• Journal of the Optical Society of Korea
• /
• v.17 no.1
• /
• pp.57-62
• /
• 2013

We have numerically implemented a receiver side all-optical signal processing method, i.e. optical backward propagation (OBP), by dispersion compensating fiber (DCF) and non-linear compensator (NLC) devised by effective negative Kerr non-linear coefficient using two highly non-linear fibers (HNLFs). The method is implemented for the post-processing of fiber transmission impairments, i.e. chromatic dispersion (CD) and non-linearities (NL). The OBP module is evaluated for dual-polarization (DP) m-ary (m=4,16,32,64,256) quadrature amplitude modulation (QAM) in 112 Gbit/s coherent transmission over 1200 km standard single mode fiber (SMF). We have also investigated an intensity limited optical backward propagation module (IL-OBP) by using a self-phase modulation-based optical limiter with an appropriate pre-chirping to compensate for the intensity fluctuations in the transmission link. Our results show that in highly non-linear sensitive 256QAM transmission, we have observed a 66% increase in the transmission distance by implementing IL-OBP as compared to conventional OBP.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.24 no.1
• /
• pp.1-9
• /
• 1987

In this paper, the acquisition performance of a receiver that utilizes a non-coherent digital correlator is analyzed. In order to analyze the acquisition performance, the probability density function of a receiver output random variable has been derived approximately. Using this function, the acquisition performance of the coarse acquisition code receiver in a global positioning system is analyzed.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.6
• /
• pp.42-48
• /
• 2010

Joint Tactical Information Distribution System (JTIDS) uses cyclic code shift keying (CCSK) for baseband symbol modulation, in which 5-bit information is mapped to one of thirty two 32-chip sequences. It is a kind of direct sequence based spread spectrum communication. In this paper, the performance of non-coherent detection of CCSK using non-orthogonal 32-chip sequence is evaluated. And a 32-chip sequence with better performance is also proposed and compared with the conventional one.

• Journal of Navigation and Port Research
• /
• v.30 no.5 s.111
• /
• pp.343-349
• /
• 2006

In order to enhance the robustness against noisy environment, the previous GPS initial synchronization method of DGPS reference stations adopts not only the coherent integration method but also the non-coherent integration method. However the previous GPS initial synchronization method muses the non-coherent integration loss, which is a dominant factor among the signal acquisition losses in noisy environment. And the non-coherent integration loss increases with the strength of noise signal. In this paper, a novel GPS initial synchronization method is proposed for robust DGPS reference stations in noisy environment. This paper presents that the proposed GPS initial synchronization method suppresses the non-coherent acquisition loss. Furthermore, with regard to the mean acquisition time, it is shown that the number of the search cells of the proposed GPS initial synchronization method is much smaller than that of the previous GPS initial synchronization method Finally, through the simulation by the GPS simulator, it is seen that the GPS signal of nigh signal-to-noise ratio can be acquired under increased noise floor using the proposed GPS initial synchronization method.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.6
• /
• pp.113-117
• /
• 2014

This paper comparatively analyze to integration case to have a influence detection range estimation about radar cross section in radar system. This paper estimate detection range used to probability of detection in radar equation that used to swerling case 1 in case of radar cross section is small and used to swerling case 3 in case of radar cross section is large. Through simulation, coherent integration and non-coherent integration about swerling case difference were comparatively analyzed. In the result of comparative analysis, non-coherent integration case is outstanding detection range and we known that coherent integration don't suitable for detection range estimation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.7
• /
• pp.521-527
• /
• 2014

Most of Sea Surveillance Radar(SSR)s which are used in Vessel Traffic Service are Magnetron-based Non-Coherent Method and use the pulse integration technique having a signal to noise ratio enhancement function to satisfy a surveillance performance about target. Especially, Pulse Integration technique has an effect on target serveillance performance through signal to noise ratio, in addition, has an effect to improve a signal interference and noise spike. In this paper, we have a simulation experiment by using MATLAB simulation tool for appling a pulse integration technique in VTS system using a Non-Coherent radar, and verify an optimum pulse integration technique through out performance analysis between frequently use pulse integration techniques.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.9
• /
• pp.1045-1050
• /
• 2008

In this paper presents a CMOS RF receiver for IR-UWB wireless communications is presented. The impulse radio based UWB receiver adopts the non-coherent demodulation that simplifies the receiver architecture and reduces power consumption. The IR-UWB receiver consists of LNA, envelop detector, VGA, and comparator and the receiver including envelope detector, VGA, and comparator is fabricated on a single chip using $0.18{\mu}m$ CMOS technology. The measured sensitivity of IR-UWB receiver is down to -70 dBm and the BER $10^{-3}$, respectively at data rate 1 Mbps. The current consumption of IR-UWB receiver except external LNA is 5 mA at 1.8 V.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.11A
• /
• pp.1086-1095
• /
• 2007

This paper proposes a novel non-coherent TOA estimation scheme using multiple correlation process on the existence of multiple simultaneously operating piconets (SOPs). Impulse radio-ultra wideband (IR-UWB) based on direct sequence spread spectrum (DSSS) using Gold sequence is employed in order to discriminate each piconet. In order to enhance the characteristic of correlation, this paper presents the method of multiple mask operation (MMO). The time of arrival (TOA) of direct line of sight (DLOS) path is estimated via two step coarse/fine timing detection. To verify the performance of proposed scheme, two distinct channel models approved by IEEE 802.15.4a Task Group (TG) are considered. According to the simulation results, it could conclude that the proposed scheme have performed better performance than the conventional method well even in densed indoor multi-path environment as well as in the existence of multiple SOPs.

• Progress in Superconductivity and Cryogenics
• /
• v.19 no.1
• /
• pp.1-4
• /
• 2017

Forefront ultrafast experimental techniques have recently proven their potential as new approaches to understand materials based on non-equilibrium dynamics in the time domain. The time domain approach is useful especially in disentangling complicated coupling among charge, spin and lattice degrees of freedom. Various ultrafast experiments on Fe-based superconductors have observed strong coherent oscillations of an $A_{1g}$ phonon mode of arsenic ions, which shows strong coupling to the electronic and magnetic states. This paper reviews the recent reports of ultrafast studies on Fe-based superconductor with a focus on the coherent oscillations. Experimental results with ultrashort light sources from the terahertz-infrared pulses to the hard X-rays from a free electron laser will be presented.

• Journal of Institute of Control, Robotics and Systems
• /
• v.16 no.7
• /
• pp.720-725
• /
• 2010

In AGPS method, user position can be obtained even in the shadow region by improving signal sensitivity. A hybrid long integration scheme employing both coherent and non-coherent integration method is commonly used in AGPS receivers. Because coherent loss increases as residual frequency become large, residual frequency should be minimized to maximize coherent integration gain. This paper presents performance analysis of residual frequency estimator using FFT in fine-time assistance AGPS method. Considering the hardware complexity and the estimation accuracy, optimal length of FFT is proposed for GPS L1 C/A signal. Signal sensitivity for estimating the residual frequency is also analysed. By field experimental results, it is found that the residual frequency can be successfully estimated using 1 second snap-shot data when GPS signal strength is larger than -150 dBm and its RMS error is 3Hz.