EMI and its Implications in Multi-Radio Integration. Harry Skinner Principal Engineer Corporate Technology Group Intel Corporation

Transcription

1 EMI and its Implications in Multi-Radio Integration Harry Skinner Principal Engineer Corporate Technology Group Intel Corporation November 15 th 2007

2 Agenda Background Problem Statement EMI / Platform Noise Impact EMI / Platform Noise Characteristics What can we do? Summary 2

3 Platform Noise, EMI & RF Interference: What is it? Focus Area Out of Box MCH RFI Memory Wireless (802.11) AP FCC Regulated ICH PCI Express EMI In-box 3 In-box environment not addressed by regulations but nevertheless critical

4 Problem Statement The unintentional meets the intentional Emissions db uv/m 54 To Meet Wireless Sensitivity Requirements EMI Limit (FCC) 24 ~ -86dBm MHz ~ 1.5GHz GHz GHz GHz 30dB 960MHz 24dBuV/m target includes translation for BW and distance 4Wireless Requirements 1000x More Stringent Than EMI Freq. Wireless Requirements 1000x More Stringent Than EMI

5 Problem Statement Platform noise at GHz EMI Regulatory Requirements 5dB NF noise floor 5 Meeting EMI regulations guarantees nothing with respect to wireless performance

6 Problem Statement Trends Platform RF Interference severely impacts wireless performance. Issue: Wireless EMC is a problem today and will only get worse if we do nothing 6 Getting worse for future platforms More Victim Radios Licensed Radios (more stringent reqs.) Higher GHz Sources (I/O & Components) UMD devices force noise closer to radios

7 Agenda Background Problem Statement EMI / Platform Noise Impact EMI / Platform Noise Characteristics What can we do? Summary 7

8 EMI / Platform Noise Impact Throughput Test Set up Shielded Enclosure Wireless Link AP Access Point interference System 8 Wireless Client Laptop Model A #1 Laptop Model A #2 Wireless Client Cabled to Antenna located in Lid assembly of interference System

9 Platform Impact Performance Throughput Test, b Channel 2, 2, Laptop Model A A 6 Without platform noise Throughput (Mbps) ~ 10 db Platform noise desense With platform noise Received Signal Strength (dbm) >50% Range Reduction due to Platform Noise

10 Platform Impact Noise Measurement due to LCD Laptop Model B LCD Off P1 P2 20MHz BW Position 1 Position 2 Position 3 Receiver Noise Floor (5dB NF) P3 ~10dB b/g EMI impacts multiple channels by up to 10dB 10

11 Platform Impact WWAN/WiMax Carrier Certification - Requirements Carrier Total Isotropic Sensitivity (TIS) Requirements -92 Low channel 870MHz Mid channel 880MHz High channel 890MHz -94 Sensitivity (dbm) Better Cingular -104 Vodafone

12 Platform Impact (Example) WWAN/WiMax Carrier Certification - Requirements TIS Measurements on Production Notebook TIS Measurements -92 Low channel 870MHz Mid channel 880MHz High channel 890MHz -94 Sensitivity (dbm) Better Cingular Platform Clock Vodafone -106 Carriers Dictate Performance Requirements. 12 It doesn t pass your Customer doesn t ship!

13 Agenda Background Problem Statement EMI / Platform Noise Impact EMI / Platform Noise Characteristics What can we do? Summary 13

14 Platform noise Characteristics GHz 5dB NF noise floor 14 Lots of Narrow band sources in this example

15 Platform Noise Characteristics Notebook E Platform Noise -70 WCDMA Band II Platform Noise (dbm/100khz) Freq (MHz) Here we have Dithered Clock Noise 15 It s neither NB or BB (Quazi Band Noise)

16 Platform Noise Characteristics Noise from PRBS High Speed Serial Interconnects Noise Power (dbm) GHz 2GHz 3GHz 4GHz 5GHz 6GHz 30dB PCIe 2.5Gb/s b/g a / n PCIe 5.0Gb/s 2007 Need to pay attention to both Sin X / X Broadband and Noise in the Nulls 16

17 Agenda Background Problem Statement EMI / Platform Noise Impact EMI / Platform Noise Characteristics What can we do? Summary 17

18 What can we do? Clearly a platform approach is needed Platforms designed with Radios in mind Radios designed with Platforms in mind 18

19 Shielding Approaches 19 Gaskets, clips, shields, ferrites and absorbers the preverbal kitchen sink There must be another way!

20 Making The Platform Radio Friendly Platform Clocks Example GTEM Capture of 166MHz BSEL Mode CK505 64pin TSSOP package Up to 30dB Difference for equivalent parts Vendor A Vendor B Vendor C Vendor D Amplitude (dbm) Frequency (MHz) Component Specifications need to include EMI requirements

21 GTEM Data Examples 21

22 Package Impacts: E 2GHz 81.9 dbuv Pk 59.5 dbuv Pk Strip-line Package Micro-strip Package Don t assume blindly that Strip-line is always better 22

23 959.4MHz Field Distribution 67 th Harmonic of MHz E Field H Field dbuv dbuv 23 Why do we need the 67 th Harmonic?

24 Near Field Scans of Clock die 1.8mm OLD 1.8mm NEW dB reduction! Noise completely removed in most cases

25 Agenda Background Problem Statement EMI / Platform Noise Impact EMI / Platform Noise Characteristics What can we do? Making Platforms Radio Friendly Making Radios Platform Robust Summary / Call to Action 25

26 Making The Radio Platform Robust Signal Acquisition 25 Production Notebook Measurements WLAN Throughput (Mbps) Without Noise With Noise Weaker Weaker SNR Reduction ~ 10 db* Signal Strength (dbm) * 10 db = > 50% loss in RF Operating Range Signal Acquisition False Alarm Stronger 20% Knowledge of Platform Noise to CTS / EDD assessment can resolve False Alarms

27 Making The Radio Platform Robust Noise Matters Not all noise is created equal. Don t assume everything is white Not all noise is Broadband Not all noise is static / stationary / steady state Not all platform noise is narrowband 27

28 Making the Radio Platform Robust Noise Matters: Gaussian or not that is the question Non-Gaussian Gaussian Platform Noise Radios today are designed for: 28 Platform Noise properties must be comprehended by radios or performance will be lost!

29 Making the Radio Platform Robust Noise Matters (example) Measured PCIe Gen2 RFI emissions vs. Gaussian Noise Platform Noise (Realistic-Non Gaussian) Thermal Noise (Theoretical-Gaussian) 29 Radio Noise floor is NOT FLAT and Statistics vary due to SIR, Bandwidths, etc. Signal to Interference, E[ξ 2 ] = 1 Sampling Rate, Fs = 200Msps

30 Statistical Analysis of PCIe (Fs=200Msps): X + η + ξ ADC ML = Maximum Likelihood Improved ML Estimation Needed. Y = X + η + ξ Non-Gaussian statistics biases Received signal (Y), due to ξ, Gaussian rather thanstatistics η. η 30 ML Receivers need to comprehend non-gaussian statistics.

31 Making the Radio Platform Robust Creating a new Channel Model Platform A to Platform B Tx Channel Rx Intra-System EMI Rx Traditional Channel Model 31 Platform Channel Model (NEW) Platform = Channel + EMI / Platform Noise

32 Agenda Background Problem Statement EMI / Platform Noise Impact EMI / Platform Noise Characteristics What can we do? Making Platforms Radio Friendly Making Radios Platform Robust Summary 32

33 Summary EMI / Platform Noise can severely impact wireless performance. Getting worse for future platforms & devices More Radios More GHz Noise Sources Ultra Mobile Devices force noise closer to radios Platform Approach Needed Make the Platform Radio Friendly Make the Radio Platform Robust 33

34 Thank You! 34

35 Backup 35

36 Making The Platform Radio Friendly Platform Clock Improvements (1) 36

37 Making The Platform Radio Friendly Platform Clock Improvements (2) 37

38 Making The Platform Radio Friendly Platform Clock Improvements (3) 38