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Perspectives on 6G Wireless Communications
Choongil Yeh,Gweon Do Jo,Young-Jo Ko,Hyun Kyu Chung 한국통신학회 2023 ICT Express Vol.9 No.1
Since its first commercialization in early 2019, 5G has been making progress around the world and penetrating daily lives. Now, research interest in wireless communication is quickly shifting to the next generation mobile system, 6G. This paper envisions the 6G as a union of physical space, cyberspace, and connectivity with intelligence. Also, interactivity is a critical component to provide users with a truly immersive experience. In this paper, 6G usage scenarios and use cases which cannot be properly supported under the 5G regime are proposed. Major key performance indicators (KPIs) to support these use cases are considered. The 6G-related state-of-the-art technologies and standardization activities are discussed in terms of interactivity, intelligence and connectivity. Also, future works to be accomplished for the completion of 6G are shortly stated.
Joon Hyung Kim,Gweon Do Jo,Jung Hoon Oh,Young Hoon Kim,Kwang Chun Lee,Jae Ho Jung IEEE 2011 IEEE transactions on microwave theory and techniqu Vol.59 No.1
<P>In this paper, efficiency-limiting physical constraint effects imposed on the knee voltage, along with a variation of the optimum load resistance, are investigated for highly efficient Class-F and Class- amplifiers. First, for an accurate analysis and comparison, new current waveform models are identified, and a realistic approach incorporated using a nonzero knee voltage and voltage-dependent nonlinear capacitance is employed to derive the voltage waveforms of the amplifiers. An analysis is performed to show the efficiency, output power, power gain, and output power compression points for both modes. Using this knowledge, along with a complete performance comparison, we provide a direction for optimizing the amplifier design. The analytic results are further verified based on the measured results of 3.54-GHz Class-F and Class- amplifiers using a commercial 60-W peak-to-envelope power gallium-nitride device. The experimental results show that Class-F and Class- amplifiers operate at drain efficiencies of 69.9% and 69.4% at saturated output powers of 47.4 and 47.2 dBm, respectively. These remarkably similar performances have excellent agreement with the predicted analysis at our operational frequency.</P>
Joon Hyung Kim,Gweon Do Jo,Jung Hoon Oh,Young Hoon Kim,Kwang Chun Lee,Jae Ho Jung,Chul Soon Park IEEE 2011 IEEE transactions on microwave theory and techniqu Vol.59 No.6
<P>In this paper, a high-efficiency envelope-tracking (ET) transmitter incorporating a novel efficiency-boosting function is proposed and implemented. An inverse Class-F power amplifier is utilized and optimized using the proposed output loading condition, which enhances its efficiency at the high probability region. This matching network can be conveniently implemented by controlling the nonlinear capacitance of the power transistor. For an accurate analysis, the output waveforms are modeled in terms of the nonlinear capacitance, and the efficiency and output power are subsequently analyzed and successfully optimized. For a high-efficiency envelope amplifier (EA), we propose a new EA utilizing a 2-bit switching stage in place of a 1-bit switching stage. This proposed architecture effectively reduces the ripple current, improving the efficiency of the EA. To verify our analysis, we have fully implemented a 3.54-GHz high-efficiency ET transmitter including a digital processing block. The experimental results show that the ET transmitter using a commercial 60-W peak-envelope-power GaN device operates at a drain efficiency of 44% and power-added efficiency of 39.6% with a gain of 10.1 dB at an average output power of 40 dBm for a 10-MHz third-generation long-term evolution signal with 8.5-dB peak-to-average power ratio. Using a digital pre-distortion function, the adjacent channel leakage ratio is less than -47.5 dBc.</P>