Jin-Seong Lee

Design of a UHF RFID fiber tag antenna with electric-thread using a sewing machine

An RFID tag antenna with electric-thread using a sewing machine is proposed. The characteristics of the electric-thread used as tag antenna are studied and the changes of conductivity for different sewing methods are analyzed. The electro-thread tag antenna is designed by the shape of alphabet characters. The radiation efficiency is about 33% and the measured maximum reading range is about 2.5m in an anechoic chamber. It is demonstrated that the electro-thread is possible to be directly applied to clothes as a brand or company marks. However, it is necessary to develop some additional technology for packaging to protect a tag chip from laundry and wrinkle.

Design of a UHF RFID metal tag for long reading range using a cavity structure

A novel UHF RFID metal tag antenna using a cavity structure for long reading range is proposed. The size of the proposed tag is 176.0 x 61.0 x 31.0 (mm3) and it can be applied for large metal materials and heavy equipments. The measured reading range is about 1 lm in free space and 15 m when attached to a metal plate. The reading range of the tag at attached to a metal is 4m better than that of the tag in free space.

Designing ground plane to reduce hand effects on mobile handsets

The modification of the ground plane is studied to mitigate users hand effect of a mobile handset. GSM/DCS band internal antenna is designed on three types of ground plane. Variation of the resonant frequency and radiation efficiency for each case is analyzed by using a hand phantom. From the measured results, the proposed structure of the ground plane in this work can reduce the hand effect compared with the conventional ground plane.

The design of power amplifier for 5.8 GHz wireless LAN application using GaAs substrate

This paper describes a compact two-stage hybrid power amplifier for 5.8 GHz-band Wireless Local Area Network (WLAN) applications. The amplifier has been fabricated on high dielectric semiconductor wafer, and then the amplifier has small dimension compared with the conventional hybrid circuits. To fabricate the amplifier, the mask pattern is produced using electron beam lithography. Then the FET, capacitors and resistors are combined with the microstrip line pattern by silver epoxy. The size of the two-stage amplifier is measured to be 2.1 cm/spl times/1.4 cm.

A novel Ka-band bandpass filter using LIGA micromachined process

A novel class of three dimensional (3-D) micromachined microwave planar filter at Ka-band is presented using LIGA process. The filter shows wide bandpass characteristic of 39% with the insertion loss of 1.7 dB at 33.2 GHz, and can be applicable in high power MMIC or MIMIC.

Folded planar monopole internal antenna for multi-band mobile phones

A new folded planar monopole antenna is proposed for multiband operations. Measured impedance bandwidth (VSWR<3) is 20% (820~1000MHz) and 119.8% (1570~6270MHz) in low and high frequency, respectively. The proposed antenna can effectively cover most mobile communication bands (CDMA, GSM, GPS, DCS, PCS, and UMTS), WiBro, S-DMB and WLAN.

Triple band internal antenna using matching circuits

In this paper, a triple-band internal antenna for mobile handsets is present. Dual band operation is generated by using a band reject filter as a matching circuit and without any transformations on its radiator. Moreover, the antenna gives a wide impedance bandwidth in high band by using an additional chip capacitor so that the antenna can operate in triple-band with only one radiator. Details of the proposed antenna are presented.

A FG-CPW single balanced diode mixer

In this paper, an FG-CPW (Finite-Ground Coplanar Waveguide) balanced diode mixer is presented. Frequency bandwidth is selected for a C-band, which is 5.72/spl sim/5.82 GHz for RF, 5.58/spl sim/5.68 GHz for LO, and 140 MHz for IF signals. A rat-race hybrid is designed for the accomplishment of single balanced type mixers. A low pass filter (LPF) with CPW structure is used for good conversion loss and unwanted harmonics suppression. When an LO signal with the power of 4 dBm at 5.635 GHz is injected, a conversion loss of 6.2 dB is obtained for the mixer. Also, LO to RF and LO to IF isolation of 30 dB and 40 dB are obtained, respectively. This mixer can be used in wireless LAN applications.

Equivalent circuit model and its application for slit discontinuity in CPW structure

In this paper, transverse slit in coplanar waveguide (CPW) transmission line is modeled as series inductance and parallel capacitance and the simple formulas for the capacitance and the inductance are induced. Also, a broad-band harmonic suppression filter (12.5/spl sim/50 GHz) and a band rejection filter using this structure are designed, fabricated, and characterized for their microwave performance.

Miniaturized microstrip antenna for a repeater system in a mobile communication cellular band

A simple technique to reduce the overall dimension of a microstrip antenna with a partially filled dielectric substrate is proposed. The miniaturized microstrip antenna for a repeater system in a mobile communication cellular band (824 MHz-894MHz) is designed with the proposed technique, and commercialized with low cost, light weight, and small size. The proposed method will be more attractive for a light-weight, small-size, and low-cost microstrip array.