Agilent Impedance Measurement Handbook A guide to measurement technology and techniques 4th Edition Table of Contents 1.0 Impedance Measurement Basics 1.1 Impedance............................................................................................................. 1-1 1.2 Measuring impedance ........................................................................................ 1-3 1.3 Parasitics: There are no pure R, C, and L components ................................. 1-3 1.4 Ideal, real, and measured values ...................................................................... 1-4 1.5 Component dependency factors ....................................................................... 1-5 1.5.1 Frequency .................................................................................................... 1-5 1.5.2 Test signal level........................................................................................... 1-7 1.5.3 DC bias ......................................................................................................... 1-7 1.5.4 Temperature................................................................................................ 1-8 1.5.5 Other dependency factors ......................................................................... 1-8 1.6 Equivalent circuit models of components........................................................ 1-8 1.7 Measurement circuit modes ............................................................................... 1-10 1.8 Three-element equivalent circuit and sophisticated component models.... 1-13 1.9 Reactance chart.................................................................................................... 1-15 2.0 Impedance Measurement Instruments 2.1 Measurement methods ....................................................................................... 2-1 2.2 Operating theory of practical instruments ..................................................... 2-4 LF impedance measurement 2.3 Theory of auto balancing bridge method ......................................................... 2-4 2.3.1 Signal source section................................................................................. 2-6 2.3.2 Auto-balancing bridge section ................................................................. 2-7 2.3.3 Vector ratio detector section.................................................................... 2-8 2.4 Key measurement functions .............................................................................. 2-9 2.4.1 Oscillator (OSC) level ............................................................................... 2-9 2.4.2 DC bias ....................................................................................................... 2-10 2.4.3 Ranging function ....................................................................................... 2-11 2.4.4 Level monitor function ............................................................................ 2-12 2.4.5 Measurement time and averaging .......................................................... 2-12 2.4.6 Compensation function ........................................................................... 2-13 2.4.7 Guarding .................................................................................................... 2-14 2.4.8 Grounded device measurement capability ........................................... 2-15 RF impedance measurement 2.5 Theory of RF I-V measurement method ........................................................... 2-16 2.6 Difference between RF I-V and network analysis measurement methods ... 2-17 2.7 Key measurement functions .............................................................................. 2-19 2.7.1 OSC level .................................................................................................... 2-19 2.7.2 Test port ..................................................................................................... 2-19 2.7.3 Calibration ................................................................................................. 2-20 2.7.4 Compensation ........................................................................................... 2-20 2.7.5 Measurement range .................................................................................. 2-20 2.7.6 DC bias ....................................................................................................... 2-20 i 3.0 Fixturing and Cabling LF impedance measurement 3.1 Terminal configuration ...................................................................................... 3-1 3.1.1 Two-terminal configuration ..................................................................... 3-2 3.1.2 Three-terminal configuration................................................................... 3-2 3.1.3 Four-terminal configuration .................................................................... 3-4 3.1.4 Five-terminal configuration ..................................................................... 3-5 3.1.5 Four-terminal pair configuration............................................................ 3-6 3.2 Test fixtures ......................................................................................................... 3-7 3.2.1 Agilent-supplied test fixtures .................................................................. 3-7 3.2.2 User-fabricated test fixtures .................................................................... 3-8 3.2.3 User test fixture example ......................................................................... 3-9 3.3 Test cables ............................................................................................................ 3-10 3.3.1 Agilent supplied test cables .................................................................... 3-10 3.3.2 User fabricated test cables ...................................................................... 3-11 3.3.3 Test cable extension ................................................................................. 3-11 3.4 Practical guarding techniques .......................................................................... 3-15 3.4.1 Measurement error due to stray capacitances...................................... 3-15 3.4.2 Guarding techniques to remove stray capacitances............................. 3-16 RF impedance measurement 3.5 Terminal configuration in RF region ............................................................... 3-16 3.6 RF test fixtures .................................................................................................... 3-17 3.6.1 Agilent-supplied test fixtures .................................................................. 3-18 3.7 Test port extension in RF region ....................................................................... 3-19 4.0 Measurement Error and Compensation Basic concepts and LF impedance measurement 4.1 Measurement error ............................................................................................. 4-1 4.2 Calibration ........................................................................................................... 4-1 4.3 Compensation ...................................................................................................... 4-3 4.3.1 Offset compensation ................................................................................. 4-3 4.3.2 Open and short compensations .............................................................. 4-4 4.3.3 Open/short/load compensation .............................................................. 4-6 4.3.4 What should be used as the load? .......................................................... 4-7 4.3.5 Application limit for open, short, and load compensations .............. 4-9 4.4 Measurement error caused by contact resistance ......................................... 4-9 4.5 Measurement error induced by cable extension ............................................ 4-11 4.5.1 Error induced by four-terminal pair (4TP) cable extension ............... 4-11 4.5.2 Cable extension without termination..................................................... 4-13 4.5.3 Cable extension with termination........................................................... 4-13 4.5.4 Error induced by shielded 2T or shielded 4T cable extension ........... 4-13 4.6 Practical compensation examples .................................................................... 4-14 4.6.1 Agilent test fixture (direct attachment type) ........................................ 4-14 4.6.2 Agilent test cables and Agilent test fixture............................................ 4-14 4.6.3 Agilent test cables and user-fabricated test fixture (or scanner)....... 4-14 4.6.4 Non-Agilent test cable and user-fabricated test fixture....................... 4-14 ii RF impedance measurement 4.7 Calibration and compensation in RF region ................................................. 4-16 4.7.1 Calibration ................................................................................................ 4-16 4.7.2 Error source model ................................................................................. 4-17 4.7.3 Compensation method ............................................................................ 4-18 4.7.4 Precautions for open and short measurements in RF region ........... 4-18 4.7.5 Consideration for short compensation ................................................ 4-19 4.7.6 Calibrating load device ..........................................................................