• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1153-1160
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• 2003

In this paper, the performance of the UWB communication systems is analyzed in the presence of the Narrow Band Interference(NBI). UWB communication systems are modeled as using the Pulse Position Modulation(PPM). In this system, a Gaussian monocycle is used as the received pulses. The NBI is considered as a zero-mean random process with a constant spectral power density over its whole bandwidth. We obtain the mathematical expressions for describing the effect of the NBI on the UWB system. And it can be shown that the suppression of the effect of NBI on the UWB systems is available by adjusting the PPM related parameter.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.308-312
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• 2002

In this paper, EPLD(Erasable Programmable Logic Device) based induction motor drives with a SRP-PWM(Separatley Randomized Pulse Position PWM) is proposed. In the proposed RPWM (Random PWM), each of three phase pulses is located randomly in each switching interval. Based on the space vector modulation technique, the duty ratio of the pulses is calculated. To verify the validity of the proposed RPWM, the experimental study was tried. Along with the randomization of PWM pulses, the space vector modulation is also executed in the TMS320C31 DSP(Digital Signal Processor). The experimental results show that the voltage and switching noise harmonics are spread to a wide band area. Also, the performance of the proposed SRP-PWM and the conventional SVM-PWM are nearly the same from the viewpoing of the v/f constant control.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.160-168
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• 2001

The RPWM (Random· Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics over a wide frequency area. By using randomly changing switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise can be spread to the wide-band area. The wide­band noise is much more comfortable and less annoying than the narrow-band one. So, the RPWM has been attracting interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position Space Vector PWM) is proposed and implemented. Each of three phase pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is also executed in the C167 micro-controller. The experimental results show that the voltage and current harmonics are spread to a wide band area and that the audible switching noise is reduced by the proposed RPPWM method.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.25-28
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• 2002

In this paper, 2 phase modulated SRPP-PWM(Separately Random Pulse Position PWM) is proposed. This PWM technique is based on the 2 phase modulated SVPWM(Space Vector Pulse Width Modulation). In according to the theory of SVPWM, 2 phase modulated SVPWM uses two pulses, not three pulses as in 3 phase modulated SVPWM. In the proposed SRPP-PWM scheme, each of two phase pulses is located randomly in each switching interval. The experimental results show that the voltage and switching noise harmonics are spread to a wide band area. Also, the performance of the proposed 2 phase modulated SRPP-PWM and the conventional SVPWM are compared to each other In result, the speed response is nearly similar to each other from the viewpoint of the v/f constant control.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.82-89
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• 2002

In this paper, a new two-phase space vector RPWM(Random PWM) is proposed. In the proposed RPWM, each of two-phase PWM pulses is located randomly in each switching interval. Based on the space vector modulation technique, the duty ratio of the pulses is calculated. Along with the randomization of the PWM pulses, we can obtain the effects of spread spectra of inverter output voltage, d.c link current and audible switching acoustic noise as in the case of randomly changed switching frequency. To verify the validity of the proposed two-phase RPWM scheme, the experiment based on the C167 micro-controller was executed. The performance of the proposed scheme was compared with traditional PWM schemes experimentally.

• Journal of IKEEE
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• v.15 no.2
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• pp.171-178
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• 2011

In this paper, a novel pulse repetition interval (PRI) jittering coder based on quasi-random M-sequence codes is proposed for improvement of counter-countermeasure capability in a radar. Each of the proposed jittered 256 PRI codes has a unique code chip combination with 256 code chips, such that any set of three consequent code chips (4 pulses) from any code appears only once among the entire code chip sequences of the codes. This indicates that only 4 of received pulses are enough to determine uniquely the exact timing position of the incoming pulse train (or code chip sequence) required for counter-countermeasure, as well as the identity of the transmitted code. To prove the proposed idea experimentally, the jittered PRI coder is implemented and demonstrated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.682-687
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• 2010

The IEEE 802.15.4a specification targets the low-rate (LR) Impulse-radio (IR) ultra-wideband (UWB) system which is now widely applied in the WPANs considering rather short distance communications with low complexity and power consumption. The physical (PHY) layer uses concatenated coding with mixed binary phase-shift keying and binary pulse-position modulation (BPSK-BPPM), and direct sequence spreading with time hopping in order that both coherent and non-coherent receiver architectures are supported. In this paper, the performances of multiple access schemes compliant with IEEE 802.15.4a specification are investigated with energy detection receiver, which allow avoiding the complex channel estimation needed by a coherent receiver. However, the performance of energy detection receiver is severely degraded by multi-user interference (MUI), which largely diminishes one of the most fascinating advantages of UWB, namely robustness to MUI as well as the possibility to allow parallel transmissions. So as to improve the performance of multiple access schemes, we propose to apply the novel TH sequences as well as to increase the number of TH positions. The simulation results show that our novel multiple access schemes significantly improve the performance against MUI.