THz Imaging Radar for Standoff Personnel Screening

Cooper, Ken B.; Dengler, Robert J.; Llombart, Nuria; Thomas, B.; Chattopadhyay, Goutam; Siegel, Peter H.

doi:10.1109/tthz.2011.2159556

Cited by 714 publications

(392 citation statements)

References 23 publications

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“…Indeed, the inherent step nature of the DDS frequency sweep matches the signal requirements for "stepped" LO CP-FT mm-wave spectroscopy. 22,30 Multiplication of a DDS chirped pulse has already been demonstrated in a hybrid DDS/PLL chirped pulse synthesizer for radar applications at 675 GHz 19 and could be used to further extend the bandwidth of the instrument.…”

Section: Discussionmentioning

confidence: 99%

“…Using an external sample clock and digital control word, a DDS generates a tunable digital signal with a numerically controlled oscillator, which is then converted into sinusoidal output with a digital-to-analog converter (DAC). 18 Their frequency agility and low phase noise capabilities have been utilized for longer (35 μs) broadband frequency sweeps at millimeter-wave frequencies for radar imaging applications, 19 as well as slow narrowband frequency sweeps (3 MHz) in a millimeter-wave fast scan absorption spectrometer. 20 To date, however, this technology has never been used for CP-FTMW spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

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A direct digital synthesis chirped pulse Fourier transform microwave spectrometer

Finneran

Holland

Carroll

et al. 2013

Review of Scientific Instruments

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Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer

Finneran

Holland

Carroll

et al. 2013

Review of Scientific Instruments

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“…Most submillimetre wave radars make use of solid-state frequency multiplier chains [3,4,5,6,7], exploiting both MMIC and Schottky diode technologies, to generate transmit powers which are typically in the milliwatt class. When combined with sensitive heterodyne or homodyne receivers, these radars can achieve high dynamic ranges.…”

Section: Overview Of Submillimetre Wave Radarmentioning

confidence: 99%

“…The challenge in achieving high fidelity radar measurements with such bandwidths is to achieve wideband chirps which have good linearity, low phase noise and short duration, especially if fast pixel rates are required [9]. This places demands on the chirp generator used to drive the multipliers, which is usually at microwave frequencies, and the spectral characteristics of all the components in the frequency multiplication chain (such as amplitude flatness and group delay variations), both of which contribute to distortion of the radar's point response [4,7].…”

Section: Overview Of Submillimetre Wave Radarmentioning

confidence: 99%

Submillimetre wave 3D imaging radar for security applications

Robertson¹,

Macfarlane²,

Cassidy³

et al. 2016

IET Colloquium on Millimetre-Wave and Terahertz Engineering [Amp ] Technology 2016

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There is ongoing worldwide interest in finding solutions to enhance the security of civilians at airports, borders and high risk public areas in ways which are safe, ethical and streamlined. One promising approach is to use submillimetre wave 3D imaging radar to detect concealed threats as it offers the advantages of high volumetric resolution (~1 cm3) with practically sized antennas (<0.5 m) such that even quite small objects can be resolved through clothing. The Millimetre Wave Group at the University of St Andrews has been developing submillimetre wave 3D imaging radars for security applications since 2007. A significant goal is to achieve near real-time frame rates of at least 10 Hz, to cope with dynamic scenes, over wide fields of view at short range with high pixel counts. We review the radar systems we have developed at 340 and 220 GHz and the underpinning technologies which we have employed to realise these goals.

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“…Compared to microwave and infrared frequencies, THz radar has some advantages, such as high spatial resolution, greater secrecy, strong penetrating capability, extremely ultra-wide bandwidth, among others1234. Therefore, THz radar has great prospects in remote sensing and military application.…”

mentioning

confidence: 99%

Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies

Liu

Wei

Yan

et al. 2016

Sci Rep

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A novel broadband and wide-angle 2-bit coding metasurface for radar cross section (RCS) reduction is proposed and characterized at terahertz (THz) frequencies. The ultrathin metasurface is composed of four digital elements based on a metallic double cross line structure. The reflection phase difference of neighboring elements is approximately 90° over a broadband THz frequency. The mechanism of RCS reduction is achieved by optimizing the coding element sequences, which redirects the electromagnetic energies to all directions in broad frequencies. An RCS reduction of less than −10 dB bandwidth from 0.7 THz to 1.3 THz is achieved in the experimental and numerical simulations. The simulation results also show that broadband RCS reduction can be achieved at an incident angle below 60° for TE and TM polarizations under flat and curve coding metasurfaces. These results open a new approach to flexibly control THz waves and may offer widespread applications for novel THz devices.

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THz Imaging Radar for Standoff Personnel Screening

Cited by 714 publications

References 23 publications

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer

Submillimetre wave 3D imaging radar for security applications

Broadband and wide-angle RCS reduction using a 2-bit coding ultrathin metasurface at terahertz frequencies

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