Digital Wireless Beamforming
Beamforming is an essential technique for mm-wave communication. Large-scale beam-beamforming mitigates the substantial path loss in an mm-wave link, rejects spatial interferers, and significantly relaxes both the transmit power and receiver sensitivity requirements. The ability to generate multiple simultaneous beams is essential for multi-input multi- output (MIMO) systems. Beam accuracy is crucial to create the narrow beams in large-scale beamforming systems; otherwise, spatial power leakage causes power loss at the desired direction and interference in other directions. Although there has been significant progress on analog mm-wave beamforming, digital beamforming has several compelling advantages for large-scale beamforming, including excellent beam-pattern accuracy, inherent flexibility, and the ability to generate multiple, simultaneous beams.
Our research demonstrated first fully-integrated single-chip digital mm- wave beamformer. A significant advantage of the single-chip approach is its small form factor. Also, a single-chip implementation dramatically reduces I/O and simplifies the substrate and packaging. Our approach is enabled by: 1) simplified mm-wave frontend and mm-wave LO distribution thanks to a high IF; 2) a band-pass ADC array with inherent FIR filtering which facilitates high IF sampling; 3) bit-stream processing for energy-efficient and compact digital
LTCC Substrate with 4x4 Patch Antenna beamforming, and; 4) a custom LTCC substrate with integrated mm-wave antenna array. The prototype integrated circuit (IC) supports 16 mm-wave antenna elements and generates four simultaneous independent beams. The prototype IC incorporates 16 mm-wave frontends, PLLs, LO generation and distribution, 64 ADCs, and complete digital beamform processing. With a custom 8-layer LTCC substrate incorporating a 4×4 patch antenna array, this is the first single- chip mm-wave-to-digital beamforming system. Over-the-air measurements confirm accurate 3D beam patterns and indicate a measured overall noise figure (NF) of 7dB.
LTCC Substrate with 4x4 Patch Antenna beamforming, and; 4) a custom LTCC substrate with integrated mm-wave antenna array. The prototype integrated circuit (IC) supports 16 mm-wave antenna elements and generates four simultaneous independent beams. The prototype IC incorporates 16 mm-wave frontends, PLLs, LO generation and distribution, 64 ADCs, and complete digital beamform processing. With a custom 8-layer LTCC substrate incorporating a 4×4 patch antenna array, this is the first single- chip mm-wave-to-digital beamforming system. Over-the-air measurements confirm accurate 3D beam patterns and indicate a measured overall noise figure (NF) of 7dB.
R. Lu, C. Weston, D. Weyer, F. Buhler, M. P. Flynn, "A 16-Element Fully Integrated 28GHz Digital Beamformer with In-Package 4×4 Patch Antenna Array and 64 Continuous-Time Band-Pass Delta-Sigma Sub-ADCs" 2020 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2020.
Boyi Zheng, Lu Jie, Runyu Wang, Michael P. Flynn, "A 6GHz 160MHz Bandwidth MU-MIMO Eight-Element Direct Digital Beamforming TX Utilizing FIR H-Bridge DAC" 2020 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2020.
R. Lu, S. Jang, Y. Hao, M. P. Flynn, "A 77dB-SFDR Multi-Phase-Sampling 16-Element Digital Beamformer with 64 4GS/s 100MHz-BW Continuous-Time Band-Pass ΔΣ ADCs," 2019 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2019.
B. Zheng, L. Jie, J. Bell, Y. He, M. P. Flynn, "A Two-Beam Eight-Element Direct Digital Beamforming RF Modulator in 40-nm CMOS," in IEEE TMTT, July 2019.
S. Jang, R. Lu, J. Jeong and M. P. Flynn, "A 1-GHz 16-Element Four-Beam True-Time-Delay Digital Beamformer," in IEEE Journal of Solid-State Circuits, February 2019.
S. Jang, R. Lu, J. Jeong and M. P. Flynn, "A True Time Delay 16-Element 4-Beam Digital Beamformer," 2018 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2018.
S. Jang, J. Jeong, R. Lu and M. P. Flynn, "A 16-Element 4-Beam 1 GHz IF 100 MHz Bandwidth Interleaved Bit Stream Digital Beamformer in 40 nm CMOS," in IEEE Journal of Solid-State Circuits, January 2018.
S. Jang, J. Jeong, R. Lu and M. P. Flynn, "A 16-element 4-beam 1GHz-IF 100MHz-bandwidth interleaved bit-stream beamformer in 40nm CMOS,” IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2017
J. Jeong, N. Collins, and M. P. Flynn, "A 260 MHz IF Sampling Bit-Stream Processing Digital Beamformer with an Integrated Array of Continuous-Time Band-Pass ΔΣ Modulators," IEEE Journal of Solid-State Circuits, May 2016.
Jaehun Jeong, Collins, N. , Flynn, M.P., "An IF 8-element 2-beam bit-stream band-pass beamformer," Radio Frequency Integrated Circuits Symposium (RFIC), May, 2015.
Boyi Zheng, Lu Jie, Runyu Wang, Michael P. Flynn, "A 6GHz 160MHz Bandwidth MU-MIMO Eight-Element Direct Digital Beamforming TX Utilizing FIR H-Bridge DAC" 2020 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2020.
R. Lu, S. Jang, Y. Hao, M. P. Flynn, "A 77dB-SFDR Multi-Phase-Sampling 16-Element Digital Beamformer with 64 4GS/s 100MHz-BW Continuous-Time Band-Pass ΔΣ ADCs," 2019 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2019.
B. Zheng, L. Jie, J. Bell, Y. He, M. P. Flynn, "A Two-Beam Eight-Element Direct Digital Beamforming RF Modulator in 40-nm CMOS," in IEEE TMTT, July 2019.
S. Jang, R. Lu, J. Jeong and M. P. Flynn, "A 1-GHz 16-Element Four-Beam True-Time-Delay Digital Beamformer," in IEEE Journal of Solid-State Circuits, February 2019.
S. Jang, R. Lu, J. Jeong and M. P. Flynn, "A True Time Delay 16-Element 4-Beam Digital Beamformer," 2018 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2018.
S. Jang, J. Jeong, R. Lu and M. P. Flynn, "A 16-Element 4-Beam 1 GHz IF 100 MHz Bandwidth Interleaved Bit Stream Digital Beamformer in 40 nm CMOS," in IEEE Journal of Solid-State Circuits, January 2018.
S. Jang, J. Jeong, R. Lu and M. P. Flynn, "A 16-element 4-beam 1GHz-IF 100MHz-bandwidth interleaved bit-stream beamformer in 40nm CMOS,” IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2017
J. Jeong, N. Collins, and M. P. Flynn, "A 260 MHz IF Sampling Bit-Stream Processing Digital Beamformer with an Integrated Array of Continuous-Time Band-Pass ΔΣ Modulators," IEEE Journal of Solid-State Circuits, May 2016.
Jaehun Jeong, Collins, N. , Flynn, M.P., "An IF 8-element 2-beam bit-stream band-pass beamformer," Radio Frequency Integrated Circuits Symposium (RFIC), May, 2015.