Download experiment 3

ECE 351
ELECTROMAGNETICS
EXPERIMENT EM2
FREQUENCY DEPENDENCE OF COMPONENTS
OBJECTIVE:
This experiment demonstrates that the characteristics
of passive components depend on frequency.
EQUIPMENT:
Agilent 4395A Network/Spectrum/Impedance Analyzer
Agilent 43961A RF Impedance Test Adapter
Agilent 16092A Spring Clip Test Fixture
Two 100  Film Resistors (1 long, 1 short leads)
One 100  Carbon Resistor
One 100  Wirewound Resistor
One 470 pF Ceramic Capacitor
One 47 pF Ceramic Capacitor
One inductor (of unknown value)
One Ferrite Bead (Fair-Rite No. 2743002122)
I.
THE NETWORK ANALYZER
A.
INTRODUCTION.
As the name implies, the Agilent 4395A Network /Spectrum
/Impedance Analyzer is a very versatile instrument that can
be used to perform a number of measurements. The “impedance
analyzer” part of the device will be used in this experiment
to examine the frequency response of several commonly used
passive components.
B.
EQUIPMENT SETUP.
The 43961A Test Adapter and the 16092A Spring Clip Fixture
should be connected to ports “RF OUT”, “R” and “A” of the
4395A. Make sure connections are solid.
C.
PROCEDURE
1. Turn the analyzer on. Channel 1 should be active, as
indicated by the light next to the “Chan 1” key on the
front panel. The calibration for this experiment has
already been stored for you. Press the Recall button and
select “16092A.STA”. Note: for some reason a red warning
message (about a floating point error) sometimes appears.
If this happens to you, press the green Preset button and
try again. Once the 16092A calibration is recalled, the
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display should be of the |Z| versus frequency, with a
Start and Stop frequencies of 100 kHz and 500 MHz,
respectively.
2.
a) Connect the 470 pF capacitor between the two spring
clips of the 16092A. Press the Scale Ref button, and
select AUTO SCALE to clearly show the entire
response. Make sure you are observing the |Z| on a
logarithmic scale by pressing the Format button and
selecting LOG Y-AXIS.
b) Assuming this is a “pure” 470 pF capacitor, calculate
the magnitude of the impedance at 1 MHz. Record this
value. Measured the value of |Z| at this frequency
by pressing the Marker button, followed by 1 MHz.
Record this value and compare with the calculated
value.
c) Repeat part (b) at 500 MHz.
d) When looking at the |Z| versus frequency, you will
probably see a response different from what a “pure
capacitor” would provide. Suggest what causes the
differences.
e) Determine the “resonant frequency” of the capacitor
by determining the frequency at which the impedance
is a minimum. Record this value.
f) Save this plot by inserting a floppy disk, and then
pressing the Save button. Make sure the STOR DEV
option is set to [DISK], and then select GRAPHICS,
and use the keyboard to give your plot a name. Note
that the plot will be stored as a TIF file, which can
be inserted into a Word document if desired. If you
prefer to create your own plot, you can select DATA
ONLY and SAVE ASCII.
g) Use Chan 2 (i.e., press the Chan 2 button) to examine
the phase of the impedance using the Meas key and
selecting PHASE. (You may want to Autoscale again
with the Scale Ref button). Use the split screen
display option by pressing Display and toggling DUAL
CHAN to ON. Observe and comment on what you see.
Save the the split screen display for your report.
h) Based on your observations, please suggest an
equivalent circuit that could be used to explain the
behavior of the “real” capacitor.
3. Repeat (2) for the 47 pF capacitor. Comment on how the
resonant frequency of the two capacitors compares.
4.
a) Repeat parts (a) and (b) of number (2) for the 100ohm film resistor with short leads.
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b) Using the Marker option, determine the frequency at
which the impedance changes from the nominal value by
more than 10%.
c) Suggest an equivalent circuit that may be used to
model the “real” resistor.
d) Save the plot of |Z|.
5. Repeat (4) for the 100-ohm film resistor with long leads.
6. Repeat (4) for the 100-ohm carbon resistor.
7. Repeat (4) for the 100-ohm wirewound resistor. In
addition, if there appears to be any sort of “resonant
frequency” please identify that frequency. You may want
to take this information into account for you equivalent
circuit.
8. Repeat (4) for the inductor. In addition, determine the
value of this inductor for low-frequency operation.
9. Ferrite beads are commonly used to provide high frequency
loss for electronic circuits. This is important when
trying to minimize electromagnetic interference. Examine
the frequency response of the ferrite bead. Plot both
the magnitude and phase of the impedance.
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