The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

The history, fabrication, theory, numerical modeling, optical properties, guidance mechanisms, and applications of photonic-crystal fibers are reviewed

Photonic-Crystal Fibers

Utilization of electromagnetic band-gap (EBG) structures is becoming attractive in the electromagnetic and antenna community. In this paper, a mushroom-like EBG structure is analyzed using the finite-difference time-domain (FDTD) method. Its band-gap feature of surface-wave suppression is demonstrated by exhibiting the near field distributions of the electromagnetic waves. The mutual coupling of microstrip antennas is parametrically investigated, including both the E and H coupling directions, different substrate thickness, and various dielectric constants. It is observed that the E-plane coupled microstrip antenna array on a thick and high permittivity substrate has a strong mutual coupling due to the pronounced surface waves. Therefore, an EBG structure is inserted between array elements to reduce the mutual coupling. This idea has been verified by both the FDTD simulations and experimental results. As a result, a significant 8 dB mutual coupling reduction is noticed from the measurements.

/pdf/microstrip-antennas-integrated-with-electromagnetic-band-gap-1t2jb53z58.pdf

Microstrip antennas integrated with electromagnetic band-gap (EBG) structures: a low mutual coupling design for array applications

Mushroom-like electromagnetic band-gap (EBG) structures exhibit unique electromagnetic properties that have led to a wide range of electromagnetic device applications. This paper focuses on the reflection phase feature of EBG surfaces: when plane waves normally illuminate an EBG structure, the phase of the reflected field changes continuously from 180/spl deg/ to -180/spl deg/ versus frequency. One important application of this feature is that one can replace a conventional perfect electric conductor (PEC) ground plane with an EBG ground plane for a low profile wire antenna design. For this design, the operational frequency band of an EBG structure is defined as the frequency region within which a low profile wire antenna radiates efficiently, namely, having a good return loss and radiation patterns. The operational frequency band is the overlap of the input-match frequency band and the surface-wave frequency bandgap. It is revealed that the reflection phase curve can be used to identify the input-match frequency band inside of which a low profile wire antenna exhibits a good return loss. The surface-wave frequency bandgap of the EBG surface that helps improve radiation patterns is very close to its input-match frequency band, resulting in an effective operational frequency band. In contrast, a thin grounded slab cannot work efficiently as a ground plane for low profile wire antennas because its surface-wave frequency bandgap and input-match frequency band do not overlap. Parametric studies have been performed to obtain design guidelines for EBG ground planes. Two novel EBG ground planes with interesting electromagnetic features are also presented. The rectangular patch EBG ground plane has a polarization dependent reflection phase and the slotted patch EBG ground plane shows a compact size.

/pdf/reflection-phase-characterizations-of-the-ebg-ground-plane-42lmwngdqd.pdf

Reflection phase characterizations of the EBG ground plane for low profile wire antenna applications

Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate and they introduce a zero degrees reflection phase shift to incident waves. In this paper the AMC operation of single-layer arrays without vias is studied using a resonant cavity model and a new application to high-gain printed antennas is presented. A ray analysis is employed in order to give physical insight into the performance of AMCs and derive design guidelines. The bandwidth and center frequency of AMC surfaces are investigated using full-wave analysis and the qualitative predictions of the ray model are validated. Planar AMC surfaces are used for the first time as the ground plane in a high-gain microstrip patch antenna with a partially reflective surface as superstrate. A significant reduction of the antenna profile is achieved. A ray theory approach is employed in order to describe the functioning of the antenna and to predict the existence of quarter wavelength resonant cavities.

/pdf/artificial-magnetic-conductor-surfaces-and-their-application-e6wrhp8oa4.pdf

Artificial magnetic conductor surfaces and their application to low-profile high-gain planar antennas

The microstrip patch antenna is a low-profile robust planar structure. A wide range of radiation patterns can be achieved with this type of antenna and, due to the ease of man- ufacture, is inexpensive compared with other types of antennas. However, patch-antenna designs have some limitations such as restricted bandwidth of operation, low gain, and a potential decrease in radiation efficiency due to surface-wave losses. In this paper, a photonic-bandgap (PBG) substrate for patch antennas is proposed, which minimizes the surface-wave effects. In order to verify the performance of this kind of substrate, a configuration with a thick substrate is analyzed. The PBG patch antenna shows significantly reduced levels of surface modes compared to conventional patch antennas, thus improving the gain and far-field radiation pattern.

Enhanced Patch-Antenna Performance by Suppressing Surface Waves Using

This paper presents the design, fabrication, and characterization of a planar broadband chessboard structure to reduce the radar cross-section (RCS) of an object. The chessboard -like configuration is formed by combining two artificial magnetic conductor (AMC) cells. The bandwidth limitations intrinsic to AMC structures are overcome in this work by properly selecting the phase slope versus frequency of both AMC structures. A 180 ° phase difference has been obtained over more than 40% frequency bandwidth with a RCS reduction larger than 10 dB. The influence of the incidence angle in the working bandwidth has been performed. A good agreement between simulations and measurements is achieved.

/pdf/broadband-radar-cross-section-reduction-using-amc-technology-2wmsiobxi1.pdf

Broadband Radar Cross-Section Reduction Using AMC Technology

The development of a 835-900-GHz biasable funda- mental balanced mixer using planar GaAs Schottky diodes is pre- sented. The monolithic microwave integrated circuit integrates two planar Schottky anodes in a balanced configuration, stripline fil- tering elements, and on-chip capacitor on a thin GaAs membrane. At 850 GHz, double side-band (DSB) mixer noise temperature of 2660 K and conversion loss of 9.25 dB are measured, respectively, at room temperature. When the mixer is cooled to 120 K, the DSB mixer noise temperature and conversion loss improve to 1910 K and 8.84 dB, respectively. Index Terms—Cryogenic test bench, fundamental balanced mixer (FBM), monolithic microwave integrated circuit (MMIC), passive cooling, planar Schottky diode, submillimeter wavelengths, vacuum chamber.

A Broadband 835-900-GHz Fundamental Balanced Mixer Based on Monolithic GaAs Membrane

The terahertz (THz) part of the electromagnetic spectrum falls between the lower frequency millimetre wave region and, at higher frequencies, the far-infrared region. As the THz region separates the more established domains of microwaves and optics, a typical THz technique will incorporate aspects of both realms, and may even draw on the best of both. The two bounding parts of the spectrum also yield distinct sets of methods of generating and detecting THz waves. As a result of breakthroughs in technology, the THz region is finally finding applications outside its traditional heartlands of remote sensing and radio astronomy. Extensive research has identified many attractive uses and has paved the technological path towards flexible and accessible THz systems. This paper discusses the range of THz applications (both space and terrestrial) and will present the components and systems that are utilised for the region, both from a sort of historic perspective and from the point of view of recent developments. A split has been made in microwave THz and optical THz technology according to the underlying basic technologies. Future trends are also discussed.


Keywords:

Terahertz technology;
submillimeter wave technology;
Terahertz applications

Terahertz Science, Engineering and Systems—from Space to Earth Applications

In this letter, a patch antenna on a photonic bandgap substrate is presented. A reduction in the leel of surface-wae mode excitation has been obtained. This leads to improed efficiency, gain, and far-field radiation pattern. Furthermore, improements in the input return loss hae been reported. Q 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 24: 213)215, 2000.

Peter de Maagt

Papers

Enhanced Patch-Antenna Performance by Suppressing Surface Waves Using

Broadband Radar Cross-Section Reduction Using AMC Technology

A Broadband 835-900-GHz Fundamental Balanced Mixer Based on Monolithic GaAs Membrane

Terahertz Science, Engineering and Systems—from Space to Earth Applications

Improved patch antenna performance by using photonic bandgap substrates