Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585462
Qian Zhang, Wen-hua Chen, Zonghao Wang, Gongzhe Su
This paper applies a single feedback digital predistortion (DPD) architecture with under-sampling technique to linearize concurrent dual-band power amplifiers, where the dual-band output is treated as a single wideband signal to be down-converted and sampled with significantly reduced sampling rate. A wideband class-AB GaN power amplifier excited by dual-band LTE signal with total bandwidth of about 320 MHz was tested to validate the proposed approach. Experimental results show that when the sampling rate is reduced by more than 6 times, the new method can improve ACPR performance by about 16dB. Moreover, even aliasing exists in the output after under-sampling, the method still works well.
{"title":"A single feedback architecture for dual-band digital predistortion with under-sampling technique","authors":"Qian Zhang, Wen-hua Chen, Zonghao Wang, Gongzhe Su","doi":"10.1109/IEEE-IWS.2016.7585462","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585462","url":null,"abstract":"This paper applies a single feedback digital predistortion (DPD) architecture with under-sampling technique to linearize concurrent dual-band power amplifiers, where the dual-band output is treated as a single wideband signal to be down-converted and sampled with significantly reduced sampling rate. A wideband class-AB GaN power amplifier excited by dual-band LTE signal with total bandwidth of about 320 MHz was tested to validate the proposed approach. Experimental results show that when the sampling rate is reduced by more than 6 times, the new method can improve ACPR performance by about 16dB. Moreover, even aliasing exists in the output after under-sampling, the method still works well.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"432 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123221896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585423
Shilin Liu, X. Lin, Peng Mei, Ping Pang, Yihong Su
An active antenna based on SPDT (single-pole double throw) switch which forms three beams with two horns is presented in this paper. The antenna which centers at 110GHz can get a maximal gain of about 17.7dB. The Y-shaped microwave switch, with an included angle of 90 degree, has a good impendence matching when single-arm or both-arms are on. The horn antenna is connected to the end of the switch as shown in Fig.1. A lateral radiation can be obtained when either arm of the switch is on, while a synthetic beam obtained with both arms on, thus forming three beams. These antennas can have a great usage in the application of THz sensing or detecting.
{"title":"A novel THz antenna forming three beams using a PIN SPDT switch","authors":"Shilin Liu, X. Lin, Peng Mei, Ping Pang, Yihong Su","doi":"10.1109/IEEE-IWS.2016.7585423","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585423","url":null,"abstract":"An active antenna based on SPDT (single-pole double throw) switch which forms three beams with two horns is presented in this paper. The antenna which centers at 110GHz can get a maximal gain of about 17.7dB. The Y-shaped microwave switch, with an included angle of 90 degree, has a good impendence matching when single-arm or both-arms are on. The horn antenna is connected to the end of the switch as shown in Fig.1. A lateral radiation can be obtained when either arm of the switch is on, while a synthetic beam obtained with both arms on, thus forming three beams. These antennas can have a great usage in the application of THz sensing or detecting.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115766886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585484
S. A. Mohadeskasaei, Xianwei Zhou, S. M. M. Demneh, Sani Umar Abdullahi
In this article, simulation and implementation of a 10 watt class-AB pulse power amplifier using LDMOS transistor in 1.2-1.4 GHz is presented. Class-AB RF amplifier is commonly used in wireless communication industry because it offers an acceptable compromise between linearity and efficiency. Load pull and source pull software utilities are employed to obtain the optimum input and output impedances of the device. Afterwards, the input and the output matching networks based on a low pass Chebyshev filter were designed and optimized via computer aided simulation. The proposed design approach of matching networks enables improvements in both linearity and efficiency at 6 dB back off input power without the need for a linearizer. The power amplifier exhibits 40-41 dBm output power at 1 dB gain compression point (P1dB), 18 dB minimum signal gain and above 50% drain efficiency throughout the band. The measurement results show that the amplifier is very suitable for use in the driver stage of a very high power amplifier due to its high gain flatness.
{"title":"A 10 watt class-AB pulse power amplifier","authors":"S. A. Mohadeskasaei, Xianwei Zhou, S. M. M. Demneh, Sani Umar Abdullahi","doi":"10.1109/IEEE-IWS.2016.7585484","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585484","url":null,"abstract":"In this article, simulation and implementation of a 10 watt class-AB pulse power amplifier using LDMOS transistor in 1.2-1.4 GHz is presented. Class-AB RF amplifier is commonly used in wireless communication industry because it offers an acceptable compromise between linearity and efficiency. Load pull and source pull software utilities are employed to obtain the optimum input and output impedances of the device. Afterwards, the input and the output matching networks based on a low pass Chebyshev filter were designed and optimized via computer aided simulation. The proposed design approach of matching networks enables improvements in both linearity and efficiency at 6 dB back off input power without the need for a linearizer. The power amplifier exhibits 40-41 dBm output power at 1 dB gain compression point (P1dB), 18 dB minimum signal gain and above 50% drain efficiency throughout the band. The measurement results show that the amplifier is very suitable for use in the driver stage of a very high power amplifier due to its high gain flatness.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125409574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585456
Kaida Dong, Jingyan Mo, Yuhong He, Zhewang Ma, Xue-xia Yang
A millimeter-wave dual-band bandpass filter using substrate integrated waveguide (SIW) dual-mode cavities is proposed in this paper. The proposed filter consists of three SIW cavities, and each cavity can provide two resonant modes, the TE201 mode and TE102 mode, as well as a transmission zero. The resonant frequencies of TE201 and TE102 modes can be adjusted by the length and width of the SIW cavity, respectively. And the transmission zero can be adjusted by the location of the coupling window between the SIW cavity and the positions of the input and output ports. An example dual-band bandpass filter is designed, and the center frequencies of the two passbands are 26.73GHz and 31.52GHz, respectively. The 3dB-passbands are 26.24-27.21GHz (3.6%) and 31.2-31.84GHz (2%), respectively, with maximum insertion loss of 0.48dB and 0.67dB, respectively, and return loss larger than 12dB in both pass-bands.
{"title":"Design of a millimeter-wave dual-band bandpass filter using SIW dual-mode cavities","authors":"Kaida Dong, Jingyan Mo, Yuhong He, Zhewang Ma, Xue-xia Yang","doi":"10.1109/IEEE-IWS.2016.7585456","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585456","url":null,"abstract":"A millimeter-wave dual-band bandpass filter using substrate integrated waveguide (SIW) dual-mode cavities is proposed in this paper. The proposed filter consists of three SIW cavities, and each cavity can provide two resonant modes, the TE201 mode and TE102 mode, as well as a transmission zero. The resonant frequencies of TE201 and TE102 modes can be adjusted by the length and width of the SIW cavity, respectively. And the transmission zero can be adjusted by the location of the coupling window between the SIW cavity and the positions of the input and output ports. An example dual-band bandpass filter is designed, and the center frequencies of the two passbands are 26.73GHz and 31.52GHz, respectively. The 3dB-passbands are 26.24-27.21GHz (3.6%) and 31.2-31.84GHz (2%), respectively, with maximum insertion loss of 0.48dB and 0.67dB, respectively, and return loss larger than 12dB in both pass-bands.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126536340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585473
S. Dong, P. Tasker, Guofeng Wang, J. Lees
The intrinsic performance of the devices is of great meaning during power amplifiers design. A method to update de-embedding network at higher frequency for packaged power devices is put forward based on physical modeling idea. The de-embedding network at 5.8 GHz of a packaged GaN HEMT is presented and its practicability is verified through error analysis. This method is prospected to be applied to other packaged microwave devices.
{"title":"A practicable de-embedding network at higher frequency of a packaged GaN device","authors":"S. Dong, P. Tasker, Guofeng Wang, J. Lees","doi":"10.1109/IEEE-IWS.2016.7585473","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585473","url":null,"abstract":"The intrinsic performance of the devices is of great meaning during power amplifiers design. A method to update de-embedding network at higher frequency for packaged power devices is put forward based on physical modeling idea. The de-embedding network at 5.8 GHz of a packaged GaN HEMT is presented and its practicability is verified through error analysis. This method is prospected to be applied to other packaged microwave devices.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114614002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585486
Hassan Bin Tila, A. Buzdar, A. Buzdar, Liguo Sun, Mehdi Khan, Usman Khan, Waqas Ahmed
A novel low cost 1-to-4 Microstrip Wilkinson Power Divider has been proposed in the frequency range of 1-4 GHz. The power divider is centered at 2.5 GHz and is ideal for use in Through Wall Sensing (TWS) applications. The design has been mathematically modeled and the results have been optimized using HFSS optimetrics. The 1-to-4 power divider has been designed by combining three 1-to-2 power dividers in cascade. The manufactured 1-to-4 power divider results have shown good parameters which are in line with simulation results.
{"title":"Novel low cost 1-to-4 Microstrip Wilkinson Power Divider","authors":"Hassan Bin Tila, A. Buzdar, A. Buzdar, Liguo Sun, Mehdi Khan, Usman Khan, Waqas Ahmed","doi":"10.1109/IEEE-IWS.2016.7585486","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585486","url":null,"abstract":"A novel low cost 1-to-4 Microstrip Wilkinson Power Divider has been proposed in the frequency range of 1-4 GHz. The power divider is centered at 2.5 GHz and is ideal for use in Through Wall Sensing (TWS) applications. The design has been mathematically modeled and the results have been optimized using HFSS optimetrics. The 1-to-4 power divider has been designed by combining three 1-to-2 power dividers in cascade. The manufactured 1-to-4 power divider results have shown good parameters which are in line with simulation results.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"32 16","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120815633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585464
Y. Zhuang, Jiafeng Zhou, Yi Huang, Anqi Chen
This paper presents the design, implementation and experimental results of a broadband high efficiency GaN-HEMT power amplifier. The source-pull and load-pull simulations were employed to determine the optimum input and output impedance of a GaN transistor over 0.9-1.5 GHz in terms of maximum power added efficiency (PAE). A low-pass network based on a closed-form solution was applied for impedance matching and then it was transferred to a band-pass network. Norton Transformation was used to scale up impedances without sacrificing bandwidth or matching. For large signals, the amplifier can achieve a power gain of 9.5-13.5 dB across 0.9-1.5 GHz while the output power is 10-22W. The corresponding power added efficiency (PAE) is 60%-86%. This power amplifier is suitable for satellite communications systems and GNSS applications.
{"title":"Design of a broadband high efficiency GaN power amplifier for GNSS applications","authors":"Y. Zhuang, Jiafeng Zhou, Yi Huang, Anqi Chen","doi":"10.1109/IEEE-IWS.2016.7585464","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585464","url":null,"abstract":"This paper presents the design, implementation and experimental results of a broadband high efficiency GaN-HEMT power amplifier. The source-pull and load-pull simulations were employed to determine the optimum input and output impedance of a GaN transistor over 0.9-1.5 GHz in terms of maximum power added efficiency (PAE). A low-pass network based on a closed-form solution was applied for impedance matching and then it was transferred to a band-pass network. Norton Transformation was used to scale up impedances without sacrificing bandwidth or matching. For large signals, the amplifier can achieve a power gain of 9.5-13.5 dB across 0.9-1.5 GHz while the output power is 10-22W. The corresponding power added efficiency (PAE) is 60%-86%. This power amplifier is suitable for satellite communications systems and GNSS applications.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"73 13","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120823192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585410
Tiezhu Yuan, Yongqiang Cheng, Yuliang Qin, Hongqiang Wang
The wavelength array (WA) originating from the frequency diverse array (FDA) can achieve strictly angle-independent pattern. But when WA is simplified to a basic FDA, the produced pattern can not be angle-independent any more, which is investigated in this paper. We adopt a basic FDA as transmitter and observe its pattern at an appropriate reference range. The observed pattern is modulated periodically in range except for a slight deviation, which has been analyzed mathematically. Several impact factors are indicated for reducing the range deviation. Finally, some numerical simulations are given to verify these results. Since array error is inevitable, our analysis provides a basis for array design in practical application of FDA.
{"title":"Deviation of the approximate angle-independent pattern with frequency diverse array antenna","authors":"Tiezhu Yuan, Yongqiang Cheng, Yuliang Qin, Hongqiang Wang","doi":"10.1109/IEEE-IWS.2016.7585410","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585410","url":null,"abstract":"The wavelength array (WA) originating from the frequency diverse array (FDA) can achieve strictly angle-independent pattern. But when WA is simplified to a basic FDA, the produced pattern can not be angle-independent any more, which is investigated in this paper. We adopt a basic FDA as transmitter and observe its pattern at an appropriate reference range. The observed pattern is modulated periodically in range except for a slight deviation, which has been analyzed mathematically. Several impact factors are indicated for reducing the range deviation. Finally, some numerical simulations are given to verify these results. Since array error is inevitable, our analysis provides a basis for array design in practical application of FDA.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115329926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-03-14DOI: 10.1109/IEEE-IWS.2016.7585414
Shujun Han, Yanhui Lu, Shou-yi Yang, X. Mu
This paper models the optimization problem of energy efficiency (EE) in multi-user cognitive multi-input-multi-output (MIMO) interference channel (IC) as a non-cooperative game, where both the per-secondary user (SU) power constraints and total interference threshold is taken into consideration. Although optimization problem of EE is non-convex and multi-objective with multi-constraint fractional problem, we reformulate it as multi-objective with multi-constraint non-fractional problem equivalently. Furthermore, we formulate distributed iterative EE Optimization algorithm (DIEEOA) in multi-user cognitive MIMO IC to obtain the Nash Equilibrium. Through simulation, we validate the effectiveness of the prosed algorithm and discuss the parameters' effect on the EE.
{"title":"Game theory-based energy efficiency optimization in multi-user cognitive MIMO interference channel","authors":"Shujun Han, Yanhui Lu, Shou-yi Yang, X. Mu","doi":"10.1109/IEEE-IWS.2016.7585414","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585414","url":null,"abstract":"This paper models the optimization problem of energy efficiency (EE) in multi-user cognitive multi-input-multi-output (MIMO) interference channel (IC) as a non-cooperative game, where both the per-secondary user (SU) power constraints and total interference threshold is taken into consideration. Although optimization problem of EE is non-convex and multi-objective with multi-constraint fractional problem, we reformulate it as multi-objective with multi-constraint non-fractional problem equivalently. Furthermore, we formulate distributed iterative EE Optimization algorithm (DIEEOA) in multi-user cognitive MIMO IC to obtain the Nash Equilibrium. Through simulation, we validate the effectiveness of the prosed algorithm and discuss the parameters' effect on the EE.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123666480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method to enhance transition performance between millimeter wave & terahertz Si-based chip and waveguide by employing improved waveguide probe coupling structure is proposed in this paper. Multi-section impedance matching structure is employed in the E-plane probe to obtain good matching/low loss performance for waveguide packaging. In order to eliminate severely higher order dielectric filled waveguide mode excited below the metal layer one in the lossy silicon substrate, a simple but effective shielding method is proposed to prevent the higher order mode loss, which can decrease the signal energy injecting into lossy substrate to improve the insertion loss performance considerably. Finally, an W-band Si-based amplifier is demonstrated, and measured results show that good agreements between the measured and simulated results are achieved.
{"title":"Low loss packaging method for Si-based chips occupying waveguide probe coupling structure","authors":"Ruitao Wang, Hailin Tang, Haitao Liu, Yihu Li, Xiaodong Deng, Y. Xiong","doi":"10.1109/IEEE-IWS.2016.7585433","DOIUrl":"https://doi.org/10.1109/IEEE-IWS.2016.7585433","url":null,"abstract":"A method to enhance transition performance between millimeter wave & terahertz Si-based chip and waveguide by employing improved waveguide probe coupling structure is proposed in this paper. Multi-section impedance matching structure is employed in the E-plane probe to obtain good matching/low loss performance for waveguide packaging. In order to eliminate severely higher order dielectric filled waveguide mode excited below the metal layer one in the lossy silicon substrate, a simple but effective shielding method is proposed to prevent the higher order mode loss, which can decrease the signal energy injecting into lossy substrate to improve the insertion loss performance considerably. Finally, an W-band Si-based amplifier is demonstrated, and measured results show that good agreements between the measured and simulated results are achieved.","PeriodicalId":185971,"journal":{"name":"2016 IEEE MTT-S International Wireless Symposium (IWS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130060097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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