Hyung Kuk Yoon

UWB wide slot antenna with band-notch function

A novel UWB wide slot antenna that has both enhanced impedance bandwidth enough to cover UWB systems and band-notch function of 5 GHz WLAN band limited by IEEE 802.11a and HIPERLAN/2 is proposed. To achieve these two characteristics of wide bandwidth and partial band-notch, a fork-shaped and tapered microstrip feed line and conductor lines in the slot are used, respectively. From the results, it is observed that wide bandwidth from 3.1 to 10.6 GHz for the VSWR<2 is achieved, while 5.15 ~ 5.825 GHz is band-notched

A Flexible Monopole Antenna with Band-notch Function for UWB Systems

A flexible monopole antenna for UWB systems is proposed. The proposed antenna has good performance over the entire UWB bandwidth, and it enhanced the impedance bandwidth by using the stepped CPW feed line. It can be easily mounted on conformal shape, because it is fabricated on PET film having the flexible characteristic. It has a band-notch function of 5 GHz WLAN band using two slits. From the results, it is observed that the proposed antenna has the similar radiation patterns and the return loss in comparison with the planar type monopole antenna, when it is rolled.

A CPW-fed flexible monopole antenna for UWB systems

A CPW-fed flexible monopole antenna on PET film for UWB systems is proposed. The proposed antenna has good performance over the entire UWB bandwidth, and it enhanced the impedance bandwidth by using the stepped CPW feed line. It can be easily mounted on conformal shape, because it is fabricated on PET film having the flexible characteristic. From the results, it is observed that the proposed antenna has the similar radiation patterns and the return loss in comparison with the planar type monopole antenna, when it is rolled.

Harmonic tuning antennas using slots and short-pins

Recently active integrated antennas have been studied for more efficiency and harmonic reduction. The designed antenna provides a good radiation pattern on resonant frequency, and reduces EMI by suppression of second and third harmonics. Also it increases PAE on the power amplifier integrated antenna by operating as shorting load on harmonics.

A CPW-fed polarization diversity antenna for UWB systems

A CPW-fed polarization diversity monopole antenna on flexible PET film for UWB systems is proposed. The antenna consists of two heptagonal monopoles orthogonally and symmetrically printed on the two sides of the extended Vshape ground plane. It covers the entire UWB bandwidth from 3.1 GHz to 10.6 GHz and shows a good port isolation under -20 dB over the entire UWB bandwidth. Also, it has a band-notch function of 5 GHz WLAN band. It can be easily mounted on conformal shape, because it is fabricated on PET film having the flexible characteristic. From the results, it is observed that the proposed antenna can provide the polarization diversity for UWB communications.

Hairpin-line/half-wave parallel-coupled-line narrowband bandpass filters using high temperature superconducting thin films

In this paper, hairpin-line and hybrid hairpin-line/half-wave parallel-coupled-line filters using High-Temperature Superconducting (HTS) thin films are proposed. The proposed structures provide more compact size than conventional parallel-coupled-line filters and hybrid hairpin-line filters reduce the spurious modes due to the surface waves in the hairpin-line filters. The designed filters using HTS have low loss, small size and narrow bandwidth characteristics with the minimum number of poles in comparison with the normal metal microstrip line filters. The 3 pole filters centered at 14.25 GHz with the bandwidth of less than 1% were designed and fabricated. These operating characteristics are simulated and fabricated using HTS and compared with the normal metal microstrip line filters.

A Flexible UWB Antenna Attachable to Various Kinds of Materials

A flexible monopole antenna fabricated on PET film for UWB systems is proposed and the effects of the various kinds of the attached materials is analyzed. The proposed antenna has good performance over the entire UWB bandwidth, and it can be mounted on various kinds of conformal materials meeting the UWB bandwidth by using the stepped CPW feed line and the beveled ground plane. From the results, it is observed that the proposed antenna has the similar radiation patterns and the return loss in comparison with the planar type monopole antenna, when it is rolled.

Fabrication and characterization of a superconducting multiplexer using laser ablated YBCO thin films

Abstract Multiplexers have been fabricated using high-temperature superconductors (HTS). Superconducting YBa 2 Cu 3 O 7− x films were deposited on MgO, a substrate by using pulsed laser deposition (PLD). A conventional photolithographic method was used to produce the superconducting multiplexer pattern. Epitaxial YBCO films with c -axis orientation were grown on MgO (100) substrates. Superconducting transition temperatures were measured at 89 K. Simulated results of the superconducting multiplexer consisting of hairpin type filters show an insertion loss of 1.2 dB. The measured frequency response of superconducting multiplexer was compared with the simulation results.

A compact polarization diversity antenna for UWB systems

Compact polarization diversity antenna fabricated on different substrates for UWB systems is proposed. To obtain the wide bandwidth, the tapered CPW line is used and extended ground plane of the slot antenna makes the proposed antenna size smaller. The different substrates with different dielectric constants are also effective in enhancing the isolation between the feed ports of the two antennas. Consequently, the proposed antenna meets the frequency band 7.2-9.2 GHz and shows the good isolation performance (S21les20 dB) and the stable radiation patterns over the upper UWB bandwidth. With the compact dimension characteristic, the proposed antenna can be used in the small types of UWB device used in indoor data transmission.

Superconducting bandpass filter using parallel microstrip line with narrow bandwidth centered at 14 GHz

We have designed and developed narrow bandpass filters using parallel superconducting microstrip line for satellite communication. High quality superconducting YBa2Cu3O7−x (YBCO) thin films have been grown on MgO substrates by pulsed laser deposition (PLD). The deposited YBCO films were patterned by conventional wet-etching process. The transition temperatures of these films were 86–89 K. The measured film thicknesses were about 500 nm. Three-pole and four-pole filters centered at 14 GHz with a bandwidth of 300 MHz were designed and fabricated.