Get documents about "Effective EMC Test Planning And Performance
Document Sample
Effective EMC Test Planning Common Mistakes
And • Not Understanding EUT Operation
• Improper Grounding Of EUT
Performance • Improper Harnessing
• Poorly Defined EUT Susceptibility Criteria
• Specifying Non-Valued Added Tests
• Not Understanding The Intent Of Specific Tests
• Improper Design of EUT Monitoring Equipment
Raymond K. Adams • Overly Dependent On Boilerplate Test Procedures
Fischer Custom Communications, Inc.
20603 Earl Street • Not Following Test Procedure
Torrance, CA 90503 • Writing Poor Test Reports
(310)303-3300
radams@fischercc.com
Successful EMC Test Planning
Successful EMC Test Planning
(Continued)
• Understand How The EUT Works • EUT Grounding
– Operational Modes – Conductive Ground Plane
– Interface Signal Types – Composite Ground Plane
• Amplitude – No Ground Plane
• Frequency • EUT Power Return
• Timing – Thru Chassis
– Dedicated Wire Return
• Select Proper Operational Modes By Test
• Carefully Select Meaningful Susceptibility Criteria
– Noisy Modes For Emissions Tests – That Can Be Monitored
– Critical Modes For Susceptibility Tests • Write Useful EMC Test Procedures
– Any Finite EUT Processing Loops To Consider? – Don’t Rely Heavily On Boilerplate EMC Test Procedures
• Understand How EUT Test Equipment Works – Understand The Intent Of Every Test
– Will It Support The EMC Tests? – Use Writing Test Procedure As A Means To Plan For A Smooth Running EMC Test
– Unique Power Requirements – Use Detailed Diagrams Of Connections And Interfaces To EUT Test Equipment
– Determine If Special Test Aids or Fixtures Are Required
• Test Equipment EMC Design Considerations
• Follow The Approved EMC Test Procedure
– Will Test Equipment Influence Test Results? – Document Deviations
– What Modifications MUST Be Made To Enable This? – Keep EMC Test Logbook
• EUT Harnessing
– Use Same Type That EUT Will Use In The Actual Installation
Harnessing EUT Grounding
• Should Be Representative Of Actual
Installation • Is EUT Mounted On Conductive or Non-
Conductive Surface?
– No Shielding
• Wrap Cables With Al Foil To “Pass” The Test – Test Setups Should Incorporate This Fact
– Too Much Shielding • Single Point or Multi-Point Ground?
• Masks Problems – Often A Source Of Confusion
• “Pass” At ALL Costs -vs- Find Problems – Improper Configuration Will Yield Different
• Usually Overlooked Prior To Test Results
– Questionable Test Results Likely
1
EUT Operation System Block Diagram
• How Does The EUT Work?
• KEY Performance Parameters
• Typical Operational Modes fcarrier fcarrier + df fif fif + df fout fout + df
200MHz
– Which Mode(s) Are Most Susceptible? Input
2900 MHz
Output
70MHz
• Critical Frequencies of System and EUT
– Pick Test Frequencies Just “OFF” Critical
Frequencies
3100 MHz 270 MHz
flo flo + df f2lo f2lo + df
Define Susceptibility Criteria Sample Susceptibility Criteria
• Power Supplies
• Parameters To Be Monitored Must Be –
–
Voltage Ripple on Secondary Voltages
DC Regulation
• Amplifiers
Determined Ahead Of Time – AM Modulation Of Carrier
– Direct Frequency Response
– Non-Linearities (Overload, Intermodulation Products)
• Which Signals Are Critical To EUT • Scientific Instruments
– Corruption of Data
Operation •
– Undesired Activation Of Mechanical Parts
Receivers and Telemetry Units
– Signal Lock
• Neglecting Out of Band Requirements •
– Bit Error Rate (BER)
Controllers
– Sensor Inputs
– Same As In-Band Requirements –
–
Mode Switches
False Commands
• Frequency Sources
– May Be Too Conservative – Close In Phase Noise
• Sensors (Sun, Earth, Star Tracker, Gyros, Inertial Reference Units)
– Increased Test Time and Cost –
–
Offset Errors
Pointing Error
– Data Corruption
Only Specify Value Added Tests Improve EMC Test Setups
• Not Understanding The Limitations Of The Test Equipment
• Understand The Intent Of Every Test – Know Your Test Equipment!
• Understand Test Amplifier Characteristics
• Understand Which Tests To Specify – Frequency Range
– Power (input, output, maximum)
• Understand Which Tests Aren’t Applicable – Intermodulation
– Broadband Noise
• Limiting The Frequency Range of Test • Understand EMI Receiver Characteristics
– Maximum Input Power
Where Appropriate – 1 dB Compression
– Linearity Specifications
– However, Sometimes It Is Easier And More – Overload Conditions
Cost Effective To Do The Test Than Argue! – Sweeptime to Resolution Bandwidth
• Understand The Effects Voltage Probes Can Have On Accuracy
2
Review EMC Design Of EUT
Estimate Required RF Isolation
Monitoring Equipment
• Good EMC Design Practices Must Also Be • Review EUT Intentional Signal Levels
Applied To EUT Monitoring Equipment! • Review EUT Susceptibility Levels
– Practice What We Preach! • Focus In On Lowest Signal Levels In Measurement
• Prevent Monitoring Equipment From Being The Chain
Dominant Noise Source • Determine Worst Case RF Susceptibility Test Levels
• Calculate Received Isotropic Power (RIP) At EUT
• Prevent Monitoring Equipment From Inducing Operating Frequency
EUT Susceptibility • Compare Lowest Signal Levels To RIP
• Prevent Monitoring Equipment From Being • Estimate Required Isolation
Susceptible • Adjust Test Setup If Required Isolation >70 - 80 dB
• Analyze Susceptibility Test Signal Coupling – Check Adapters, Cables, Waveguide Flanges, Couplers, RF
Paths Switches and Attenuators
– Minimize Connections Where Possible
Potential RS103 Leakage Points Check RF Leakage of Test Setup
Power Amp
Power Amp
Sample Isolation Budgets Received Isotropic Power
60
Spur Requirement -55 dBc 50
2 V/m
20 V/m
200 V/m
E-Field Level 20 V/m 40
EUT Frequency 2 GHz
Received Isotropic Pow (dBm)
30
20
er
10
Spur Level RIP Isolation
0
(dBm) (dBm) (dB)
Pinput -2 dBm -57 3 60 -10
EUT Gain 55 dB 0 -20
Poutput 53 dBm -2 3 5 -30
Coupling Factor 40 dB -15 -40
Coupler Output 13 dBm -42 3 45
-50
1.0E+08 1.0E+09 1.0E+10 1.0E+11
Frequency (Hz)
3
Potential RE102 RF Leakage Points Check RE Test Setups
Test Performance Troubleshooting
• Follow Test Procedure As Written • Carefully Review Test Data Prior To Performing
Troubleshooting
• If Deviations Are Necessary
– Make Sure There Is Problem With EUT
– Consult With Proper Authority – Make Sure Test Equipment Is Not The Culprit
– Document All Deviations – Make Sure Test Requirements Are Correct
– Redline The Test Procedure • Carefully Plan Your Troubleshooting Approach
– Only Change ONE Variable At A Time!
– Have An Idea Of What To Expect
– Make Sure Cause/Effect Is Repeatable
Test Reports Summary
• Keep A Detailed Test Log (You Will Soon Forget What You Just Did!)
–
–
Document Special Configurations
Document Troubleshooting Configurations
• Successful EMC Tests Are Possible
• Test Equipment List
– Model Numbers • Careful Preparation Necessary
– Serial Number
– Calibration Due Dates – EUT Operation Must Be Understood
• Summarize Tests Performed And Results
–
–
Tests Passed
Tests Failed
– EUT Test Equipment Must Not Influence Test Data
• Test Setup Photographs
–
–
Document Test Setup Details
Take Useful Photos But Don’t Overload It With Photos!
• Thorough EMC Test Procedures Are Required
• Test Data
– Tabular Form For Susceptibility Test Data
– Documenting What Was Done Is VERY Important
– X-Y Plots of Emissions Test Data
– Carefully Annotate Plots With Test Point, Operational Mode, Antenna Polarization, Time, and Date – Redline EMC Test Procedure
• Transducer Factors
– Antenna Factors – Troubleshooting Must Be Disciplined
– Current Probe Transfer Impedance
–
–
Low Noise Amplifier Gain
Test Cable Insertion Loss
– Always Keep A Detailed Test Logbook
• Copy of Redlined Test Procedure
4
Related docs
