The Agilent Technologies tracking generator is a built-in option for the N9000 CXA signal
analyzer and is used to characterize the behavior of components or subsystems, such as frequency
response and insertion loss or gain. This brief video shows how this option provides
you with a cost effective solution for scalar network analysis.
The optional tracking generator works from 9 kHz - 3 GHz or 9 kHz - 6 GHz. It offers
the best performance in the industry and the fastest measurement speed. That allows you
to benefit from the tracking generator's -50 to 0 dBm amplitude output and a dynamic
range up to 110 dB. Plus, for amplifier test, the CXA tracking generator provides a power
sweep mode to verify performance, such as gain compression, linearity, and cut off power
level. In the following CXA tracking generator demonstration, we will use a band-pass filter
as the device under test to show how to set up connections between the CXA and the DUT,
apply normalization to improve measurement accuracy and perform stimulus response tests
to characterize your DUT.
To perform the CXA tracking generator demonstrations, your CXA will need option T03, the 3 GHz tracking
generator, or option T06, the 6 GHz tracking generator. Alternatively, you can use the
CXA express configuration N9000AEP-003 or N9000AEP-004.
To begin this demonstration, connect the DUT between the RF input and RF output of the
analyzer. Next, preset the instrument using the "mode preset" key. Enter the tracking
generator mode by pressing the "source" hard key. Use the up and down keys to move
the selection highlight to the internal tracking generator and select the source from the table.
In a transmission measurement, the frequency response error of the test system must first
be measured and then eliminated through a procedure called normalization. To begin,
measurement the frequency response of the test system by configuring the system as desired
for the DUT tests. Set the "center frequency" to 897.5 MHz and "sweep span" to 300 MHz.
Next, replace the DUT with a through connection.
Turn on the RF output. The default amplitude output is -10 dBm. The yellow line on the
screen is the frequency response of the test system. Implement normalization under the
trace detector menu. Store the frequency response curve of the test system to trace #3 to use
as the reference. Toggle the normalize key to on. You will see the results of the normalization
with the reference, i.e. the test system response, displayed in purple.
Now, remove the through connection and reconnect the DUT. You will see the DUT response displayed on the
CXA screen in yellow and in dB relative to the reference line displayed in purple.
The next step measures the shape factor of the filter. Setting trace average will provide
a smoother trace view. To determine the 3 dB bandwidth of the filter, select marker
one and rotate the knob to the center of the pass-band. There is an N dB point shortcut
soft key for bandwidth measurements under the "mes set up" hard key. Here you may
enter -3 dB directly, rotate the knob or press the up or down button to move the horizontal
arrows to show -3 dB. Read the bandwidth at -3 dB roll off. Enter -60 dB to move the horizontal
arrows to show -60 dB. Read the bandwidth at -60 dB roll off. The filter's shape factor
can be calculated by the ratio of the 60 dB to 3 dB bandwidths.
Now let us measure the rejection range of this band-pass filter. Move marker #1 to the
center of the pass-band and set the delta marker 120 MHz above the center of the pass-band.
Narrow down the resolution bandwidth until the delta value remains constant. The marker
readout now displays the rejection range of the filer. In this case, the filter rejection
range is around 95 dB.
It should be noted that only an instrument that has a dynamic range higher than 100 dB,
such as the CXA, will allow you to accurately measure such a high rejection filter. Additionally,
if you look at the lower right corner of the screen, you will see the quickness of the
CXA tracking generator's sweep speed. Using the CXA to make this measurement took just
50 milliseconds. Using a competitive spectrum analyzer or Agilent's legacy product can
take up to 30 seconds. That means the CXA can provide results 600 times faster than
alternative options.
In this part of our demonstration, we will illustrate how to determine the filter's
pass-band ripple. To begin, narrow down the span to 50 MHz and set the amplitude scale
to 1 dB per division. Use peak search to obtain the peak value readout and press marker delta.
Rotate the knob to move the delta marker to the trough of the pass-band. The delta marker
readout now displays the pass-band ripple of the filter.
While this concludes our video demonstrations, we invite you to take a closer look at how
valuable the N9000A CXA signal analyzer and tracking generator can be in meeting your
measurement requirements by visiting our website at agilent.com/find/CXA.