Notch Antennas

Lee, Richard Q.

doi:10.1002/0471654507.eme297

Cited by 2 publications

(2 citation statements)

References 28 publications

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“…A thicker substrate separation between top and bottom parts increases the directivity (and sidelobes), and the higher the permittivity of the substrate, the narrower the main beam [20]. However, standard thickness FR-4 is used for the substrate material since it is both low cost and easy to manufacture.…”

Section: Experimental Systemmentioning

confidence: 99%

Impulse radar imaging system for concealed object detection

et al. 2013

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Electromagnetic systems for imaging concealed objects at checkpoints typically employ radiation at millimetre and terahertz frequencies. These systems have been shown to be effective and provide a sufficiently high resolution image. However there are difficulties and current electromagnetic systems have limitations particularly in accurately differentiating between threat and innocuous objects based on shape, surface emissivity or reflectivity, which are indicative parameters. In addition, water has a high absorption coefficient at millimetre wavelength and terahertz frequencies, which makes it more difficult for these frequencies to image through thick damp clothing. This paper considers the potential of using ultra wideband (UWB) in the low gigahertz range. The application of this frequency band to security screening appears to be a relatively new field. The business case for implementing the UWB system has been made financially viable by the recent availability of low-cost integrated circuits operating at these frequencies. Although designed for the communication sector, these devices can perform the required UWB radar measurements as well. This paper reports the implementation of a 2 to 5 GHz bandwidth linear array scanner. The paper describes the design and fabrication of transmitter and receiver antenna arrays whose individual elements are a type of antipodal Vivaldi antenna. The antenna's frequency and angular response were simulated in CST Microwave Studio and compared with laboratory measurements.The data pre-processing methods of background subtraction and deconvolution are implemented to improve the image quality. The background subtraction method uses a reference dataset to remove antenna crosstalk and room reflections from the dataset. The deconvolution method uses a Wiener filter to "sharpen" the returned echoes which improves the resolution of the reconstructed image. The filter uses an impulse response reference dataset and a signal-to-noise parameter to determine how the frequencies contained in the echo dataset are normalised. The chosen image reconstruction algorithm is based on the back-projection method. The algorithm was implemented in MATLAB and uses a pre-calculated sensitivity matrix to increase the computation speed.The results include both 2D and 3D image datasets. The 3D datasets were obtained by scanning the dual sixteen element linear antenna array over the test object. The system has been tested on both humans and mannequin test objects. The front surface of an object placed on the human/mannequin torso is clearly visible, but its presence is also seen from a tell-tale imaging characteristic. This characteristic is caused by a reduction in the wave velocity as the electromagnetic radiation passes through the object, and manifests as an indentation in the reconstructed image that is readily identifiable. The prototype system has been shown to easily detect a 12 mm x 30 mm x70 mm plastic object concealed under clothing.*frank.podd@manchester.ac.uk

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Section: Experimental Systemmentioning

confidence: 99%

Impulse radar imaging system for concealed object detection

et al. 2013

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“…The tapered slot antenna 4 and Vivaldi antenna have demonstrated very broad-bandwidths. The difficulty in designing these antennas is the feed network that transforms a microstrip or stripline, as seen in Fig.…”

Section: Stripline To Balanced Antipodal Finlinementioning

confidence: 99%

High-frequency transmission line transitions

Hall

Hansen

Abbott

2005

Smart Structures, Devices, and Systems II

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This paper demonstrates the use of modern electromagnetic simulation software to design and develop a selection of three novel transmission line transitions, for operation at mm-wavelengths, and an improvement in the performance of existing transitions. Specifically, our three case studies analyse (i) a microstrip-to-stripline transition, (ii) an inverted microstrip transition, and (iii) a stripline-to-finline transition. The important concepts are described and the tools available are explained. A number of novel and effective designs are presented as examples.

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Notch Antennas

Cited by 2 publications

References 28 publications

Impulse radar imaging system for concealed object detection

Impulse radar imaging system for concealed object detection

High-frequency transmission line transitions

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