Changsoo Eun

Compact Multiband Microstrip Antenna Using Inverted-L- and T-Shaped Parasitic Elements

By placing inverted-L- and T-shaped parasitic elements at both the radiating apertures of a microstrip patch antenna, a low-profile, compact single-layer multiband microstrip antenna operable in various bands has been developed. These bands include LTE TDD No. 34 (2.0175 GHz), WLAN (2.45 GHz), and WiMAX (3.5 GHz) bands. The antenna has dimensions of 0.26 λ_L ×0.25 λ_L ×0.03 λ_L, where λ_L is the free-space wavelength at 2.0175 GHz, and resonance in the parasitic elements occurs through coupling and perturbations to the microstrip patch. In each band, the measured -10-dB bandwidths cover the required bandwidths at 28 MHz (1.39%), 91 MHz (3.71%), and 255 MHz (7.29%). Within each of the designed bands, a broadside radiation pattern is observed.

Analysis on the shielding effect by metallic pipe line against electromagnetic induced voltage

The induced voltages are measured to verify whether there is a shielding effect by a metal pipeline like a gas or water provision against electromagnetic induction emitted from power line onto communication line. We installed the first pipeline, 300m, with a telecommunication cable and measured induced voltages. And then we installed again the second pipeline and measured the voltages. There was a around 20% shielding effect by the first pipeline and 30% shielding effect by the second pipeline together against the usual induced voltage, 3V in this experiment case, on the communication cable. We see that there would be a shielding effect by pipeline against electromagnetic induction from this result and could apply into the effectiveness of protection measures.

Digital feedforward compensation scheme for the non-linear power amplifier with memory

In wideband communication systems, memory effect manifests itself as inter-symbol interference, which combined with the non-linearity, complicates the non-linear compensation. We propose a digital feedforward linearisation method to compensate for the non-linearity of a power amplifier (PA) with memory. The PA is modelled with a Wiener model, which is a linear time-invariant system followed by a memoryless non-linear system. The advantage of the proposed scheme is that the compensation is implemented in baseband by using a digital signal processing technique. Simulation results are given to verify the validity of the proposed scheme.

Characteristics of the Voltages between the Communication Lines and Ground Induced by the Adjacent Artificial High-Voltage or Current ELF Source

The measurements were performed to verify experimentally that the voltage arising on a telecommunication line by a power line is due to the induction phenomena because there has been an opinion that the arising voltage on a telecommunication line is not by induction, but by other causality. The voltage appeared on the telecommunication line by way of an electric field or magnetic field generated by the source apparatus that had been artificially made to provide intentional constant high-voltage or current in ELF, that is, 60 ㎐ as an emulated commercial power.

The effect of HPA non-linearity on the repeater signal with feedback and combined compensation

Cancellation of echoes in mobile communication systems using repeaters and satellites is an on-going research issue. We show that the echoes in the repeaters can be eliminated if the non-linearity of HPA (High Power Amplifier) at the re-transmitter is compensated. We propose an echo cancellation using the indirect learning architecture (ILA) along with the pre-distorter for the HPA. We verify the performance of the proposed echo cancellation through computer simulation.

The local minima convergence state detector for QPSK equalizer

A LMS (least mean square) algorithm for the channel estimation is possible to converge on a local minimum point. In this paper, we proposed a local minimum point convergence state (LMPC) detector using a distribution property of the phase difference of the LMPC state. We present the missing and false alarm probability of the detector through computer simulation and prove that it is efficient to detect the LMPC state through hardware implementation.

Experimental Verification of Induction Phenomenon on Telecommunication Lines by Applying Its Occurrence Mechanisms Using an Artificial ELF Source Generator

In this paper, an electromagnetic induction on a telecommunication line by the distribution line of a power provision system or a feeder line of an electrified railway system has been verified through experiments. The basic cause of induction occurrence by these practical power provision systems is the returning current through the earth. This principle has been confirmed by the experiments documented in this paper which implemented these mechanisms to incur an induction. Experimental methods were used to produce the returning current through the earth. The experiment to find a relationship between inducing strength and the distance between the two phase lines in a power provision line has also been included to confirm that, when the distance is enlarged, the induction effect increases as the crossnullification effect of magnetic fluxes decreases. An experiment for the existence of a shielding effect by another conduction length material has been addedas a protection measure against the induction.

Adaptive Time Division/Frequency Hopping Multiple Access for Decentralized Mobile Ad-hoc Networks

We propose a new MAC protocol for small-scale mobile ad hoc networks that autonomously constructs a network without any fixed infrastructure or a centralized administration, and minimizes collisions between nodes under a dynamic network topologies. The proposed protocol consists of an adaptive TDMA (time division multiple access) and an FHMA (frequency hopping multiple access) method. The simulation result shows a better performance even than the general FHMA, not to mention the conventional CSMA or ALOHA