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Hidenori Muramatsu - One of the best experts on this subject based on the ideXlab platform.
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Consideration to Terminating Condition of Mains Cable for Radiated Emission Measurement Caused by Different Disturbance Sources
IEEE Transactions on Electromagnetic Compatibility, 2020Co-Authors: Kunihiro Osabe, Nobuo Kuwabara, Shinichi Okuyama, Hidenori MuramatsuAbstract:Very high frequency (VHF)-line impedance stabilization network (VHF-LISN), which is defined as the termination device for mains cable of equipment under test to specify the input impedance of each line at the mains power supply outlet, can improve correlation between test sites that perform radiated Emission Measurement. Balanced and unbalanced types of VHF-LISN are currently under proposal with International Special Committee on Radio Interference (CISPR) as a device for prescribing the terminating condition of the power supply cable. Simulation analysis with common mode (CM)/differential mode (DM) signal sources was performed to investigate the Emission characteristics with the two types of termination devices under several Measurement arrangements that used two-wire and three-wire mains cables. Furthermore, to confirm the validity of the simulation analysis, Measurement of a versatile comb-generator-operated by ac mains was performed under the same test arrangement and two types of termination devices. Quasi CM/DM signal from an ac-operated comb generator was injected back into the mains cable of the same comb generator. This article explains how we ascertained the radiated Emission characteristics with each termination device, and provides guidance for their appropriate usage.
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verification of suitability of the aan shown in fig g 3 of cispr 32 for conducted Emission Measurement on single and two pair unscreened balanced cables
International Symposium on Electromagnetic Compatibility, 2019Co-Authors: Nozomi Miyake, Koichi Kakuda, Hidenori MuramatsuAbstract:CISPR 32[1]specifies several types of asymmetric artificial network (AAN) for conducted Emission Measurement on unscreened balanced pair cables. The AAN circuit diagram shown in Figure G.3 of CISPR 32[1]is an example of a transformer-type-AAN, thought to be suitable for Measurement on single, two, three and four unscreened balanced pairs even though EUT port of the AAN is a balanced four-pair connector. In this paper, we explain how we experimentally verified the suitability of this transformer-type-AAN by measuring common mode termination impedance and voltage division factor (VDF) while changing the balanced pairs to be measured. The results show that deviations among the measured values were sufficiently small and all measured values were met the requirements of CISPR 16-1-2[2]. We concluded that this transformer-type-AAN is suitable for conducted Emission Measurement on any unscreened balanced pairs.
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Comparison of configurations for conducted Emission Measurement specified in CISPR 32 and CISPR 13
2017 Asia-Pacific International Symposium on Electromagnetic Compatibility (APEMC), 2017Co-Authors: Nozomi Miyake, Koichi Kakuda, Yoshiaki Hiratsuka, Hidenori MuramatsuAbstract:Configurations, such as the physical layout of the Measurement setup and operation conditions of equipment under test (EUT) especially the complexity of the displayed image for conducted Emission Measurements specified in CISPR 32[1] differ from those in CISPR 13 [2]. CISPR 32 requires a typical system configuration but CISPR 13 does not require the system. After CISPR 32 was published, multimedia equipment (MME), which has broadcast receiver functions measured with the configuration in CISPR 13 shall be measured with that in CISPR 32. Therefore, effects of differences in configurations for conducted Emission Measurement have to be clarified to obtain equivalent results. From the results of investigations into asymmetric mode conducted Emission Measurements, more practical operations of EUT can be simulated with the physical layout in CISPR 32. Also, the conducted Emissions did not significantly change due to the complexity of the images displayed on the monitor.
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improvement of radiated Emission Measurement reproducibility with vhf lisn obtained from final results of international inter laboratory comparison on termination control of power line
Asia-Pacific Symposium on Electromagnetic Compatibility, 2015Co-Authors: Shinichi Okuyama, Nobuo Kuwabara, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, power supply impedance of radiated Emission Measurement site is not specified in any testing standards. In Measurement of radiated Emission from desktop equipment, noise emitted from power line of the EUT is a factor that worsens site correlations because the noise varies with the impedance between power line and the ground. Under such circumstances, VCCI developed VHF-LISN to stabilize power supply facilities for the purpose of improving the reproducibility of radiated Emission Measurement. To assess its effectiveness, an international inter-laboratory comparison program was carried out, provided with EUTs and termination control devices including the VHF-LISN to ensure identical setup across sites. Until February 2014, this international program was promoted at 16 sites in 9 countries. From the final results, we conclude that the VHF-LISN is the best device to improve the reproducibility of radiated Emission Measurement.
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Investigation on the effect of impedance changes in broadband antennas with varying antenna height on radiated Emission Measurement below 1 GHz
2015 IEEE International Symposium on Electromagnetic Compatibility (EMC), 2015Co-Authors: Shinichi Okuyama, Ikuo Makino, Hiroyuki Shimanoe, Hidenori MuramatsuAbstract:According to the standard method for calibration of receive antennas to be used in radiated Emission Measurement below 1 GHz, the sensitivity of receive antenna is defined as a free-space antenna factor obtained by applying a given correction factor to a near free-space factor that is determined by horizontally polarized antenna calibration at a 2 m antenna height. In actual radiated Emission Measurement performed while varying the receive antenna height, however, the sensitivity of receive antenna varies with antenna impedance changes at different antenna heights. In this situation, the authors measured how the antenna impedance changes with the antenna height and examined how such impedance changes affect radiated Emission Measurement results, using biconical, log-periodic dipole, and hybrid antennas under test that are typical below 1 GHz. The authors also studied on a method to estimate an antenna height free from antenna impedance changes and suitable for obtaining free-space factors.
Shinichi Okuyama - One of the best experts on this subject based on the ideXlab platform.
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Consideration to Terminating Condition of Mains Cable for Radiated Emission Measurement Caused by Different Disturbance Sources
IEEE Transactions on Electromagnetic Compatibility, 2020Co-Authors: Kunihiro Osabe, Nobuo Kuwabara, Shinichi Okuyama, Hidenori MuramatsuAbstract:Very high frequency (VHF)-line impedance stabilization network (VHF-LISN), which is defined as the termination device for mains cable of equipment under test to specify the input impedance of each line at the mains power supply outlet, can improve correlation between test sites that perform radiated Emission Measurement. Balanced and unbalanced types of VHF-LISN are currently under proposal with International Special Committee on Radio Interference (CISPR) as a device for prescribing the terminating condition of the power supply cable. Simulation analysis with common mode (CM)/differential mode (DM) signal sources was performed to investigate the Emission characteristics with the two types of termination devices under several Measurement arrangements that used two-wire and three-wire mains cables. Furthermore, to confirm the validity of the simulation analysis, Measurement of a versatile comb-generator-operated by ac mains was performed under the same test arrangement and two types of termination devices. Quasi CM/DM signal from an ac-operated comb generator was injected back into the mains cable of the same comb generator. This article explains how we ascertained the radiated Emission characteristics with each termination device, and provides guidance for their appropriate usage.
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improvement of radiated Emission Measurement reproducibility with vhf lisn obtained from final results of international inter laboratory comparison on termination control of power line
Asia-Pacific Symposium on Electromagnetic Compatibility, 2015Co-Authors: Shinichi Okuyama, Nobuo Kuwabara, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, power supply impedance of radiated Emission Measurement site is not specified in any testing standards. In Measurement of radiated Emission from desktop equipment, noise emitted from power line of the EUT is a factor that worsens site correlations because the noise varies with the impedance between power line and the ground. Under such circumstances, VCCI developed VHF-LISN to stabilize power supply facilities for the purpose of improving the reproducibility of radiated Emission Measurement. To assess its effectiveness, an international inter-laboratory comparison program was carried out, provided with EUTs and termination control devices including the VHF-LISN to ensure identical setup across sites. Until February 2014, this international program was promoted at 16 sites in 9 countries. From the final results, we conclude that the VHF-LISN is the best device to improve the reproducibility of radiated Emission Measurement.
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Investigation on the effect of impedance changes in broadband antennas with varying antenna height on radiated Emission Measurement below 1 GHz
2015 IEEE International Symposium on Electromagnetic Compatibility (EMC), 2015Co-Authors: Shinichi Okuyama, Ikuo Makino, Hiroyuki Shimanoe, Hidenori MuramatsuAbstract:According to the standard method for calibration of receive antennas to be used in radiated Emission Measurement below 1 GHz, the sensitivity of receive antenna is defined as a free-space antenna factor obtained by applying a given correction factor to a near free-space factor that is determined by horizontally polarized antenna calibration at a 2 m antenna height. In actual radiated Emission Measurement performed while varying the receive antenna height, however, the sensitivity of receive antenna varies with antenna impedance changes at different antenna heights. In this situation, the authors measured how the antenna impedance changes with the antenna height and examined how such impedance changes affect radiated Emission Measurement results, using biconical, log-periodic dipole, and hybrid antennas under test that are typical below 1 GHz. The authors also studied on a method to estimate an antenna height free from antenna impedance changes and suitable for obtaining free-space factors.
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effectiveness evaluation of devices for ac mains cable termination control to improve reproducibility of radiated Emission Measurement based on the interim results of international inter laboratory comparison
International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:Specifications for the terminating condition of EUT cables leaving from test area have not been specified in any standards, although it is one of the sources of poor Measurement uncertainty for the radiated Emission Measurement. To improve the reproducibility of a radiation Emission Measurement among test sites, VHF-LISN is proposed to simulate artificially AC mains network as the device for specifying the termination condition of the EUT power cable. For proposing standardization of VHF-LISN, an international inter-laboratory comparison test was proposed and it is being performed now by CISPR/SCI/WG2. Although the main purpose of the inter-laboratory comparison was to compare the result with Measurement conditions of VHF-LISN and without the device, this comparison study has been performed with also including CMAD which was already standardized to a termination condition control device and CDNE which is currently planned to standardize, as the effectiveness evaluation of AC mains-cable termination control devices. From an intermediate result of the inter-laboratory comparison Measurement, the standard deviation and the average value of data were summarized for two EUTs and five test conditions. As a tentative conclusion, the predominance of VHF-LISN has been confirmed with the factors analysis of cause in this paper.
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Improvement of radiated Emission Measurement reproducibility by VHF-LISN — Interim results of international inter-laboratory comparison
2014 International Symposium on Electromagnetic Compatibility Tokyo, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, radiated Emission Measurement standards do not specify the common mode impedance for the outlet terminal of mains network to equipment under test (EUT) in the test site. Because of the difference in the terminating condition of EUT power cable which dominantly causes radiated Emission in the frequency range between 30 MHz and 300 MHz, radiated Emission Measurements of a tabletop EUT are poor in reproducibility. In an effort to resolve this issue, we developed a device called very high frequency line impedance stabilization network (VHF-LISN) and investigated its effectiveness. After performing the domestic inter-laboratory comparison, we proposed an international inter-laboratory comparison program to CISPR Subcommittee I, and the proposal was accepted. For the comparison purpose, we have investigated the reproducibility also by using a common mode absorbing device (CMAD) and a versatile coupling/decoupling network of AC mains for Emission testing (CDNE-M). This investigation is just in progress as a future work of CISPR SC-I WG2 until February, 2014. As a glance from an interim result, we could find that all devices are effective to improve the reproducibility of radiated Emission Measurement in comparison with the case of no such device. But also we were able to presume that the effectiveness of devices to the Measurement reproducibility differs with the type of EUT.
Kunihiro Osabe - One of the best experts on this subject based on the ideXlab platform.
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Consideration to Terminating Condition of Mains Cable for Radiated Emission Measurement Caused by Different Disturbance Sources
IEEE Transactions on Electromagnetic Compatibility, 2020Co-Authors: Kunihiro Osabe, Nobuo Kuwabara, Shinichi Okuyama, Hidenori MuramatsuAbstract:Very high frequency (VHF)-line impedance stabilization network (VHF-LISN), which is defined as the termination device for mains cable of equipment under test to specify the input impedance of each line at the mains power supply outlet, can improve correlation between test sites that perform radiated Emission Measurement. Balanced and unbalanced types of VHF-LISN are currently under proposal with International Special Committee on Radio Interference (CISPR) as a device for prescribing the terminating condition of the power supply cable. Simulation analysis with common mode (CM)/differential mode (DM) signal sources was performed to investigate the Emission characteristics with the two types of termination devices under several Measurement arrangements that used two-wire and three-wire mains cables. Furthermore, to confirm the validity of the simulation analysis, Measurement of a versatile comb-generator-operated by ac mains was performed under the same test arrangement and two types of termination devices. Quasi CM/DM signal from an ac-operated comb generator was injected back into the mains cable of the same comb generator. This article explains how we ascertained the radiated Emission characteristics with each termination device, and provides guidance for their appropriate usage.
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improvement of radiated Emission Measurement reproducibility with vhf lisn obtained from final results of international inter laboratory comparison on termination control of power line
Asia-Pacific Symposium on Electromagnetic Compatibility, 2015Co-Authors: Shinichi Okuyama, Nobuo Kuwabara, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, power supply impedance of radiated Emission Measurement site is not specified in any testing standards. In Measurement of radiated Emission from desktop equipment, noise emitted from power line of the EUT is a factor that worsens site correlations because the noise varies with the impedance between power line and the ground. Under such circumstances, VCCI developed VHF-LISN to stabilize power supply facilities for the purpose of improving the reproducibility of radiated Emission Measurement. To assess its effectiveness, an international inter-laboratory comparison program was carried out, provided with EUTs and termination control devices including the VHF-LISN to ensure identical setup across sites. Until February 2014, this international program was promoted at 16 sites in 9 countries. From the final results, we conclude that the VHF-LISN is the best device to improve the reproducibility of radiated Emission Measurement.
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effectiveness evaluation of devices for ac mains cable termination control to improve reproducibility of radiated Emission Measurement based on the interim results of international inter laboratory comparison
International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:Specifications for the terminating condition of EUT cables leaving from test area have not been specified in any standards, although it is one of the sources of poor Measurement uncertainty for the radiated Emission Measurement. To improve the reproducibility of a radiation Emission Measurement among test sites, VHF-LISN is proposed to simulate artificially AC mains network as the device for specifying the termination condition of the EUT power cable. For proposing standardization of VHF-LISN, an international inter-laboratory comparison test was proposed and it is being performed now by CISPR/SCI/WG2. Although the main purpose of the inter-laboratory comparison was to compare the result with Measurement conditions of VHF-LISN and without the device, this comparison study has been performed with also including CMAD which was already standardized to a termination condition control device and CDNE which is currently planned to standardize, as the effectiveness evaluation of AC mains-cable termination control devices. From an intermediate result of the inter-laboratory comparison Measurement, the standard deviation and the average value of data were summarized for two EUTs and five test conditions. As a tentative conclusion, the predominance of VHF-LISN has been confirmed with the factors analysis of cause in this paper.
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Improvement of radiated Emission Measurement reproducibility by VHF-LISN — Interim results of international inter-laboratory comparison
2014 International Symposium on Electromagnetic Compatibility Tokyo, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, radiated Emission Measurement standards do not specify the common mode impedance for the outlet terminal of mains network to equipment under test (EUT) in the test site. Because of the difference in the terminating condition of EUT power cable which dominantly causes radiated Emission in the frequency range between 30 MHz and 300 MHz, radiated Emission Measurements of a tabletop EUT are poor in reproducibility. In an effort to resolve this issue, we developed a device called very high frequency line impedance stabilization network (VHF-LISN) and investigated its effectiveness. After performing the domestic inter-laboratory comparison, we proposed an international inter-laboratory comparison program to CISPR Subcommittee I, and the proposal was accepted. For the comparison purpose, we have investigated the reproducibility also by using a common mode absorbing device (CMAD) and a versatile coupling/decoupling network of AC mains for Emission testing (CDNE-M). This investigation is just in progress as a future work of CISPR SC-I WG2 until February, 2014. As a glance from an interim result, we could find that all devices are effective to improve the reproducibility of radiated Emission Measurement in comparison with the case of no such device. But also we were able to presume that the effectiveness of devices to the Measurement reproducibility differs with the type of EUT.
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improvement of radiated Emission Measurement reproducibility by vhf lisn interim results of international inter laboratory comparison
International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, radiated Emission Measurement standards do not specify the common mode impedance for the outlet terminal of mains network to equipment under test (EUT) in the test site. Because of the difference in the terminating condition of EUT power cable which dominantly causes radiated Emission in the frequency range between 30 MHz and 300 MHz, radiated Emission Measurements of a tabletop EUT are poor in reproducibility. In an effort to resolve this issue, we developed a device called very high frequency line impedance stabilization network (VHF-LISN) and investigated its effectiveness. After performing the domestic inter-laboratory comparison, we proposed an international inter-laboratory comparison program to CISPR Subcommittee I, and the proposal was accepted. For the comparison purpose, we have investigated the reproducibility also by using a common mode absorbing device (CMAD) and a versatile coupling/decoupling network of AC mains for Emission testing (CDNE-M). This investigation is just in progress as a future work of CISPR SC-I WG2 until February, 2014. As a glance from an interim result, we could find that all devices are effective to improve the reproducibility of radiated Emission Measurement in comparison with the case of no such device. But also we were able to presume that the effectiveness of devices to the Measurement reproducibility differs with the type of EUT.
Katsuyuki Tanakajima - One of the best experts on this subject based on the ideXlab platform.
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effectiveness evaluation of devices for ac mains cable termination control to improve reproducibility of radiated Emission Measurement based on the interim results of international inter laboratory comparison
International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:Specifications for the terminating condition of EUT cables leaving from test area have not been specified in any standards, although it is one of the sources of poor Measurement uncertainty for the radiated Emission Measurement. To improve the reproducibility of a radiation Emission Measurement among test sites, VHF-LISN is proposed to simulate artificially AC mains network as the device for specifying the termination condition of the EUT power cable. For proposing standardization of VHF-LISN, an international inter-laboratory comparison test was proposed and it is being performed now by CISPR/SCI/WG2. Although the main purpose of the inter-laboratory comparison was to compare the result with Measurement conditions of VHF-LISN and without the device, this comparison study has been performed with also including CMAD which was already standardized to a termination condition control device and CDNE which is currently planned to standardize, as the effectiveness evaluation of AC mains-cable termination control devices. From an intermediate result of the inter-laboratory comparison Measurement, the standard deviation and the average value of data were summarized for two EUTs and five test conditions. As a tentative conclusion, the predominance of VHF-LISN has been confirmed with the factors analysis of cause in this paper.
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Improvement of radiated Emission Measurement reproducibility by VHF-LISN — Interim results of international inter-laboratory comparison
2014 International Symposium on Electromagnetic Compatibility Tokyo, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, radiated Emission Measurement standards do not specify the common mode impedance for the outlet terminal of mains network to equipment under test (EUT) in the test site. Because of the difference in the terminating condition of EUT power cable which dominantly causes radiated Emission in the frequency range between 30 MHz and 300 MHz, radiated Emission Measurements of a tabletop EUT are poor in reproducibility. In an effort to resolve this issue, we developed a device called very high frequency line impedance stabilization network (VHF-LISN) and investigated its effectiveness. After performing the domestic inter-laboratory comparison, we proposed an international inter-laboratory comparison program to CISPR Subcommittee I, and the proposal was accepted. For the comparison purpose, we have investigated the reproducibility also by using a common mode absorbing device (CMAD) and a versatile coupling/decoupling network of AC mains for Emission testing (CDNE-M). This investigation is just in progress as a future work of CISPR SC-I WG2 until February, 2014. As a glance from an interim result, we could find that all devices are effective to improve the reproducibility of radiated Emission Measurement in comparison with the case of no such device. But also we were able to presume that the effectiveness of devices to the Measurement reproducibility differs with the type of EUT.
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improvement of radiated Emission Measurement reproducibility by vhf lisn interim results of international inter laboratory comparison
International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:At present, radiated Emission Measurement standards do not specify the common mode impedance for the outlet terminal of mains network to equipment under test (EUT) in the test site. Because of the difference in the terminating condition of EUT power cable which dominantly causes radiated Emission in the frequency range between 30 MHz and 300 MHz, radiated Emission Measurements of a tabletop EUT are poor in reproducibility. In an effort to resolve this issue, we developed a device called very high frequency line impedance stabilization network (VHF-LISN) and investigated its effectiveness. After performing the domestic inter-laboratory comparison, we proposed an international inter-laboratory comparison program to CISPR Subcommittee I, and the proposal was accepted. For the comparison purpose, we have investigated the reproducibility also by using a common mode absorbing device (CMAD) and a versatile coupling/decoupling network of AC mains for Emission testing (CDNE-M). This investigation is just in progress as a future work of CISPR SC-I WG2 until February, 2014. As a glance from an interim result, we could find that all devices are effective to improve the reproducibility of radiated Emission Measurement in comparison with the case of no such device. But also we were able to presume that the effectiveness of devices to the Measurement reproducibility differs with the type of EUT.
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Effectiveness evaluation of devices for AC mains cable termination control to improve reproducibility of radiated Emission Measurement - based on the interim results of international inter-laboratory comparison -
2014 International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Shinichi Okuyama, Katsuyuki Tanakajima, Kunihiro Osabe, Hidenori MuramatsuAbstract:Specifications for the terminating condition of EUT cables leaving from test area have not been specified in any standards, although it is one of the sources of poor Measurement uncertainty for the radiated Emission Measurement. To improve the reproducibility of a radiation Emission Measurement among test sites, VHF-LISN is proposed to simulate artificially AC mains network as the device for specifying the termination condition of the EUT power cable. For proposing standardization of VHF-LISN, an international inter-laboratory comparison test was proposed and it is being performed now by CISPR/SCI/WG2. Although the main purpose of the inter-laboratory comparison was to compare the result with Measurement conditions of VHF-LISN and without the device, this comparison study has been performed with also including CMAD which was already standardized to a termination condition control device and CDNE which is currently planned to standardize, as the effectiveness evaluation of AC mains-cable termination control devices. From an intermediate result of the inter-laboratory comparison Measurement, the standard deviation and the average value of data were summarized for two EUTs and five test conditions. As a tentative conclusion, the predominance of VHF-LISN has been confirmed with the factors analysis of cause in this paper.
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A round-robin test on effectiveness of a VHF LISN for radiated Emission Measurements
2011 IEEE International Symposium on Electromagnetic Compatibility, 2011Co-Authors: Chiharu Miyazaki, Katsuyuki Tanakajima, Masanori Yamaguchi, Kiyoshi Endo, Hidenori Muramatsu, Jiro KawanoAbstract:VCCI Technical Sub-committee has investigated the dispersion of radiated Emission Measurement results. It was confirmed that one of the main cause of the dispersion of radiated Emission Measurement results was the difference of the power line-to-ground impedance of the power supply for the equipment under test (EUT). For the improvement of the dispersion, VCCI Council manufactured the experimental VHF LISN (Very High Frequency Line Impedance Stabilization Network). And we performed a round-robin test on the effectiveness of the VHF LISN.
Chu Wang - One of the best experts on this subject based on the ideXlab platform.
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real world operation conditions and on road Emissions of beijing diesel buses measured by using portable Emission Measurement system and electric low pressure impactor
Science of The Total Environment, 2011Co-Authors: Zhihua Liu, Kent C Johnson, Asad Naeem Shah, Jianwei Tan, Chu WangAbstract:Abstract On-road Measurement is an effective method to investigate real-world Emissions generated from vehicles and estimate the difference between engine certification cycles and real-world operating conditions. This study presents the results of on-road Measurements collected from urban buses which propelled by diesel engine in Beijing city. Two widely used Euro III Emission level buses and two Euro IV Emission level buses were chosen to perform on-road Emission Measurements using portable Emission Measurement system (PEMS) for gaseous pollutant and Electric Low Pressure Impactor (ELPI) for particulate matter (PM) number Emissions. The results indicate that considerable discrepancies of engine operating conditions between real-world driving cycles and engine certification cycles have been observed. Under real-world operating conditions, carbon monoxide (CO) and hydrocarbon (HC) Emissions can easily meet their respective regulations limits, while brake specification nitrogen oxide (bsNO x ) Emissions present a significant deviation from its corresponding limit. Compared with standard limits, the real-world bsNO x Emission of the two Euro III Emission level buses approximately increased by 60% and 120% respectively, and bsNO x of two Euro IV buses nearly twice standard limits because Selective Catalytic Reduction (SCR) system not active under low exhaust temperature. Particle mass were estimated via particle size distribution with the assumption that particle density and diameter is liner. The results demonstrate that nanometer size particulate matter make significant contribution to total particle number but play a minor role to total particle mass. It is suggested that specific certified cycle should be developed to regulate bus engines Emissions on the test bench or use PEMS to control the bus Emissions under real-world operating conditions.