• International Journal of Aeronautical and Space Sciences
• /
• 제16권3호
• /
• pp.475-483
• /
• 2015

We propose a numerical scheme to simulate the time-domain echo signals at tracking radar for a realistic scenario where an EAD (expendable active decoy) and an airborne target are both in dynamic states. On various scenarios where the target takes different maneuvers, the trajectories of the EAD ejected from the target are accurately calculated by solving 6-DOF (Degree-of-Freedom) equations of the motion for the EAD. At each sampling time of the echo signal, the locations of the EAD and the target are assumed to be fixed. Thus, the echo power from the EAD can be simply calculated by using the Friis transmission formula. The returned power from the target can be computed based on the pre-calculated scattering matrix of the target. In this paper, an IPO (iterative physical optics) method is used to construct the scattering matrix database of the target. The sinc function-interpolation formulation (sampling theorem) is applied to compute the scattering at any incidence angle from the database. A simulator is developed based on the proposed scheme to estimate the echo signals, which can consider the movement of the airborne target and EAD, also the scattering of the target and the RF specifications of the EAD. For applications, we consider the detection probability of the target in the presence of the EAD based on Monte Carlo simulation.

• Korean Journal of Materials Research
• /
• 제12권4호
• /
• pp.296-303
• /
• 2002

For potential application to quantum mechanical devices, nano-composite thin films, consisting of GaAs quantum dots dispersed in SiO$_2$ glass matrix, were fabricated and studied in terms of structural, chemical, and optical properties. In order to form crystalline GaAs quantum dots at room temperature, uniformly dispersed in $SiO_2$matrix, the composite films were made to consist of alternating layers of GaAs and $SiO_2$in the manner of a superlattice using RF magnetron sputter deposition. Among different film samples, nominal thickness of an individual GaAs layer was varied with a total GaAs volume fraction fixed. From images of High Resolution Transmission Electron Microscopy (HRTEM), the formation of GaAs quantum dots on SiO$_2$was shown to depend on GaAs nominal thickness. GaAs deposits were crystalline and GaAs compound-like chemically according to HRTEM and XPS analysis, respectively. From measurement of optical absorbance using a spectrophotometer, absorption edges were determined and compared among composite films of varying GaAs nominal thicknesses. A progressively larger shift of absorption edge was noticed toward a blue wavelength with decreasing GaAs nominal thickness, i.e. quantum dots size. Band gaps of the composite films were also determined from Tauc plots as well as from PL measurements, displaying a linear decrease with increasing GaAs nominal thickness.

• Current Photovoltaic Research
• /
• 제3권3호
• /
• pp.80-84
• /
• 2015

We suggest new emitter formation method using solid-phase epitaxy (SPE); solid-phase epitaxy emitter (SEE). This method expect simplification and cost reduction of process compared with furnace process (POCl3 or BBr3). The solid-phase epitaxy emitter (SEE) deposited a-Si:H layer by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) on substrate (c-Si), then thin layer growth solid-phase epitaxy (SPE) using rapid thermal process (RTP). This is possible in various emitter profile formation through dopant gas ($PH_3$) control at deposited a-Si:H layer. We fabricated solar cell to apply solid-phase epitaxy emitter (SEE). Its performance have an effect on crystallinity of phase transition layer (a-Si to c-Si). We confirmed crystallinity of this with a-Si:H layer thickness and annealing temperature by using raman spectroscopy, spectroscopic ellipsometry and transmission electron microscope. The crystallinity is excellent as the thickness of a-Si layer is thin (~50 nm) and annealing temperature is high (<$900^{\circ}C$). We fabricated a 16.7% solid-phase epitaxy emitter (SEE) cell. We anticipate its performance improvement applying thin tunnel oxide (<2nm).

• Journal of Biosystems Engineering
• /
• 제37권6호
• /
• pp.352-358
• /
• 2012

Purpose: The inexpensive black box system was developed to acquire and save driving information, to give the slope information, and to transmit SOS and theft signal. Method: The device consists of a main micro controller to acquire and save data, a GPS sensor module, a CDMA module, a touch LCD module, a RF (Radio Frequency) ID module, a SD (Secure Digital) card module, an emergency electric power source, a theftproof circuit, and a sensing device. The sensing device consists of a 8 bit micro controller, a accelerometer to detect impulse, two slope sensors to detect roll and pitch angle and a circuit to detect operation of 6 lighting devices. Results: Test results are as follows: 1) a tractor can be start up only with an electronic key (password or RFID card), 2) theft signal was transmitted when a tractor moved without an electronic key, 3) SOS was transmitted at conditions that rollover or crash happened. 4) 5 more than per 1s data are recorded at 5 minute intervals as new file name in SD card. Conclusions: This system can be used to save travelling record, reduce accident, prevent theft and rescue life in the accidents.

• Progress in Superconductivity and Cryogenics
• /
• 제16권3호
• /
• pp.21-25
• /
• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제23권9A호
• /
• pp.2153-2164
• /
• 1998

This paper has presented the parameters for the coexistence between two systems in macro/microcell ovelaid W-CDMA WLL (wideband CDMA wireless local loop) and has calculated the capacity of forward/reverse link in microcell. To produce the capacity for analyzing system interference effects, we have shown tables and graphs with the parameters sucyh as RF channel bandwidth of WLL(W), the transmission rate of service message(R), the required signal power to noise power ratio( $E_{b/}$ $N_{0}$) for achieving accepatable error rate, te user number ( $N_{W1}$, $N_{W2}$) of the neighboring system, the signal power to interference power ratio(.GAMMA.$_{C1B}$, .GAMMA.$_{C2B}$) of the neighboring system, the normalized distance(d) between microcell and macrocell base-station, and microcell to macrocell radius ratio ( $R_{d}$). From the results, we have convinced that the capacity of microcell diminishes as increasing the user number ( $N_{W2}$) in macrocell, increasing the microcell radius, and decreasing the normalized distance(d) between microcell and macrocell base-station. Especially, we have known that when $R_{d}$=0.1, $N_{W2}$ must be below 24 at .GAMMA.$_{C2B}$ = 0 dB and below 8 at .GAMMA.$_{C2B}$ = 4 dB for the acceptable capacity raito to be over 80%. Therfore, this paper is usefult to design microcell W-CDMA WLL for accommodating more user number under the interference effects of macrocell W-CDMA WLL and is expected to be reference in power control if base-station.ation.ion.ation.ation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• 제14권12호
• /
• pp.1292-1299
• /
• 2003

In this paper, we fabricated new GaAs-based dielectric-supported air gapped microstriplines(DAMLs) using the surface MEMS and the LPF for Ka-band using the fabricated DAMLs. We elevated the signal lines from the substrate, in order to reduce the substrate dielectric loss and obtain low losses at millimeter-wave frequency band with wide impedance range. We fabricated LPF with DAMLs for Ka-band. Due to reducing the dielectric loss of DAMLs, the insertion loss of LPF can be reduced. Miniature is essential to integrate LPF with active devices, so that we fabricated LPF with the slot on the ground to reduce the size of the LPF. We compared a characteristic to LPF with the slot and LPF without the slot.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• 제14권8호
• /
• pp.863-870
• /
• 2003

The digital transmission system entered in a RF region as digital system use IC chips of the speeder edge rate and clock speed nowadays. Optical path really was used in order to obtain the more capacity. In this paper, we described importance of electrical interconnect to get the signal integrity in optical module by simulation and experiment. 12 channel${\times}$2.5 G/ps optical parallel transmitter modules were manufactured by two different method ; access lines with microstrip and stripline type. We have clearly shown that the optical module adopting microstrip type with S$\sub$11/ $\geq$ -10 dB presents distortion but the optical module adopting stripline type with S$\sub$11/ $\leq$ : 15 dB obtains eye opening in 2.5 Gbis optical eye pattern response.

• Journal of the Korean Magnetics Society
• /
• 제25권1호
• /
• pp.22-26
• /
• 2015

In this paper, a magneto-inductive wave generated in a chain of LC resonators fabricated with Ni-Zn ferrite cores and chip capacitors is presented. RF signal propagates to neighbor resonator one by one as a consequence of the magnetical coupling between two resonators in the device. The magnetical coupling is due to the mutual inductances along the chain of resonators. So, the signal amplitude (${\approx}$ coupling intensity) is dependent of the mutual inductance which can be adjusted by applied magnetic field. In order to demonstrate the device, some experiments have been carried out systemically. The transmission characteristics of a magneto-inductive wave could be controlled by applied external magnetic field. The device composed of 5 resonators; the center frequencies were estimated to be 32 MHz and 38 MHz with the external magnetic flux density of 75 Oe and 222 Oe, respectively. We expect that the reported results could open a promising way to a high variety of applications in one- and two-dimensional functional devices, such as transducers, delay lines, power dividers and couplers.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제36권3A호
• /
• pp.189-197
• /
• 2011

OFDM systems are much studied for the recent high speed wireless optical communication system. OFDM system has basically high PAPR and ICI easily generated because of non-linearity and RF impairments. In the wireless optical communication system, optical output power driven by current of LED is not linear so that transmission signals are distorted. Therefore, research about reception performance of this nonlinear optical output emitted by non-linear LED transfer function and OFDM signal has been conducted. Nonlinear effect of LED is different from nonlinear effect of OFDM system in the conventional radio communication system, which degrades the BER performance. In this paper, we apply non-linear transfer function of recently studied LED into OFDM system. So, for reducing the PAPR and suppressing the ICI in frequency domain of receiver, we suggest a new PAPR reduction technique to reduce non-linear distortion of LED and an adaptive ICI suppression algorithm so that BER performance may be improved. Also, the proposed method is verified through simulation results.