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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 1 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. 2 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. 3