Measurement Guide
Agilent Technologies ESA Spectrum Analyzers
This manual provides documentation for the following instruments:
Agilent 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)
and
Agilent ESA-L Series
E4411B (9 kHz – 1.5GHz)
E4403B (9 kHz – 6.7 GHz)
E4408B (9 kHz – 26.5 GHz)
Manufacturing Part Number: E4401-90175
Supersedes E4401-90111
Printed in USA
March 2000
© Copyright 2000 Agilent Technologies
The information contained in this document is subject to change
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ii
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iii
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iv
Contents
1. Making Basic Measurements
What is in This Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2
Comparing Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
Example 1:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
Example 2:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5
Resolving Signals of Equal Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7
Resolving Small Signals Hidden by Large Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-9
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-10
Making Better Frequency Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-12
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-12
Decreasing the Frequency Span Around the Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-14
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-14
Tracking Drifting Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-16
Example 1:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-16
Example 2:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-18
Measuring Low Level Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-20
Example 1:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-20
Example 2:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-23
Example 3:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-24
Example 4:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-26
Identifying Distortion Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-28
Distortion from the Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-28
Third-Order Intermodulation Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-31
Measuring Signal-to-Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-34
Making Noise Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-36
Example 1:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-36
Example 2:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-38
Example 3:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-39
Example 4:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-41
Demodulating AM Signals (Using the Analyzer As a Fixed Tuned Receiver) . . . . . . . . . . .1-43
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-43
Demodulating FM Signals
(Without Option BAA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-46
2. Making Measurements
What’s in This Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2
Making Stimulus Response Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3
What Are Stimulus Response Measurements? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3
Using An Analyzer With A Tracking Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3
Stepping Through a Transmission Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4
Tracking Generator Unleveled Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8
Measuring Device Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9
Making a Reflection Calibration Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-12
Example: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13
Reflection Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13
Measuring the Return Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-14
Demodulating and Listening to an AM Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-15
v
Contents
Example 1: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
Example 2: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
Measuring Harmonics and Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-19
Example:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
Demodulating and Viewing Television Signals
(Option B7B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
Example 1: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
Example 2: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29
TV Trig Setup Menu Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30
Using External Millimeter Mixers
(Option AYZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33
Example 1: Making measurements with unpreselected millimeter-wave mixers . . . . . . 2-33
Example 2: Making Measurements with HP/Agilent 11974 Series Preselected
Millimeter-Wave Mixers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-37
vi
1 Making Basic Measurements
1-1
Making Basic Measurements
What is in This Chapter
What is in This Chapter
This chapter demonstrates basic analyzer measurements with
examples of typical measurements; each measurement focuses on
different functions. The measurement procedures covered in this
chapter are listed below.
• “Comparing Signals” on page 1-3
• “Resolving Signals of Equal Amplitude” on page 1-6
• “Resolving Small Signals Hidden by Large Signals” on page 1-9
• “Making Better Frequency Measurements” on page 1-12
• “Decreasing the Frequency Span Around the Signal” on page 1-14
• “Tracking Drifting Signals” on page 1-16
• “Measuring Low Level Signals” on page 1-20
• “Identifying Distortion Products” on page 1-28
• “Measuring Signal-to-Noise” on page 1-34
• “Making Noise Measurements” on page 1-36
• “Demodulating AM Signals (Using the Analyzer As a Fixed Tuned
Receiver)” on page 1-43
• “Demodulating FM Signals (Without Option BAA)” on page 1-46
To find descriptions of specific analyzer functions, refer to the user’s
guide.
1-2 Chapter1
Making Basic Measurements
Comparing Signals
Comparing Signals
Using the analyzer, you can easily compare frequency 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 or when only one appears on the
screen.
Example 1:
Measure the differences between two signals on the same display
screen.
1. Connect the 10 MHz REF OUT from the rear panel to the
front-panel INPUT.
2. Set the center frequency to 30 MHz and the span to 50 MHz by
pressing
FREQUENCY, 30 MHz, SPAN, 50 MHz.
3. Set the reference level to 10 dBm by pressing
The 10 MHz reference signal and its harmonics appear on the
display.
4. Press
display. (The
Peak Search to place a marker at the highest peak on the
Next Peak, Next Pk Right and Next Pk Left keys are
available to move the marker from peak to peak.) The marker should
be on the 10 MHz reference signal. See Figure 1-1.
Figure 1-1 Placing a Marker on the 10 MHz Signal
AMPLITUDE, 10 dBm.
Chapter 1 1-3
Making Basic Measurements
Comparing Signals
5. Press Marker, Delta, to activate a second marker at the position of the
first marker. Move the second marker to another signal peak using
the knob, or by pressing
Next Pk Left.
Peak Search and Next Peak, Next Pk Right or
6. The amplitude and frequency difference between the markers is
displayed in the active function block and in the upper right corner
of the screen. See Figure 1-2. The resolution of the marker readings
can be increased by turning on the frequency count function. Press
Freq Count. Both signals are counted.
Press
Marker, Off to turn the markers off.
Figure 1-2 Using the Marker Delta Function
1-4 Chapter1
Making Basic Measurements
Comparing Signals
Example 2:
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 tests when narrow span and narrow bandwidth
are necessary to measure the low level harmonics.)
1. Connect the 10 MHz REF OUT from the rear panel to the
front-panel INPUT.
2. Set the center frequency to 10 MHz and the span to 5 MHz by
pressing
FREQUENCY, 10 MHz, SPAN, 5 MHz.
3. Set the reference level to 10 dBm by pressing
4. Press
5. Press
Peak Search to place a marker on the peak.
Marker→, Mkr→CF Step to set the center frequency step size
AMPLITUDE, 10 dBm.
equal to the frequency of the fundamental signal.
6. Press Marker, Delta to anchor the position of the first marker and
activate a second marker.
7. Press FREQUENCY, Center Freq and the (↑) key to increase the center
frequency by 10 MHz. The first marker remains on the screen at the
amplitude of the first signal peak.
The annotation in the upper right corner of the screen indicates the
amplitude and frequency difference between the two markers. See
Figure 1-3.
8. To turn the markers off, press
Marker, Off.
Figure 1-3 Frequency and Amplitude Difference Between Signals
Chapter 1 1-5
Making Basic Measurements
Resolving Signals of Equal Amplitude
Resolving Signals of Equal Amplitude
Two equal-amplitude input signals that are close in frequency can
appear as one on the analyzer display. Responding to a single-frequency
signal, a swept-tuned analyzer traces out the shape of the selected
internal IF (intermediate frequency) filter. As you change the filter
bandwidth, you change the width of the displayed response. If a wide
filter is used and two equal-amplitude input signals are close enough in
frequency, then the two signals appear as one. Thus, signal resolution is
determined by the IF filters inside the analyzer.
The bandwidth of the IF filter tells us how close together equal
amplitude signals can be and still be distinguished from each other. The
resolution bandwidth function selects an IF filter setting for a
measurement. Resolution bandwidth is defined as the 3 dB bandwidth
of the filter.
Generally, to resolve two signals of equal amplitude, the resolution
bandwidth must be less than or equal to the frequency separation of the
two signals. If the bandwidth is equal to the separation and the video
bandwidth is less than the resolution bandwidth, a dip of
approximately 3 dB is seen between the peaks of the two equal signals,
and it is clear that more than one signal is present. See Figure 1-5.
In order to keep the analyzer measurement calibrated, sweep time is
automatically set to a value that is inversely proportional to the square
of the resolution bandwidth (for resolution bandwidths ≥ 1kHz). So, if
the resolution bandwidth is reduced by a factor of 10, the sweep time is
increased by a factor of 100 when sweep time and bandwidth settings
are coupled. (Sweep time is proportional to
2
1/BW
.) For shortest
measurement times, use the widest resolution bandwidth that still
permits discrimination of all desired signals.The analyzer allows you to
select from 1 kHz to 3 MHz resolution bandwidths in a 1, 3, 10 sequence
and 5 MHz for maximum measurement flexibility.
Option 1DR adds narrower resolution bandwidths, from 10 Hz to
300 Hz, in a 1-3-10 sequence. These bandwidths are digitally
implemented and have a much narrower shape factor than the wider,
analog resolution bandwidths. Also, the autocoupled sweeptimes when
using the digital resolution bandwidths are much faster than analog
bandwidths of the same width.
1-6 Chapter1
Example:
Resolve two signals of equal amplitude with a frequency separation of
100 kHz.
1. Connect two sources to the analyzer input as shown in Figure 1-4.
Figure 1-4 Setup for Obtaining Two Signals
Making Basic Measurements
Resolving Signals of Equal Amplitude
2. Set one source to 300 MHz. Set the frequency of the other source to
300.1 MHz. The amplitude of both signals should be approximately
−20 dBm.
3. On the analyzer, press
Preset, Factory Preset (softkey), if present. Set
the center frequency to 300 MHz, the span to 2 MHz, and the
resolution bandwidth to 300 kHz by pressing
SPAN, 2 MHz, then BW/Avg, Resolution BW, 300 kHz. A single signal
FREQUENCY, 300 MHz,
peak is visible.
NOTE If the signal peak cannot be found, increase the span to 20 MHz by
pressing
FREQUENCY, Signal Track (On), then SPAN, 2 MHz to bring the signal to
center screen. Then press
SPAN, 20 MHz. The signal should be visible. Press Search,
Signal Track (Off) to turn the signal track
function off.
4. Since the resolution bandwidth must be less than or equal to the
frequency separation of the two signals, a resolution bandwidth of
100 kHz must be used. Change the resolution bandwidth to 100 kHz
by pressing
BW/Avg, 100 kHz. Two signals are now visible as shown in
Figure 1-5. Use the knob or step keys to further reduce the
resolution bandwidth and better resolve the signals.
5. Decrease the video bandwidth to 10 kHz, by pressing
Video BW (Man), 10 kHz.
Chapter 1 1-7
Making Basic Measurements
Resolving Signals of Equal Amplitude
Figure 1-5 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 factory preset conditions, the resolution bandwidth 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. (Also see
the
Auto Couple key description in the user’s guide.)
NOTE To resolve two signals of equal amplitude with a frequency separation
of 200 kHz, the resolution bandwidth must be less than the signal
separation, and resolution of 100 kHz must be used. The next larger
filter, 300 kHz, would exceed the 200 kHz separation and would not
resolve the signals.
1-8 Chapter1
Making Basic Measurements
Resolving Small Signals Hidden by Large Signals
Resolving Small Signals Hidden by Large
Signals
When dealing with the resolution of signals that are close together and
not equal in amplitude, you must consider the shape of the IF filter of
the analyzer, as well as its 3 dB bandwidth. (See “Resolving Signals of
Equal Amplitude” on page 1-6 example for more information.) The
shape of a filter is defined by the selectivity, which is the ratio of the
60 dB bandwidth to the 3 dB bandwidth. (Generally, the IF filters in
this analyzer have shape factors of 15:1 or less for resolution
bandwidths ≥1kHz and 5:1 or less for resolution bandwidths ≤ 300 Hz).
If a small signal is too close to a larger signal, the smaller signal can be
hidden by the skirt of the larger signal. To view the smaller signal, you
must select a resolution bandwidth such that k is less than a. See
Figure 1-6.
Figure 1-6 Resolution Bandwidth Requirements for Resolving Small
Signals
The separation between the two signals (a) must be greater than half
the filter width of the larger signal (k) measured at the amplitude level
of the smaller signal.
Chapter 1 1-9
Making Basic Measurements
Resolving Small Signals Hidden by Large Signals
Example:
Resolve two input signals with a frequency separation of 155 kHz and
an amplitude separation of 60 dB.
1. To obtain two signals with a 155 kHz separation, connect the
equipment as shown in the previous section, “Resolving Signals of
Equal Amplitude” on page 1-6. Set one source to 300 MHz at
−20 dBm.
2. Set the analyzer center frequency to 300 MHz and the span to
2 MHz: press
NOTE If the signal peak cannot be found, increase the span to 20 MHz by
pressing
FREQUENCY, Signal Track (On), then SPAN, 2 MHz to bring the signal to
SPAN, 20 MHz. The signal should be visible. Press Search,
center screen. Then press
function off.
3. Set the second source to 300.155 MHz, so that the signal is 155 kHz
higher than the first signal. Set the amplitude of the signal to
−80 dBm (60 dB below the first signal).
FREQUENCY, 300 MHz, then SPAN, 2 MHz.
Signal Track (Off) to turn the signal track
4. Set the 300 MHz signal to the reference level by pressing
Search, Meas Tools, then Mkr → Ref Lvl.
5. Place a marker on the smaller signal by pressing
Delta, Next Pk Right.
Peak
If a 10 kHz filter with a typical shape factor of 15:1 is used, the filter
will have a bandwidth of 150 kHz at the 60 dB point. The
half-bandwidth (75 kHz) is narrower than the frequency separation,
so the input signals will be resolved. See Figure 1-7.
1-10 Chapter1
Making Basic Measurements
Resolving Small Signals Hidden by Large Signals
Figure 1-7 Signal Resolution with a 10 kHz Resolution Bandwidth
If a 30 kHz filter is used, the 60 dB bandwidth could be as wide as
450 kHz. Since the half-bandwidth (225 kHz) is wider than the
frequency separation, the signals most likely will not be resolved. See
Figure 1-8. (In this example, we used the 60 dB bandwidth value. To
determine resolution capability for intermediate values of amplitude
level differences, assume the filter skirts between the 3 dB and 60 dB
points are approximately straight.)
Figure 1-8 Signal Resolution with a 30 kHz Resolution Bandwidth
Chapter 1 1-11
Making Basic Measurements
Making Better Frequency Measurements
Making Better Frequency Measurements
A built-in frequency counter increases the resolution and accuracy of
the frequency readout. When using this function, if the ratio of the
resolution bandwidth to the span is too small (less than 0.002), the
Marker Count: Widen Res BW message appears on the display. It
indicates that the resolution bandwidth is too narrow.
Example:
Increase the resolution and accuracy of the frequency readout on the
signal of interest.
1. Turn on the internal 50 MHz alignment signal of the analyzer (if you
have not already done so).
For the E4401B and E4411B, use the internal 50 MHz alignment
signal of the analyzer as the signal being measured. Press
Factory Preset (if present), Input/Output, Amptd Ref (On).
Preset,
Forall other models connect a cable between the front-panel AMPTD
REF OUT to the analyzer INPUT, then press Preset, Factory Preset
(if displayed), Input/Output, Amptd Ref Out (On).
2. Set the center frequency to 50 MHz by pressing
3. Set the span to 80 MHz by pressing
4. Press
Freq Count. (Note that Marker Count On Off has On
SPAN, 80 MHz.
FREQUENCY, 50 MHz.
underlined turning the frequency counter on.) The frequency and
amplitude of the marker and the word Marker will appear in the
active function area (this is not the counted result). The counted
result appears in the upper-right corner of the display.
5. Move the marker,with the front-panel knob, half-way down the skirt
of the signal response. Notice that the readout in the active function
changes while the counted result (upper-right corner of display) does
not. See Figure 1-9. To get an accurate count, you do not need to
place the marker at the exact peak of the signal response.
NOTE Marker count properly functions onlyon CW signals or discrete spectral
components. Marker must be >26 dB above the noise.
6. Increase the counter resolution by pressing
Resolution (Man) and
then entering the desired resolution using the step keys or the
numbers keypad. For example, press 1 kHz. The marker counter
readout is in the upper-right corner of the screen. The resolution can
be set from 1 Hz to 100 kHz.
1-12 Chapter1
7. The marker counter remains on until turned off.Turn off the marker
counter by pressing
Freq Count, then Marker Count (Off). Marker, Off
also turns the marker counter off.
Figure 1-9 Using Marker Counter
Making Basic Measurements
Making Better Frequency Measurements
Chapter 1 1-13
Making Basic Measurements
Decreasing the Frequency Span Around the Signal
Decreasing the Frequency Span Around the
Signal
Using the analyzer signal track function, 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.
Example:
Examine a signal in a 200 kHz span.
1. Turn on the internal 50 MHz alignment signal of the analyzer (if you
have not already done so).
For the E4401B and E4411B, use the internal 50 MHz alignment
signal of the analyzer as the signal being measured. Press
Factory Preset (if present), Input/Output, Amptd Ref (On).
Preset,
Forall other models connect a cable between the front-panel AMPTD
REF OUT to the analyzer INPUT, then press Preset, Factory Preset
(if present), Input/Output, Amptd Ref Out (On).
2. Set the stop frequency to 1 GHz by pressing
1 GHz.
3. Press
4. Press
Peak Search to place a marker at the peak.
FREQUENCY, Signal Track (On) and the signal will move to the
FREQUENCY, Stop Freq,
center of the screen, if it is not already positioned there. (Note that
the marker must be on the signal before turning signal track on.)
Because the signal track function automatically maintains the
signal at the center of the screen, you can reduce the span quickly for
a closer look. If the signal drifts off of the screen as you decrease the
span, use a wider frequency span.
5. Press
SPAN, 200 kHz. The span decreases in steps as automatic zoom
is completed. See Figure 1-10. You can also use the knob or step keys
to decrease the span or use the
Press
NOTE When you are finished with the example, turn off the signal tracking
Signal Track (Off) again to turn off the signal track function.
Span Zoom function under SPAN.
function.
1-14 Chapter1
Decreasing the Frequency Span Around the Signal
Figure 1-10 After Zooming In on the Signal
Making Basic Measurements
Chapter 1 1-15
Making Basic Measurements
Tracking Drifting Signals
Tracking Drifting Signals
The signal track function is useful for tracking drifting signals that
drift relatively slowly.
Signal Track On Off may be used to track these drifting signals. Use Peak
Search to place a marker on the signal you wish to track. Pressing
FREQUENCY, Signal Track (On) will bring that signal to the center
frequency of the graticule and adjust the center frequency every sweep
to bring the selected signal back to the center. (
menu, is a quick way to perform the Search, FREQUENCY, Signal Track
On Off, SPAN key sequence.)
Note that the primary function of the signal track function is to track
unstable signals, not to track a signal as the center frequency of the
analyzer is changed. If you choose to use the signal track function when
changing center frequency, check to ensure that the signal found by the
tracking function is the correct signal.
Span Zoom, in the SPAN
Example 1:
Use the signal track function to keep a drifting signal at the center of
the display and monitor its change.
This example requires a signal generator. The frequency of the signal
generator will be changed while you view the signal on the display of
the analyzer.
1. Connect a signal generator to the analyzer input. Press
Factory Preset (if present).
2. Set the signal generator frequency to 300 MHz with an amplitude of
−20 dBm.
3. Set the center frequency of the analyzer to 300 MHz by pressing
FREQUENCY, 300 MHz.
4. Press
5. Set the span to 10 MHz by pressing
6. Press
Marker and move the marker to the peak of your signal.
SPAN, 10 MHz.
SPAN, Span Zoom, 500 kHz.
Notice that the signal has been held in the center of the display.
Preset,
1-16 Chapter1
Making Basic Measurements
Tracking Drifting Signals
7. The signal frequency drift can be read from the screen if both the
signal track and marker delta functions are active. Press
Delta. The marker readout indicates the change in frequency and
amplitude as the signal drifts.
8. Tune the frequency of the signal generator. Notice that the center
frequency of the analyzer changes in < 10 kHz increments,centering
the signal with each increment. See Figure 1-11.
Figure 1-11 Using Signal Tracking to Track a Drifting Signal
Marker,
Chapter 1 1-17
Making Basic Measurements
Tracking Drifting Signals
Example 2:
The analyzer can measure the short and long-term stability of a source.
The maximum amplitude level and the frequency drift of an input
signal trace can be displayed and held by using the maximum-hold
function. You can also use the maximum hold function if you want to
determine how much of the frequency spectrum a signal occupies.
1. Connect a signal generator to the analyzer input. Press
Factory Preset (if present).
Preset,
2. Set the signal generator frequency to 300 MHz with an amplitude of
−20 dBm.
3. Set the center frequency of the analyzer to 300 MHz by pressing
FREQUENCY, 300 MHz.
4. Press
5. Set the span to 10 MHz by pressing
6. Press
7. Turn off the signal track function by pressing
Track (Off).
8. To measure the excursion of the signal, press
Hold. As the signal varies, maximum hold maintains the maximum
Marker and move the marker to the peak of your signal.
SPAN, 10 MHz.
SPAN, Span Zoom, 500 kHz.
FREQUENCY, Signal
View/Trace then Max
responses of the input signal.
Annotation on the left side of the screen indicates the trace mode.
For example, M1 S2 S3 indicates trace 1 is in maximum-hold mode,
trace 2 and trace 3 are in store- blank mode. See “Display
Annotation” in Chapter 2 of the User’s Guide.
9. Press
when 2 is underlined.) Press
View/Trace, Trace 1 2 3, to select trace 2. (Trace 2 is selected
Clear Write to place trace 2 in clear-write
mode, which displays the current measurement results as it sweeps.
Trace 1 remains in maximum hold mode, showing the frequency
shift of the signal.
Slowly change the frequency of the signal generator ± 50 kHz. Your
analyzer display should look similar to Figure 1-12.
1-18 Chapter1
Making Basic Measurements
Tracking Drifting Signals
Figure 1-12 Viewing a Drifting Signal With Max Hold and Clear Write
Chapter 1 1-19
Making Basic Measurements
Measuring Low Level Signals
Measuring Low Level Signals
The ability of the analyzer to measure low level signals is limited by the
noise generated inside the analyzer. A signal may be masked by the
noise floor so that it is not visible. This sensitivity to low level signals is
affected by the measurement setup.
The analyzer input attenuator and bandwidth settings affect the
sensitivity by changing the signal-to-noise ratio. The attenuator affects
the level of a signal passing through the instrument, whereas the
bandwidth affects the level of internal noise without affecting the
signal. In the first two examples in this section, the attenuator and
bandwidth settings are adjusted to view low level signals.
If, after adjusting the attenuation and resolution bandwidth, a signal is
still near the noise, visibility can be improved by using the video
bandwidth and video averaging functions, as demonstrated in the third
and fourth examples.
Example 1:
If a signal is very close to the noise floor, reducing input attenuation
brings the signal out of the noise. Reducing the attenuation to 0 dB
maximizes signal power in the analyzer.
CAUTION The total power of all input signals at the analyzer input must not
exceed the maximum power level for the analyzer.
1. Connect a signal generator to the analyzer input. Press
Factory Preset (if present).
2. Set the signal generator frequency to 300 MHz with an amplitude of
−80 dBm.
3. Set the center frequency of the analyzer to 300 MHz by pressing
FREQUENCY, 300 MHz.
4. Set the span to 5 MHz by pressing
5. Set the reference level to −40 dBm by pressing
40 −dBm.
6. Place the signal at center frequency by pressing
Tools, Mkr→CF.
SPAN, 5 MHz.
AMPLITUDE, Ref Level,
Peak Search, Meas
Preset,
7. Reduce the span to 1 MHz. Press
SPAN, and then use the step-down
key (↓). See Figure 1-13.
1-20 Chapter1
Figure 1-13 Low-Level Signal
Making Basic Measurements
Measuring Low Level Signals
8. Press
AMPLITUDE, Attenuation (Man). Press the step-up key (↑) twice
to select 20 dB attenuation. Increasing the attenuation moves the
noise floor closer to the signal.
A # mark appears next to the Atten annotation at the top of the
display, indicating the attenuation is no longer coupled to other
analyzer settings.
9. To see the signal more clearly, enter 0 dB. Zero attenuation makes
the signal more visible. See Figure 1-14.
Before connecting other signals to the analyzer input, increase the RF
attenuation to protect the analyzer input: press
press
Auto Couple.
Attenuation (Auto) or
Chapter 1 1-21
Making Basic Measurements
Measuring Low Level Signals
Figure 1-14 Using 0 dB Attenuation
1-22 Chapter1
Making Basic Measurements
Measuring Low Level Signals
Example 2:
The resolution bandwidth can be decreased to view low level signals.
1. As in the previous example, set the analyzer to view a low level
signal. Connect a signal generator to the analyzer input. Press
Preset, Factory Preset (if present).
2. Set the signal generator frequency to 300 MHz with an amplitude of
−80 dBm.
3. Set the center frequency of the analyzer to 300 MHz by pressing
FREQUENCY, 300 MHz.
4. Set the span to 5 MHz by pressing
5. Set the reference level to −40 dBm by pressing
40 −dBm.
6. Press
BW/Avg, then ↓. The low level signal appears more clearly
because the noise level is reduced. See Figure 1-15.
Figure 1-15 Decreasing Resolution Bandwidth
SPAN, 5 MHz.
AMPLITUDE, Ref Level,
A # mark appears next to the Res BW annotation at the lower left corner
of the screen, indicating that the resolution bandwidth is uncoupled.
As the resolution bandwidth is reduced, the sweep time is increased to
maintain calibrated data.
Chapter 1 1-23
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