Yongjin Kim

CPW-fed planar ultra-wideband antenna with hexagonal radiating elements

Planar UWB antennas with hexagonal radiating elements are presented and their bandwidth characteristics with respect to geometrical parameters have been investigated. Optimized parameters for small size provide an antenna measuring 22 mm /spl times/ 31.3 mm, which may be the smallest planar antenna reported while satisfying VSWR < 2 for 3.1-10.6 GHz. Measurement results have been presented for the gain and the group delay in the boresight direction as a function of frequency.

Suppression of Cable Leakage Current for Edge-Fed Printed Dipole UWB Antennas Using Leakage-Blocking Slots

A simple method is presented for suppressing cable leakage current for printed dipole ultrawideband (UWB) antennas using thin leakage-blocking slots. Their effects on VSWR and pattern characteristics are demonstrated by comparing the performances of two identical coplanar waveguide (CPW)-fed printed dipoles except for the presence of the slots. Two thin slots along the feeding CPW trace effectively block a strong leakage current component from flowing over the outer surface of the feeding coaxial cable. While not significantly affecting the antennas VSWR performance over wide bandwidth, the slots have the effects of increasing the antenna gain in the azimuth plane and reducing the strengths of strong radiation lobes close to the direction of cable attachment especially in the low-frequency range.

Planar ultra wide band slot antenna with frequency band notch function

The development of ultra wide band (UWB) antennas for high resolution and high data transmission rates in modern communication systems is growing rapidly due to the difficult requirements of UWB antennas such as small size, non-dispersive and ultra wide-band characteristics. This paper describes a planar UWB slot antenna having frequency band notch characteristics. By inserting a V-shaped thin slot on the planar antenna, a narrow frequency band notch function has been created. Also, the notched frequency band can be varied by adjusting the length of the slot. Antenna performance including VSWR and azimuthal gain pattern of the new antenna are presented.

A wideband vertical transition between co-planar waveguide and parallel-strip transmission line

A wideband vertical transition between co-planar waveguide (CPW) and parallel strip transmission line is presented. It functions as an unbalanced-to-balanced (balun) transformer as well. The transition is realized in back-to-back configurations for 50 /spl Omega/ and 75 /spl Omega/ characteristic impedance cases to verify their transition performances. The CPW-parallel strip-CPW transitions are found to have distinct resonant frequencies where the length of the parallel strips is equal to multiples of half wavelength, which is not characteristic of a single transition, but a result of two CPW-parallel strip transitions interacting with each other. Away from the resonant frequencies, the back-to-back configurations have low insertion loss over wide frequency band.

Small Printed Combined Electric-Magnetic Type Ultrawideband Antenna With Directive Radiation Characteristics

A small printed antenna structure is presented featuring directive radiation patterns over ultrawide frequency band without relying on large antenna dimensions. The antenna comprises virtually two antennas-one electric-type antenna and one magnetic-type antenna-excited simultaneously in close proximity via one feed point. This combination of radiated fields from different types of sources result in directive radiation patterns without increasing antenna sizes as typically observed in antennas using only one type of sources. Two printed prototypes of the combined antenna are fabricated and their measured VSWR and radiation gain pattern characteristics are discussed.

A small ceramic chip antenna for ultra-wideband systems

A ceramic chip antenna suitable for UWB communication applications using the 3.1-10.6 GHz frequency band is presented. The antenna uses the dipole configuration with a ceramic radiating element and a square ground plane. The ceramic element measures 10/spl times/5/spl times/1 mm, which is the smallest size reported for UWB applications. The size of the required ground plane is 30/spl times/30 mm. The antenna satisfies VSWR <2.3 for the entire UWB frequency band.

Small Low-Profile Loop Wideband Antennas With Unidirectional Radiation Characteristics

Small low-profile wideband loop antennas featuring unidirectional radiation characteristics are presented. Directive radiation characteristic is achieved by proper combination of fields radiated by symmetric and anti-symmetric current components supported by any loop antenna. Relative strengths of the symmetric and the anti-symmetric radiations change according to shape of the loop. Prototype loop antennas are fabricated and their impedance and radiation gain patterns are measured. The gain patterns show directive characteristics in both major planes. It is shown that the gain measured in the desired direction of maximum radiation exceeds the maximum achievable practical gain for omnidirectional antennas of the same dimensions over wide frequency band

Compact low cost antenna for passive RFID transponder

This work discloses a new compact planar antenna for low cost RFID passive transponders. The proposed antenna takes advantage of its unique topology in order to assure conjugate matching with essentially complex impedance of the electronic chip directly embedded into radiator. Good performance is predicted theoretically and confirmed experimentally over an operating bandwidth of actual RFID system

A wide band metamaterial ZOR antenna of a patch coupled to a ring mushroom

We present a new low-profile composite right- and left-handed metamaterial zeroth order resonance (ZOR) antenna of the simulated and measured fractional bandwidth 30 and 57%, respectively, for a center frequency 2.5 GHz and gain over 3 dBi, while other ZOR antennas have narrow bandwidths much less than 10% with low antenna gain below or around 0 dBi. The proposed antenna shows the monopolar radiation pattern over the entire band. The design approach is verified by the circuit and 3D EM simulations, and measurement.

Pattern-Reconfigurable MIMO Antenna for High Isolation and Low Correlation

In this letter, a reconfigurable radiation pattern antenna for multiple-input-multiple-output (MIMO) applications on mobile devices is proposed. The operating frequency band of the antenna is 5.15-5.35 GHz for a wireless local area network (WLAN) 802.11a service. Each antenna is composed of a loop-and-dipole structure, as well as two switches for the reconfigurable radiation pattern, to generate a beam in three different directions. The proposed antenna is designed to have an orthogonally directional radiation pattern with high isolation and a low-correlation coefficient in the MIMO environment.