetic aperture; near range; 3D passive imaging; FRFT I. INTRODUCTIONRadiometer is a high sensitive receiver that receipts weak energy radiation from object. MMW radiometer passive imaging technology has been widely applied in many fields. The imaging regime mainly includes focal plane array, phased array, interferometric synthetic aperture and mechanical scanning. As MMW has the abilities of distinction metal object and the surroundings and certain penetration, it is greatly significant to develop MMW imaging technology for target recognition. Many works are made in MMW-SAR passive imaging technology [1-7], but those remote sensing types are not appropriate for near range passive imaging.Near range MMW passive imaging technology is used for detection and identification target within several meters [8], for example medical imaging can detect lesions location of patients, security department can detect concealed weapons and the dangerous the like, traffic management can monitor vehicles, in addition navigation can land automatically under the adverse climatic conditions. In May 2007, an airport in Amsterdam hires a millimeter human security scanner, greatly simplifying the airport security procedures. A near range human body image with a hidden metal ring is shown in Fig. 1. In recent years, near range MMW-SAR passive imaging technology has been developed, and imaging prototypes have been reported by Japanese NEC Corp.[9] and Australian ICT

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