An Introduction to High-Frequency Circuits and Signal Integrity

Transcription

1 An Introduction to High-Frequency Circuits and Signal Integrity 1 Outline The electromagnetic spectrum Review of market and technology trends Semiconductors industry Computers industry Communication industry Signal Integrity 2 1

2 Electromagnetic Spectrum (D. M. Pozar, Microwave Engineering, Wiley, 2005) 3 Practical RF and Microwave Regions Radio frequency (RF) systems: FM radio, cell phones, TV, wireless phones, GPS, etc. Frequency range: 30MHz to 3GHz Wavelength in air: 10m to 10cm Microwave (MW) systems: microwave ovens, satellite circuits, radar, remote sensing, microwave antennas, ultra high-speed interconnects, etc. Frequency range: 3GHz to 30GHz Wavelength in air: 10cm to 1cm 4 2

3 Semiconductor Industry Technology Trends The use of new semiconductor and dielectric materials and manufacturing processes has been enabling faster and smaller transistors The minimum dimension of transistors has been continuously decreasing: 25 μm in 1960 to 45nm in 2008 (about 220 silicon atoms) 5 Decreasing Dimension of Transistors 6 3

4 Decreasing Dimension of Transistors (cont) 7 Decreasing Dimension of Transistors (cont) State-of-the-art silicon transistors can operate above 1 THz 8 4

5 Computer Industry Technology Trends The number of transistors per chip has continue to double every 1.5 year (Moore s law) CPU operating frequency has continuously increase Denser and faster buses have appeared Faster memories are required Cost of interconnects remain a small fraction (< 5%) of the system cost 9 Moore s Law 10 5

6 CPU Operating Frequency Frequency [MHz] Processor Frequency Frequency Year DX 486DX2 486DX4 Pentium Pentium Pro Pentium II Celeron Pentium III Pentium 4 (H. Heck, 2005) 11 Denser and Faster Buses 486DX2 Processor (~1992) Pentium 4 Processor (2003) 3 major buses 4 major buses 33 MHz max frequency MHz max frequency 4 byte bus width 4-16 byte bus width CPU 100 MHz 32 bit 33 MHz L2 Cache FPM/EDO DRAM 32 bit 12 MHz PCI Chipset 32 bit 33 MHz PCI Slots (H. Heck, 2005) 12 6

7 Denser and Faster Buses (cont) Frequency [MHz] System Bus Frequency System Bus Frequency Year (H. Heck, 2005) DX 486DX2 486DX4 Pentium Pentium Pro Pentium II Celeron Pentium III Pentium 4 13 Faster and Denser Memories Peak Bandwidth [MB/s] Year (H. Heck, 2005) 14 7

8 Cost of Interconnects Interconnect makes up < 5% of the system cost Most technical problems can be solved with $ High volume PC market can t afford extra cost Designing Multi-GHz interconnects to fit in sub $1000 PCs is a huge challenge Approximate Cost Breakdown of a PC O/S Sound + Case Speakers Motherboard & Connectors (< 5% of total) Memory Fax/Modem CDROM CPU Hard Disk Monitor + Video Card Power Supply Motherboard Components (H. Heck, 2005) 15 Cost of Interconnects (cont) FR4 has been the standard choice for PCBs in the last four decades Other dielectrics have better performance: polyethylene (PE), polytetrafluoroethylene (PTFE) PTFE-based laminates can cost up to US$100 per squared foot FR4 is US$2/sq ft (D. Reed, 2003) 16 8

9 High-Speed Digital Design Physical design becomes crucial: connectors, backplanes, packages, PCB structures, material properties, etc. Analog techniques (analog electronics, RF and microwave engineering) are used to solve most signal integrity problems Copyright 2003 Agilent Technologies, Inc. 17 High-Speed Digital Design (cont) Eye Diagrams (for a 25-inch channel) 1 Gbps, 200 psec/div 2.5 Gbps, 80 psec/div 5 Gbps, 40 psec/div 7.5 Gbps, 27 psec/div Copyright 2003 Agilent Technologies, Inc. 18 9

10 Communications Industry Drive An extremely fast growth has been consistently occurring in: Cellular phone service Direct Broadcast Satellite (DBS) television Wireless Local Area Networks (WLAN) Global Positioning Satellite (GPS) service Radio Frequency Identification (RFID) systems In early 1980 s a marketing firm hired by AT&T forecasted less than 900,000 cell phone users in USA by the year In 1998, the number of cell phone subscribers in USA was over 6 millions (D.M. Pozar, 2001) 19 Cell Phone Transceiver Frequency range: 824 MHz 1.9GHz (R. Ludwig and P. Bretchko, RF Circuit Design, Prentice Hall, 2000) 20 10

11 Cell Phone Transceiver (cont) Power amplifier circuit: (R. Ludwig and P. Bretchko, RF Circuit Design, Prentice Hall, 2000) 21 Cell Phone Transceiver (cont) Two-stage power amplifier implementation: (R. Ludwig and P. Bretchko, RF Circuit Design, Prentice Hall, 2000) 22 11

12 What is Signal Integrity (SI)? It is an engineering practice that aims at ensuring reliable high-speed data transmission and reception, without polluting the electromagnetic spectrum SI combines concepts and techniques from the following disciplines: microwave and RF engineering electromagnetics physical design analog electronics communications, and digital design 23 SI Problems Appear at Different Levels (M. Nakhla, 2004) 24 12

13 SI Problems Appear at Different Levels (cont) (A. Weisshaar, 2004) 25 Systems on Packages (SOP) 26 13

14 Effective Signal Integrity Practices Tracking down the cause of signal integrity problems after the hardware has been created can be extremely complicated (R. Mellitz, 2003) 27 Signal Integrity Issues 28 14

15 Tools and Concepts for Signal Integrity Issues 29 CAD Tools for SI CAD tools allow addressing many signal integrity issues during simulation Appropriate simulation strategies improve the understanding of highly complex signal integrity phenomena If the simulation is accurate enough, many signal integrity problems can be solved before they actually exist 30 15