Agilent 10 Hints for Making Better Network Analyzer Measurements Application Note 1291-1B

2

Contents

HINT 1. Measuring high-power amplifiers

HINT 2. Compensating for time delay in cable measurements

HINT 3. Improving reflection measurements

HINT 4. Using frequency-offset for mixer, converter and tuner measurements

HINT 5. Increasing the accuracy of noninsertible device measurements

HINT 6. Aliasing in phase or delay format

HINT 7. Quick VNA calibration verification

HINT 8. Making your measurements real-time, accurate and automated

HINT 9. Making high dynamic range measurements

HINT 10. Simplifying multiport measurements

Introduction

This application note contains a vari-ety of hints to help you understandand improve your use of networkanalyzers, along with a quicksummary of network analyzers andtheir capabilities.

Overview of network analyzers

Network analyzers characterizeactive and passive components, suchas amplifiers, mixers, duplexers,filters, couplers, and attenuators.These components are used in sys-tems as common and low-cost aspagers, or in systems as complex andexpensive as communications orradar systems. Components can haveone port (input or output) or manyports. The ability to measure theinput characteristics of each port, aswell as the transfer characteristicsfrom one port to another, givesdesigners the knowledge to configurea component as part of a largersystem.

Types of network analyzers

Vector network analyzers (VNAs)are the most powerful kind of net-work analyzer and can measure fre-quencies from 5 Hz up to 110 GHz.Designers and final test in manufac-turing use VNAs because theymeasure and display the completeamplitude and phase characteristicsof an electrical network. These char-acteristics include S-parameters,magnitude and phase, standing waveratios (SWR), insertion loss or gain,attenuation, group delay, return loss,reflection coefficient, and gaincompression.

VNA hardware consists of a sweep-ing signal source (usually internal), atest set to separate forward andreverse test signals, and a multi-channel, phase-coherent, highly sen-sitive receiver (figure 1). In the RFand microwave bands, typical mea-sured parameters are referred to asS-parameters, and are also com-monly used in computer-aideddesign models.

Scalar network analyzersA scalar network analyzer (SNA) measures only the amplitude portionof the S-parameters, resulting in measurements such as transmissiongain and loss, return loss, and SWR.Once a passive or active componenthas been designed using the totalmeasurement capability of a VNA, an SNA may be a more cost-effectivemeasurement tool for the productionline to reveal out-of-specification components. While SNAs require anexternal or internal sweeping signalsource and signal separation hardware, they only need simpleamplitude-only detectors, rather than complex (and more expensive)phase-coherent detectors.

Network/spectrum analyzersA network/spectrum analyzer elimi-nates the circuit duplication in abenchtest setup of a network andspectrum analyzer. Frequency cover-age ranges from 10 Hz to 1.8 GHz.These combination instruments can be economical alternatives in designand test of active components likeamplifiers and mixers, where analy-sis of signal performance is alsoneeded.

RECEIVER / DETECTOR

PROCESSOR / DISPLAY

REFLECTED(A)

TRANSMITTED(B)

INCIDENT (R)

SIGNALSEPARATION

SOURCE

Incident

Reflected

Transmitted

DUT

Figure 1. Network analyzer block diagram

HINT 1.How to boost and attenuate signal levels when measuring high-power amplifiers

Testing high-power amplifiers cansometimes be challenging since thesignal levels needed for test may bebeyond the stimulus/response range of the network analyzer. High-poweramplifiers often require high input levels to characterize them under conditions similar to actual opera-tion. Often these realistic operatingconditions also mean the outputpower of the amplifier exceeds thecompression or burn-out level of theanalyzer’s receiver.

When you need an input level higherthan the network analyzer’s sourcecan provide, a preamplifier can beused to boost the power level prior to the amplifier under test (AUT).

By using a coupler on the output ofthe preamplifier, a portion of theboosted input signal can be used forthe analyzer’s reference channel(figure 2). This configurationremoves the preamplifier’s frequen-cy response and drift errors (byratioing), which yields an accuratemeasurement of the AUT alone.

When the output power of the AUTexceeds the input compression level of the analyzer’s receiver, some type of attenuation is needed to reducethe output level. This can be accom-plished by using couplers, attenua-tors, or a combination of both. Caremust be taken to choose componentsthat can absorb the high power fromthe AUT without sustaining damage.Most loads designed for small-signaluse can only handle up to about onewatt of power. Beyond that, specialloads that can dissipate more powermust be used.

The frequency-response effects ofthe attenuators and couplers can beremoved or minimized by using theappropriate type of error-correction.One concern when calibrating withextra attenuation is that the input levels to the receiver may be low during the calibration cycle. Thepower levels must be significantlyabove the noise floor of the receiverfor accurate measurements. For thisreason, network analyzers that havenarrowband, tuned-receivers are typically used for high-powerapplications since their noise flooris typically ≤ 90 dBm, and theyexhibit excellent receiver linearityover a wide range of power levels.

Some network analyzers with full two-port S-parameter capabilityenable measuring of the reverse characteristics of the AUT to allow full two-port error correction. In thisconfiguration, the preamplifier mustbe added in the signal path beforethe port 1 coupler (figure 3).Otherwise, the preamplifier's reverseisolation will prevent accurate mea-surements from being made on port1. If attenuation is added to the out-put port of the analyzer, it is best touse a higher power in the reverse direction to reduce noise effects inthe measurement of S22 and S12.Many VNAs allow uncoupling of thetest-port power to accommodatedifferent levels in the forward andreverse directions.

Network analyzer

DUT

Attenuator

Attenuator

Attenuator

"R" Channel in

Coupler

Attenuator

AttenuatorRF amplifier

Power divider

Switch

Figure 2. High-powered foward measurementconfiguration

Figure 3. High-powered forward and reverse measurement configuration

3

4

HINT 2.Compensate for time delay forbetter cable measurements

A network analyzer sweeps itssource frequency and tuned receiverat the same time to make stimulus-response measurements. Since thefrequency of a signal coming from adevice under test (DUT) may not beexactly the same as the network ana-lyzer frequency at a given instant oftime, this can sometimes lead to con-fusing measurement results. If theDUT is a long cable with time delayT and the network analyzer sweeprate is df/dt, the signal frequency atthe end of the cable (input to thevector network analyzer’s receiver)will lag behind the network analyzersource frequency by the amountF=T*df/dt. If this frequency shift isappreciable compared to the net-work analyzer’s IF detection band-width (typically a few kHz), then themeasured result will be in error bythe rolloff of the IF filter.

Figure 4 shows this effect when measuring the transmissionresponse of a 12-foot cable on an8714ET network analyzer. The uppertrace shows the true response of thecable, using a 1-second sweep time.The lower trace uses the defaultsweep time of 129 msec, and thedata is in error by about –0.5 dB dueto the frequency shift through thecable. This sweep time is too fast forthis particular DUT.

The lower trace of figure 5 shows aneven more confusing result whenmeasuring the same cable on an 8753ES with 100-msec sweep time. Not only is there an error in thedata, but the size of the error makessome sharp jumps at certainfrequencies. These frequencies arethe band-edge frequencies in the8753ES, and the trace jumps becausethe network analyzer’s sweep rate(df/dt) changes in different bands.This leads to a different frequencyshift through the cable, and hence, adifferent amount of error in thedata. In this case, instead of increas-ing the sweep time, the situation canbe corrected by removing the R-channel jumper on the front panel ofthe 8753ES and connecting a secondcable of about the same length as theDUT cable. This balances the delaysin the reference and test paths, sothat the network analyzer’s ratioedtransmission measurement does nothave the frequency-shift error. Theupper trace of figure 5 shows a mea-surement of the DUT using the same100-msec sweep time, but with thematching cable in R channel.

Start 10.000 MHz

2:Off

8714 1SEC VS 0.129SEC

1:Transmission &M Log Mag 0.5 dB/ Ref 0.00 dB

Stop 3 000.000 MHz

1

M1

Figure 4. Reduce measurement error by increasing swap time

Start .300 000 MHz

S21 &M Log MAG

8753 100mSEC WITH & WITHOUT EXTENSION

0.5 dB/ Ref 0.00 dB

Hld

*PRm

Cor

CH1

Stop 3 000.000 MHz

Figure 5. Reduce measurement error by balancing reference path

5

HINT 3.Proper termination —Key to improving reflectionmeasurements

Making accurate reflection measure-ments on two-port devices with transmission/reflection (T/R)-basedanalyzers (such as the 8712ET and8714ET RF analyzers) requires agood termination on the unmea-sured port. This is especially true forlow-loss, bidirectional devices suchas filter passbands and cables. T/R-based analyzers only offer one-portcalibration for reflectionmeasurements, which corrects forerrors caused by directivity, sourcematch and frequency response, butnot load match.

One-port calibration assumes a goodtermination at port 2 of the deviceunder test (the port not being measured), since load match is notcorrected. One way to achieve this is by connecting a high-quality load (a load from a calibration kit, forexample) to port 2 of the device. This technique yields measurementaccuracy on a par with more expen-sive S-parameter-based analyzersthat use full two-port calibration.

However, if port 2 of the device is connected directly to the networkanalyzer’s test port, the assumption of a good load termination is notvalid. In this case, measurementaccuracy can be improved consider-ably by placing an attenuator (6 to10 dB, for example) between port 2of the device and the test port of theanalyzer. This improves the effectiveload match of the analyzer by twicethe value of the attenuator.

Figure 6 shows an example of how this works. Let’s say we are meas-uring a filter with 1 dB of insertionloss and 16 dB of return loss (figure6A). Using an analyzer with an 18 dBload match and 40 dB directivitywould yield a worst-case measure-ment uncertainty for return loss of–4.6 dB, +10.4 dB. This is a ratherlarge variation that might cause a fil-ter that didn’t meet its specificationsto pass, or a good filter to fail. Figure6B shows how adding a high-quality(for example, VSWR = 1.05, or 32 dBmatch) 10-dB attenuator improvesthe load match of the analyzer to 29dB [(2 x 10 + 18 dB) combined with32 dB]. Now our worst-case measure-ment uncertainty is reduced to +2.5dB, –1.9 dB, which is much morereasonable.

An example where one-port calibra-tion can be used quite effectively without any series attenuation is when measuring the input match ofamplifiers with high-reverse isola-tion. In this case, the amplifier’s iso-lation essentially eliminates theeffect of imperfect load match.

DUT16 dB return loss (0.158)1 dB loss (0.891)

Analyzer port 2 match:18 dB (0.126)

0.158

Measurement uncertainty: –20 * log (.158 + 0.100 + 0.010) = 11.4 dB (–4.6dB)

–20 * log (0.158 – 0.100 – 0.010) = 26.4 dB (+10.4 dB)

0.891*0.126*0.891 = 0.100

Directivity:40 dB (0.010)

DUT16 dB return loss (0.158)1 dB loss (0.891)

Load match:18 dB (.126)

10 dB attenuator (0.316) SWR = 1.05 (0.024)

0.158

(0.891)(0.316)(0.126)(0.316)(0.891) = 0.010

(0.891)(0.024)(0.891) = 0.019

Directivity:40 dB (.010)

Worst-case error = 0.01 + 0.01 + 0.019 = 0.039

Measurement uncertainty: -20 * log (0.158 + 0.039) = 14.1 dB (-1.9 dB)

-20 * log (0.158 - 0.039) = 18.5 dB (+2.5 dB)

Figure 6B. Measurement uncertainty improvementFigure 6A. Reflection measurement uncertainty

6

HINT 4.Use frequency-offset mode for accurate measurements ofmixers, converters and tuners

Frequency-translating devices suchas mixers, tuners, and converterspresent unique measurement chal-lenges since their input and outputfrequencies differ. The traditionalway to measure these devices is withbroadband diode detection. Thistechnique allows scalar measur-ments only, with medium dynamicrange and moderate measurementaccuracy.

For higher accuracy, vector networkanalyzers such as the 8753ES and8720ES offer a frequency-offsetmode where the frequency of theinternal RF source can be arbitrarilyoffset from the analyzer’s receivers.Narrowband detection can be usedwith this mode, providing high dy-namic range and good measurementaccuracy, as well as the ability tomeasure phase and group delay.

There are two basic ways that frequency-offset mode can be used.The simplest way is to take the out-put from the mixer or tuner directlyinto the reference input on the ana-lyzer (figure 7A). This techniqueoffers scalar measurements only,with up to 35 dB of dynamic range;beyond that, the analyzer’s sourcewill not phase lock properly. Formixers, an external LO must be pro-vided. After specifying the measure-ment setup from the front panel, theproper RF frequency span is calcu-lated by the analyzer to produce thedesired IF frequencies, which thereceiver will tune to during thesweep. The network analyzer willeven sweep the RF source backwardif necessary to provide the specifiedIF span.

For high-dynamic-range amplitudemeasurements, a reference mixermust be used (figure 7B). This mixerprovides a signal to the R channel for proper phase lock, butdoes not affect measurements of theDUT since it is not in the measure-ment path. For phase or delay measurements, a reference mixermust also be used. The referencemixer and the DUT must share a common LO to guarantee phasecoherency.

When testing mixers, either tech-nique requires an IF filter to removethe mixer’s undesired mixing prod-ucts as well as the RF and LOleakage signals.

FREQON off

LOMENU

DOWNCONVERTER

UPCONVERTER

RF > LO

RF < LO

VIEWMEASURE

RETURN

1 2

Ref IN

start: 900 MHzstop: 650 MHz

FIXED LO: 1 GHzLO POWER: 13 dBm

start: 100 MHzstop: 350 MHz

|

|

Figure 7B. High dynamic range conversion loss measurement (left) and high dynamic range setup (right)

Figure 7A. Mixer measurement setup

CH1 CONV MEAS log MAG 10 dB/ REF 10 dB

START 640.000 000 MHz STOP 660.000 000 MHz

H

ACTIVE CHANNEL

RESPONSE

STIMULUS

ENTRY

INSTRUMENT STATE R CHANNEL

R L T S

HP-IB STATUS

8753DNETWORK ANALYZER

30 KHz-3GHz

PROBE POWER FUSED

Ref In

10 dB

Reference Mixer

3 dB

10 dB10 dB

Signal Generator

Lowpass Filter

Ref OutIF

LO

RF

LO

DUT

PORT 1 PORT 2

HINT 5.Increasing the accuracy ofnoninsertible device measurements

Full two-port error correctionprovides the best accuracy whenmeasuring RF and microwavecomponents. But if you have a non-insertible device (for example, onewith female connectors on bothports), then its test ports cannot bedirectly connected during calibra-tion. Extra care is needed whenmaking this through connection, especially while measuring a devicethat has poor output match, such asan amplifier or a low-loss device.

There are five basic ways to handlethe potential errors with a throughconnection for a noninsertibledevice:

1. Use electronic calibration (ECal)modules. This is the simplest andfastest non-insertible calibrationmethod in existence. This methoduses an ECal module with the sameconnectors that match the deviceunder test. Full two-port error cor-rection, defined at the test ports, isachievable. All Agilent ECal modulesare characterized at the factory andprovide a traceable calibration path.

2. Use a very short through. Thisallows you to disregard the potentialerrors. When you connect port 1 toport 2 during a calibration, the ana-lyzer calculates the return loss of thesecond port (the load match) as well as the transmission term. Whenthe calibration kit definition does not contain the correct length of the through, an error occurs in the measurement of the load match. If abarrel is used to connect port 1 to port 2, the measurement of the port2 match will not have the correctphase, and the error-correction algo-rithm will not remove the effects ofan imperfect port 2 impedance.

This approach will work well enough if the through connection is quiteshort. However, for a typical network analyzer, “short” means less thanone-hundredth of a wavelength. Ifthe through connection is one-tenthof a wavelength (at the frequency ofinterest), the corrected load match isno better than the raw load match.As the through length approaches a one-quarter wavelength, the residualload match can actually get as highas 6 dB worse than the raw loadmatch. For a 1-GHz measurement,one-hundredth of a wavelengthmeans less than 3 mm (about 0.12inches).

3. Use swap-equal-adapters.In this method you use two matchedadapters of the same electricallength, one with male/femaleconnectors and one that matches thedevice under test.

Suppose your instrument test portsare both male, such as the ends of a pair of test-port cables, and yourdevice has two female ports. Put a female-to-female through adapter,usually on port 2, and do the transmission portion of the calibra-tion. After the four transmissionmeasurements, swap in the male-to-female adapter (now you have twomale test ports), and do the reflec-tion portion of the calibration(figure 8). Now you are ready tomeasure your device. All theadapters in the calibration kits areof equal electrical length (even iftheir physical lengths are different).

4. Modify the through-line-standard. If your application is manufacturing test, the “swap-equal-adapters” method’s requirement for additional adapters may be a drawback. Instead, it is possible tomodify the calibration kit definitionto include the length of the throughline. If the calibration kit has beenmodified to take into account theloss and delay of the through, thenthe correct value for load match willbe measured. It’s easy to find thesevalues for the male-to-male throughand the female-to-female through.First, do a swap-equal-adaptercalibration, ending up with bothfemale or both male test ports. Thensimply measure the “noninsertible”through and look at S21 delay (usethe midband value) and loss at 1GHz. Use this value to modify thecalibration kit.

5. Use the adapter-removal technique. Many Agilent vector network analyzer models offer anadapter-removal technique to elim-inate all effects of through adapters.This technique yields the most accurate measurement results, butrequires two full two-portcalibrations.

7

��

Port 1

DUTPort 1 Port 2

�Port 1 Port 2Adapter A

Adapter B

Port 2

Non-insertible device

1. Transmission cal using adapter A.

2. Reflection cal using adapter B. Length of adapters must be equal.

3. Measure DUT using adapter B.DUTPort 1 Port 2

�Adapter

B

Figure 8. Swap-equal-adapters method

8

HINT 6.Check for aliasing in phase or delay format

When measuring a device under test(DUT) that has a long electricallength, use care to select appropriatemeasurement parameters. The VNAsamples its data at discrete frequen-cy points, then “connects the dots”on the display to make it more visu-ally appealing. If the phase shift ofthe DUT changes by more than 180degrees between adjacent frequencypoints, the display can look like thephase slope is reversed! The data isundersampled and aliasing occurs.This is analogous to filming a wagonwheel in motion, where typically toofew frames are shot to accuratelyportray the motion and the wheelappears to spin backward.

In addition, the VNA calculatesgroup delay data from phase data. Ifthe slope of the phase is reversed,then the group delay will changesign. A surface acoustic wave (SAW)filter may appear to have negativegroup delay—clearly not a correctanswer. If you suspect aliasing inyour measurements, try this simpletest. Just decrease the spacingbetween frequency points and see ifthe data on the VNA’s displaychanges. Either increase the numberof points, or reduce the frequencyspan.

Figure 9 shows a measurement of aSAW bandpass filter on an 8714ET RF economy network analyzer, with 51 points in the display. The indicat-ed group delay is negative—a physi-cal impossibility. But if the numberof points increases to 201 (figure10), it becomes clear that the VNAsettings created an aliasing problem.

Start 130.000 MHz Stop 150.000 MHz

1: Transmission2: Transmission

DelayPhase

1

51 POINT TRACE Meas1:Mkr1 140.000 MHz–1.1185

/500 ns/100

Ref 0 sRef 0.00

s

Ref = 0 seconds

Delay Appears Negative

2:

Start 130.000 MHz

1:

Stop 150.000 MHz

1: Transmission2: Transmission

DelayPhase

1201 POINT TRACE Meas1:Mkr1 140.000 MHz

–1.3814

/500 ns/100

Ref 0 sRef 0.00

s

Ref = 0 seconds

Delay KnownPositive

Figure 9. Filter measurement with insufficient number of points

Figure 10. Filter measurement with correct number of points

9

HINT 7.Quick calibration verification

If you’ve ever measured a device andthe measurements didn’t look quiteright, or you were unsure about aparticular analyzer’s accuracy orperformance, here are a few “quickcheck” methods you can use to verifyan instrument’s calibration orperformance. All you need are a fewcalibration standards.

Verifying reflection measurementsTo verify reflection (S11) measure-ments on the source port (port 1),perform one or more of the followingsteps:

1. For a quick first check, leave port1 open and verify that the magnitudeof S11 is near 0 dB(within about ±1 dB).

2. Connect a load calibration stan-dard to port 1. The magnitude of S11should be less than the specified calibrated directivity of the analyzer(typically less than –30 dB)(figure 11).

3. Connect either an open or short circuit calibration standard to port1. The magnitude of S11 should beclose to 0 dB(within a few tenths of a dB).

To verify transmission (S21) measurements:1. Connect a through cable from port1 to port 2. The magnitude of S21should be close to 0 dB(within a few tenths of a dB).

2. To verify S21 isolation, connecttwo loads: one on port 1 and one onport 2. Measure the magnitude ofS21 and verify that it is less than thespecified isolation(typically less than –80 dB).

To get a more accurate range ofexpected values for these measure-ments, consult the analyzer’s specifi-cations. You might also considerdoing these verifications immediate-ly after a calibration to verify thequality of the calibration. To ensurethat you are performing a calibrationverification, and not a connectionrepeatability test, be sure to use aset of standards that are differentthan those used as part of the cali-bration process.

Figure 11. Measurement of load standard after calibration

10

HINT 8.Making your measurementsreal-time, accurate and automated

Tuning and testing RF devices in aproduction environment oftenrequires speed and accuracy from anetwork analyzer. However, at fastsweep speeds an analyzer’s optimumaccuracy may be unavailable.

Using a segmented sweepMany network analyzers have theability to define a sweep consistingof several individual segments. Eachsegment can have its own stop andstart frequency, number of datapoints, IF bandwidth, and powerlevel. Using a segmented sweep, themeasurement can be optimized forspeed and dynamic range(figure 12).

Data resolution can be made highwhere needed (more data points)and low where not needed (less datapoints); frequency ranges can beskipped where data is not needed atall; the IF bandwidth can be largewhen high dynamic range is notnecessary, which decreases thesweep time, and small when highdynamic range is required; thepower level can be decreased in thepassband and increased in thestopband for devices that contain afilter followed by an amplifier (forexample, a cellular-telephone base-station receiver filter/LNAcombination).

Instrument automationFor more complex testing such as final test, an analyzer with IBASIC(8712/8714, E5100), or Micorsoft®VBA (ENA) programming capabilityprovides complex computation andcontrol so you can easily automatemeasurements.

Using the program doesn’t requireprogramming experience. You can easily customize each test orcombination of tests and activatethem by a softkey or footswitch toautomatically set up system para-meters for each device you test.

Figure 12. Optimize filter measurements with segment list mode

HINT 9.Making high dynamic rangemeasurements

Extend the dynamic range measure-ment capability of your network ana-lyzer by bypassing the coupler at testport 2 (for forward transmissionmeasurements). Since the coupler isno longer in the measurement path,the associated loss through the cou-pled arm no longer impacts the mea-surement. This increases the effec-tive sensitivity of the analyzer. Sincethe coupler is no longer part of thesignal path, it is no longer possibleto make reverse measurements.

To take advantage of this increasedsensitivity, the power level into thereceiver must be monitored to pre-vent compression. For devices suchas filters, this is easily done using asegmented sweep, where the poweris set high in the stopbands (+10dBm typically), and low in the pass-band (-6 dBm typically).

Maintain full S-parameter errorcorrectionDepending on the particular networkanalyzer configuration, it is possibleto configure a signal path that main-tains usage of the port 2 coupler, butsimply reverses the direction of sig-nal travel (figure 13). By reversingthe port 2 coupler, the transmittedsignal travels to the "B" receiver viathe main arm of the coupler, insteadof the coupled arm. Reverse dynamicrange measurements will be lowerbecause the stimulus signal mustnow travel via the coupled arm.Since both forward and reverse mea-surements are possible, it is still pos-sible to apply full two-port errorcorrection.

11

A B

ReferenceReceiver

ReferenceReceiver

CouplerIN

R1 R2

Source

Switch/Splitter/Leveler

Measurement Receivers

DUT

R1OUT

R1IN

AOUT

70 dB 70 dB

36 dB

AIN

BIN

R2IN

R2OUTSource

OUTSource

OUT

36 dB

CouplerIN

BOUT

Figure 13. High dynamic range configuration that allows both forward and reverse measurements

HINT 10.Simplifying multiportmeasurements

High-volume tuning and testing ofmultiport devices (devices withmore than two ports) can be greatlysimplified by using a multiportnetwork analyzer, or a multiport testset with a traditional two-portanalyzer.

A single connection to each port ofthe device under test (DUT) allowsfor complete testing of all transmis-sion paths and port reflection char-acteristics. Multiport test systemseliminate time-consuming reconnec-tions to the DUT, keeping produc-tion costs down and throughput up.By reducing the number of RF con-nections, the risk of misconnectionsis lowered, operator fatigue isreduced, and the wear on cables, fix-tures, connectors, and the DUT isminimized.

By internet, phone, or fax, get assistancewith all your test & measurement needs

Online assistance:www.agilent.com/find/assist

Phone or FaxUnited States:(tel) 1 800 452 4844

Canada:(tel) 1 877 894 4414(fax) (905) 282-6495

China:(tel) 800-810-0189(fax) 1-0800-650-0121

Europe:(tel) (31 20) 547 2323(fax) (31 20) 547 2390

Japan:(tel) (81) 426 56 7832(fax) (81) 426 56 7840

Korea:(tel) (82-2) 2004-5004 (fax) (82-2) 2004-5115

Latin America:(tel) (305) 269 7500(fax) (305) 269 7599

Taiwan:(tel) 080-004-7866 (fax) (886-2) 2545-6723

Other Asia Pacific Countries:(tel) (65) 375-8100 (fax) (65) 836-0252Email: tm_asia@agilent.com

Product specifications and descriptionsin this document subject to change with-out notice.

© Agilent Technologies, Inc. 2001Printed in USA October 25, 20015965-8166E

Measuring balanced devicesWhile ideal balanced componentsonly respond to or produce differen-tial (out-of-phase) signals, real-world devices also respond to orproduce common-mode (in-phase)signals. Newer analyzers (such asAgilent's ENA Series and PNASeries) provide built-in firmware(figure 14) and/or software pack-ages that performs a series of sin-gle-ended stimulus/response mea-surements on all measurementpaths of the DUT, and then calcu-lates and displays the differentialmode, common-mode, and modeconversion S-parameters.

Figure 14. Single-ended and corresponding mixed-mode measurement parameters

Additional web resourcesVisit:

www.agilent.com/find/nafor more information on Agilent's complete offering of network analyzers.

www.agilent.com/find/multiportfor more information on Agilent's multiport solutions.

www.agilent.com/find/balancedfor more information on Agilent's balanced-measurement solutions.

www.agilent.com/find/ecalfor more details on Agilent's electronic calibration modules.