The implementation of TS MAC (transmitter station monitor, alarmand control) system for digital DBS system

The implementation of TS MAC system for KOREASAT DBS (direct broadcast satellite) system is presented. This TS MAC controls and monitors the status of the TS equipment and gathers the alarm for them. The advantage of this system is the center-concentrated, real time processing, remote control, and object oriented module decomposing     

Computation of the average power pattern of a reflector antennawith random surface errors and misalignment errors

To specify manufacturing tolerances of a reflector antenna, various errors such as random surface errors and misalignment errors must be considered at one time because superposition of the effects of those errors may not hold. Based on the Rahmat-Samii's formulation (1983), a method for computing efficiently the average power pattern of a reflector antenna with those errors is presented. Simulation results show that superposition of the effects of errors does not generally hold and demonstrate how those errors degrade the peak-gain and sidelobe levels     

A 500-Mb/s quadruple data rate SDRAM interface using a skewcancellation technique

A quadruple data rate (QDR) synchronous DRAM (SDRAM) interface processing data at 500 Mb/s/pin with a 125-MHz external clock signal is presented. Since the QDR interface has a narrower data timing window, a precise skew control on data signals is required. A salient skew cancellation technique with a shared skew estimator is proposed. The skew cancellation circuit not only reduces the data signal skews on a printed circuit board down to 250 ps, but also aligns the data signals with an external clock signal. The entire interface, fabricated in a 0.35-μm CMOS technology, includes a high-speed data pattern generator and consumes 570 mW of power at 3.0-V supply. The active die area of the chip with the on-chip data pattern generator is 2.4 mm²     

Channel width effect for organic thin film transistors using TIPS-pentacene employed as a dopant of poly-triarylamine

The effects of the physical channel width on the characteristics of organic thin film transistors (OTFTs), made with 6,13-bis(triisopropyl-silylethynyl)-pentacene (TIPS-pentacene) embedded into poly-triarylamine (PTAA, hole conductor within an active channel), have been examined in this paper. The devices are estimated by measuring the drain-source current (I_DS) for different contact metals such as Au and Ag, at fixed gate and drain voltages. The results show that the threshold voltage (V_T) and I_DS increase with increasing channel width. Furthermore, it has been observed that the field effect mobility is dependent on V_T, which is influenced by the channel width. The OTFTs, produced using Au and Ag contacts, exhibited the highest values of mobility in the saturation regime, namely 5.44 × 10^?2 and 1.33 × 10^?2 cm²/Vs, respectively.     

Control of Crystal Growth toward Scalable Fabrication of Perovskite Solar Cells

With the impressive record power conversion efficiency (PCE) of perovskite solar cells exceeding 23%, research focus now shifts onto issues closely related to commercialization. One of the critical hurdles is to minimize the cell‐to‐module PCE loss while the device is being developed on a large scale. Since a solution‐based spin‐coating process is limited to scalability, establishment of a scalable deposition process of perovskite layers is a prerequisite for large‐area perovskite solar modules. Herein, this paper reports on the recent progress of large‐area perovskite solar cells. A deeper understanding of the crystallization of perovskite films is indeed essential for large‐area perovskite film formation. Various large‐area coating methods are proposed including blade, slot‐die, evaporation, and post‐treatment, where blade‐coating and gas post‐treatment have so far demonstrated better PCEs for an area larger than 10 cm². However, PCE loss rate is estimated to be 1.4 × 10^?2% cm^?2, which is 82 and 3.5 times higher than crystalline Si (1.7 × 10^?4% cm^?2) and thin film technologies (≈4 × 10^?3% cm^?2) respectively. Therefore, minimizing PCE loss upon scaling‐up is expected to lead to PCE over 20% in case of cell efficiency of >23%.     

High Areal Capacitance of N‐Doped Graphene Synthesized by Arc Discharge

The lack of cost effective, industrial‐scale production methods hinders the widespread applications of graphene materials. In spite of its applicability in the mass production of graphene flakes, arc discharge has not received considerable attention because of its inability to control the synthesis and heteroatom doping. In this study, a facile approach is proposed for improving doping efficiency in N‐doped graphene synthesis through arc discharge by utilizing anodic carbon fillers. Compared to the N‐doped graphene (1–1.5% N) synthesized via the arc process according to previous literature, the resulting graphene flakes show a remarkably increased doping level (≈3.5% N) with noticeable graphitic N enrichment, which is rarely achieved by the conventional process, while simultaneously retaining high turbostratic crystallinity. The electrolyte ion storage of synthesized materials is examined in which synthesized N‐doped graphene material exhibits a remarkable area normalized capacitance of 63 µF cm^?2. The surprisingly high areal capacitance, which is superior to that of most carbon materials, is attributed to the synergistic effect of extrinsic pseudocapacitance, high crystallinity, and abundance of exposed graphene edges. These results highlight the great potentials of N‐doped graphene flakes produced by arc discharge in graphene‐based supercapacitors, along with well‐studied active exfoliated graphene and reduced graphene oxide.     

End‐to‐end security‐reliability analysis of multi‐hop cognitive relaying protocol with TAS/SC‐based primary communication,total interference constraint and asymmetric fading channels

In this paper, we analyze the tradeoff between outage probability (OP) and intercept probability (IP) for a multi‐hop relaying scheme in cognitive radio (CR) networks. In the proposed protocol, a multi‐antenna primary transmitter (PT) communicates with a multi‐antenna primary receiver (PR), using transmit antenna selection (TAS) / selection combining (SC) technique, while a secondary source attempts to transmit its data to a secondary destination via a multi‐hop approach in presence of a secondary eavesdropper. The secondary transmitters such as source and relays have to adjust their transmit power to satisfy total interference constraint given by PR. We consider an asymmetric fading channel model, where the secondary channels are Rician fading, while the remaining ones experience the Rayleigh fading. Moreover, an optimal interference allocation method is proposed to minimize OP of the primary network. For the secondary network, we derive exact expressions of end‐to‐end OP and IP which are verified by Monte Carlo simulations.     

λ/64‐spaced compact ESPAR antenna via analog RF switches for a single RF chain MIMO system

In this study, an electronically steerable parasitic array radiator (ESPAR) antenna via analog radio frequency (RF) switches for a single RF chain MIMO system is presented. The proposed antenna elements are spaced at λ/64, and the antenna size is miniaturized via a dielectric radome. The optimum reactance load value is calculated via the beamforming load search algorithm. A switch simplifies the design and implementation of the reactance loads and does not require additional complex antenna matching circuits. The measured impedance bandwidth of the proposed ESPAR antenna is 1,500 MHz (1.75 GHz–3.25 GHz). The proposed antenna exhibits a beam pattern that is reconfigurable at 2.48 GHz due to changes in the reactance value, and the measured peak antenna gain is 4.8 dBi. The reception performance is measured by using a 4  4 BPSK signal. The measured average SNR is 17 dB when using the proposed ESPAR antenna as a transmitter, and the average SNR is 16.7 dB when using a four‐conventional monopole antenna.     

A novel phase noise reduction technique in oscillators usingdefected ground structure

A new technique to reduce the phase noise in microwave oscillators is developed using the resonant characteristic of the defected ground structure (DGS). Two kinds of oscillators have been designed and measured for the examination of the reduction of phase noise by the DGS. The first adopts the DGS section under the microstrip line at the gate circuit, while the second has only the conventional microstrip line. Measurement shows reduced phase noise by 10-15 dB in the oscillator with the DGS compared to the conventional one     

2D Image Construction from Low Resolution Response of a New Non‐invasive Measurement for Medical Application

This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important.