HP e4401b, 252c02b, 252c03b, 252c04b, 252c05b schematic

...

Measurement Guide and Programming

Examples

PSA and ESA Series Spectrum Analyzers

This manual provides documentation for the following instruments:

Agilent Technologies PSA Series

E4443A (3 Hz - 6.7 GHz) E4445A (3 Hz - 13.2 GHz) E4440A (3 Hz - 26.5 GHz)

E4446A (3 Hz - 44 GHz)

E4448A (3 Hz - 50 GHz)

Agilent Technologies ESA-E Series

E4401B (9 kHz - 1.5 GHz) E4402B (9 kHz - 3.0 GHz) E4404B (9 kHz - 6.7 GHz)

E4405B (9 kHz - 13.2 GHz)

E4407B (9 kHz - 26.5 GHz)

Agilent Technologies ESA-L Series

E4411B (9 kHz - 1.5 GHz) E4403B (9 kHz - 3.0 GHz)

E4408B (9 kHz - 26.5 GHz)

Manufacturing Part Number: E4401-90482

Supersedes: E4401-90466

Printed in USA

April 2004

Notice

The information contained in this document is subject to change without notice.

Agilent T echnologies makes no war ranty of any kind with r egard to this material, including but not limited to, the implied warranties of merchantability and fitness for a partic ular purpose. Agilent Technologies shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material.

Safety Information

The following safety symbols are used throughout this manual. Familiarize yourself with the symbols and their meaning before operating this instrument.

WARNING Warning denotes a hazard. It calls attention to a procedure

which, if not correctly performed or adhered to, could result in injury or loss of life. Do not proceed beyond a warning note until the indicated conditions are fully understood and met.

CAUTION Caution denotes a hazard. It calls attention to a procedure that, if not

correctly performed or adhered to, could result in dam a g e to or destruction of the instrument. Do not proceed beyond a caution sign until the indicated conditions are fully understood and met.

NOTE Note calls out special information for the user’s attention. It provides

operational information or additional instructions of which the user should be aware.

The instruction documentation symbol. The product is

marked with this symbol when it is necessary for the user to refe r to th e instructions in the docu mentation .

This symbol is used to mark the on position of the

power line switch.

This symbol is used to mark the s tandby p osit ion o f the

power line switch.

This symbol indicates that the input power required is

AC.

WARNING This is a Safety Class 1 Product (provided with a protective

earth ground incorporated in the power cord). The mains plug shall be inserted only in a socket outlet provided with a protected earth contact. Any interruption of the protective conductor inside or outside of the product is likely to make the product dangerous. Intentional interruption i s prohib ited.

WARNING No operator serviceable parts inside. Refer servicing to

qualified personnel. To prevent electrical shock do not remove covers.

WARNING If this product is not used as specified, the protection provided

by the equipment could be impaired. This product must be used in a normal condition (in which all means for protection are intact) only.

CAUTION Always use the three-prong AC power cord supplied with this product.

Failure to ensure adequate grounding may cause product damage.

Where to Find the Latest Information

Documentation is updated periodically. Fo r the latest information about Agilent Technologies PSA and ESA spectrum analyzers, including firmware upgrades and application information, please visit the following Internet URL:

http://www .agilent.com/find/psa http://www.agilent.com/find/esa

Microsoft is a U.S. registered trademark of Microsoft Corporation.

Bluetooth is a trademark owned by its proprietor and used under license.

Contents

1. Recommended Test Equipment

2. Measuring Multiple Signals

Comparing Signals on the Same Screen Using Marker Delta . . . . . . . . . . . . . . . . . . . . . . . 12

Comparing Signals on the Same Screen Using Marker Delta Pair . . . . . . . . . . . . . . . . . . . . 14

Comparing Signals not on the Same Screen Using Marker Delta . . . . . . . . . . . . . . . . . . . . 15

Resolving Signals of Equal Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Resolving Small Signals Hidden by Large Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Decreasing the Frequency Span Around the Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3. Measuring a Low−Level Signal

Reducing Input Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Decreasing the Resolution Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Using the Average Detector and Increased Sweep Time . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Trace Averaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4. Improving Frequency Resolution and Accuracy

Using a Frequency Counter to Improve Frequency Resolution and Accuracy . . . . . . . . . . 32

5. Tracking Drifting Signals

Measuring a Source’s Frequency Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Tracking a Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6. Making Distortion Measurements

Identifying Analyzer Generated Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Third-Order Intermodulation Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Measuring TOI Distortion with a One-Button Measurement . . . . . . . . . . . . . . . . . . . . . . . . 44

Measuring Harmonics and Harmonic Distortion with a One-Button Measurement . . . . . . 45

7. Measuring Noise

Measuring Signal-to-Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Measuring Noise Using the Noise Marker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Measuring Noise-Like Signals Using Marker Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Measuring Noise-Like Signals Using the Channel Power Measurement . . . . . . . . . . . . . . . 54

8. Making Time-Gated Measurements

Generating a Pulsed-RF FM Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Connecting the Instruments to Make Time-Gated Measurements . . . . . . . . . . . . . . . . . . . . 61

Gated LO Measurement (PSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Gated Video Measurement (ESA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Gated FFT Measurement (PSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Contents

Table of Contents

9. Measuring Digital Communications Signals

Making Burst Power Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

Making Statistical Power Measurements (CCDF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

Making Adjacent Channel Power (ACP) Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . .74

Making Multi-Carrier Power (MCP) Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

10.Using External Millimeter Mixers (Option AYZ)

Making Measurements With Agilent 11970 Series Harmonic Mixers . . . . . . . . . . . . . . . . .82

Setting Harmonic Mixer Bias Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84

Entering Conversion-Loss Correction Data for Harmonic Mixers . . . . . . . . . . . . . . . . . . . .85

Making Measurements with Agilent 11974 Series Preselected Harmonic Mixers . . . . . . . .86

Frequency Tracking Calibration with Agilent 11974 Series Preselected Harmonic Mixers .88

11.Demodulating AM and FM Signals

Measuring the Modulation Rate of an AM Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92

Measuring the Modulation Index of an AM Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94

Demodulating an AM Signal Using the ESA Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96

Demodulating an FM Signal Using the ESA-E Series (Requires Option BAA) . . . . . . . . . .98

12.Using Segmented Sweep (ESA-E Series Spectrum Analyzers)

Measuring Harmonics Using Standard Sweep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102

Measuring Harmonics Using Segmented Sweep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104

Using Segmented Sweep With Limit Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

Using Segmented Sweep to Monitor the Cellular Activity of a cdmaOne Band . . . . . . . .108

13.Stimulus Response Measurements (ESA Options 1DN and 1DQ)

Making a Stimulus Response Transmission Measurement . . . . . . . . . . . . . . . . . . . . . . . . .112

Calculating the N dB Bandwidth Using Stimulus Response . . . . . . . . . . . . . . . . . . . . . . . .114

Measuring Stop Band Attenuation Using Log Sweep (ESA-E Series) . . . . . . . . . . . . . . . .116

Making a Reflection Calibration Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118

Measuring Return Loss using the Reflection Calibration Routine . . . . . . . . . . . . . . . . . . .120

14.Demodulating and Viewing Television Signals (ESA-E Series Option B7B)

Demodulating and Viewing Television Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122

Measuring Depth of Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126

15.Concepts

Resolving Closely Spaced Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130

Harmonic Distortion Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132

Time Gating Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133

Trigger Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153

Contents

AM and FM Demodulation Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

Stimulus Response Measurement Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

16.ESA/PSA Programming Examples

Examples Included in this Chapter: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Finding Additional Examples and More Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

Programming Examples Information and Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 166

Programming in C Using the VTL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Using C to Make a Power Suite ACPR Measurement on a cdmaOne Signal . . . . . . . . . . 176

Using C to Serial Poll the Analyzer to Determine when an Auto-alignment is Complete . 179 Using C and Service Request (SRQ) to Determine When a Measurement is Complete . . 182

Using Visual Basic® 6 to Capture a Screen Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Using Visual Basic® 6 to Transfer Binary Trace Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

Using Agilent VEE to Transfer Trace Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

Table of Contents

17.ESA Programming Examples

Examples Included in this Chapter: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

Programming Examples System Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

Using C with Marker Peak Search and Peak Excursion Measurement Routines . . . . . . . 202

Using C for Marker Delta Mode and Marker Minimum Search Functions . . . . . . . . . . . . 206

Using C to Perform Internal Self-Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Using C to Read Trace Data in an ASCII Format (over GPIB) . . . . . . . . . . . . . . . . . . . . . 214

Using C to Read Trace Data in a 32-Bit Real Format (over GPIB) . . . . . . . . . . . . . . . . . . 218

Using C to Read Trace Data in an ASCII Format (over RS-232) . . . . . . . . . . . . . . . . . . . 223

Using C to Read Trace Data in a 32-bit Real Format (over RS-232) . . . . . . . . . . . . . . . . . 228

Using C to Add Limit Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Using C to Measure Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Using C to Enter Amplitude Correction Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

Using C to Determine if an Error has Occurred . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

Using C to Measure Harmonic Distortion (over GPIB) . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

Using C to Measure Harmonic Distortion (over RS-232) . . . . . . . . . . . . . . . . . . . . . . . . . 261

Using C to Make Faster Power Averaging Measurements . . . . . . . . . . . . . . . . . . . . . . . . . 269

18.PSA Programming Examples

Examples Included in this Chapter: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278

Programming Examples Information and Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 279

Using C with Marker Peak Search and Peak Excursion Measurement Routines . . . . . . . . 280

Using C for Saving and Recalling Instrument State Data . . . . . . . . . . . . . . . . . . . . . . . . . 283

Using C to Save Binary Trace Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

Using C to Make a Power Calibration Measurement for a GSM Mobile Handset . . . . . . 291

Using C with the CALCulate:DATA:COMPress? RMS Command . . . . . . . . . . . . . . . . . 297

Using C Over Socket LAN (UNIX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

Contents

Table of Contents

Using C Over Socket LAN (Windows NT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .323

Using Java Programming Over Socket LAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .326

Using the VXI Plug-N-Play Driver in LabVIEW® . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335

Using LabVIEW® 6 to Make an EDGE GSM Measurement . . . . . . . . . . . . . . . . . . . . . . .336

Using Visual Basic® .NET with the IVI-Com Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338

Using Agilent VEE to Capture the Equivalent SCPI Learn String . . . . . . . . . . . . . . . . . . .342

Recommended Test Equipment

1 Recommended Test Equipment

Recommended Test Equipment

NOTE To find descriptions of specific analyzer functions, for the ESA, refer to

the Agilent Technologies ESA Series Spectrum Analyzers User’s/Programmer’s Reference Guide and for the PSA, refer to the Agilent Technologies PSA Series Spectrum Analyzers User’s and Programmer’s Reference Guide.

Test Equipment Specifications Recommended Model

Signal Sources

Signal Generator (2) 0.25 MHz to 4.0 GHz

Ext Ref Input

Adapters

Type-N (m) to BNC (f) (3) 1250-0780 Termination, 50

Type-N (m)

Recommended Test Equipment

Cables

(3) BNC, 122-cm (48-in) 10503A

Miscellaneous

Directional Bridge 86205A Bandpass Filter Center Frequency:

Lowpass Filter (2) Cutoff Frequency:

RF Antenna 08920-61060

Ω

200 MHz Bandwidth: 10 MHz

300 MHz

E443XB series or E4438C

908A

0955-0455

10 Chapter 1

2 Measuring Multiple Signals

Measuring Multiple Signals

Comparing Signals on the Same Screen Using Marker Delta

Using the analyzer, you can easily compare freque ncy and amplitude differences between signals, such as radio or television signal spectra. The analyzer delta marker function lets you compare two signals when both appear on the screen at one time .

In this procedure, the analyzer 10 MHz signal is used to measure frequency and amplitude differences between two signals on the same screen. Delta marker is used to demonstrate this comparison.

Figure 2-1 An Example of Comparing Signals on the Same Screen

Step 1. Preset the an alyzer:

Press

Step 2. (PSA)

Preset, Factory Preset (if present).

a. Enable the rear panel 10 MHz output.

Measuring Multiple Signals

Press

System, Reference, 10 MHz Out (On).

b. Connect the 10 MHz OUT (SWITCHED) from the rear panel to t he front panel RF input.

(ESA) Connect the rear panel 10 MHz REF OUT to the front panel RF input.

Step 3. Set the analyzer center frequency, span and reference level to view the

10 MHz signal and its harmonics up to 50 MHz: Press

Press Press

12 Chapter 2

FREQUENCY Channel, Center Freq, 30, MHz. SPAN X Scale, Span, 50, MHz. AMPLITUDE Y Scale, Ref Level, 10, dBm.

Measuring Multiple Signals

Comparing Signals on the Same Screen Using Marker Delta

Step 4. Place a marker at the highest peak on the display (10 MHz):

Press The

Peak Search.

Next Pk Right and Next Pk Left softkeys are available to move the

marker from peak to peak. The marker should be on the 10 MHz reference si g n a l :

Step 5. Anchor the first marker and activate a second marker:

Press

Marker, Delta.

The label on the first marker now reads 1R , indicating that it is the reference point.

Step 6. Move the second marker to another signal peak using the front-panel

knob or by using the Press

Press

Peak Search, Next Peak or Peak Search, Next Pk Right or Next Pk Left.

Peak Search key:

The amplitude and frequency difference between the markers is displayed in the active function block. For ESA see the lef t side of

Figure 2-2 and the right side for PSA.

Figure 2-2 Using the Delta Marker Function (ESA left, PSA right)

NOTE The resolution of the marker readings can be increased by turning on

the frequency count function.

Measuring Multiple Signals

Chapter 2 13

Measuring Multiple Signals

Comparing Signals on the Same Screen Using Marker Delta Pair

In this procedure, the analyzer 10 MHz signal is used to measure frequency and amplitude differences between two signals on the same screen using the delta pair marker function.

Step 1. Refer to the previous procedure “Comparing Signals on the Same

Screen Using Marker Delta” on page 12 and follow steps 1, 2 and 3.

Step 2. Turn on Delta Pair reference marker to compare the 10 MHz signal and

the 30 M Hz signal: Press Note that the

Step 3. Use the knob or Peak Search to move the second marker (labeled 1) to

Peak Search, Marker, Delta Pair (ref).

Delta Pair marker does not anchor the first marker.

the 30 MHz peak: Press

Step 4. Use the front panel knob to move the ref marker to the 20 MHz peak:

Peak Search, Next Peak or Next Pk Right.

The active function displays the amplit ude and frequency difference between the 20 MHz and 30 MHz peaks as shown in Figure 2-3.

Figure 2-3 Using the Delta Pair Marker Function (ESA left, PSA right)

Measuring Multiple Signals

NOTE In Figure 2-3 notice that the active function reado ut has moved to the

top left of the analyzer display. The active function position has three positions: top, center and bott om. To modify the active function pos ition:

Press

Display, Active Fctn Position, Top (Center, or Bottom).

Center position is the factory default setting.

14 Chapter 2

Measuring Multiple Signals

Comparing Signals not on the Same Screen Using Marker Delta

Measure the frequency and amplitude difference between two signals that do not appear on the screen at one time. (This technique is useful for harmonic distortion tes ts when narr ow span and narrow b andwidth are necessary to measure the low level harmonics.)

In this procedure, the analyzer 10 MHz signal is used to measure frequency and amplitude differences bet we en one signal on screen and one signal off screen. Delta marker is used to demonstrate this comparison.

Figure 2-4 Comparing One Signal on Screen with One Signal Off Screen

Step 1. Preset the an alyzer:

Press

Step 2. (PSA)

a. Enable the rear panel 10 MHz output: Press b. Connect the 10 MHz OUT (SWITCHED) from the rear panel to t he front

panel RF input: (ESA)

Connect the rear panel 10 MHz REF OUT to the front panel RF input.

Preset, Factory Preset (if present).

System, Reference, 10 MHz Out (On).

Measuring Multiple Signals

Chapter 2 15

Measuring Multiple Signals

Comparing Signals not on the Same Screen Using Marker Delta

Step 3. Set the center frequency, span and reference level to view only the

10 MHz signal: Press

Press Press

Step 4. Place a marker on the 10 MHz peak and then set the center frequency

FREQUENCY Channel, Center Freq, 10, MHz. SPAN X Scale, Span, 5, MHz. AMPLITUDE Y Scale, Ref Level, 10, dBm.

step size equal to the marker frequency (10 MHz): Press

Press

Step 5. Activate the marker delta function:

Press

Step 6. Increase the center frequency by 10 MHz:

Press

Peak Search. Marker →, Mkr → CF Step.

Marker, Delta.

FREQUENCY Channel, Center Freq, ↑.

The first marker moves to the left edge of the screen, at the amplitude of the first sign a l peak.

Figure 2-5 shows the reference annotation for the delta marker (1R) at

the left side o f th e display, indicating that th e 10 MHz refere n ce si g n a l is at a lower frequency than the frequency range currently displayed.

The delta marker appears on the peak of the 20 MHz component. The delta marker annotation displays the amplitude and frequency difference between the 10 and 20 MHz signal peaks.

Figure 2-5 Delta Marker with Reference Signal Off-Screen (ESA)

Measuring Multiple Signals

Step 7. Turn the markers off:

Press

Marker, Off.

16 Chapter 2

Resolving Signals of Equal Amplitude

In this procedure a decrease in resol ution bandwidth is used in combination with a decrease in video bandwidth to resolve two signals of equal amplitude with a freq uency s eparation of 100 kHz. Notice that the final RBW selection to resolve the signals is the same width as the signal separation while the VBW is slightly narrowe r than the RBW.

Step 1. Connect two sources to the analyzer input as shown in Figure 2-6.

Figure 2-6 Setup for Obtaining Two Signals

Measuring Multiple Signals

Resolving Signals of Equal Amplitude

Step 2. Set one source to 300 MHz. Set the frequency of the other source to

300.1 MHz. Set both source amplitudes to both signals should be approximately

−20 dBm. The amplitude of

−20 dBm at the output of the

bridge.

Step 3. Setup the analyzer to view the signals:

Press Press

Preset, Factory Preset (if present). FREQUENCY Channel, Center Freq, 300, MHz.

Press BW/Avg, Res BW, 300, kHz. Press

SPAN X Scale, Span, 2, MHz.

A single signal peak is visible. See Figure 2-7 for an ESA example.

NOTE If the signal peak is not present on the display, span out to 20 MHz,

turn signal tracking on, span back to 2 MHz and turn signal tracking off.:

Press Press Press

SPAN, Span, 20, MHz. Peak Search, FREQUENCY, Signal Track (On). SPAN, 2, MHz.

Press FREQUENCY, Signal Track (Off)

Measuring Multiple Signals

Chapter 2 17

Measuring Multiple Signals

Resolving Signals of Equal Amplitude

Figure 2-7 Unresolved Signals of Equal Amplitude (ESA)

Step 4. Change the resolution bandwidth (RBW) to 100 kHz so that the RBW

setting is less than or equal to the frequency separation of the two signals:

Press

BW/Avg, Res BW, 100, kHz.

Notice that the peak of the signal has become flattened indicating that two signals may be present .

Step 5. Decrease the vi d e o b a n dw i dth to 10 kHz:

Press

Video BW, 10, kHz.

Two signals are now visible as shown with the ESA on the left side in

Figure 2-8 and the PSA on the right side. Use the front-panel knob or

step keys to further reduce the resolution bandwidth and better resolve the signals.

Figure 2-8 Resolving Signals of Equal Amplitude (ESA left, PSA right)

Measuring Multiple Signals

18 Chapter 2

Measuring Multiple Signals

Resolving Signals of Equal Amplitude

As the resolution bandwidth is decreased, resolution of the individual signals is improved and the sweep time is increased. For fastest measurement times, use the widest possible resolution bandwidth. Under factor y pr eset conditi o n s, the re so l u ti on bandwidt h is “coupled” (or linked) to the span.

Since the resolution bandwidth has been changed from the coupled value, a # mark appears next to Res BW in the lower-left corner of the screen, indicating that the resolution bandwidth is uncoupled. (For more infor m a ti on on coupli n g, ref e r to the

Auto Couple key descr i ption

in the Agilent Technologies ESA Spectrum Analyzers User’s/Programmer’s Reference Guide and the PSA Spectrum Analyzers User’s/Programmer’s Reference Guide.)

NOTE To res olve two signals of equal amplitude with a frequency separation

of 200 kHz, the resolution bandwidth must be less than the signal separation so a resolution bandwidth of 100 kHz must be used. (For analyzers that use a 1-3-10 RBW step sequence, a 100 kHz RBW is the best choice for signal separation, but for high performance analyzers, like the PSA, a 180 kHz RBW can be selected by fine tuning the RBW filters at 10% increments.) Filter widths above 200 kHz exceed the 200 kHz signal separation and would not resolve the signals.

Measuring Multiple Signals

Chapter 2 19

Measuring Multiple Signals

Resolving Small Signals Hidden by Large Signals

This procedure uses narrow resoluti on bandwidths to res olve two input signals with a frequency separation of 155 kHz and an amplitude difference of 60 dB .

Step 1. Connect two sources to the analyzer input as shown in Figure 2-6. Step 2. Set one source to 300 MHz at −10 dBm. Set the second source to

300.05 MHz, so that the signal is 50 kHz higher than the first signal. Set the amplitude of the signal to signal).

Step 3. Set the analyzer as follows:

−70 dBm (60 dB below the first

Press Press Press Press

NOTE If the signal peak is not present on the display, span out to 20 MHz,

Preset, Factory Preset (if present). FREQUENCY Channel, Center Freq, 300, MHz. BW/Avg, 30, kHz. SPAN X Scale, Span, 500, kHz.

turn signal tracking on, span back to 2 MHz and turn signal tracking off:

Press Press Press

SPAN, Span, 20, MHz. Peak Search, FREQUENCY, Signal Track (On). SPAN, 2, MHz.

Press FREQUENCY, Signal Track (Off).

Step 4. Set the 300 MHz signal to the reference level:

Press

Measuring Multiple Signals

NOTE The ESA 30 kHz filter shape factor of 15:1 (PSA is 4.1:1) has a

bandwidth of 450 kHz at the 60 dB point (PSA has a BW of 123 kHz).

Peak Search, Mkr →, Mkr → Ref Lvl.

The half-bandwidth (225 kHz for ESA and 61.5 kHz for PSA) is NOT narrower than the frequency separation of 50 kHz, so the input signals can not be resolved.

20 Chapter 2

Measuring Multiple Signals

Resolving Small Signals Hidden by Large Signals

Figure 2-9 Signal Resolution with a 30 kHz RBW (ESA left, PSA right)

Step 5. Reduce the resolution bandwidth filter to view the smaller hidden

signal. Place a delta marker on the smaller signal: Press

Press

NOTE The ESA 1 kHz filter shape factor of 15:1 (PSA is 4.1:1) has a

BW/Avg, 1, kHz. Peak Search, Marker, 50, kHz.

bandwidth of 15 kHz at the 60 dB point (PSA has a BW of 4.1 kHz). The half-bandwidth (7.5 kHz for ESA and 2.05 kHz for PSA) is narrower than 50 kHz, so the input signals can be resolved.

Figure 2-10 Signal Resolution with a 1 kHz RBW (ESA left, PSA right)

Measuring Multiple Signals

NOTE To determine the resolution capability for intermediate amplitude

differences, assume the filter skirts between the 3 dB and 60 dB points are parabolic, like an ideal Gaussian filter. The resolution capability is approximately:

∆f



12.04 dB

-------------

•



RBW

where ∆f is the separation between the signals.

Chapter 2 21

Measuring Multiple Signals

Decreasing the Frequency Span Around the Signal

Using the analyzer signal track func tion, you can quickly decrease the span while keeping the signal at center frequency. This is a fast way to take a closer look at the area around the signal to identify signals that would otherwise not be resolved.

This procedure uses signal trac king and span zoom to view the analyzer 50 MHz reference signal in a 200 kHz span.

Step 1. Perform a factory preset:

Press

Step 2. Enable the internal 50 MHz amplitude reference signal of the analyzer

Preset, Factory Preset (if present).

as follows: (PSA)

Press

Input/Output, Input Port, Amptd Ref.

(ESA E4401B and E4411B) Press

Input/Output, Amptd Ref (On).

(ESA E4402B, E4403B, E4404B, E4405B, E4407B and E4408B) Connect a cable from the front panel AMPTD REF OUT to the analyz er RF input: Press

Step 3. Set the start frequency to 20 MHz and the stop frequency to 1 GHz:

Press Press

Step 4. Place a marker at the peak:

Press

Measuring Multiple Signals

Step 5. Turn on the signal tracking function to move the signal to the center of

Input/Output, Amptd Ref Out (On).

FREQUENCY Channel, Start Freq, 20, MHz. FREQUENCY Channel, Stop Freq, 1, GHz.

Peak Search.

the screen (if it is not already positioned there): Press

FREQUENCY Channel, Signal Track (On).

See the left-side of figure Figure 2-11. (Note that the marker must be on the signal before turning signal track on.)

NOTE Because the signal track f unction automaticall y maintains the sig nal at

the center of the screen, you can reduce the span quic k l y for a closer look. If the signal drifts off of the screen as you decrea se the span, use a wider frequency span. (You can also use as a quick way to perform the

SPAN key sequence.)

22 Chapter 2

Peak Search, FREQUENCY, Signal Track,

Span Zoom, in the SPAN menu,

Measuring Multiple Signals

Decreasing the Frequency Span Around the Signal

Step 6. Reduce span and resolution bandwidth to zoom in on the marked

signal: Press

NOTE If the span change is large enough, the span decreases in steps as

SPAN X Scale, Span, 200, kHz.

automatic zoom is completed . See Figure 2-11 on the right side. You can also use the front-panel knob or step k eys to decrease the span and resolution bandwidth values.

Step 7. Turn off signal tracking:

Press

FREQUENCY Channel, Signal Track (Off).

Figure 2-11 Signal Tracking

LEFT: Signal tracking on before span decrease RIGHT: After zooming in on the signal

Measuring Multiple Signals

Chapter 2 23

Measuring Multiple Signals

Decreasing the Frequency Span Around the Signal

Measuring Multiple Signals

24 Chapter 2

3 Measuring a Low−Level Signal

Measuring a Low

−

Level Signal

Measuring a Low−Level Signal

Reducing Input Attenuation

The ability to measure a low-level signal is limited by internally generated noise in the spectrum analyzer. The measurement setup can be changed in several ways to improve the analyzer sensitivity.

The input attenuator affects the level of a signal pas sing through the instrument. If a signal is very close to the noise floor, reducing input attenuation can bring the signal out of the noise.

CAUTION Ensure that the total power of all input signals at the analyzer RF

input does not exceed +30 dBm (1 watt).

Step 1. Preset the an a l y z er:

Press Preset, Factory Preset (if present).

Step 2. Set the freque n cy o f th e si g n a l so u r ce to 30 0 MHz. Set the source

amplitude to RF INPUT.

−80 dBm. Connect the source RF OUTPUT to the analyzer

Step 3. Set the center frequency, span and reference level:

Press Press Press

FREQUENCY Channel, Center Freq, 300, MHz. SPAN X Scale, Span, 5, MHz. AMPLITUDE Y Scale, Ref Level, 40, −dBm.

Step 4. Move the desired peak (in this example, 300 MHz) to the center of the

display: Press

Peak Search, Marker ➞, Mkr ➞ CF.

Step 5. Reduce the span to 1 MHz (as shown in Figure 3 -1) and if necessary

re-center the peak: Press

Span, 1, MHz.

Figure 3-1 Measuring a Low-Level Signal (ESA Display)

Level Signal

−

Measuring a Low

26 Chapter 3

Step 6. Set the attenuation to 20 dB:

Measuring a Low−Level Signal

Reducing Input Attenuation

Press

AMPLITUDE Y Scale, Attenuation, 20, dB.

Note that increasing the attenuation moves the noise floor closer to the signal level.

A “#” mark appears next to the Atten annotation at the top of the display, indicating that the attenuation is no longer coupled to other analyzer settings.

Step 7. To see the signal more clearly, set the attenuation to 0 dB:

Press

AMPLITUDE, Attenuation, 0, dB.

See Figure 3-2 shows 0 dB input attenuation.

Figure 3-2 Measuring a Low-Level Signal Using 0 dB Attenuation (ESA)

CAUTION When you finish this example, increase the attenuation to protect the

analyzer’s RF inpu t: Press AMPLITUDE Y Scale, Attenuation (Auto) or press Auto Couple.

NOTE All figures in this chapter are screen captures from an ESA. Display

and numerical results may be different for a PSA.

Chapter 3 27

Measuring a Low

−

Level Signal

Measuring a Low−Level Signal

Decreasing the Resolution Bandwidth

Resolution bandwidth settings affect the level of internal noise without affecting the level of continuous wave (CW) signals. Decreasing the RBW by a decade reduces the noise floor by 10 dB.

Step 1. Refer to the first procedure “Reducing In put Attenuation” on page 26 of

this chapter and follow steps 1, 2 and 3.

Step 2. Decrease the resolution bandwidth:

Press

BW/Avg, ↓.

The low-level signal appears more clearly because the noise level is reduced (see Figure 3-3).

Figure 3-3 Decreasing Resolution Bandwidth

A “#” mark appears next to the Res BW annotation in the lower left corner of the screen, indicating that the resolution bandwidth is uncoupled.

RBW Selections You can use the step keys to change the RBW in a 1

−3−10 sequence.

For ESA, RBWs below 1 kHz are digital and have a selectivity ratio of 5:1 while RBWs at 1 kHz and higher have a 15:1 selectivity ratio. The ESA’s maximum RBW is 5 MHz a nd the minimum is 1 Hz (optional).

All PSA RBWs are digital and have a selectivity ratio of 4.1:1. For PSA, choosing the next lower RBW for better sensitivity increases the sweep

Level Signal

−

time by about 10:1 for swept measurements, and about 3:1 for FFT measurements (within the limits of RBW). Using the knob or keypad, you can select RBWs from 1 Hz to 3 MHz in approximately 10% increments, plus 4, 5, 6 and 8 MHz. This enables you to make the trade off between sweep tim e a n d se n s i t ivity with finer resolut i on.

Measuring a Low

28 Chapter 3

Measuring a Low−Level Signal

Using the Average Detector and Increased Sweep Time

When the analyzer’s noise masks low-level signals, changing to the average detector and increasing the sweep time smooths the noise and improves the signal’s visibility. Slower sweeps are required to average more noise variations.

Step 1. Refer to the first procedure “Reducing In put Attenuation” on page 26 of

this chapter and follow steps 1, 2 and 3.

Step 2. Select the average detector:

Press

Det/Demod, Detector, Average.

A “#” mark appears next to the Avg annotation, indicating that the detector has been chosen manually (see Figure 3-4).

Step 3. Increase the sweep time to 100 ms:

Press

Sweep, Sweep Time, ↑.

Note how the noise smooths out, as there is more time to average the values for each of the displ ayed data points .

Step 4. With the sweep time at 100 ms, change the average type to

log averaging: (ESA) Press

(PSA) Press

BW/Avg, Avg Type, Video Avg. BW/Avg, Avg/VBW Type, Log-Pwr.

Figure 3-4 Varying the Sweep Time with the Average Detector

Chapter 3 29

Measuring a Low

−

Level Signal

Measuring a Low−Level Signal

Trace Averaging

Averaging is a digital proces s in which each trace point is aver aged with the previous average for the same trace point. Selecting averaging, when the analyzer is autocoupled, changes the detection mode (from peak in ESA and normal in PSA) to sample, smoothing the displa ye d noise level. ESA sample mode displays the instantaneous value of the signal at the end of the time or frequency interval represented by each display point (for PSA it is t he ce nter of the t ime or fr equency interval), rather than the value of the peak during the interval. Sample mode may not measure a signal’s amplitude as accurately as normal mode, because it may not find the true peak.

NOTE This is a trace processing function and is not the same as using the

average detector (as described on page 29).

Step 1. Refer to the first procedure “Reducing In put Attenuation” on page 26 of

this chapter and follow steps 1, 2 and 3.

Step 2. Turn video averaging on:

Press

BW/Avg, Average (On).

As the averaging routine smooths the trace, low level signals become more visible. Average 100 appears in the active function block.

Step 3. With average as the active function, set the number of averages to 25:

Press

25, Enter.

Annotation on the left side of the graticule shows the type of averaging (the annotation for ESA is VAvg and is LgAv for PSA), and the number of traces averaged.

Changing most active functions res tarts the averag ing , as do es toggling

Average key. Once the set number of sweeps com pletes , the analyzer

the continues to provide a running average based on this se t nu mbe r.

NOTE If you want the measurement to stop after the set number of sweeps,

use single sweep: Press

Sweep, Sweep (to select Single), or press Single

and then toggle the Average key.

Level Signal

−

Measuring a Low

30 Chapter 3

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