Jong-Won Yu

Wideband planar monopole antennas with dual band-notched characteristics

Wideband planar monopole antennas with dual band-notched characteristics are presented. The proposed antenna consists of a wideband planar monopole antenna and the multiple cup-, cap-, and inverted L-shaped slots, producing band-notched characteristics. In order to generate dual band-notched characteristic, we propose nine types of planar monopole antennas, which have two or three cap (cup or inverted L)-shaped slots in the radiator. This technique is suitable for creating ultra-wideband antenna with narrow frequency notches or for creating multiband antennas

Multiple band-notched planar monopole antenna for multiband wireless systems

A multiple band-notched planar monopole antenna for multiband wireless systems is presented. The proposed antenna consists of a wideband planar monopole antenna and the multiple U-shape slots, producing band-notched characteristics. In order to generate two band-notched characteristics, we propose that three U-shape slots are required. This technique is suitable for creating ultra-wideband (UWB) antenna with narrow frequency notches or for creating multiband antennas.

Contactless Energy Transfer Systems Using Antiparallel Resonant Loops

Due to the convenience of using electronic devices, contactless energy transfer (CET) systems have garnered interest in various fields of industry. In this paper, a new design approach that uses antiparallel resonant loops for CET systems is presented. Forward and reverse loops forming an antiparallel resonant structure stabilize the transfer efficiency and therefore prevent it from dramatic distance-related changes, a phenomenon that can occur in CET systems with nonradiative methods (or resonant methods). This paper proposes frequency-insensitive antiparallel resonant loops and the optimal design of these loops for uniform transfer efficiency according to the distance. The proposed technique achieves frequency variation that is one-sixth that of conventional unidirectional loops, thus improving the power efficiency to a maximum of 87%. The improved performance of data transmissions for near-field communication is also verified.

Design of Low-Cost Chipless System Using Printable Chipless Tag With Electromagnetic Code

In this letter, a printable chipless tag with electromagnetic code using split ring resonators is proposed. A 4 b chipless tag that can be applied to paper/plastic-based items such as ID cards, tickets, banknotes and security documents is designed. The chipless tag generates distinct electromagnetic characteristics by various combinations of a split ring resonator. Furthermore, a reader system is proposed to digitize electromagnetic characteristics and convert chipless tag to electromagnetic code.

A Passive Circulator with High Isolation using a Directional Coupler for RFID

In radio-frequency identification (RFID) system, a directional coupler has been used to isolate RX from TX due to its simplicity and low cost compared with a circulator. Nevertheless, a conventional microstrip directional coupler has inherent drawback of poor isolation due to unequal phase velocity between even and odd mode. In this paper, a newly proposed circulator using a microstrip directional coupler is proposed to achieve good isolation between TX and RX. The proposed circulator is used for UHF band RFID reader with a single antenna, of which the operating frequency band is 860 MHz-960 MHz. The measurement of the fabricated circulator using a modified directional coupler exhibits excellent isolation of 64 dB and directivity of 49 dB in its frequency band. The validity of the proposed circulator is demonstrated by comparing the TX leakage at the RX port of RFID reader system with that of a conventional directional coupler

High Isolation Internal Dual-Band Planar Inverted-F Antenna Diversity System with Band-Notched Slots for MIMO Terminals

Internal dual-band planar inverted-F antenna (PIFA) diversity system for portable devices, operating in the 2.4-GHz band (2400-2484MHz) and 5.2-GHz band (5150-5350MHz), is presented. To reduce the mutual coupling and get the high isolation between the two internal dual-band antennas, we proposed the band-notched lambda/4 slots on the ground plane. The optimized band-notched slots for high isolation, high radiation efficiency and high effective diversity gain are analyzed. The band-notched slots can be used to the small MIMO terminals which require high isolation between antennas

RFID Reader Front-End Having Robust Tx Leakage Canceller for Load Variation

A novel front-end structure for ultra-high-frequency RF identification reader is proposed. The proposed front-end consists of a balanced coupler and four-port feed antenna system. The proposed balanced coupler structure has high transmit/receiver isolation feature and good insensitivity to load variations. The proposed four-port feed antenna system is applied for removing the coupling among antennas, which deteriorates the isolation. The proposed system is numerically analyzed and verified experimentally as well.

Compact Six-Port Transceiver for Time-Division Duplex Systems

A compact six-port transceiver for time-division duplex systems is proposed. The proposed transceiver only uses a single six-port junction for the Tx and Rx mode. Also, we propose the new radio frequency (RF) and baseband interface component, which consists of switch, reflection coefficient generator, and the power detector. The prototype circuits are fabricated to validate the new transceiver with 15-Mbps quadrature phase shift keying (QPSK) digital modulator and 10-Mbps QPSK demodulator at the carrier frequency of 2.4GHz. The proposed six-port transceiver can provide a simple, low-cost, low-power, and reconfigurable RF design platform

A 60 GHz Wideband Phased-Array LNA With Short-Stub Passive Vector Generator

This letter presents 60 GHz 5 b phased-array low noise amplifier (LNA) implemented in 90 nm CMOS for a short range wireless application. The design consists of common source two-stage LNA, short-stub vector generator, I/Q modulator with 5 b digital to analog converter and differential to single amplifier. All the proposed amplifiers are designed using a transformer coupled method which results in wideband operation to meet the frequency requirement of the standard. The proposed circuit provides 360 phase controllability over 50-70 GHz band while achieving 12.5 dB gain, 6.55 dB NF and consuming 50 mA from 1.2 V. The measured rms phase error is in the phase accuracy limitation (differential phase array) and gain variation is quite low (<; 0.92 dB) over 5 b control range.

Tunable Band-notched Ultra Wideband (UWB) Planar Monopole Antennas Using Varactor

A new tunable band-notched ultra wideband (UWB) planar monopole antenna is presented. The proposed antenna consists of a wideband planar monopole antenna, resonating stubs and varactor diodes. In order to generate tunable band-notched characteristic, we applied quarter-wavelength stubs with varactor diode to the wideband planar monopole antenna. We interpret the mechanism for notch characteristics using surface current distributions. This new approach is suitable for designing wideband antenna with narrow band interferer rejection characteristics.