Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company 1 Copyright 2006 by Lockheed Martin Corporation. CURRENCY NOTICE: A hard copy of this document may not be the document currently in effect. The current version is always the version in the Lockheed Martin Network. Evaluating and Improving Radiated Immunity Test Systems Performance John D. Osburn

2 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Introduction Purpose This presentation is intended to: a.) review basic immunity system design, and b.) identify serious issues in system design and c.) suggest possible corrections for these problems. Scope The discussion is limited to the test equipment setup. Other problems such as test system interaction with the test environment and monitoring for immunity failures are not discussed.

3 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Purpose of Immunity or Susceptibility Testing Determine if EUT responds to incident electromagnetic radiation at a specific level. Failure to respond to specified electromagnetic levels assures continued proper operation of the EUT in a hostile electromagnetic ambient environment. Standard conditions of testing and test equipment performance are required to allow inter-comparison of test results, between labs and over time.

Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company 4 Copyright 2006 by Lockheed Martin Corporation. CURRENCY NOTICE: A hard copy of this document may not be the document currently in effect. The current version is always the version in the Lockheed Martin Network. Immunity Test System Design

5 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company The Immunity Test Equipment Setup The list of test equipment for immunity testing is straight forward, and can be derived from the requirements of IEC The specific list of required equipment is: RF Signal Generator Power Amplifier Linearly Polarized Radiating Antenna Power Level Measurement Device Optional Equipment Low Pass or Band Pass Filters

6 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Idealized Immunity Test System Block Diagram

7 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Idealized E-Field Generation Test System Equipment and Function Signal Generator - Source of test signal, amplitude to 0 dBm and frequency, MHz, 80% AM w/ 1 kHz sinusoid Amplifier - Increases level of test signal to achieve desired test field values Forward/Reverse Power Coupler - Samples forward and reflected power to radiating device Power Meter - Reads power values in forward and reverse channels, allows calculation of net forward power to antenna (radiated power) Antenna - Generates test field at 3 m Field Meter - Reads generated field levels, provides feedback loop

8 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Immunity Test System Design The basic design equation is: Note that all values of the design equation are functions of frequency, and linear performance is implied. Cable losses are neglected.

9 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Fundamental Test System Design: Frequency Coverage Test System operating range is set by the operating range of the components Valid System Response

10 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Fundamental Immunity System Design RF Power Requirements DESIRED FIELD = 10 V/m = 140 dB µV/m TAF=-8.66 dB m -1 V in = dB µV SG out = 101dB µV = -7 dBm

11 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Idealized Equipment Performance - Signal Generator Generates basic signal Requires at least 0.X dBm resolution for amplitude for calibration of test setup dB µV setting desirable for greater resolution of output Level at reference point must be within -0, +10% or lower to achieve -0, +6 dB calibration Must cover frequency range Must provide 80% AM

12 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Idealized Equipment Performance - Power Amplifier Wide bandwidth power amplifiers have large ripple values, as much as 4 dB Rated gain is typically at 0 dBm input (maximum value of input) Linear gain region is at 1 dB compression Maximum gain is at saturation (increase in input produces no increase in output) Should operate in linear region for repeatable results

13 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Idealized Equipment Performance - Antenna Two important parameters of antenna, Transmit Antenna Factor, and input VSWR TAF is evaluated at a specific distance, under specific conditions VSWR should be 2:1 for optimum results, giving 1 dB error

14 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Theoretical Probe System Response Probe system used diode detector, loses frequency information Responds to sum of all signals present Must use calibration factors for adequate accuracy

15 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Other System Component Constraints Cables should have transmission and reflection loss measured periodically Very short cable from the F/R coupler to the antenna, compensate for cable loss in design Do NOT over tighten RF connectors Antenna mount should be non conducting Cable should be routed straight back from transmit antenna for 2 m for repeatability Once calibration complete, position of antenna, etc., very important

16 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Summary of Fundamental System Design Fundamental design allows: Definition of equipment requirements Selection of equipment Establishing of basic operating parameters Many or even most immunity test system designs are felt to be complete at this point

Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company 17 Copyright 2006 by Lockheed Martin Corporation. CURRENCY NOTICE: A hard copy of this document may not be the document currently in effect. The current version is always the version in the Lockheed Martin Network. Practical Issues in Immunity Test System Design

18 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Technical Issues Begins with fundamental design complete Addresses: Non ideal performance of sub-system components Interaction between non-ideal components Assures test repeatability and meaningful inter-lab comparisons

19 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Signal Generator Non-Ideal Characteristics Significant harmonics of the fundamental can be present Transient behavior on switching in amplitude and/or frequencies Inadequate resolution for precision control during calibration

20 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Real Performance - Signal Generator Output 1st Harmonic is 46 dB down 12 Discernible harmonics present

21 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Signal Generator Switching Characteristics 12 dB Overshoot

22 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Power Amplifier Non-Ideal Performance Characteristics Gain varies over as much as 9 dB range (1 dB compression values) 17 + discernible harmonic signals present Non-saturated output assumed Linear operation assumed

23 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Amplifier Gain vs Frequency

24 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Real Performance - Power Amplifier with Some Signal Generator Harmonics present 1 st harmonic is -29 dBc 96 dB µV

25 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Test Signal Generation Antenna Performance Antenna - free space mismatch is large below 80 MHz Ideal operation at VSWR 2:1 not possible at frequencies below 120 MHz Must size amplifier to accommodate VSWR 2:1 80 MHz 4:1

26 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Correction for Additional Power Due to Antenna Mismatch

27 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Actual Probe Response Probe systems respond to all signals present in the environment If harmonics are present, their value will be added to the fundamental response The actual indication from the probe is the Peak Envelope power, computed from

28 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Actual Probe Response to Harmonic Rich Spectrum Probe Reading for this Spectrum = dB µV Actual Level = dB µV

29 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Actual Probe System Response

30 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Incorporating Real Equipment Constraints in an Immunity Test Setup Remember Osburns Second Law Precision is achieved at the cost of complexity. Additional subsystem components needed to control equipment problems: Attenuator to control Signal Generator Switching transients Series of low pass, high power filters to control harmonic content, improve accuracy, computer switched

31 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Recommended Test Instrumentation Setup

32 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Continuous Monitoring of Test System Performance` Addition of a simple sense antenna, at a convenient location, allows a independent measurement of the existence of the test signal Will probably not read test level, look for changes from signal received during calibration Assures no harmonic content in test signal Uses readily available existing equipment

33 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Recommendations for Better Immunity Test Setups Control non-ideal behavior of system components Signal Generator Transients Harmonics Amplifier Harmonic generation Gain issues Output power requirements Probe Sum of all signals response

34 Use or disclosure of the information contained herein is subject to the restrictions on the Cover Page Lockheed Martin Aeronautics Company Summary Have reviewed fundamental immunity test system design Have identified second tier design problems and proposed solutions Have looked deeper into issues of immunity testing, hopefully in an organized manner, to address problems that while recognized, might not have been adequately addressed.