Agilent Technologies 4294A Specifications

Agilent TechnologiesImpedance MeasurementHandbookJuly 2006

1-4. True, effective, and indicated valuesA thorough understanding of true, effective, and indicated values of a component, as well as theirsignifican

Figure 5-36. Measurement setup5-26

5-11. Battery measurementThe internal resistance of a battery is generally measured using a 1 KHz AC signal. When a batteryis connected directly to t

5-12. Test signal voltage enhancementWhen measuring the impedance of test signal level dependent devices, such as liquid crystals, induc-tors and high

Figure 5-39. Connection diagram of test signal voltage enhancement circuit5-29

5-13. DC bias voltage enhancementDC biased impedance measurement is popularly used to evaluate the characteristics of the deviceunder the conditions w

Figure 5-40. External DC bias measurement setupExternal DC voltage bias protection in 4TP configurationIf the measurement frequency is above 2 MHz or

5-14. DC bias current enhancementDC current biasing is used for inductor and transformer measurement. In low frequency region, theE4980A or 4284A pre

Take caution of electrical shock hazards when using the external DC bias circuit.A large energy is charged in L1 and L2 as well as the DUT (Lx) by a b

5-15. Equivalent circuit analysis and its applicationAgilent’s impedance analyzers are equipped with an equivalent circuit analysis function. The pur

Figure 5-44. Equivalent circuit modelsIf the simulated frequency response curve partially fits the measurement results, it can be said thatthe selecte

1-5. Component dependency factorsThe measured impedance value of a component depends on several measurement conditions, suchas frequency, test signal

Figure 5-45. Frequency response simulation for a low-value inductorFigure 5-46. Equivalent circuit enhancement5-3610 DIM Ztrc(1:201,1:2),Fmta$[9],Fmtb

Measurement accuracy can be improved by taking advantage of the equivalent circuit analysis.Figure 5-47 (a) shows an Ls-Q measurement example for an i

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APPENDIX AThe concept of a test fixture’s additional error1. System configuration for impedance measurement Very often, the system configured for impe

A-2The equation for the test fixture’s additional error is shown below:Ze = ± { A + (Zs/Zx + Yo•Zx) × 100} (%)De = Ze/100 (D ≤ 0.1)Ze : Additional er

A-3Open offset error:The term, Yo•Zx × 100 is called open offset error. If the same analysis is carried out with admittance,then it can be concluded

A-4Terminal connection method:In order to make short repeatability small, there are test fixtures which utilize the 4-terminal con-nection method (for

A-5obtained. For open repeatability, measure the admittance of the test fixture’s open condition. In thesame way, determine open repeatability by meas

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B-1APPENDIX BOpen and short compensationThe open/short compensation used in Agilent’s instrument models the residuals as a linear networkrepresented b

Figure 1-9. Capacitor frequency responseTest signal level:The test signal (AC) applied may affect the measurement result for some components. For exa

B-2Figure B-1. Open/short compensation (2 of 2)

C-1APPENDIX COpen, short and load compensationThe open/short/load compensation requires the measurement data of a standard DUT with knownvalues in add

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D-1APPENDIX DElectrical length compensationA test port extension can be modeled using a coaxial transmission line as shown in Figure D-1.When an imped

D-2When a (virtual) transmission line in which the signal wavelength is equal to the wavelength in vac-uum is assumed, the virtual line length ( e) th

E-1APPENDIX EQ Measurement accuracy calculationQ measurement accuracy for auto balancing bridge type instruments is not specified directly as ±%.Q

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Figure 1-11. DC bias dependencies of ceramic capacitors and cored-inductorsTemperature:Most types of components are temperature dependent. The temper

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SECTION 2Impedance measurement instruments2-1. Measurement methodsThere are many measurement methods to choose from when measuring impedance, each of

2-2While the RF I-V measurement method is based on the sameprinciple as the I-V method, it is configured in a differentway by using an impedance match

Figure 2-1. Impedance measurement method (3 of 3)2-3The current, flowing through the DUT, also flows through resistor R. Thepotential at the “L” poin

Table 2-1. Common impedance measurement methodsNote: Agilent Technologies currently offers no instruments for the bridge method and the resonant metho

2-2. Operating theory of practical instrumentsThe operating theory and key functions of the auto balancing bridge instrument are discussed in theparag

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The measurement circuit is functionally divided into following three sections.The signal source section generates the test signal applied to the unkno

Figure 2-4. Auto balancing bridge section block diagramFigure 2-5. Vector ratio detector section block diagram2-7

2-4. Key measurement functionsThe following discussion describes the key measurement functions for advanced impedance mea-surement instruments. Thoro

2-4-2. DC biasIn addition to the AC test signal, a DC voltage can be output through the Hc terminal and applied tothe DUT. A simplified output circui

2-4-3. Ranging functionTo measure impedance from low values to high values, impedance measurement instruments haveseveral measurement ranges. General

2-4-4. Level monitor functionMonitoring the test signal voltage or current applied to the DUT is important for maintaining accu-rate test conditions,

Averaging function calculates the mean value of measured parameters from the desired number ofmeasurements. Averaging has the same effect on random n

The induced errors are dependent upon test frequency, test fixture, test leads, DUT connection con-figuration, and surrounding conditions of the DUT.

Figure 2-11. Guarding techniques2-4-8. Grounded device measurement capabilityGrounded devices such as the input/output of an amplifier can be measured

Figure 2-12. Low-grounded device measurement2-15

iThe Impedance Measurement HandbookA Guide to Measurement Technology and TechniquesCopyright®2000-2003 Agilent Technologies Co. LtdAll rights reserve

2-5. Theory of RF I-V measurement methodThe RF I-V method featuring Agilent’s RF impedance analyzers and RF LCR meters is an advancedtechnique to meas

Figure 2-13. Simplified block diagram for RF I-V method2-17

2-6. Difference between RF I-V and network analysis measurement methodsWhen testing components in the RF region, the RF I-V measurement method is ofte

Figure 2-14. Relationship of reflection coefficient to impedanceFigure 2-15. Measurement sensitivity of network analysis and RF I-V methods2-19

Figure 2-16. Comparison of typical Q accuracy2-7. Key measurement functions2-7-1. OSC levelThe oscillator output signal is output through the coaxial

2-7-3. CalibrationMost of the RF vector measurement instruments such as network analyzers need to be calibratedeach time a measurement is initiated or

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SECTION 3Fixturing and cablingWhen interconnecting a device under test (DUT) to the measurement terminals of the auto balancingbridge instrument, ther

The four-terminal pair (4TP) configuration solves the mutual coupling problem because it uses coaxialcable to isolate the voltage sensing cables from

Figure 3-2. Three-terminal (3T) configurationFigure 3-3. Four-terminal (4T) configuration3-3

iiSECTION 3 Fixturing and cabling––––––– LF impedance measurement –––––––Paragraph 3-1 Terminal configuration ...

Figure 3-4. Five-terminal (5T) configurationFigure 3-5. Four-terminal pair (4TP) configuration3-4

3-2. Using test cables at high frequenciesThe 4TP configuration is the best solution for wide-range impedance measurement. However, inbasic 4TP measu

Table 3-1. Test fixture’s DUT connection configuration and applications3-3-2. User fabricated test fixturesIf the DUT is not applicable to Agilent sup

3-3-3. User test fixture exampleFigure 3-7 shows an example of a user fabricated test fixture. It is equipped with alligator clips asthe contact elec

3-4. Test cablesWhen the DUT is tested apart from the instrument, it is necessary to extend the test ports(UNKNOWN terminals) using cables. If the ca

Figure 3-8. Specifications of recommended cable (Agilent PN 8121-1218)3-4-3. Test cable extensionIf the required test cable is longer than 1 m, 2 m, o

Figure 3-9. 4TP-4TP extensionFigure 3-10. Shielded 2T extension3-10

Figure 3-11. Shielded 4T extensionTable 3-2. Summary of cable extension3-11Measurement frequency100 kHz and below 100 kHz and aboveLowTypically 4TP-4T

3-5. Eliminating the stray capacitance effectsWhen the DUT has high impedance (e.g. Low Capacitance), the effects of stray capacitance are notnegligib

Figure 3-13. Coaxial test port circuit configuration3-7. RF test fixturesRF test fixtures are designed so that the lead length (electrical path length

iii4-7-1 Variance in residual parameter value ... 4-194-7-2 A difference in contact condition ...

3-7-1. Agilent supplied RF test fixturesAgilent Technologies offers various types of RF test fixtures that meet the type of the DUT andrequired test f

3-8. Test port extension in RF regionIn RF measurements, connect the DUT closely to the test port to minimize additional measurementerrors. When ther

Figure 3-15. Calibration plane extensionFigure 3-16. Practical calibration and compensation at extended test port3-16

SECTION 4Measurement error and compensation4-1. Measurement errorFor real-world measurements, we have to assume that the measurement result always con

4-2-1. Offset compensationWhen a measurement is affected by only a single component of the residuals, the effective value canbe obtained by simply sub

Figure 4-3. Open/short compensation4-2-3. Precautions for open and short measurementsWhen an open measurement is made, it is important to accurately m

Figure 4-4. Example of shorting device. (Agilent PN: 5000-4226)4-2-4. Open, short and load compensationsThere are numerous measurement conditions wher

Figure 4-5. Open/short/load compensation4-2-5. What should be used as the load?The key point in open/short/load compensation is to select a load whose

Figure 4-6. Electrode distance in load measurementFigure 4-7. Load value must be close to DUT’s value4-6

Figure 4-8. Actual open/short load measurement example4-2-6. Application limit for open, short and load compensationsWhen the residuals are too signif

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Figure 4-9. Effect of contact resistance4-8If RH = RL = Rhp = Rlc and Chp = Clp, D errorsof 2-terminal and 4-terminal become the samewhen Cx = ChpThis

4-4. Measurement cable extension induced errorExtending a 4TP measurement cable from the instrument will cause a magnitude error and phaseshift of the

Figure 4-11. Measurement error due to extended cable lengthThe cable length compensation works for test cables whose length and propagation constants

k value is a decimal number mostly within the range of -1 to +1 and different for different instru-ments. As the above equation shows, the error rapi

Figure 4-12. Compensation examples4-12

4-6. Calibration and compensation in RF region4-6-1. CalibrationWhether the RF I-V method or network analysis, the open, short and load calibration mi

When the test port is extended, calibration should be performed at the end of extension cable, asdiscussed in section 3. Thereby, the calibration pla

4-6-3. Compensation methodAs the error source model is different for the coaxial and non-coaxial sections of the test fixture,compensation method is a

Accordingly, the residual parameters have greater effects on higher frequency measurements andbecome a primary factor of measurement errors. The accu

Conceptually, there are two methods of defining the short bar’s impedance: One is to assume theimpedance to be zero. This has been a primordial metho

SECTION 1Impedance measurement basics1-1. ImpedanceImpedance is an important parameter used to characterize electronic circuits, components, and thema

4-6-7. Electrical length compensationIn the lower frequency region, using the open/short compensation function can minimize most oftest fixture residu

4-6-8. Practical compensation techniqueThe calibration and compensation methods suitable for measurement are different for how the testcable or fixtur

Figure 4-17. Difference in residual parameter values due to DUT positioning4-7-2. A difference in contact conditionChange in contact condition of the

4-7-3. A difference in open/short compensation conditionsImproper open/short measurements deteriorate accuracy of compensated measurement results. If

Figure 4-20. Eddy current effect and magnetic flux directivity of device4-7-5. Variance in environmental temperatureTemperature influences on the elec

SECTION 5Impedance measurement applications and enhancementsImpedance measurement instruments are used for a wide variety of applications. In this se

Table 5-1. Capacitor typesType Application Advantage DisadvantageFilm Blocking, buffering. Wide range of capacitance Medium costbypass, coupling. and

When we measure capacitors, we have to consider these parasitics. Impedance measurementinstruments measure capacitance in either the series mode (Cs-

Precautions for capacitor measurement depend on the capacitance value being measured.High-value capacitance measurement is a low impedance measurement

5-2. Inductor measurementAn inductor consists of wire wound around a core and is characterized by the core material used.Air is the simplest core mate

Reactance takes two forms - inductive (XL) and capacitive (Xc). By definition, XL=2πfL andXc=1/(2πfC), where f is the frequency of interest, L is ind

±0.001, the maximum measurable Q value is 90.9. See Appendix E for Q accuracy calculation equa-tion.) Except for resonant method, the impedance measu

Figure 5-11. Q measurement accuracyFigure 5-12. Q measurement errorFurthermore, the following phenomena may occur when a cored inductor is measured us

Figure 5-13. Harmonic distortion caused by inductor5-8

5-3. Transformer measurementA transformer is one end-product of an inductor. So, the measurement techniques are the same asfor inductor measurement.

Inter-winding capacitance (C) between the primary and the secondary is measured by connecting oneside of each winding to the instrument as shown in Fi

Turns ratio (N) Approximate the turns ratio (N) by connecting a resistor in the secondary as shown inFigure 5-19 (a). From the impedance value measur

The 4263B’s transformer measurement function enables the measurement of the N, M, L1 and theDC resistance of the primary by changing measurement circu

5-4. Diode measurementThe junction capacitance of a switching diode determines its switching speed and is dependent onthe reverse DC voltage applied t

5-5. MOS FET measurementEvaluating the capacitances between the source, drain, and gate of an MOS FET is important indesign of high frequency and swit

5-6. Silicon wafer C-V measurementThe C-V (capacitance vs. DC bias voltage) characteristic of a MOS structure is an important mea-surement parameter f

1-2. Measuring impedanceTo find the impedance, we need to measure at least two values because impedance is a complexquantity. Many modern impedance m

Figure 5-26. C-V measurement setup5-16

As a result of extremely high integration of logic LSIs using MOS FETs, the thickness of the MOSFETs’ gate oxide is becoming thinner (less than 2.0 nm

5-7. High-frequency impedance measurement using the probeAs shown in Table 5-3, an RF I-V instrument can be used for a wafer’s L, C, and R measurement

Figure. 5-28. 5-19

5-8. Resonator measurementThe resonator is the key component in an oscillator circuit. Crystal and ceramic resonators arecommonly used in the kHz and

2. It is important to properly set the oscillator output level; resonators are test signal dependent.The minimum impedance value and the series resona

Figure 5-31. Resonator equivalent circuit mode5-22(a) (b)

5-9. Cable measurementsThe characteristic impedance Z(Ω), capacitance per unit length C (pF/m) and the propagation con-stants α (dB/m) and β (rad/m) a

Figure 5-33. Measurement resultBalanced cable measurementA balun transformer is required for measuring balanced cable because the instrument’s UNKNOWN

5-10. Balanced device measurementWhen a balanced DUT (such as balanced cable or the balanced input impedance of a differentialamplifier) is measured,