Noise Figure Analysis in Hybrid Beamforming Systems

This document discusses the theoretical study of noise figure (NF) and gain in hybrid beamforming systems, focusing on the impact of additional RF blocks, such as phase shifters and combiners, on noise figure calculations. It explains how the received signals from multiple antennas are phase-corrected and combined in RF combiners, affecting the carrier-to-noise ratio (CNR) calculations. Illustrative block diagrams and calculations for noise figure are presented, highlighting the importance of proper consideration in hybrid beamforming designs.

• Noise Figure
• Hybrid Beamforming
• RF Blocks
• Antenna Arrays
• Signal Processing

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1. July 2015 doc.: IEEE 802.11-15/0889r0 Effective Noise Figure in Hybrid BF system Date: YYYY-MM-DD Authors: Name Young-Chai Ko Affiliations Address Korea University Phone email koyc@korea.ac.kr Seoul, Korea Myeong-Jin Kim Korea University Seoul, Korea smjkmj1004@korea.ac. kr arnoldjiho@korea.ac.kr Ji-Ho Lee Korea University Seoul, Korea Submission Slide 1 Ji-Ho Lee, Korea University

2. July 2015 doc.: IEEE 802.11-15/0889r0 Abstract This contribution presents the theoretical results of noise figure (NF) and gain in hybrid beamforming systems. Submission Slide 2 Ji-Ho Lee, Korea University

3. July 2015 doc.: IEEE 802.11-15/0889r0 Motivation In hybrid beamforming systems, the received signals from multiple antennas are phase corrected by phase shifter and then combined in RF combiner, usually before down-converting at RX. The additional RF blocks (i.e., phase shifter and combiner) are added to RF chain, which increases noise figure. Note that the RF combiner has multiple input signals and single output signals (multi-to-one RF path). In this case, the NF should be appropriately considered for the calculation of carrier to noise ratio (CNR). Submission Slide 3 Ji-Ho Lee, Korea University

4. July 2015 doc.: IEEE 802.11-15/0889r0 Block Diagram of Hybrid Beamforming Phase shifter LNA Low-pass filter Down- converting ADC Baseband Space-time processing Phase shifter LNA Low-pass filter Down- converting ADC The received signals from each antenna are phase-shifted by phase shifter and combined by combiner after LNA. At baseband, the conventional MIMO space-time processing is performed for multiplexing gain or/and diversity gain. Submission Slide 4 Ji-Ho Lee, Korea University

5. Month Year doc.: IEEE 802.11-15/0889r0 Noise Figure Calculation Phase shifter LNA ??, ?? ??1,??1 ??2,??2 ?? RF chain Equivalent ?? RF chain ???: ?? RF block s gain of ?? RF path ???: ?? RF block s noise figure of ?? RF path ??: Overall gain of ?? RF path ?? : Overall noise figure of ?? RF path Overall Noise Figure (Friis Equation) Overall Gain +??3 1 ??1??2 ??= ??1+??2 1 ??= ??1??2 ??? + ??1 Submission Slide 5 John Doe, Some Company

6. July 2015 doc.: IEEE 802.11-15/0889r0 Multi-to-One Path system Combiner ??out,1 ??in,1,??in,1 ?1, ?1, ?1 ?1 ??in,2,??in,2 ??out,2 ?2 ?2, ?2, ?2 Array output ??out,??out ?? ??in,?,??in,? ??out,? ??, ??, ?? ??out,?: Output noise power of ?? RF path ??: Amplitude combining coefficient of ?? RF path ??out : Output signal power of combiner ??out : Output noise power of combiner ??in,?: Input signal power of ?? RF path ??in,? : Input noise power of ?? RF path ??: Overall gain of ?? RF path ?? : Overall noise figure of ?? RF path ?? : Insertion phase shift of ?? RF path Submission Slide 6 Ji-Ho Lee, Korea University

7. July 2015 doc.: IEEE 802.11-15/0889r0 Equivalent Single-Path system ??in,1,??in,1 ?1, ?1, ?1 ?1 ??in,2,??in,2 ?2 ?2, ?2, ?2 Array output ??out,??out ??in,eff,??in,eff Array output ??out,eff,??out,eff ?eff, ?eff ?eff: Effective overall gain of single RF path ?eff : Effective overall noise figure of single RF path ??in,eff,??out,eff: Effective signal power of single RF path ??in,eff,??out,eff: Effective noise power of single RF path ??in,?,??in,? ?? ??, ??, ?? For an analysis purpose, a multi-to-one path system is converted into an equivalent single-path system. We assume that the total input, output power of multi-to-one-path system and equivalent single-path system are identical, such that the above two figures are equivalent. Submission Slide 7 Ji-Ho Lee, Korea University

8. July 2015 doc.: IEEE 802.11-15/0889r0 Effective Gain ??in,eff,??in,eff Array output ??out,eff,??out,eff ?eff, ?eff The effective gain of the array system is given to be [1] 2 ? ??out,eff ??in,eff =1 ?? ??? ?(? 1) ? ?? ????= ? ?=1 If all signal paths are identical (?1= ?2= ??= ?),we have 2 ? ????=? ? ?? ?=1 If all the ?? are 1 (?1= ?2= = ??= 1),we have ????= ? Submission Slide 8 Ji-Ho Lee, Korea University

9. July 2015 doc.: IEEE 802.11-15/0889r0 Effective Noise Figure ??in,eff,??in,eff Array output ??out,eff,??out,eff ?eff, ?eff The effective noise figure of the array system is given to be [1] ? 2 ??out,eff ?eff ??in,eff ? ?=1 ?? ?? ?? ????= = 2 ? ?? ??? ?(? 1) ? ?? ?=1 If all signal paths are identical (?1= ?2= = ??= ?),we have ? 2 ????= ? ? ?=1 ?? 2 ? ?=1 ?? If all the ?? are 1 (?1= ?2= = ??= 1),we have ????= ? Submission Slide 9 Ji-Ho Lee, Korea University

10. July 2015 doc.: IEEE 802.11-15/0889r0 Conclusion We contribute to calculating the noise figure and gain in hybrid beamforming system. Submission Slide 10 Ji-Ho Lee, Korea University

11. July 2015 doc.: IEEE 802.11-15/0889r0 References 1. Junghyun Kim, Jinho Jeong, and Sanggeun Jeon, "Improvement of Noise Performance in Phased-Array Receivers", ETRI Journal, vol. 33, no.2, pp. 176-183, April (2011) Submission Slide 11 Ji-Ho Lee, Korea University