Sang-Hyun Chang

Holistic Design Considerations for Environmentally Adaptive 60 GHz Beamforming Technology

Proliferation of all forms of smart devices has driven the demand for high-data-rate Wi-Fi in recent years. Utilizing wide bandwidth in high frequency is the most efficient way of guaranteeing the explosive data demands. In spite of the notable advancements of RF technologies at millimeter wave, the relatively high propagation loss remains problematic. The authors present efficient beamforming technology to mitigate this challenge. In this article, we first discuss the principles and major applications of beamforming technology. Afterward, we present the challenges for optimizing the efficiency of beamforming as well as the solutions to tackle them by proposing enhanced algorithms and advanced design architectures based on our hands-on experience and knowledge. Lastly, experimental results are discussed to deduce insight and vision of future Wi-Fi.

Quantization effects of phase shifters on 5G mmWave antenna arrays

In this paper, we investigate the phase shifter quantization effect on the performance of mmWave antenna arrays for future 5G applications. Given a 2-bit phase shifter, 8-element antenna array configuration, the phase-shifter degrades the antenna array gain up to 3 dB for non-boresight directions. Also, spherical sector coverage over beamforming sector sweeps is reduced, so that the mobile radio becomes susceptible to the time variation of devices orientation rotation. To evaluate the performance of an array antenna, the results shows that the robustness on the phase shifter degradation effects needs to be examined.

A robust beamforming scheme with low power and complexity for IEEE 802.11n systems

Due to the extremely increased interference of multiple-input multiple-output systems, designing efficient transmit beamforming schemes is significant to degrade the interference. A novel beamforming scheme is addressed by incorporating a multiple hypothesis testing problem with the characteristics of the wireless channel. The proposed beamforming scheme is operated by the implicit beamforming protocol in the IEEE 802.11n standard. From the simulation results, it is confirmed that the proposed scheme has high SNR gain. The proposed beamforming scheme is implemented in Toshiba 40nm low power process and shows a gate count of only 33K and power consumption of 3.39mW. Field test results show that the maximum increase of the data rate with the proposed scheme is about 42 percent and the increase of coverage with the proposed scheme is 85 percent, while maintaining the robustness of incorrect channel state information.