The Experts below are selected from a list of 90543 Experts worldwide ranked by ideXlab platform
Bumman Kim - One of the best experts on this subject based on the ideXlab platform.
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linear doherty power amplifier with an enhanced back off efficiency mode for handset applications
IEEE Transactions on Microwave Theory and Techniques, 2014Co-Authors: Yunsung Cho, Jooseung Kim, Byungjoon Park, Daehyun Kang, Kyunghoon Moon, Bumman KimAbstract:This paper presents a linear Doherty power amplifier (PA) with enhanced back-off efficiency mode for handset applications. For linear Doherty operation, we analyze the gain modulation as well as the cancellation of the third-order intermodulation distortion in order to improve the linearity. A compact design method is also discussed to implement on a single chip for a handset. The proposed Doherty PA delivers good performance with regard to the third-generation (3G)/fourth-generation (4G) modulation Signals. A switched-load power-mode PA is adopted in the proposed Doherty PA to enhance the efficiency in the low-power region with over 10-dB back-off. For demonstration purposes, the PA is implemented using an InGaP/GaAs heterojunction bipolar transistor and AlGaAs/InGaAs pseudomorphic high electron-mobility transistor process. The PA is tested at 1.85 GHz using both a long-term evolution Signal with 16-quadrature amplitude modulation, 7.5-dB peak-to-average power ratio, and 10-MHz bandwidth (BW) and a wideband code division multiple Access Signal with 3.3-dB PAPR and 3.84-MHz BW. The proposed linear Doherty PA with an enhanced back-off efficiency mode delivers good performance in both the high- and low-power modes, implying that the dual-power-mode Doherty PA configuration can be a promising candidate for extending the battery life of handheld devices in 3G and 4G wireless communication systems.
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a multimode multiband power amplifier with a boosted supply modulator
IEEE Transactions on Microwave Theory and Techniques, 2010Co-Authors: Daehyun Kang, Yunsung Cho, Jooseung Kim, Dongsu Kim, Jinsung Choi, Bumman KimAbstract:A multimode/multiband power amplifier (PA) with a boosted supply modulator is developed for handset applications. A linear broadband class-F amplifier is designed to have a constant fundamental impedance across 1.7-2 GHz and its second and third harmonic impedances are located at the high-efficiency area. To reduce the circuit size for handset application, the harmonic control circuits are merged into the broadband output matching circuit for the fundamental frequency. An envelope-tracking operation delivers high efficiency for the overall power. The linearity is improved by envelope tracking (ET) through intermodulation-distortion sweet-spot tracking at the maximum output power level. The efficiency and bandwidth (BW) are enhanced by a boosted supply modulator. Multimode operation is achieved by an ET technique with a programmable hysteresis control and automatic switching current adaptation of the hybrid supply modulator. For demonstration purpose, the PA and supply modulator are implemented using an InGaP/GaAs heterojunction bipolar transistor and a 65-nm CMOS process. For a long-term evolution Signal, the envelope-tracking (ET) PA delivers a power-added efficiency (PAE) and an error vector magnitude of 33.3%-39% and 2.5%-3.5%, respectively, at an average power of 27.8 dBm across 1.7-2 GHz. For a wideband code-division multiple-Access Signal across 1.7-2 GHz, the ET PA performs a PAE, an ACLR1, and an ACLR2 of 40%-46.3%, from -39 to -42.5ndBc, and -51 to -58ndBc, respectively, at an average output power of 30.1 dBm. The ET PA with an EDGE Signal delivers a PAE, an ACPR1, and an ACPR2 of 37%-42%, from -56.5 to -59.3ndBc, and -63.5 to -69.5ndBc, respectively, at an average power of 28 dBm across the 300-MHz BW. These results show that the proposed design achieves highly efficient and linear power amplification for multimode/multiband wireless communication applications.
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analysis of a fully matched saturated doherty amplifier with excellent efficiency
IEEE Transactions on Microwave Theory and Techniques, 2008Co-Authors: Jangheon Kim, Junghwan Moon, Young Yun Woo, Sungchul Hong, Ildu Kim, Jungjoon Kim, Bumman KimAbstract:A saturated Doherty amplifier based on class-F amplifiers is analyzed in terms of its load modulation behavior, efficiency, and linearity. Simulations included the amplitude ratio and phase difference between the fundamental and third harmonic voltages, the current/voltage waveforms, load lines, and the third-order intermodulation amplitudes/phases of the carrier and peaking amplifiers. The saturated doherty power amplifier was implemented using two Eudyna EGN010MK GaN HEMTs with a 10-W peak envelope power. For a 2.14-GHz forward-fink wideband code-division multiple-Access Signal, the doherty amplifier delivers an excellent efficiency of 52.4% with an acceptable linearity of -28.3 dBc at an average output power of 36 dBm. Moreover, the amplifier can provide the high linearity performance of -50 dBc using the digital feedback predistortion technique.
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optimum operation of asymmetrical cells based linear doherty power amplifiers uneven power drive and power matching
IEEE Transactions on Microwave Theory and Techniques, 2005Co-Authors: Jangheon Kim, Ildu Kim, Jeonghyeon Cha, Bumman KimAbstract:We developed a Doherty amplifier with uneven input drive and optimized individual matching for the carrier and peaking cells. In the proposed amplifier, higher input power is delivered to the peaking cell rather than the carrier cell for optimized linear power operation, especially for appropriate load modulation. Both cells are matched differently to further optimize the performance. We analyzed the efficiency of the proposed amplifier as a function of the input drive ratio for the two cells. To interpret the linearity related to the load modulation and harmonic cancellation mechanisms, we simulated the third-order intermodulation amplitude and phase of each cell of the proposed amplifier. For verification, we implemented the asymmetric power amplifier with uneven drive and optimized power matching using Motorola's MRF281SR1 LDMOSFET with a 4-W peak envelope power. For a 2.14-GHz forward-link wireless code-division multiple-Access Signal, the measured drain efficiency of the amplifier is 40%, and the measured average output power is 33 dBm at an adjacent channel leakage ratio (ACLR) of -35 dBc, while those of the comparable class-AB amplifier are 21% and 30.6 dBm at the same ACLR level, respectively.
Yang Leng - One of the best experts on this subject based on the ideXlab platform.
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hysteresis current control for multilevel converter in parallel form switch linear hybrid envelope tracking power supply
IEEE Transactions on Power Electronics, 2019Co-Authors: Yazhou Wang, Xinbo Ruan, Yang LengAbstract:Parallel-form switch-linear hybrid (SLH) envelope tracking (ET) power supply is constituted by a linear amplifier and a switched-mode converter connected in parallel. The switched-mode converter is usually implemented by a buck converter with hysteresis current control. However, the slew rates of the load current and the inductor current of the buck converter cannot match well when the slew rate of the load current has a wide variation range. The unmatched slew rates will lead to a high switching frequency of the buck converter or a large loss of the linear amplifier, which degrades the overall efficiency. In this paper, a multilevel converter is adopted to replace the buck converter in the parallel-form SLH ET power supply, and the hysteresis current control scheme is proposed for the multilevel converter to dynamically adjust its inductor current slew rate to approach that of the load current to improve the overall efficiency. The optimal design for the efficiency-related parameters including the inductor, the current hysteresis, and the number and values of the voltage levels in the multilevel converter is given. A prototype of the parallel-form SLH ET power supply with hysteresis current controlled multilevel converter is fabricated and tested in the lab. The measured overall efficiency is 79.4% when tracking the envelope of wideband code division multiple Access Signal with 5 MHz bandwidth and outputs 18 W average power, and a 3.8% efficiency improvement is achieved over that with the hysteresis current controlled buck converter.
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quasi interleaved current control for switch linear hybrid envelope tracking power supply
IEEE Transactions on Power Electronics, 2018Co-Authors: Yazhou Wang, Xinbo Ruan, Qian Jin, Yang Leng, Fan Meng, Xiaowei ZhuAbstract:An envelope-tracking (ET) technique can greatly enhance the efficiency of the power amplifier in wireless communication system. Among the structures of the ET power supply, the switch-linear hybrid (SLH) structure can obtain both high-tracking bandwidth and high efficiency. An implementation of series–parallel-form SLH ET power supply is proposed in this paper, which includes one multilevel converter, one linear amplifier, and two buck converters. The two buck converters adopt current sensor-less prediction control and are operated at critical conduction mode (CRM). In order to ensure the operation of CRM and provide as much load current as possible, a quasi-interleaved current control scheme is proposed for the two buck converters. Moreover, a peak current restriction method is proposed to prevent the output current of the two interleaved buck converters from excessively exceeding the load current, avoiding the increase of the power loss in the linear amplifier. Finally, a prototype is fabricated with the specifications as 5-MHz tracking bandwidth, 9.6–26.4-V output voltage, and 20-W average output power. The overall measured efficiency is 81.0%, and the normalized-mean-square error is 0.28% when tracking the envelope of wideband code division multiple Access Signal.
Yazhou Wang - One of the best experts on this subject based on the ideXlab platform.
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hysteresis current control for multilevel converter in parallel form switch linear hybrid envelope tracking power supply
IEEE Transactions on Power Electronics, 2019Co-Authors: Yazhou Wang, Xinbo Ruan, Yang LengAbstract:Parallel-form switch-linear hybrid (SLH) envelope tracking (ET) power supply is constituted by a linear amplifier and a switched-mode converter connected in parallel. The switched-mode converter is usually implemented by a buck converter with hysteresis current control. However, the slew rates of the load current and the inductor current of the buck converter cannot match well when the slew rate of the load current has a wide variation range. The unmatched slew rates will lead to a high switching frequency of the buck converter or a large loss of the linear amplifier, which degrades the overall efficiency. In this paper, a multilevel converter is adopted to replace the buck converter in the parallel-form SLH ET power supply, and the hysteresis current control scheme is proposed for the multilevel converter to dynamically adjust its inductor current slew rate to approach that of the load current to improve the overall efficiency. The optimal design for the efficiency-related parameters including the inductor, the current hysteresis, and the number and values of the voltage levels in the multilevel converter is given. A prototype of the parallel-form SLH ET power supply with hysteresis current controlled multilevel converter is fabricated and tested in the lab. The measured overall efficiency is 79.4% when tracking the envelope of wideband code division multiple Access Signal with 5 MHz bandwidth and outputs 18 W average power, and a 3.8% efficiency improvement is achieved over that with the hysteresis current controlled buck converter.
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quasi interleaved current control for switch linear hybrid envelope tracking power supply
IEEE Transactions on Power Electronics, 2018Co-Authors: Yazhou Wang, Xinbo Ruan, Qian Jin, Yang Leng, Fan Meng, Xiaowei ZhuAbstract:An envelope-tracking (ET) technique can greatly enhance the efficiency of the power amplifier in wireless communication system. Among the structures of the ET power supply, the switch-linear hybrid (SLH) structure can obtain both high-tracking bandwidth and high efficiency. An implementation of series–parallel-form SLH ET power supply is proposed in this paper, which includes one multilevel converter, one linear amplifier, and two buck converters. The two buck converters adopt current sensor-less prediction control and are operated at critical conduction mode (CRM). In order to ensure the operation of CRM and provide as much load current as possible, a quasi-interleaved current control scheme is proposed for the two buck converters. Moreover, a peak current restriction method is proposed to prevent the output current of the two interleaved buck converters from excessively exceeding the load current, avoiding the increase of the power loss in the linear amplifier. Finally, a prototype is fabricated with the specifications as 5-MHz tracking bandwidth, 9.6–26.4-V output voltage, and 20-W average output power. The overall measured efficiency is 81.0%, and the normalized-mean-square error is 0.28% when tracking the envelope of wideband code division multiple Access Signal.
Ananthram Swami - One of the best experts on this subject based on the ideXlab platform.
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a survey of dynamic spectrum Access Signal processing and networking perspectives
International Conference on Acoustics Speech and Signal Processing, 2007Co-Authors: Qing Zhao, Ananthram SwamiAbstract:In this paper, we provide a survey of dynamic spectrum Access techniques. Various approaches envisioned for dynamic spectrum Access are broadly categorized under three models: dynamic exclusive use model, open sharing model, and hierarchical Access model. Based on this taxonomy, we provide an overview of the technical challenges and recent advances under each model.
Xiaowei Zhu - One of the best experts on this subject based on the ideXlab platform.
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quasi interleaved current control for switch linear hybrid envelope tracking power supply
IEEE Transactions on Power Electronics, 2018Co-Authors: Yazhou Wang, Xinbo Ruan, Qian Jin, Yang Leng, Fan Meng, Xiaowei ZhuAbstract:An envelope-tracking (ET) technique can greatly enhance the efficiency of the power amplifier in wireless communication system. Among the structures of the ET power supply, the switch-linear hybrid (SLH) structure can obtain both high-tracking bandwidth and high efficiency. An implementation of series–parallel-form SLH ET power supply is proposed in this paper, which includes one multilevel converter, one linear amplifier, and two buck converters. The two buck converters adopt current sensor-less prediction control and are operated at critical conduction mode (CRM). In order to ensure the operation of CRM and provide as much load current as possible, a quasi-interleaved current control scheme is proposed for the two buck converters. Moreover, a peak current restriction method is proposed to prevent the output current of the two interleaved buck converters from excessively exceeding the load current, avoiding the increase of the power loss in the linear amplifier. Finally, a prototype is fabricated with the specifications as 5-MHz tracking bandwidth, 9.6–26.4-V output voltage, and 20-W average output power. The overall measured efficiency is 81.0%, and the normalized-mean-square error is 0.28% when tracking the envelope of wideband code division multiple Access Signal.
