There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications. By Christophe Caloz and Tatsuo Itoh.

Foundations For Microwave Engineering

일본은 지진이 상당히 많은 나라로 그중에서도 목조건물이 1300년간 계속해서
 바람.지진 등에 견디면서도 지금까지 남아있는 것은 인간의 위대한 힘의 결과라고
 안다. 이와 같이 과학과 기술은 상당한 차이의 내용을 갖고 있다. 이것이 18C에
 들어서면서 근대과학과 기술과의 관계가 생기게 되었다.

구조물의 내진설계 ( Earthquake-Resistant Design of Structures )

A two-element multiple-input–multiple-output (MIMO) dielectric resonator antenna having wideband characteristics is presented The wideband operation is achieved by using a mushroom shaped dielectric resonator excited by a conformal trapezoidal patch In order to realise two-element MIMO configuration, two wideband radiators are arranged orthogonally which offers polarisation diversity The measured bandwidth (VSWR ≤ 2) for Port1 is 61% (508–950 GHz), whereas for Port2 it is 65% (489–961 GHz) The isolation between the two ports is better than 20 dB for the desired frequency band The antenna exhibits broadside radiation with cross polar level below 15 dB The peak gain of antenna varies from 334 to 740 dBi at Port1 and from 234 to 79 dBi at Port2 Moreover, the various MIMO performance metrics including envelope correlation coefficient (ECC), diversity gain, channel capacity loss and total active reflection coefficient are investigated The ECC is less than 001 and capacity loss is under 05 bps/Hz throughout the operating bandwidth The results confirm that the antenna offers effective MIMO/diversity performance The proposed antenna can be suitable for WLAN and upper ultra wideband frequency band applications

Wideband multiple-input–multiple-output dielectric resonator antenna

In this communication, a novel compact high gain composite right/left-handed (CRLH) based leaky-wave antenna (LWA) is presented at Ku band. A half-mode substrate-integrated waveguide incorporated with a suitably oriented complementary quad spiral resonator (CQSR) is used to achieve a CRLH LWA. The unit cell is realised by a CQSR in such a way that the orientation of spirals exhibits higher leakage loss having a minimum cross coupling between them. The antenna is capable of scanning backward to forward along with a broadside direction in visible space. The proposed configuration has a length of 4.85
 λ
 0
 which can scan within the frequency range of 13.5-17.8 GHz having a beam scanning range of 86° (-66° to 20°) and a maximum gain of 16 dBi. The simulated reflection coefficient of the proposed antenna is below -10 dB throughout the working frequency range with a side-lobe level of below -10 dB. The designed prototype is more compact in nature having high gain, fair scanning range, and good cross-polarisation level along with simpler design methodology and tuning capability to enhance the gain as well as radiation efficiency maintaining a fixed size. The proposed antenna could be a promising candidate in Ku-band applications like fixed satellite services, and broadcast satellite services etc.

/pdf/composite-right-left-handed-based-compact-and-high-gain-2cpy9c2scu.pdf

Composite right/left-handed based compact and high gain leaky-wave antenna using complementary spiral resonator on HMSIW for Ku band applications

A-shaped wideband dielectric resonator antenna for wireless communication systems and its MIMO implementation

A novel single-feed circularly polarized microstrip antenna with compact size is proposed for indoor wireless local area network (WLAN) applications. The antenna structure consists of eight slits which are introduced at the boundary and the corners in the radiating square patch with a cross-slot at the center. The proposed antenna shows a compactness of 42% compared with the conventional circularly polarized antenna design at indoor WLAN frequency band. It is found that the resonance frequency of the proposed structure is highly depending on length and width of cross-slot and corner slit for entire band of circular polarization. The 3 dB axial ratio bandwidth of the proposed antenna is 1.9%. Proposed structure is fabricated on the FR-4 epoxy substrate and fed by a single coaxial probe. Measured results show a good agreement with the simulated results. Antenna shows stable radiation characteristics for the entire operating band. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1313–1317, 2014

Single‐feed cross‐slot loaded compact circularly polarized microstrip antenna for indoor WLAN applications

A novel polarization diverse substrate integrated waveguide (SIW)-based leaky-wave antenna (LWA) is proposed for larger radiation coverage by frequency beam scanning in X-band. For feeding purpose, the SIW-based power divider, the directional coupler, and the 180° power splitter are used in the design. For radiation, +45°/−45° tilted slots are etched on top and bottom faces of the structure such that the radiated quad beam scans all the four quadrants. By varying the means of excitation at two input ports, multiple polarization states are realized. The antenna shows ±45° dual polarization (+45° and −45° are co-existing), horizontal and vertical polarization, and two types of circular dual-polarization (left handed and right handed simultaneously). The proposed antenna is capable of scanning in each of the four quadrants simultaneously with the scanning range of 62° having the maximum gain of 12.6 dBi and an improved cross-polarization level better than −20 dB. The quad beam covers overall scanning range of 248° with different polarization states. The S-parameters, radiation patterns, gain, and axial ratio are calculated and demonstrated. The proposed LWA shows desirable advantages, such as simultaneous four-quadrant frequency beam scanning having polarization diversity capabilities, which leads to a flexible design for practical utilization.

Abhishek Sharma

Papers

Wideband multiple-input–multiple-output dielectric resonator antenna

Composite right/left-handed based compact and high gain leaky-wave antenna using complementary spiral resonator on HMSIW for Ku band applications

A-shaped wideband dielectric resonator antenna for wireless communication systems and its MIMO implementation

Single‐feed cross‐slot loaded compact circularly polarized microstrip antenna for indoor WLAN applications

SIW-Based Quad-Beam Leaky-Wave Antenna With Polarization Diversity for Four-Quadrant Scanning Applications