Characterization of the near-field and the far-field for a vertically radiating antenna over a ground plane.

A novel and practical approach is presented providing improved antenna performance without enlarging the antenna or the ground plane. The approach electrically extends the ground plane using wire(s) that behave as surface metal extensions of the ground plane. The wire extensions can be accommodated within typical handset housing or as part of the stylish metal used on the handset’s exterior perimeter; hence don’t require enlargement of the device. Consequently, this approach avoids the costs and limitations traditionally associated with physically lengthening of a ground plane. Eight variations are presented and compared with baseline antenna performance. Both far-field patterns and near-field electromagnetic scans demonstrate that the proposed approach controls the electrical length of the ground plane and hence its chassis wavemodes, without negatively impacting the characteristics of the antenna. Improvements in performance of up to 56% in bandwidth at 900 MHz and up to 12% in efficiency with a reduction of up to 12% in the specific absorption rate (SAR) are achieved. An 8% increase in efficiency with a 1.3% improvement in bandwidth and a 20% reduction in SAR is achieved at 1880 MHz. Thus, improvements in bandwidth are achieved without compromising efficiency. Further, improvements at lower frequencies do not compromise performance at higher frequencies.

Download Full-text

Miniaturized beamsplitters realized by X-ray waveguides

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s205327331601144x ◽

2016 ◽

Vol 72 (5) ◽

pp. 515-522 ◽

Cited By ~ 3

Author(s):

Sarah Hoffmann-Urlaub ◽

Tim Salditt

Keyword(s):

Interference Pattern ◽

Phase Retrieval ◽

Near Field ◽

Retrieval Algorithm ◽

Far Field ◽

X Ray ◽

Reconstructed Field ◽

Propagation Methods ◽

Cladding Material

This paper reports on the fabrication and characterization of X-ray waveguide beamsplitters. The waveguide channels were manufactured by electron-beam lithography, reactive ion etching and wafer bonding techniques, with an empty (air) channel forming the guiding layer and silicon the cladding material. A focused synchrotron beam is efficiently coupled into the input channel. The beam is guided and split into two channels with a controlled (and tunable) distance at the exit of the waveguide chip. After free-space propagation and diffraction broadening, the two beams interfere and form a double-slit interference pattern in the far-field. From the recorded far-field, the near-field was reconstructed by a phase retrieval algorithm (error reduction), which was found to be extremely reliable for the two-channel setting. By numerical propagation methods, the reconstructed field was then propagated along the optical axis, to investigate the formation of the interference pattern from the two overlapping beams. Interestingly, phase vortices were observed and analysed.

Download Full-text

Near-field and far-field characterization of Active Electronically Scanned Antennas (AESA) using electro-optic field probes

2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting ◽

10.1109/apusncursinrsm.2017.8072835 ◽

2017 ◽

Cited By ~ 1

Author(s):

Kazem Sabet ◽

Richard Darragh ◽

Ali Sabet ◽

Kamal Sarabandi

Keyword(s):

Near Field ◽

Far Field ◽

Electro Optic

Download Full-text

Characterization of the Far-Field Environment of Antennas Located Over a Ground Plane and Implications for Cellular Communication Systems

IEEE Antennas and Propagation Magazine ◽

10.1109/map.2010.5723218 ◽

2010 ◽

Vol 52 (6) ◽

pp. 19-40 ◽

Cited By ~ 21

Author(s):

A De ◽

T K Sarkar ◽

M Salazar-Palma

Keyword(s):

Communication Systems ◽

Ground Plane ◽

Cellular Communication ◽

Far Field ◽

Field Environment ◽

Cellular Communication Systems

Download Full-text

Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials

Optics Express ◽

10.1364/oe.24.007019 ◽

2016 ◽

Vol 24 (7) ◽

pp. 7019 ◽

Cited By ~ 14

Author(s):

Valentina Parigi ◽

Elodie Perros ◽

Guillaume Binard ◽

Céline Bourdillon ◽

Agnès Maître ◽

...

Keyword(s):

Near Field ◽

Far Field ◽

Speckle Patterns

Download Full-text

Box-Scan: A Novel 3DXRD Method for Studies of Recrystallization and Grain Growth

Materials Science Forum ◽

10.4028/www.scientific.net/msf.715-716.518 ◽

2012 ◽

Vol 715-716 ◽

pp. 518-520 ◽

Cited By ~ 2

Author(s):

Allan Lyckegaard ◽

Henning Friis Poulsen ◽

Wolfgang Ludwig ◽

Richard W. Fonda ◽

Erik M. Lauridsen

Keyword(s):

Spatial Resolution ◽

Near Field ◽

Polycrystalline Materials ◽

High Temporal Resolution ◽

Far Field ◽

X Ray Diffraction ◽

The Individual ◽

Individual Grains ◽

Non Destructive

Within the last decade a number of x-ray diffraction methods have been presented for non-destructive 3D characterization of polycrystalline materials. 3DXRD [1] and Diffraction Contrast Tomography [2,3,4] are examples of such methods providing full spatial and crystallographic information of the individual grains. Both methods rely on specially designed high-resolution near-field detectors for acquire the shape of the illuminated grains, and therefore the spatial resolution is for both methods limited by the resolution of the detector, currently ~2 micrometers. Applying these methods using conventional far-field detectors provides information on centre of mass, crystallographic orientation and stress state of the individual grains [5], at the expense of high spatial resolution. However, far-field detectors have much higher efficiency than near-field detectors, and as such are suitable for dynamic studies requiring high temporal resolution and set-ups involving bulky sample environments (e.g. furnaces, stress-rigs etc.)

Download Full-text