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 (epsivr = 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 90 % ) and is suitable for mm-wave radars and high data-rate communication systems.

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

The system design of a cryogenic 2-13 GHz feed is considered with emphasis on its application in future wideband radio telescope systems. The feed is based on the so-called Eleven antenna and the design requires careful integration of various sub-designs in order to realize cryogenic operation. The various sub-designs include the electrical design of the Eleven antenna, design of the critical center puck, alternative solutions for integrating the Eleven antenna with low-noise amplifiers (LNAs), mechanical and cryogenic design and tests, and system noise temperature estimation and measurements. A great deal of simulated and measured results are presented throughout this paper, including the electrical, mechanical and cryogenic performance, and an assessment of the system noise temperature. The objective of this work is to present a good feed candidate that is well-suited for VLBI2010 and SKA radio telescopes. Further developments needed to completely fulfill the requirements for these future wideband radio telescopes are also discussed.

Cryogenic 2–13 GHz Eleven Feed for Reflector Antennas in Future Wideband Radio Telescopes

A compact planar printed quasi-Yagi antenna is presented. The proposed antenna consists of a microstrip line to slotline transition structure, a driver dipole and two parasitic strips. The driver dipole is connected to the slotline through coplanar stripline (CPS). The ground plane is modified by symmetrically adding two extended stubs to reduce the lateral size. Experimental and simulated results show that the proposed quasi-Yagi antenna has a wide bandwidth and good unidirectional radiation characteristics. Compared with conventional printed quasi-Yagi antennas, the width of the proposed quasi-Yagi antenna is reduced by approximately 16.7%. The proposed antenna presents an excellent end-fire radiation with a front-to-back ratio greater than 10 dB. Its measured bandwidth is from 3.6-11.6 GHz with a ratio of about 3.22: 1. A moderate gain, which is better than 4 dBi, is obtained.

Bandwidth Enhancement of a Planar Printed Quasi-Yagi Antenna With Size Reduction

In this work we demonstrate for the first time, to the best of our knowledge, a continuously tunable 360° microwave phase shifter spanning a microwave bandwidth of several tens of GHz (up to 40 GHz) by slow light effects. The proposed device exploits the phenomenon of coherent population oscillations, enhanced by optical filtering, in combination with a regeneration stage realized by four-wave mixing effects. This combination provides scalability: three hybrid stages are demonstrated but the technology allows an all-integrated device. The microwave operation frequency limitations of the suggested technique, dictated by the underlying physics, are also analyzed.

/pdf/wideband-360-degrees-microwave-photonic-phase-shifter-based-2np6f7vqmk.pdf

Wideband 360 degrees microwave photonic phase shifter based on slow light in semiconductor optical amplifiers.

A 1.4-GHz LC voltage-controlled oscillator has been implemented in a MOSIS 0.5-/spl mu/m CMOS process. Complementary cross-coupled PMOS and NMOS transistors enhance single-ended symmetry at each of the resonant nodes, reducing close-in phase noise. Tapped bond wires provide a resonant tank with high Q. At an offset frequency of 100 kHz, the measured phase noise is -10/sup 7/ dBc/Hz with 3 mW power dissipation from a 3.0 V supply. NMOS gate capacitors achieve a 17% tuning range.

A 1.4-GHz 3-mW CMOS LC low phase noise VCO using tapped bond wire inductances

A novel ultra-wideband microstrip-to-CPS (coplanar stripline) transition has been developed. The transition is designed to provide the field and impedance matching between adjacent transmission lines. The proposed design is applicable to substrates with any dielectric constant. The transition provides the balun role as well as the impedance transformation. The fabricated transition in back-to-back configuration provides the insertion loss less than 1 dB per transition and the return loss better than 10 dB for frequencies from 5.39 GHz to over 40 GHz. In addition, a simulation study indicates that this transition can possess a 3 dB bandwidth of ~ 100 GHz.

A New Ultra-wideband Microstrip-to-CPS Transition

A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B0 = 17∼35 T) This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE

/pdf/quasi-3d-ece-imaging-system-for-study-of-mhd-instabilities-37rpq7nnjo.pdf

Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR

In this study, a systematic and simplified design procedure for quasi-Yagi antennas is presented. The design is based on the simple field and impedance matching among antenna components. This new antenna design is possible due to the newly developed ultra-wideband balun. Two types of wideband quasi-Yagi antennas are successfully designed and implemented in Ku- and Ka-band with frequency bandwidths of 53.2% and 29.1%, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2068–2071, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23563

Design of quasi‐Yagi antennas using an ultra‐wideband balun

New dielectric-covered waveguide-to-microstrip transitions at Ka-band have been developed. These transitions are probe-type, but the dielectric material completely covers the waveguide opening in order to provide a moisture barrier and robustness. These transitions are also designed to be less sensitive to fabrication tolerances. The transition structures have been comprehensively analyzed using a 3-D EM software. The resonance phenomena caused by the waveguide-wall discontinuity have been removed by placing vias around the waveguide aperture. These transitions have also been fabricated and measured. The measured insertion loss of the transition is less than 0.4 dB and the return loss is about 15 dB over the entire Ka-band.

https://ieeexplore.ieee.org/iel5/8599/27270/01212564.pdf

New dielectric-covered waveguide-to-microstrip transitions for Ka-band transceivers

A new UWB antenna in bow-tie-type has been designed and implemented by utilizing the new ultra-wideband balun. In order to reduce antenna size, the balun is bended without sacrificing the balun performance. The fabricated antenna provides the operating frequency ranges from 3.2 to 11.2 GHz covering for the whole UWB frequency. The antenna maintains gains from 2.5 - 4.9 dBi for the operating frequencies with quasi- omni directional radiation patterns.

Dong-Sik Woo

Papers

A New Ultra-wideband Microstrip-to-CPS Transition

Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR

Design of quasi‐Yagi antennas using an ultra‐wideband balun

New dielectric-covered waveguide-to-microstrip transitions for Ka-band transceivers

Design of bow-tie-type UWB antennas using an ultra-wideband balun