Planar Yagi-Uda Antenna Research Articles

In brief

PAGE 1633 InAsP/InP photonic crystal slab nanolasers with uniquely shaped alphabet letter-like near-field emission modes have been created in work from the US, Spain and France. The work demonstrates that photonic crystals have the capability to manipulate the propagation of light on the nanoscale in anomalous but controllable ways. PAGE 1630 Researchers in Japan report a technique for etching the overcladding layer of perfluorinated graded-index polymer optical fibre (PFGI-POF) using chloroform and water. This has allowed them to observe a clear Brillouin signal, important for developing Brillouin-based distributed strain/temperature sensors and flexible Brillouin devices including optical storage, phase conjugators and slow light generators. The slab nanolasers presented show photonic crystals’ capability to manipulate light propagation at nanoscale PAGE 1632 In research from China, monolithic integration of triple terahertz quantum cascade lasers into an array has yielded a peak power of 213 mW obtained at 10 K with a threshold current density of only 257 A/cm2. The highest operating temperature of the array laser is identical to that of the single ridge laser, indicating good heat dissipation design in the array. The etching technique for PFGI-POF has allowed observation of a clear Brillouin signal PAGE 1629 A novel p-n− -metal SiC photodiode structure with higher quantum efficiency in the deep UV spectrum than previously demonstrated by pin or n-Schottky diode SiC structures is presented in work from the US. The work is aimed at high sensitivity deep UV photodetectors for applications including chemical and biological identification, optical wireless communications, and UV sensing systems. Peak power of 213 mW was achieved with the monolithically integrated terahertz quantum cascade laser array PAGE 1593 Research from Ireland presents a gain enhanced planar Yagi-Uda antenna with pattern reconfiguration, implemented in a simpler way. The developed single element high-gain pattern reconfigurable antenna can be kept as a single element to enhance the performance of various already established basic array antenna models, and the technique can be used in various array configurations to enhance the gain and pattern reconfiguration together. Aimed at high sensitivity deep UV photodetectors the p-n− metal SiC photodiode structure has improved quantum efficiency The simpler implementation of a planer Yagi-Uda antenna is suitable for use in a variety of established array antenna models

Experimental Investigation of MIMO Performance Using Passive Repeater in Multipath Environment

A passive repeater (PR), comprising a four-element folded-patch antenna (FPA) array, a planar Yagi-Uda antenna, and a power combiner, was fabricated to experimentally investigate the multiple-input-multiple-output (MIMO) performance in multipath environment. It was found that the PR could realize polarization transition and broad-angle scattering. The received power and the MIMO channel capacity, which reflect MIMO performance, were discussed to demonstrate the effectiveness of the four-unit PR in improving the propagation channel in MIMO communications. It was found that the medians of the received power of Rx1 and Rx2 were improved by about 17 dB as compared to those without the PR. Also, when the received noise level was supposed to be -120 dBm/Hz, the median of the MIMO channel capacity with the PR was increased by 6.4 bps/Hz as compared to that without the PR.

High-Gain Yagi-Uda Antennas for Millimeter-Wave Switched-Beam Systems

A high-efficiency microstrip-fed Yagi-Uda antenna has been developed for millimeter-wave applications. The antenna is built on both sides of a Teflon substrate (epsiv <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.2) which results in an integrated balun for the feed dipole. A 7-element design results in a measured gain of 9-11 dB at 22-26 GHz with a cross-polarization level of < - 16 dB. The antenna is matched to 50 Omega (microstrip feed). A mutual coupling of < - 20 dB is measured between two Yagi-Uda antennas with a center-to center spacing of 8.75 mm (0.7 lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at 24 GHz), and a two-element array results in a measured gain of 11.5-13 dB at 22-25 GHz. The planar Yagi-Uda antenna results in high radiation efficiency ( > 90 % ) and is suitable for mm-wave radars and high data-rate communication systems.

Development of microwave imaging reflectometry in large helical device

Three key devices of the microwave imaging reflectometry (MIR) are under development in large helical device (LHD). The 2-D mixer array is developed by stacking the one-dimensional array of the planar Yagi-Uda antenna. The new type of the bandpass filter bank is modified to match the requirement of the MIR. The low-cost quadrature demodulator is also developed for the phase detection system. By using the low-price commercial wireless devices, the development cost becomes much lower than the expensive waveguide system. These devices enable the development of 2-D/3-D microwave imaging system for the plasma diagnostics and industrial applications.