Copyright: (c) Copyright Agilent Technologies, 2000, 2001


About 89600-Series Applications

The Agilent 89600 series software provides two applications that are two different analyzers: a spectrum analyzer or a vector signal analyzer. To run an application, click the appropriate icon on your Windows desktop or click Start > Programs > Agilent 89600 VSA > either Spectrum Analyzer or Vector Signal Analyzer.

	This icon runs the Spectrum Analyzer application. Use this application to identify signals present in a wide span and to evaluate small signals very close to the noise floor. For example, in evaluating an oscillator you can use the Spectrum Analyzer application to identify spurs and harmonic distortion products and evaluate them with very narrow resolution bandwidths.
	This icon runs the Vector Signal Analyzer application. After you have identified signals using the wide-span Spectrum Analyzer application, use the Vector Signal Analyzer application to quantify and analyze the important signals with phase and time data capabilities. In the oscillator example above, you could use the Vector Signal Analyzer application to measure oscillator sidebands.
See Also

Controlling the Application

How the Application Affects Your Measurement

About the Spectrum Analyzer Application

About the Vector Signal Analyzer Application


Controlling the Application

89600-series applications run on your Windows NT or Windows 2000 workstation. Running an application creates a GUI (Graphical User Interface) window on your workstation. You can control the application using menus and dialog boxes in the window, or you can control the application via the application's COM API or macro programming language.

Using the COM API

The application's COM API lets you programmatically access all of the application's features. Using the COM API, you can easily automate measurements or access measurement data. You can access the COM API several ways, such as:

•	C or Visual Basic programs.

•	MATLAB programs.

•	Agilent VEE programs

•	VBA (Visual Basic for Applications), which is included with many Windows applications such as MS Excel or MS Word.

•	Macro programming language (see "Using Macros" below).

For more on the COM API, see COM Overview in the COM API portion of online help.

Using Macros

The macro programming language is another tool that allows you to access the application's COM API. Macros are written in VBScript. You create a VBScript macro by running the application and clicking Utilities > Macros from the main menu. The application then displays a dialog box that lets you create, edit, and run VBScript macros.

Tip

VBScript is not as powerful as C or Visual Basic. However, you don't have to be a programmer to use VBScript. Using VBScript, you can quickly automate many operations. In fact, 89600-series applications let you record keystrokes to automatically create equivalent VBScript code.

For more on VBScript and macros, see About Macros in the macro portion of online help.


How the Application Affects Your Measurement

The application that you select determines the type of analyzer used to measure and analyze your signal (or data). For example, the Spectrum Analyzer application configures the VXI hardware to make scalar measurements and displays the Spectrum Analyzer window on your PC. Likewise, the Vector Signal Analyzer application configures the VXI hardware to make vector measurements and displays the Vector Signal Analyzer window on your PC.

For further details about each application see Spectrum Analyzer Application and Vector Signal Analyzer Application .

For a comparison of available features for each application, see About this Reference.


Multiple Applications with the Same Hardware

You can run more than one 89600 application at a time using one set of measurement hardware. For example, you may want to run the Spectrum Analyzer application to look for a signal over a wide frequency range and run the Vector Signal Analyzer application to zoom in and analyze the signal.

When running multiple applications using one set of measurement hardware, note the following:

•	You can run one or more copies of each application at the same time, but only one can own (run) the measurement. When you run a measurement with one application, the other application pauses its measurement. It is the act of starting or continuing a measurement that stops the current measurement in any other application. In other words, you cannot make concurrent measurements with more than one application using the same measurement hardware.

•	You can copy several frequency parameters from the Spectrum Analyzer application into the Vector Signal Analyzer application. From the main menu in the Vector Signal Analyzer application, click MeasSetup > Frequency > From Spec Analyzer button (for details, see From Spec Analyzer). There is no way to copy the parameters back to the Spectrum Analyzer application.

•	Changes in hardware configuration, display appearance, and menus/toolbars are remembered for one instance of an application. You can run more than one instance of an application (for example, two instances of the Spectrum Analyzer application), but only the first instance remembers changes in hardware configuration, display appearance, and menus/toolbars.

•	A recording is stored in a temporary Active File. When you run multiple instances of the Vector Signal Analyzer application, a separate default recording file is used for each instance.

•	Hardware is reconfigured when you switch between the Spectrum Analyzer and Vector Signal Analyzer applications. For example, if you switch from the Spectrum Analyzer application to the Vector Signal Analyzer application, the Vector Signal Analyzer application detects that another program has used the hardware and, therefore, reinitializes the hardware.


Multiple Applications with Different Hardware

You can run more than one 89600 application concurrently using separate sets of measurement hardware. For example, you may want to run multiple 89640 analyzers using different measurement hardware to capture multi-channel information simultaneously. Or you may want to run an 89610 analyzer concurrently with an 89640 analyzer.

Several example macros have been created that allow you to set up multiple simultaneous 89600 applications. To use the macros, you must first recall and edit them:

1.	Click Utilities > Macros > Recall.

2.	Browse to this directory:  Program Files/Agilent/89600 VSA/Examples/Macros.

3.	Recall the following macros:
AUTOSTART.vbs
 	HwCfg_Default.vbs
 	HwCfg_SimulatedBaseband.vbs
 	HwCfg_SimulatedRF.vbs

4.	Edit each macro to suit your needs. The macros are documented within the files.

After you recall the AUTOSTART macro, it runs each time you start 89600 software. It presents a list of hardware configurations, from which you can select the configuration you want for each application. You can add and edit HwCfg macros for each configuration (be sure to assign different file names to new macros).

You can also modify the AUTOSTART macro to do such things as run a Visual BASIC program on startup, or start the analyzer with a particular setup. For details on using macros, see About Macros.

Special Considerations

•	Be sure to avoid address conflicts with your measurement hardware. If you are using VXI measurement hardware, refer to the Hardware Installation chapter in the Installation and Service Guide for information on changing address switches. For other measurement hardware, refer to the installation documentation for that hardware.

•	Source:  Only one application at a time can control a source. Be sure to unselect the source in the Hardware Configuration dialog box for subsequent applications.

•	Macros:  If you change or create a macro in one application, the changes do not appear in other applications until you close and restart those applications (or recall the macro into other applications). You can save macros with the same name from multiple applications. The macro file will be overwritten without warning by subsequent saves from other applications.

•	Math functions:  If you change or create a math definition in one application, the changes do not appear in other applications until you close and restart the applications. You can save math functions with the same name from multiple applications. The math function file will be overwritten without warning by subsequent saves from other applications.

•	Configuration: The module parameters you set up in the Hardware Configuration dialog box are set for every module of the same type listed in the corresponding tab in the Select Hardware dialog box. For example, setting Lock Reference to False for one E1439 will set Lock Reference to False for every E1439 listed on the ADC tab.


About the Spectrum Analyzer Application

If you've used a spectrum analyzer before, you should have no trouble using the Spectrum Analyzer application. This application makes scalar measurements. Scalar measurements are implemented differently than measurements in the traditional swept-tuned spectrum analyzer, but the results will appear familiar to you.

Scalar Measurements provide displays of amplitude versus frequency for both narrow and wide spans.

Scalar measurements step the application's local oscillator (LO) during the measurement. Each step of the LO produces a segment of the selected frequency span. In other words, the application sets its LO, performs an FFT, then steps its LO to a higher frequency, performs another FFT, and so forth, as shown below.

Scalar measurements change the local oscillator frequency in sequential steps over time and measures multiple frequency points at one time.
The number of steps, or segments, depends on the frequency span and the resolution bandwidth (RBW). For higher ratios of RBW/span, the application is able to compute the entire frequency spectrum without stepping its LO.

For lower ratios of RBW/span, the application must step its LO two or more times to compute the entire frequency spectrum−in this case, the frequency spectrum is made up of 2 or more segments.

Because Scalar measurements "piece" together the frequency spectrum, it is seldom used for transient signals (transients that occur outside of the segment being evaluated are missed).

Instead, Scalar measurements are best for characterizing stationary signals. In fact, Scalar measurements provide the same results as swept analyzers but with additional capabilities. For low-resolution bandwidths, Scalar measurements are much faster than swept analyzers.

Reasons to Use Scalar Measurements

Use Scalar measurements when you need:

•	Very narrow resolution bandwidth with high speed

•	Very low noise floor with wide spans

•	High signal-to-noise dynamic range

•	Maximum flexibility of frequency span, resolution bandwidth, and speed

•	Wider frequency spans

Specific examples of applications for which you would use Scalar measurements include:

•	Looking at spurious signals or noise

•	Looking for low level distortion products

Prominent Features

Some prominent features available for Scalar measurements are:

•	Marker calculations (frequency count and band power).

•	Linear sweep type.

•	Signal tracking.

Features Not Available with Scalar Measurements

The following are not available when making scalar measurements:

•	Phase information

•	Time data displays

•	Time selective (gated) frequency domain measurements

•	Data recording and playback

•	ADS integration

•	Time averaging

•	Demodulation of the input signal


Spectrum Analyzer Block Diagram

The following block diagram shows how the spectrum analyzer application performs scalar measurements.


Sweep Time Limitations (Scalar)

Sweep time is the time required for the application to complete one full sweep on the display. With the standard swept-tuned analyzer, sweep time is limited by analog IF filter dynamics because the filter must have time to respond to the input signal before accurately measuring a frequency.

When performing scalar measurements with Agilent 89600 series products, the digital IF and FFT act like a parallel filter bank. This means the sweep speed is limited by data collection and digital processing time rather than filters (there are digital filters in the digital IF which do require some settling time, but this is negligible when compared to the settling time of analog filters). For this reason, scalar measurements for low-resolution bandwidths can run much faster than would be the case with a swept analyzer. The sweep time is adjusted automatically—the analyzer selects the optimum sweep time based on the frequency span, window, resolution bandwidth, and other parameters.


Resolution Bandwidth Limitations (Scalar)

The standard swept analyzer uses the last in a series of analog IF filters to determine resolution bandwidth. In contrast, the Agilent 89600 series analyzers use a digital IF and a DSP algorithm to determine resolution bandwidth (RBW). For this reason, the narrowest practical RBW with Scalar measurements is constrained by the length of time you are willing to wait for a measurement to be performed.

With scalar measurements, the widest RBW is limited by the frequency span. The maximum RBW decreases as you narrow the frequency span and increases as you increase the frequency span.


Detectors (Scalar)

For vector measurements, the output of the FFT yields as many measurement points as there are frequency points. For Scalar measurements, the output of the FFT can yield more measurement points than there are frequency points. Measurement points refer to the number of points output by the FFT. Frequency points refers to the number of points displayed on the screen.

Because the FFT may produce more measurement points than can be displayed on the screen, scalar measurements use a min/max detector to evaluate multiple measurement points into a single frequency point. This process of reducing measurement points is called detection. For scalar measurements, the analyzer always lists a min and max value for each frequency point, even if the values are the same.

The number of frequency points  affects the display resolution−the higher the number of frequency points, the better the resolution, as shown in the following formula:

For example, if the frequency span is 4 kHz and the number of frequency points is 401, the resolution (spacing between frequency points) is 10 Hz. This means the closest frequency you can resolve is 10 Hz. The start frequency determines the first frequency point, the stop frequency the last frequency point, and the remaining frequency points are spaced at 10 Hz intervals.

During scalar measurements, the analyzer measures the energy (power) at all frequencies within the displayed frequency span. Thus, the analyzer measures energy that occurs at all frequencies, but can only display energy that occurs at the frequency points. The detector adjusts the value displayed at a frequency point to include energy measured between frequency points. Thus, the detector, in effect, improves display resolution by taking into account energy between frequency points.

The min/max detector plots a vertical line at each frequency point, representing the minimum and maximum energy found between the current and previous frequency points. The following illustration is a scalar measurement that uses x-scale markers to zoom in on the X scale. Zooming in on the X-axis makes it easy to see the effects of the min/max detector.


Display Resolution (Scalar)

For scalar measurements, you can select a fixed number of frequency points or you can select auto (auto is the default). Auto sets the number of frequency points equal to the number of pixels in the displayed trace. With auto, resizing a window changes the number of frequency points. Increasing the window size increases the number of frequency points; decreasing the window size decreases the number of frequency points.

Note

With auto frequency points, if you resize a window while a measurement is paused, the number of frequency points is not updated until the start of the next measurement.

If you select a fixed number of frequency points, you should size your windows so that the number of pixels doesn't exceed the number of frequency points. If the window has more pixels than frequency points, the analyzer fills the pixels using the fixed number of frequency points, which decreases the display resolution. For example, if the number of frequency points is fixed at 401 and the trace consists of 1604 pixels, the value of one frequency point is used for every four pixels.


Band Power Markers (Scalar)

As explained in Detectors (Scalar), scalar measurements use a min/max detector to combine multiple measurement points into a single, displayed frequency point.

After detection, the analyzer may discard the measurement points. Because all measurement points are needed to accurately calculate band power markers, the analyzer calculates band-power information for the entire trace before discarding the measurement points and stores that information with each trace.

Tip

If you save or recall a trace, band-power information is saved or recalled with the trace. Therefore, band power markers are completely operational on recalled traces.


About the Vector Signal Analyzer Application

The Vector Signal Analyzer application makes vector measurements, which provide extremely fast measurements of magnitude and phase. The Vector Signal Analyzer application also lets you easily change between the frequency and time domains. These capabilities are especially useful in characterizing transient or non-stationary signals.

If you've used a swept-tuned spectrum analyzer before, you already know that narrow resolution bandwidth measurements of small frequency spans are very time-consuming. Traditionally, swept-tuned analyzers have required very long sweep times for narrow resolution bandwidths due to the sweep rate of the narrow filters. The narrower the resolution bandwidth, the more time it takes for the resolution bandwidth filters to settle. In fact, a swept-tuned analyzer's sweep time is inversely proportional to the square of the resolution bandwidth. As you choose increasingly narrower resolution bandwidths (for example, when trying to resolve close-in sidebands) the time it takes to make a measurement increases. This characteristic is common to all conventional swept-tuned analyzers.

However, the 89610 and 89640  analyzers can make narrow band measurements very quickly in Vector Mode. This lets you make measurements for spans from 1Hz to 39.06 MHz (with resolution bandwidths from 1 mHz to 10 MHz) much faster than you can with a swept spectrum measurement. For vector measurements, the analyzer uses the FFT (Fast Fourier Transform) to convert the input signal from the time domain to the frequency domain. The result is measurement capability up to 1000 times faster than conventional swept spectrum analyzers.

If you have previously used FFT or dynamic signal analyzers, Vector measurements will seem familiar to you. However, with most FFT analyzers you are restricted to low frequency measurements, often to less than 100 kHz. But in this analyzer, Vector measurements let you perform FFT measurements up to 39.06 MHz for baseband measurements (Agilent 89610) and up to 36 MHz for RF measurements (Agilent 89640).

Use Vector measurements when you need:

•	Time selective (gated) frequency domain measurements

•	Time data display

•	Phase information

•	Time capture/playback

•	Narrow span with high speed

Specific examples of applications for which you would use Vector measurements include:

•	Characterizing spurious response of an oscillator

•	Characterizing a burst signal in both the time and frequency domain

Vector measurements set the analyzer's local oscillator (LO) to a single frequency during the measurement. Because of this, it is best for:

•	Characterizing transient or non-stationary signals.

•	Measurements that require speed with excellent resolution.

Some prominent features available with vector measurements are:

•	Phase information

•	Time selective (gated) frequency-domain measurements.

•	Time-Data Displays

•	Recordings

•	Signal Tracking

Note

Lower resolution bandwidths are achieved by Scalar measurements than by Vector measurements.


Vector Signal Analyzer Block Diagram

The following block diagram shows how the analyzer performs vector measurements. Note that the top block applies only for analyzers using VXI measurement hardware. If your analyzer uses other measurement hardware, see the documentation for that hardware for block diagrams.


Understanding Parameter Interactions (Vector)

The characteristic time/resolution bandwidth relationship for vector measurements is a natural part of the FFT process and is common to all FFT analyzers, not just 89600-series analyzers. However, 89600-series analyzers are unique in allowing you to change span and resolution bandwidth independently.

The following illustration shows the inverse relation of several key parameters. The arrows indicate inversely related parameters.

Notice from the above illustration that:

•	Resolution bandwidth changes always affect time length for a given window.

•	Time length changes always affect resolution bandwidth.

•	Span changes always affect Δt.

•	Δt is related to sample rate and is not user-accessible—it is only affected by changing span.

•	Span and resolution bandwidth may be adjusted independently.


Measuring Time Data (Vector)

Vector measurements let you view and analyze time-domain data (you cannot analyze time-domain data with scalar measurements). Time data provides a time-domain view of the input data before FFT processing. The following points will help you interpret time data:

•	Time data may look similar to an oscilloscope display in some cases but you will see distortion, particularly at high frequencies. The distortion occurs because the waveform is made up of the discrete samples from a time record, which is optimized for FFT measurements. FFT measurements require a lower sample rate than would be required for an optimum time domain display.

•	The analyzer must be in baseband mode to display data similar to an oscilloscope. In other words the measurement must start at 0 Hz and the center frequency must not be set explicitly. You can enter zoom mode either by setting the center frequency explicitly or by selecting Time Data: Zoom (from the MeasSetup > Frequency menu). In zoom (band-selectable) measurements the time data is displayed relative to the center (local oscillator) frequency rather than relative to DC. Therefore, zoom time data has a different appearance because baseband data is real while zoom data is complex. Because the local oscillator is tuned to the center frequency for zoom measurements, the time data is represented as the difference frequency between the local oscillator and the input signal frequencies.

•	Time and time exponential averaging are the only types of averaging which affect time data displays. Other average types only display the most recent time record.

•	In baseband mode with maximum span, some signals, particularly square waves and transients, may appear to have excess distortion or ringing because of the abrupt frequency cut-off of the anti-alias filters.


Display Resolution: Spectral Displays (Vector)

For spectral displays with vector measurements, the output of the FFT yields more measurement points than there are frequency points. Measurement points refer to the number of points output by the FFT. Frequency points refers to the number of points displayed on the screen.

Most FFT analyzers have a finite number of frequency points (often called lines or bins), and use the same number of frequency points regardless of frequency span. However, with vector measurements in Agilent 89600 series analyzers, you may select a variable number of frequency points. Vector measurements have a default resolution of 801 frequency points but you may select from 51 to 102401 points of display resolution. However, for a given number of frequency points, narrower spans have finer display resolution. This is because the same number of frequency points represents a smaller range of frequencies.

For each frequency span, the vector measurement assigns a discrete frequency value to each frequency point, such that:

The vector measurement then uses the specified start frequency to calculate nominal frequency values for each of the remaining points.

To better understand the concept of display resolution, move the main marker from display point to display point (use the left and right arrows on the keyboard). Notice how the marker jumps to each point—you cannot put the marker between points. As you move the marker, also notice how the marker readout steps through a series of discrete frequencies that correspond to each frequency point.

Hint

For a given display resolution and window selection, the best frequency resolution is achieved with the RBW mode set to arbitrary and RBW coupling set to auto.

See also

Frequency points

Frequency span


Enhancing the Measurement Speed

You can make several choices to maximize measurement speed and/or to enhance real-time bandwidth (for Vector Signal Analyzer measurements only), as shown in the following tables. Some choices are not applicable to both vector and scalar measurements (as indicated by N/A, Not Applicable).

To increase measurement speed, do this:	Vector	Scalar
• Turn calculation off for unused traces (click Trace > Data > No Data) .	Yes	Yes
• Reduce the number of frequency points to the minimum required for your measurement in order to reduce internal vector sizes.	Yes	N/A
• Choose a cardinal span:   100 MHz/2.56/2^n or 39.0625 MHz/2^n †	Yes	N/A
• Turn the marker off.	Yes	Yes
• If averaging is used, select fast averaging.	Yes	Yes
• If you have a two-channel analyzer, turn off channel 2 if it is unused     (click Input > Channels > 1 Channel).	Yes	Yes
• If time calibrations are enabled, disable them. †	Yes	N/A
†This information applies only for VXI measurement hardware.
   See separate topics for enhancing measurement speed with Agilent E4406 or Agilent ESA measurement hardware.

To enhance real-time bandwidth, do this: ††	Vector	Scalar
• Perform any of the suggestions listed above except reducing the number of frequency points. To enhance real-time bandwidth, increase the number of frequency points.	Yes	N/A
• Set ResBW mode to arbitrary.	Yes	N/A
• Set ResBW Coupling to auto.	Yes	N/A
• Minimize the display size	Yes	N/A
†† This information applies only for VXI measurement hardware.
     See separate topics for enhancing measurements with Agilent E4406 or Agilent ESA measurement hardware.


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Acknowledgements

The following products are mentioned in one or more places in the Agilent 89600-series documentation.

Product	Acknowledgement
Adobe® and Acrobat®	These products are trademarks of Adobe Systems Incorporated.
Microsoft®, Windows NT®, Windows®, and MS Windows®	These products are U.S. registered trademarks of Microsoft Corporation.
MS Excel, MS Word, MS Office, VBScript	These products are products of Microsoft Corporation.
MATLAB	MATLAB is a product of The MathWorks, Inc.


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1999-2002, Agilent Technologies


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This document was not available for inclusion in the online help. You can download the PDF from the 89600 [image] Web page .


This document was not available for inclusion in the online help. You can download the PDF from the 89600 [image] Web page .


This document was not available for inclusion in the online help. You can download the PDF from the 89600 [image] Web page .