Sungtek Kahng

Design of an Internal Multiresonant Monopole Antenna for GSM900/DCS1800/US-PCS/S-DMB Operation

A design is proposed of a multiresonant monopole antenna for a personal wireless communication handset. Multiresonant operation is achieved through the use of a bent tuning stub, a shorting strip line, a U-shaped slit and the addition of a narrow resonant slit to the main radiator. The first resonant frequency is determined by the main radiator of the proposed antenna, and the second resonant frequency is controlled by the length of the bent tuning stub. The third resonant frequency is generated by adding a narrow resonant slit to the perimeter of the main radiator. The three resonant frequencies of the designed antenna can be independently controlled by tuning the length of the individual elements of the proposed antenna. The measurement shows the intended four wireless communication services: global system for mobile communication (GSM900), digital communication system (DCS1800), US-personal communication system (US-PCS), and satellite-digital multimedia broadcasting (S-DMB). The proposed antenna is small enough to be built into a practical wireless mobile handset. The parameters determining the antennas multiresonant characteristics are analyzed, and experimental results of the constructed prototype are presented and discussed.

GA Optimized S-Band Quadrafilar Antenna with the Lowest Back Radiation for a Communication Satellite

In this paper, a quadrafilar antenna is designed to have a lower profile as an essential part of the size reduction technique and lower back radiation(i.e. higher forward radiation) for the S-band telemetry/telecommand(TM/TC) function of a communication satellite. Particularly, to meet the challenging requirements on the higher isolation between the TM/TC antennas and simultaneously a smaller size, the lowest back radiation and lowest cross-polarization, the optimal physical dimensions of the quadrafilar antenna are found by using the Genetic Algorithm(GA). To prove the validity of the proposed antenna design, its 3D electromagnetic analysis and measured results are compared, showing good agreement.

Study on Wave Absorption of 1D-/2D-Periodic EBG Structures and/or Metamaterial Layered Media as Frequency Selective Surfaces

This paper conducts a study on the frequency-dependent filtering and blocking effects of a variety of periodic structures, dubbed frequency selective surface(FSS). The periodic structures of interest are 1D and 2D repeated patterns of metal patches or slots sitting on the interface between the two different regions in the layered media which will show the capacitive or inductive behaviors and incorporated with the electromagnetic bandgap(EBG) geometry as another stratified media. Besides the normal substances so called double positive(DPS)-type in the layered media, metamaterials of double negative(DNG) are considered as layering components on the purpose of investigating the unusual electromagnetic phenomena. Frequency responses of transmission(absorption in terms of scattering) and reflection will be calculated by a numerical analysis which can be validated by the comparison with the open literature and demonstrated for the periodic structures embedding metamaterials or not. Most importantly, numerous examples of FSS will present the useful guidelines to have absorption or reflection properties in the frequency domain.

Design of CP Antenna with a Fenced Ground for a Handheld RFID Reader

A design of circular polarized(CP) microstrip antenna with a fenced ground is proposed and the equivalent circuit is derived. The antenna consists of a square radiating patch with a pair of truncated corners, a bottom ground and a fenced ground. From conducted experiments, a patch size reduction using the metal fence as large as 25 % from the conventional patch structure, has been obtained. The input admittance of the extracted equivalent circuit is shown to agree with that of the measurement. And the design parameters and performance of the proposed antenna are examined by analyzing the fields and circuit behaviors.

Dual-band Dipole Antenna for ISO 18000-6/ISO 18000-4 Passive RFID Tag Applications

In this paper, a slot coupled dipole antenna was presented for dual band passive RFID tag applications. Structures using a slot coupled feed and a resonator are explored to achieve dual band operation. It shows good impedance and radiation characteristics from 860 MHz to 960 MHz (ISO 18000-6) and from 2.40 GHz to 2.50 GHz (ISO 18000-4). The return loss is verified by comparing the calculations and measurements, which show good agreement. Radiation patterns are omni-directional for operation frequencies. Numerical results are calculated using Ansoft HFSS (High Frequency Structure Simulator)

GA-Optimized Compact Broadband CRLH Band-Pass Filter Using Stub-Inserted Interdigital Coupled Lines

The design of a new compact band-pass filter is proposed, which is based on the microstrip composite right- and left-handed transmission-line (CRLH-TL) structure. Particularly, the interdigital coupled (IDC) lines of the CRLH geometry are proposed to be parted by inserting open stubs to meet the specifications on the passband. In addition, there is another pair of stubs to complete the design in a limited space. These are considered in the TL-based analysis and the design parameters are calculated by genetic algorithm optimization. The measurement is shown to be acceptable and agreeable with the circuit and electromagnetic field simulations. In addition, the zerothorder resonance (ZOR) phenomenon is verified.

An efficient impedance matrix calculation using the spline-type divided-difference interpolation technique

In this work, a spline-type divided-difference interpolation scheme is proposed to evaluate the impedance matrix elements in the method of moments (MoM) efficiently. This method is combined with the fast computational method of the basis-expanded and tested Greens functions introduced in a recent literature. The proposed method is applied to analyze the characteristics of a microstrip gap discontinuity and an aperture coupled patch antenna. Numerical results obtained by using this approach are in good agreement with those of other approaches.

Compact Dual-Band Three-Way Metamaterial Power-Divider with a Hybrid CRLH Phase-Shift Line

A compact dual-band three-way metamaterial power divider is proposed that has three in-phase outputs. Fully printed composite rightand left-handed (CRLH) unequal and equal power dividers are first implemented for 900-MHz and 2.4-GHz bands with the power-division ratios of 2:1 and 1:1, respectively. An initial 1:1:1 power divider is then achieved by incorporating the input of the two-way equal block into an output of the unequal block, and trimming the interconnection parameters. The condition of an identical phase at the three outputs of the power divider is then met by devising a hybrid CRLH phase-shift line to compensate for the different phase errors at the two frequencies. This scheme is confirmed by predicting the performance of the power divider with circuit analysis and full-wave simulation and measuring the fabricated prototype. They results show agreement; the in-phase outputs as well as the desirable power-division are accomplished and outdo the conventional techniques.

Prediction of the Radiated Emission(RE)s due to the PCB Power-Bus` Resonance Modes and Mitigation of the RE Levels

PCB Power-Bus (comprising power/ground planes) impedance and fields are evaluated by an efficient series expansion method that is suggested in this paper. It is used to investigate the structures radiated emission(RE) levels and find acceptable ways of loading the power/ground planes such as decoupling capcitor(DeCap)s, balanced feeding and slits, in order to reduce the interferences. Also, the calculations and measurements of a proposed geometry are verified by vector fitting as a analysis model to check the behavior of the slit.

The Design of a Dielectric Rod Antenna Using Genetic Algorithm Optimization for Vessel's Collision Avoidance Applications

In this paper, we present the development of an antenna specialized for the maritime collision avoidance system. This antenna is configured as the dielectric rod partially embedded in the metal cavity to reduce the overall size, simultaneously assuring the mechanical sturdiness against the challenging oceanic weather conditions. More importantly, the design has been carefully done to meet the requirements on the radiation pattern(with the slope＜5 dB/deg in the elevation(E-plane), circular in the azimuth) suitable to receiving the reflected signals from the other objects on the sea. To find the optimal design parameters, the genetic algorithm has been used to meet the goals of the desired return loss and pattern. This design methodology is validated by the good agreement between the calculation and measurement.