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Dr.P.H.Rao Scientist SAMEER- Center for Electromagnetics Chennai

RF and Antenna Design Challenges i n Indigenous 5G Test bed Development. Dr.P.H.Rao Scientist SAMEER- Center for Electromagnetics Chennai. OUTLINE. Introduction. 5G Challenges. TOPICS. 5G RF System and Antenna Testing. Indigenous 5G Test Bed. Antenna Design Challenges

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Dr.P.H.Rao Scientist SAMEER- Center for Electromagnetics Chennai

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  1. RF and Antenna Design Challenges in Indigenous 5G Test bed Development Dr.P.H.Rao Scientist SAMEER-Center for Electromagnetics Chennai

  2. OUTLINE Introduction 5G Challenges TOPICS • 5G RF System and Antenna Testing • Indigenous 5G Test Bed • Antenna Design Challenges • Beamformerdesign challenges • Conclusions

  3. Introduction • No matter how 5G will ultimately be implemented, higher data-rates, more capacity and many more connected “things” will be parts of the wireless future. • The emerging definition of 5G envisions dramatic performance improvements in network capacity, mobile connections, latency, cost, data rates and coverage • The 5G requirements for high data rates and low latency demand the implementation of technologies with large bandwidth in sub 6GHz and mm wave bands. RF and antenna developments and challenges specific to "Indigenous 5G test bed" both for sub 6GHz and mm wave bands. • Complex RF and Antenna technologies • Compact and small form factor • The interface issues • RF integration and fabrication issues • The  MIMO antennas at sub 6GHz • Phased array and Hybrid beam forming developments at mm wave • Alternative solutions in mm wave antenna developments for 1D and  2D beam switching

  4. A changing telecoms landscape • 5G Technology development and implementation • Enable true human-centric and connected machine-centric networks to redefine end user mobility along with the entire landscape of the global telecoms industry. • 5G will herald an even greater rise in the prominence of mobile access for realizing total ICT network growth and expansion. 4

  5. 5G Deployment 5 Source Qualcomm vision document

  6. Heterogeneous Network 6

  7. Challenges and Requirements • As with any major advance in communications technology, 5G presents a whole new set of technical RF challenges. • Unprecedented bandwidth, with carriers up to 100 MHz wide in FR1 and 400 MHz in FR2 and new waveforms will generate very high peak-to power ratios. • Implementation of Massive MIMO • Beam steering to deliver multi-gigabit data rates. • An escalation in bandwidth, demand for high linearity in RF systems. • MIMO and beam former measurements

  8. Realizing mmwavefor 5G 8 Source Qualcomm vision document

  9. Challenges and Requirements : Hand set • 5G specifications stipulate that handsets must support four downlink paths for bands above 1 GHz, to enable higher data rates. This requires four antennas and four independent RF pathways. • For many handsets, the change will mean a substantial increase in RF content, signal-routing complexity, and antenna bandwidth. • mm wave antennas and RF need complex designs for beam forming. • It will be challenging to squeeze even more content into already crowded space allocated to the RF front end, and highly integrated solutions will be needed to minimize solution size and increase performance.

  10. Dual Connectivity : RF Interference Challenges • Most initial eMBB deployments will use 5G NSA. This adds significant complexity because it requires dual 4G LTE and 5G connectivity. • NSA will continue to present challenges for handset RF design over at least the next decade, until all mobile operators convert to SA. • Dual connectively can create extremely complex RF challenges. • The NSA specification also allows the handset to transmit on one or more LTE bands while receiving on the 5G band.

  11. Higher Bandwidth, New Waveform • FR1 bands provide unprecedented single-carrier bandwidth up to 100 MHz, five times the LTE maximum of 20 MHz. While this is critical for multi-gigabit data rates, it also produces power-management challenges. • The higher peak-to-average power ratios (PARs), together with massive bandwidth, require greater PA backoff to stay within regulatory limits and maintain linearity. • This potentially reduces the efficiency of the Tx chain and creates a challenging high linear power requirement for PA design.

  12. ECC • If you have used S parameter approximation (as proposed by Smith et al.) it is not very acceptable in real environment • Since the approximation from S parameters is based on isotropic assumption. • The best way to calculate ECC is by using far field parameters. 12

  13. Interference • Base-station architectures must also manage the risk that a Tx signal will feed into the Rx chain, damaging sensitive components like the LNA. • This requires a switch capable of driving high-power signals to a load. The challenge is minimizing insertion loss and the resulting increase in the Rx chain noise figure, while maximizing power handling in an integrated module.

  14. 5G: RF and Antenna Testing Top challenges testing 5G NR device throughput include : • Configuring 5G NR frame structures for higher throughput. • Configuring 5G NR devices for optimal link adaptation. • Optimizing 5G NR beamforming performance at mmWavefrequencies.

  15. 5G: RF and Antenna Testing Beamforming performance at mmWavefrequencies: • Beam acquisition and tracking • Beam refinement • Beam feedback • Beam switching Source Keysight document

  16. 5G: RF and Antenna Testing Many factors at different layers of the protocol stack impact beamforming performance. Locating bottlenecks and testing different structures is vital for optimizing throughput. In addition, testing beamforming at mmWave frequencies requires over- the-air (OTA) test methods that further complicate the test solution. Source Keysight document

  17. 5G: RF and Antenna Testing Source Keysight document

  18. 5G: RF and Antenna Testing Beam steering/forming is implemented by applying Phase and Amplitude adjustments on signals transmitted by an array of antenna elements, thereby providing high gain radiation in specific spatial directions Source Keysight document

  19. 5G: RF and Antenna Testing • mmWave initial access: • New initial access procedures provide a mechanism by which both the UE and 5G node (gNB) establish suitable beam directions for directional communications. • Once the initial access procedure is completed, the UE enters a ‘connected’ state and further beam tracking / refinement is performed using closed loop beam adjustment procedures.

  20. 5G: RF and Antenna Testing • Beam refinement: • Using the channel state reporting (CSI) mechanism, the 5G node can track the state of downlink beams with periodic reference signal (CSI- RS) measurements. If the serving beam is sub-optimal, the 5G node can instruct the UE to switch to a different beam. • The highly directional nature of beamformed signals makes it critical to test initial access, beam tracking, and beam switching procedures with beams coming from different angular directions. This requires a real-time OTA test environment.

  21. 5G: RF and Antenna Testing • Top challenges testing mmWave beamforming include: • Issues testing mmWave devices in the far-field • OTA test methodologies are still being defined

  22. Indigenous 5G Testbed FR1 : RF System • Dual Polarized, high isolation Antennas • MIMO and Massive MIMO Antenna development • C-Ran and Massive MIMO antennas@ 2.4GHz • RF Front End system integration • UE Antenna development 14

  23. Indigenous 5G Testbed SAMEER-Responsibility and Activities : Fr2 FR2 : mmWave RF System • mm wave Beam steered phased array • Phased array design and development • Beam forming RF Network design • RF and Antenna on a multilayer stack up ( 12 layers) • Hybrid beam forming Antennas • Switched beam arrays @ Fr2 • SIW based Switched beam array • Lens based Switched beam array: 64 positions • Rotman Beam forming Network • UE antennas 15

  24. Indigenous 5G Testbed FR1 : MIMO System • 4x4 Array antenna • Dual slant Polarised • Printed planar feed configuration to enable the integration with RF board 16

  25. mm wave System SPECIFICATIONS 3GPP requirements : for beamformer • Frequency band (n261) : 275000 : 28350 MHz • Channel Bandwidth : 400 MHz • Duplex Mode : TDD • Base station output Power : at antenna Port) • Medium range BS : <=38 dBm • Local area BS : <= 24 dBm • Wide Area : No Limit • Base station output Power : Radiated Power) • Medium range BS : <=38 dBm + 10Log(N) • Local area BS : <=24 dBm + 10Log(N) • On/OFF Transition period : 10 uS

  26. Simulations EIRP Beamwidth Input power to antenna from BF : 10 dBm No of elements : 64 Antenna Element Gain : 5 dBi EIRP : 51 dBm No of elements : 64 3 dB Beamwidth: 12 Deg

  27. Phase shifter resolution with beam steering resolution Assumptions • Negligible loss • Mutual coupling not considered • Isotropic radiator

  28. 3dB beamwidth with number of elements HPBW Single Element - 110 Deg N= 64 HPBW = 12.86 Deg

  29. Feed network simulation

  30. Mobile front End Module 22 * Resonant White paper

  31. Power divider Characteristics 28 GHz - 2Way Wilkinson Power Divider

  32. Beamforming Network Types of beamforming networks • Analog beamforming • Digital beamforming • Hybrid beamforming Analog beamforming is used in FR2 due to • Cost • Complexity • Realization Analog beamforming Digital beamforming

  33. 5G NR transceiver blocks SAMEER BF BF BF BF PD PD PD PD PD IITM IITM+CEWiT BF BF BF BF PD PD Baseband hardware RF Up down Converter PD Beamforming network with antenna BF BF BF BF PD PD PD PD PD BF BF BF BF PD PD Power supply and Control

  34. Design challenges General Antenna • Components availability at 28 GHz • 3GPP compliance [EIRP] • Antenna and RF Integration Beamforming errors • Cross talk • Antenna mutual coupling • Impedance mismatch • Phase control resolution • Antenna element design • Element spacing • Polarization • Feeding methods

  35. Design challenges RF design EM Simulation PCB substrate selection • For printed antenna • For RF circuits • Substrate Losses (Tan D) • Board thickness • Prepreg property • Surface roughness • Multi layer design [10 Layers] • Thin substrate [8 mils] • High frequency operation • Large number of Vias • Complex design • PCB artwork to EM simulation • Simulation time Power supply filtering and power supply layers Via design at 28 GHz

  36. Layout constraints Layout design Addressing the challenges Availability of PCB laminates Availability and compatibility of bonding material [PTFE, teflon non stick] Design for manufacturability [DFM] Track width, clearance, via size Cost of fabrication SI/PI design - Tx and RX switching current EMI issues PCB stackup details and stackup issues Start with single chip design, simple configuration Part by part Design and simulation [X Microwave]

  37. Design Challenges • Components availability • Integration with antenna • Layout constraints • Polarization • Power output and EIRP • Components assembly and testing • Small components, Handling issues • ESD sensitive • EM Simulation • Multi layer design (Import from PCB software) • Thin substrate • High frequency • Large number of vias • Complex design • Layout conversion between PCB design and EM simulation

  38. Layout constraints Thermal design challenges Heat dissipation (Approximate) - 16 Devices Tx mode : 42 Watts, Rx mode : 26 Watts Average : 32 Watts Heat dissipation through solder balls Heat sink design Thermal Via design

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  40. Conclusions • As with any major advance in communications, 5G presents significant RF challenges for mobile devices and infrastructure, and will require innovative new solutions. When making technology choices, the cost and complexity of adding 5G content will be weighed against the performance benefits. • 5G is designed to work with diverse application and the complexity is one of the major challenges to address. Since 5G is a platform for many wireless technologies to co-exist, technology providers has to overcome challenges in terms of signal spectrum, transmission protocols, security and network compatibility etc… Due to huge demand for a smarter network, 5G standard has been evolving faster than expected timeline.

  41. Outlook: Visions and research directions for the Wireless World, WWRF, Oct 2011 Roadmap and workplan on future technologies(2020) from 3GPP, ITU, WRC, APT, CJK, China IMT2020, etc. Radiationblockagereduction in Antennasusing Radio Frequencycloaks”IEEE-AP magazine:June2018. "Miniaturisation of switchedbeamarrayantennausingphasedelayproperties of CSRR-loadedtransmission line,“ IET Microw. Antennas Propag.,2018,Vol.12 Iss.12,pp.1960-1966. "Full-Duplex CommunicationsforFuture Wireless Networks,” 2018 IEEE Global CommunicationsConference Globecomm-2018.

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