LABORATORY MANUAL DEPARTMENT OF ELECTRICAL & COMPUTER ENGINEERING

Transcription

1 LABORATORY MANUAL DEPARTMENT OF ELECTRICAL & COMPUTER ENGINEERING UNIVERSITY OF CENTRAL FLORIDA EEL 5555 RF & MICROWAVE COMMUNICATIONS Revised March 2004

2 TABLE OF CONTENTS SAFETY RULES AND OPERATING PROCEDURES LABORATORY SAFETY INFORMATION EXPERIMENT # 1 EXPERIMENT # 2 Automatic Network Analyzer Basics S-Parameters and Time Domain Reflectometry Components, Resonance circuits and Transmission Lines EXPERIMENT # 3 Lump Element Circuit Matching EXPERIMENT # 4 Microstrip Fabrication and Matching EXPERIMENT # 5 Extraction of S-Parameters of a BJT EXPERIMENT # 6 EXPERIMENT # 7 Design, Fabrication, Measurement, and Analysis of 1 GHz Amplifier Design, Fabrication, Measurement, and Analysis of 1090 MHz Oscillator APPENDIX RESISTOR COLOR CODE TUTORIAL 2

3 Safety Rules and Operating Procedures 1. Note the location of the Emergency Disconnect (red button near the door) to shut off power in an emergency. Note the location of the nearest telephone (map on bulletin board). 2. Students are allowed in the laboratory only when the instructor is present. 3. Open drinks and food are not allowed near the lab benches. 4. Report any broken equipment or defective parts to the lab instructor. Do not open, remove the cover, or attempt to repair any equipment. 5. When the lab exercise is over, all instruments, except computers, must be turned off. Return substitution boxes to the designated location. Your lab grade will be affected if your laboratory station is not tidy when you leave. 6. University property must not be taken from the laboratory. 7. Do not move instruments from one lab station to another lab station. 8. Do not tamper with or remove security straps, locks, or other security devices. Do not disable or attempt to defeat the security camera. 9. ANYONE VIOLATING ANY RULES OR REGULATIONS MAY BE DENIED ACCESS TO THESE FACILITIES. I have read and understand these rules and procedures. I agree to abide by these rules and procedures at all times while using these facilities. I understand that failure to follow these rules and procedures will result in my immediate dismissal from the laboratory and additional disciplinary action may be taken. Signature Date Lab # 3

4 Laboratory Safety Information Introduction The danger of injury or death from electrical shock, fire, or explosion is present while conducting experiments in this laboratory. To work safely, it is important that you understand the prudent practices necessary to minimize the risks and what to do if there is an accident. Electrical Shock Avoid contact with conductors in energized electrical circuits. Electrocution has been reported at dc voltages as low as 42 volts. 100ma of current passing through the chest is usually fatal. Muscle contractions can prevent the person from moving away while being electrocuted. Do not touch someone who is being shocked while still in contact with the electrical conductor or you may also be electrocuted. Instead, press the Emergency Disconnect (red button located near the door to the laboratory). This shuts off all power, except the lights. Make sure your hands are dry. The resistance of dry, unbroken skin is relatively high and thus reduces the risk of shock. Skin that is broken, wet, or damp with sweat has a low resistance. When working with an energized circuit, work with only your right hand, keeping your left hand away from all conductive material. This reduces the likelihood of an accident that results in current passing through your heart. Be cautious of rings, watches, and necklaces. Skin beneath a ring or watch is damp, lowering the skin resistance. Shoes covering the feet are much safer than sandals. If the victim isn t breathing, find someone certified in CPR. Be quick! Some of the staff in the Department Office are certified in CPR. If the victim is unconscious or needs an ambulance, contact the Department Office for help or call 911. If able, the victim should go to the Student Health Services for examination and treatment. Fire Transistors and other components can become extremely hot and cause severe burns if touched. If resistors or other components on your proto-board catch fire, turn off the power supply and notify the instructor. If electronic instruments catch fire, press the Emergency Disconnect (red button). These small electrical fires extinguish quickly after the power is shut off. Avoid using fire extinguishers on electronic instruments. Explosions When using electrolytic capacitors, be careful to observe proper polarity and do not exceed the voltage rating. Electrolytic capacitors can explode and cause injury. A first aid kit is located on the wall near the door. Proceed to Student Health Services, if needed. 4

5 Experiment #1 Automatic Network Analyzer Basics S-Parameters and Time Domain Reflectometry Objective : The purpose of the first laboratory is to become familiar with a Network Analyzer and the measurement of various parameters of 2 different SAW filters. You will be using Agilent 8753ES Network analyzer and will be performing frequency domain measurements. Equipment: 1) Agilent 8753ES Network Analyzer 2) Standards Open, Short, 50 ohms load 3) 2 SAW filters Introduction: Figure 1: Network Analyzer 8753 ES A network analyzer is a device capable of accurately measuring both the magnitude and phase of a sinusoidal voltage signal. Networks analyzers may be used to 5

6 characterize a wide range of microwave networks. They can display a huge range of plots like linear, log, polar and Smith Chart. The accuracy of the network analyzer is due to the complex RF circuitry and the microprocessor circuitry inside. Both frequency domain and time domain measurements can be performed using this instrument. One of the most important uses of a network analyzer is the measurement of S parameters, which is the means of explaining how a device would respond to a microwave stimulus. You will learn more about these parameters in the forthcoming labs. The network analyzer has two ports, one to produce a sinusoidal signal with a frequency that can be swept between 10 KHz to 3 GHz and the other to measure the complex voltage. There are always errors that are generated at the time of measurement of various parameters. These errors might be due to the cables or receiving system. Hence, network analyzers should always be calibrated each time a new measurement is taken. Connecting standard loads to the cables, whose responses are already known, performs the required calibration. The standard loads used are open, short, and 50 ohm terminations. The system response is measured at every frequency, the results of which are used to find the system error coefficients at each frequency. These error coefficients are used to correct the raw data measured. Procedure: 1) Standards, and Filters: Keep your standards (which are the open, short and 50 ohm load) and the given 2 SAW filters near you so that you don t have to locate them after you start your experiment. 2) Start Up: Turn the Network Analyzer ON using the button LINE which is on the left side of the Analyzer, and if it s already ON, then press PRESET. 3) Calibration: a) The first step after you switch on the analyzer is to calibrate it. This will automatically subtract most parasitic effects of the measuring system in the frequency range of interest. b) Input the frequency range ( the default frequency range is 30 KHz 3 GHz which is generally more than what we need ). c) Push Start button for inputting the start frequency. You can find the Start button under the Stimulus function block. d) You can change the start frequency by using the numeric keypad in the Entry function block. For example, to set the start frequency to 10 MHz, press: Start 10 M / µs e) Similarly, push the Stop button for inputting the stop frequency. f) You can change the stop frequency in a similar fashion as you did for the start frequency. For example, to set the stop frequency to 200 MHz, press: 6

7 Stop 100 M / µs g) The next step is to change the number of measurement data points. You will want to have the maximum number of data points to get a smoother graph. The maximum value for this analyzer is h) Use the Sweep Setup button under the Stimulus function block to set this parameter. After pressing the Sweep Setup button, you can see a number of options in the Analyzer Display. Select the Number of Points option and input the value. Sweep Setup Number of Points i) Now we start the actual calibration of the analyzer. Press Cal Calibrate Menu Full 2 Port Reflection j) First, Connect the Open Standard to the SMA cable coming out from PORT 1 (reflection port) and press Open under the Forward option. The analyzer would now prompt for the short. k) Remove the Open and connect the Short Standard and repeat the above procedure. l) Do the same for the 50 ohms load. After this, PORT 1 is calibrated. m) Perform the steps j l for PORT 2 ( transmission port ). With this step, PORT 2 is also calibrated for reflection measurements. n) Now press the Standards Done option to come out of reflection calibration. o) You will be directed to the Calibrate Menu screen. Press Transmission option. p) Connect the Thru Standard to both cables coming from both the ports and press the Do Both Fwd + Rev. q) You will be directed to the Calibrate Menu screen once again as the Transmission calibration is done. Press Isolation Omit Isolation r) You will be directed back to the Calibrate Menu screen. Press Done 2-port Cal and you are done with 2 port Calibration. You are now all set to record the data from the 2 filters given to you. 4) Characteristics of the Filter: INSERTION LOSS: a) Connect the first filter to the cables coming from both the transmission and the reflection ports; the direction of the filter is not important. 7

8 b) Press the Meas button under the Response function block. This will bring up various options in the Analyzer display which we have to measure. That includes S11, S12, S21, S22. c) Select the option Trans: Fwd S21 ( B/R ) to find the insertion loss of the given filter. d) Once S21 is selected, press the Format button under the response function block and choose Log Mag option from the display. e) At this moment you will not be able to view anything on the Analyzer display because it s not set to scale properly. f) So the next step would be to scale it. For this you have to press Scale Ref from the response function block and choose Autoscale option from the analyzer display menu. It s preferred to scale the graph to 10dB/div. g) The graph, which you would see on the display, would be the logarithmic magnitude of Insertion loss of the given filter. h) To view the phase of the insertion loss, press Format and select the Phase option from the display menu. NOTE: You can view both the magnitude and the phase blocks at the same time by following the steps given below Chan 2 Display Dual Quad Setup Dual Chan ON Format Phase Use of Markers: Markers are used to display the numerical values of the data. The network analyzer has different marker functions such as finding the minimum point and maximum point of a trace. Also the bandwidth of a response can be automatically calculated using one of the marker functions. You will learn more about markers while you perform the experiment. Press Marker Marker 1 This will get marker 1 onto the display screen and you can position the marker with the help of the circular knob in the entry function block. You can have up to 5 markers on the screen. GROUP DELAY: a) Group delay is the measurement of signal transmission time through a test device. It is defined as the derivative of the phase characteristic with respect to frequency. Since the derivative is basically the instantaneous slope, a perfectly 8

9 linear phase shift results in a constant slope and therefore a constant group delay. b) To get the group delay using the network analyzer, Press Format Delay Scale Ref Autoscale NOTE: The resulting graph would be the delay of the filter. Use the marker option to find out its value. All circuits have noise interference. The network analyzer provides a way in which the noise can be reduced. Smoothing is the technique, which is used to set the aperture for group delay measurements. To activate this, Press Marker Avg Smoothing aperture Increase the smoothing aperture value to 2 % or 3 % and then Press Smoothing ON INPUT RETURN LOSS: a) Press Meas Refl: Fwd S11(A/R) This will bring up the log magnitude of input return loss. To find the phase follow the same steps as mentioned above. 3 db BANDWIDTH: a) Also known as the half power bandwidth, this can be measured using the marker utilities in the analyzer. b) Set the frequency range in the analyzer to show just the passband of the filter alone. This can be done by changing the Start and Stop frequency values. Also set the scale to 1 db / div. c) Then, Press Marker Search Search : Max This would place the first marker in the maximum point of the passband. d) Now noting this value calculate the 3dB points on both sides of the center frequency. 9

10 e) Place Markers 2 and 3 at those points on the display. The difference between the frequency values at these points gives you the 3 db bandwidth of the filter. NULL BANDWIDTH: a) This can also be found out in a similar fashion as you found the 3 db bandwidth. b) Position the markers at the points where the passband meets the reference and note the difference between the frequencies at these points. That is the null bandwidth of the filter. RIPPLE: a) Every filter response has ripple associated with it. To observe the associated ripple of the given filter, it s better to view the response in the linear magnitude format. b) Press Format Lin Mag c) Then, press Scale Ref Autoscale c) This will bring up the linear magnitude graph of the insertion loss of the filter. Now to get a clear picture of the ripple, Press Scale Ref Reference Value Increase or decrease this value depending on the default position of the reference so that the reference now comes to the lower ripple limit. d) Press Reference position in the display menu and position the reference in the center of the display. Note - changing the reference value changes just the reference and the graph doesn t move, whereas changing the reference position moves the entire graph up or down. e) Press Scale / Div and increase it so that the ripple is much more clear and bigger and can be analyzed. SWR: a) Standing wave ratio is defined as the ratio of maximum standing wave voltage to the minimum standing wave voltage. b) Press Format SWR 10

11 Then press Autoscale to find the SWR. TIME DOMAIN MEASUREMENTS: a) To transform the data from the frequency domain to the time domain and set the sweep from 0s to 6 µs, Press System Transform Menu Bandpass Transform ON Start 0 G/n Stop 6 M/µ b) To better view the measurement trace, press Scale Ref Reference value The measure the peak response from the main path, press Marker Search Search : Max c) To access the gate function menu, press: System Transform menu Specify Gate Center To set the gate parameters, by entering the marker value, press: 1.6 M/µ d) To set the gate span, press Span 1.2 M/µ Then to activate the gating function to remove any unwanted responses, press: Gate ON SAVING MEASUREMENT RESULTS: a) Press Save / Recall Define Disk-Save Graphics ON Press Save File Formats Save File This will save the measurement results in the floppy disk, which should be put inside the disk drive before starting to save your results. 11

12 Laboratory Report: 1) Present all the results neatly in the report. 2) What was the measured center frequency, insertion loss, input return loss and group delay of the first filter? 3) What was the measured center frequency, insertion loss, input return loss and group delay of the first filter? 12

13 Experiment # 2 Components, Resonance circuits and Transmission Lines Objective: The purpose of the second laboratory is to measure reflection properties and impedances of components and T- lines over frequency. Pre - Laboratory: 1. Read the chapter on matching networks. 2. MathCAD will be used for analyzing all the data obtained. 3. Be sure to bring a floppy disk with you to lab for saving your data. Equipment: 1) Agilent 8753ES Network Analyzer 2) Standards Open, Short, 50 ohms load 3) SMA connectors 4) Resistors, Capacitors, Inductors and Variable Capacitors 5) Co-axial Cables Introduction: A wire, no matter how short and straight, has values of inductance and resistance. Current flow through a wire induces a magnetic field around it. The magnetic field induces a voltage in the wire that opposes a change in the current flow through the wire. This effect is known as self-inductance. The value of inductance depends on wire size, but 20 nh per inch is typical for passive component leads. Thus, component leads in high frequency circuits should be kept as short as possible. Surface mount components have the obvious advantage of eliminating leads, but may be difficult to solder for experimental circuits. A resistor is a far more complicated component than the ideal value of resistance indicated on the label. A resistor also has elements of capacitance and inductance. The reactance of the resistor may be either inductive or capacitive depending on the frequency. A resistor of smaller physical size (lower power rating) will usually have a lower reactance value. Inductors, in addition to inductance, have values of resistance and capacitance. Inductors have a self-resonate frequency. The impedance is inductive below the resonate frequency, resistive at resonance, and capacitive above resonance. Capacitors, in addition to capacitance, have values of resistance and inductance. The impedance is capacitive below the self-resonate frequency. The impedance drops to its lowest value and is resistive at the self-resonate frequency, also called the series resonate frequency (SRF). As the frequency is increased above the SRF, the impedance is 13

14 inductive until another resonance frequency is reached, called the parallel resonance frequency (PRF). There may be more than one PRF. The capacitor s physical size, composition materials, internal construction, and leads affect its high frequency performance. A capacitor of smaller physical size (lower voltage rating) will usually have a lower inductance value. Procedure: 1) First, a Ground Strap should be worn around the wrist in order to prevent high voltage from affecting the network analyzer due to electrostatic charges. 2) Start Up: Turn the Network Analyzer ON using the button LINE which is on the left side of the Analyzer, and if it s already ON, then press PRESET. 2) Calibration: a) The first step after you switch on the analyzer is to calibrate it. This will automatically subtract most parasitic effects of the measuring system in the frequency range of interest. Calibration is accomplished using the short, open and 50 ohm calibration standards with SMA connectors. b) Input the frequency range 10MHz to 1.5 GHz with 1601 points. For this follow the same steps as you did in your first experiment. c) As the Device under test ( DUT ) is one port, its enough to perform one port calibration. For that, Press Cal Calibrate Menu S11 1-Port After you go through the steps indicated above the Analyzer Display would have three options under Forward, namely open, short and load. d) Before we start the calibration, its important to note that the various components are connected to SMA connectors, which offers considerable impedance at high frequencies. e) Hence, the network analyzer should be calibrated with the SMA connector to eliminate its effect on the measurements. f) Connect a SMA connector to the SMA cable coming out from PORT 1 and press Open under the Forward option. The analyzer would now prompt for the short. g) Remove the Open and connect the Short Standard and repeat the above procedure. h) Do the same for the 50 ohms load. After this, PORT 1 is calibrated. Press Done 1-port Cal option, and you are done with 1 port Calibration. 3) Resistor Measurements: a) Solder a resistor, given by the lab instructor, to the SMA connector and connect it to the cable coming from PORT 1. b) Press the Format button under the Response function block and choose Smith Chart option from the display. c) Before connecting the DUT, you can cross check your calibration by using the standard load, short and open standards. An open circuit load should be at the right end, a short circuit load should be at the left end and a matched load should be at the center of the real axis in the Smith Chart. 14

15 d) After connecting the DUT, you can see the impedance response of the resistor in the smith chart. Save your results in both JPG format and CSV format. e) Calculate the DC resistance value of the resistor. This is the value which you 10 MHz ( since its 0 when compared to microwave frequency ). f) Calculate the value of resistor at 5 other different frequencies up to 1 GHz. Tabulate your results. g) Save the log plot of S11 and the phase plot of S11. Also save the Real and imaginary plots of S11. 4) LC circuit Measurements: Two-element Circuit a) Solder a capacitor and an inductor to the SMA connector in such a way that they both form parallel resonant circuit. b) Connect the SMA connector to PORT 1. c) Note the frequencies where the curve crosses the real axis in the smith chart. d) Record the size of the inductor, the approximate wire size and the number of turns. e) Save the Smith Chart, Log plot of S11 and the phase plot of S11. Three-element Circuit a) Solder a capacitor in series with an inductor, the whole combination of which is in parallel with tunable capacitor, to the SMA connector and connect it to PORT 1. b) Now vary the capacitor from its maximum value to its minimum value and notice the changes in impedance. c) Measure and store 2 traces of the three element parallel resonant circuit from 10 MHz to 500 MHz at its minimum capacitance value and maximum capacitance value (you ll need to determine which is which later). d) Note the frequencies where it crosses the real axis. e) Record the size of the inductor, the approximate wire size and the number of turns. 5) T - Line Measurements: Line A: a) Connect thru standard to the cable coming from the network analyzer. This will be the OPEN for the T- line measurements. b) Now perform one port calibration. For that, Press Cal Calibrate Menu S11 1-Port c) After you go through the steps indicated above the Analyzer Display will have three options under Forward, namely open, short and load. d) Press Open under the Forward option. The analyzer will now prompt for the short. 15

16 e) Connect male Short Standard to the thru standard and repeat the above procedure. f) Do the same for the male 50 ohm load. After this, PORT 1 is calibrated. g) Press Done 1-port Cal option, and you are done with 1 port Calibration. h) Measure the physical length of the T- line A. Measure the open circuit (OC) input impedance from 10 MHz to 500 MHz. Determine the frequencies of minimum and maximum impedance from the measurements. Line B: a) Take out T- line A and connect T- line B. b) Measure the physical length of the delay line B. Measure the open circuit (OC) and short circuit (SC) input impedance from 10 MHz to 500 MHz. Determine the frequencies of minimum and maximum impedance from the measurements. c) Then connect the resistor done in part A of your procedure onto the end of the T- line and measure and record the reflection coefficient, i.e., S11 from 10 MHz to 500 MHz. Laboratory Report: 1) Present all the results neatly in the report. 2) Using MathCAD, graph S11 versus frequency for the resistor you measured (magnitude and phase). Record the DC value. Is it what you expected? At 1 GHz, what is the input impedance? Graph the real and imaginary part of the input impedance versus frequency. Graph the ratio of the imaginary part over the real part. 3) Using MathCAD, write the equivalent circuit for the 2-element circuit. Using your measurements, extract the best values for the elements. Given the physical appearance of the inductor and the number of turns, is your extracted inductance value reasonable. 4) Using MathCAD, write the equivalent circuit for the 3-element circuit. Using your measurements, find the series and parallel resonance points for both data sets. How do the resonance points change as you varied the variable capacitance? Using your measurements, extract the best values for the elements for the two plots you obtained data. Given the physical appearance of the inductor and the number of turns, is your extracted inductance value reasonable. 5) For T- line A, at what frequencies would you calculate to obtain the minimum and maximum impedances. How do they compare to your physical measurement? 6) For T- line B, at what frequencies would you calculate to obtain the minimum and maximum impedances. How do they compare to your physical measurement? 7) For T- line B with the resistor connected to the end, graph S11 versus frequency. Graph the real and imaginary part versus frequency. Record the values of input impedance at its minimum and maximum value. Are they what you expected and why? Show your work. 16

17 Experiment#3 Lumped Element Circuit Matching Objective: The purpose of the third laboratory is to design two Tee networks to transform the load impedance, consisting of a 100-ohm resistor in series with an inductor, to the input impedance Zin = 50 ohms with given Q s 1 and 5 respectively at 500 MHz. Equipment: 1) Agilent 8753ES Network Analyzer 2) Standards Open, Short, 50 ohms load 3) SMA connectors and Barrell Connectors 4) Resistors, Capacitors and Inductors 5) Printed Circuit Boards 6) Soldering Iron Kit 7) ZY Smith Charts Pre-lab: 1) Read Chapter 2. Matching Networks and Signal Flow Graphs from your textbook. 2) Determine the inductance value of an inductor having 4 turns of 22-gauge wire on a screw. (Check out the website) 3) Using a Smith Chart, design a Tee matching network with a Q less than or equal to 1. Determine the components and be sure they are reasonable values. 4) Using a Smith Chart, design a Tee matching network with a Q less than or equal to 5. Determine the components and be sure they are reasonable values. 5) Bring your pre-lab results to the laboratory. 6) Also make sure you bring a floppy disk with you for saving your results. Procedure: 1) First, a Ground Strap should be worn around the wrist in order to prevent high voltage from affecting the network analyzer due to electrostatic charges. 2) Power Up: Turn the Network Analyzer ON using the button LINE which is on the left side of the Analyzer, and if it s already ON, then press PRESET. 3) Calibration: a) The first step after you switch on the analyzer is to calibrate it. This will automatically subtract most parasitic effects of the measuring system in the frequency range of interest. b) Input the frequency range 10MHz to 1 GHz with 1601 points. For this follow the same steps as you did in your first experiment. 17

18 c) As the Device under test ( DUT ) is one port, it s enough to perform one port calibration. For that, Press Cal Calibrate Menu S11 1-Port After you go through the steps indicated above the Analyzer Display will have three options under Forward, namely open, short and load. d) Before we start the calibration, it s important to note that the various components are connected to SMA connectors, which offers considerable impedance at high frequencies. e) Hence, the network analyzer should be calibrated with the SMA connector to eliminate its effect on the measurements. f) Connect a SMA connector to the SMA cable coming out from PORT 1 ( reflection port ) and press Open under the Forward option. The analyzer would now prompt for the short. g) Remove the Open and connect the Short Standard and repeat the above procedure. h) Do the same for the 50 ohm load. After this, PORT 1 is calibrated. Press Done 1-port Cal option, and you are done with 1-port Calibration. 4) Load Impedance Measurements: a) Wind a varnished 22 gauge wire on a screw with 4 turns to have an inductance value of 47.6 nh ( check the table of inductance values ). b) The reactance of this inductor at 500 MHz is found to be ohms. Solder this inductor in series with a resistor of 100 ohms, and solder the entire assembly to the ground plane of the SMA connector. c) Connect this SMA connector having the load to the cable coming out from PORT 1, which is already calibrated. d) Press the Format button under the Response function block and choose Smith Chart option from the display. e) You can see the impedance response of the resistor in the Smith chart. Save your results in both JPG format. f) Calculate the DC resistance value of the resistor. This is the value which you get 10 MHz ( since its 0 when compared to microwave frequency ). g) Calculate the Inductor value at 500 MHz h) And finally record the value of load impedance at 4 different frequencies up to 1 GHz. Tabulate your results. 5) Tee matching network with Q ~ 1 at 500 MHz: a) Recalibrate the network analyzer from 100 MHz to 1 GHz. b) Build a Tee network to match the load to 50 ohms at 500 MHz, designed using the ZY Smith Chart in your pre-lab, on a small Printed Circuit Board. c) Before that make sure that the PCB is cleaned well to remove all oxides, which affect the soldering. And then solder the components appropriately on the PCB. 18

19 d) Now use a Barrel connector to attach the load to the PCB output. The input is given from the reflection output of the network analyzer and view the characteristics in the Smith Chart display. e) Check whether the circuit matches perfectly at 500 MHz and measure S11 values and record over frequency from 100 MHz to 1 GHz. f) Record the input Z at 500 MHz. g) Record the measure S11 and phase ( S11 ) and comment. What is your network Q? 6) Tee matching network with Q ~ 5 at 500 MHz: a) Recalibrate the network analyzer from 100 MHz to 1 GHz. b) Build a Tee network to match the load to 50 ohms at 500 MHz, designed using the ZY Smith Chart in your pre-lab, on a small Printed Circuit Board. c) Before that make sure that the PCB is cleaned well to remove all oxides, which affect the soldering. And then solder the components appropriately in the PCB. d) Now use a Barrel connector to attach the load to the PCB output. The input is given from the reflection output of the network analyzer and view the characteristics in the Smith Chart display. e) Check whether the circuit matches perfectly at 500 MHz and measure S11 values and record over frequency from 100 MHz to 1 GHz. f) Record the input Z at 500 MHz. g) Record the measure S11 and phase ( S11 ) and comment. What is your network Q? Laboratory Report: 1) Present all the results neatly in the report 2) As part of the report: i. Calculate the input impedance to the impedance to the line with the given load. ii. Compare measurement results to predictions via the Smith charts. Comment as appropriate. iii. Record all component values and data. iv. Attach your Smith Chart matching prediction. 3) Report any problems, suggestion, etc. 19

20 Experiment # 4 Microstrip Fabrication and Matching Objective: The purpose of the fourth laboratory is to design and fabricate stripline matching circuits at 1 GHz. Equipment: 1) Agilent 8753ES Network Analyzer 2) Standards Open, Short, 50 ohms load 3) SMA connectors 4) Resistors 55 ohms and 50 ohms 5) Printed Circuit Boards 6) Copper Etch 7) Soldering Iron Kit 8) Z Smith Chart Pre Lab: 1) Read section 2.5 Microstrip Matching Networks from your textbook. 2) Determine the widths of the stripline necessary to make a 50 ohm transmission line. Assume double sided copper boards having a thickness of inches ( 64 mils ) and relative permittivity of ) Design a 50-ohm stripline transmission line that is ¼ wavelength long at 1 GHz. 4) You will be given a load resistor, Z L, which has an input impedance of 55 ohms at DC which is approximately j ohms at 1GHz. Transmission Line Impedance Transformer Z in Z o1 L o1 Z L 5) Design a transmission line impedance transformer with Z 01 and length L 01 to transform the load resistor, Z L to Z in = 30 j10 ohms at 1GHz. 20

21 6) Design a single stub matching network using transmission lines having Z0 = 50 ohms to match Z L = 30 j 10 ohms to 50 ohms at 1 GHz. Determine the electrical lengths and use the shortest lines possible. Your design should use balanced stubs. Single Stub Transmission Line Matching Network 50Ω Ζ ο1 = 50Ω L 1 Ζ ο2 = 50Ω Z L L 2 Procedure: 1) Design Matching Circuits using Corel Draw: a) Produce a mask of stripline in Corel Draw for ¼ length and width calculated in pre-lab steps 2 and 3 for 50 ohm transmission line. b) Produce a mask of stripline in Corel Draw using the calculated length and width for transmission line with Z 01 and length L 01 designed in Pre lab step 5 c) Produce a mask of the single stub matching network in Corel Draw using the design done in Pre lab step 6. Note that you will b using the design of step 5 as the load for this part. d) You can use the pattern of step (f) with proper layout and extremely short connections, or you can redesign with the load, 30 j10 ohm, connected directly at the end of the T line. 2) Fabrication of PC boards: a) Print the layout designed using Math CAD and Corel Draw on a specially made transfer paper known as the Toner Transfer System. It s a 5 mil, looserag, light basis weight paper that has a special coating of Dextrin applied by a very large and expensive knifecoater, which applies a very thin and uniform coat. 21

22 b) You will be provided with double sided - copper boards of size inches (64mils) and relative permittivity of 4.7. c) The copper board is packaged with a inches copper protective carrier over the base lamination. d) Remove the carrier copper sheet on one side of the board by lifting up a corner and ripping it off. e) Cut the transfer paper to appropriate size such that it has all the layouts in it and place this paper on the side of the copper board where there is no protective layer and tape it. f) Now send the board through the Toner image applicator, which transfers the image from the paper to the copper board. g) Once the board comes out of the TIA, place it in water till the paper gets peeled off leaving the ink on the board. h) Place a piece of Green TRF paper over the board covering all the layouts and tape it to the board 22

23 i) Send the board through TIA once again. Peel the Green TRF once the board comes out of the TIA. You will find that the Green TRF sticks only over the toner image. j) This forms a double protective layer on the copper below the ink. k) Place the copper board in the beaker containing etching solution prepared by the lab instructor. Leave it until the entire copper except for the layouts, is etched off. l) Wash this board with acetone to remove the black ink thereby leaving copper layouts on the board. m) Finally, remove the carrier copper sheet on the other side of the board by again lifting up one corner and ripper it off. This side acts as the ground. 23

24 n) The PC board is ready for testing now. 3) Power Up: Turn the Network Analyzer ON using the button LINE which is on the left side of the Analyzer, and if it s already ON, then press PRESET. 4) Calibration: a) The first step after you switch on the analyzer is to calibrate it. This will automatically subtract most parasitic effects of the measuring system in the frequency range of interest. b) Input the frequency range 100MHz to 1.2 GHz with 1601 points. For this follow the same steps as you did in your first experiment. c) As the Device under test ( DUT ) is one port, its enough to perform one port calibration. For that, Press Cal Calibrate Menu S11 1-Port After you go through the steps indicated above the Analyzer Display would have three options under Forward, namely open, short and load. d) Before we start the calibration, it s important to note that the various components are connected to SMA connectors, which offers considerable impedance at high frequencies. e) Hence, the network analyzer should be calibrated with the SMA connector to eliminate its effect on the measurements. f) Connect a SMA connector to the SMA cable coming out from PORT 1 and press Open under the Forward option. The analyzer would now prompt for the short. g) Remove the Open and connect the Short Standard and repeat the above procedure. h) Do the same for the 50 ohm load. After this, PORT 1 is calibrated. Press Done 1-port Cal option, and you are done with 1 port Calibration. 5) Measurements using the ANA: a) Measure S11 and Zin over frequency for the ¼ wavelength transmission line with an open circuit, short circuit and 50 ohm load. Store the results. b) Solder the nominal 55 ohms resistor to the transmission line which has the design of Zin = 30 j 10 ohms. Keep the resistor wire lengths extremely short since they can have a huge effect at 1 GHz. c) Measure S11 and Zin over frequency for this line and store your results. d) Measure S11 and Zin over frequency for the single stub matching network with ZL = 30 j10 ohms and store your results. 24

25 Laboratory Report: 1) Present all the pre laboratory design results. 2) How good was the 50-ohm transmission line design based on the open, short and 50 ohm terminating impedances? What was your measured Z 0 and actual line length? 3) How close was the measured Zin of 30 j 10 ohms? Compare and comment on your design versus measurements over frequency. 4) What was the measured input impedance of the single stub-matching network? Comment on reasons for discrepancies. Compare your measured versus simulated results over frequency. 25

26 Experiment # 5 Extraction of S Parameters of a BJT Objective: The objective of this experiment is to build a simple calibration board and test fixture for a BJT and extract the S parameters. Equipment: 1) Agilent 8753ES Network Analyzer 2) Voltage supply 3) Standards Open, Short, 50-ohm load 4) SMA connectors 5) Resistors 55 ohms and 50 ohms 6) Printed Circuit Boards 7) Copper Etch 8) Soldering Iron Kit Introduction: The scattering parameters (S parameters) of a two-port network, namely S 11, S 12, S 21, S 22, represent reflection and transmission coefficients measured at port 1 and 2. Transistors can be completely characterized by S parameters that vary with both frequency and bias level. For all measurements, the transistors must be properly biased at the desired Q point, and small-signal conditions must be maintained. The bias circuit should have a coupling capacitor and a large inductor (RFC). The radio frequency coil (RFC) offers high impedance to the collector voltage and zero impedance to the dc signal thereby preventing the high frequency RF signal from entering the DC power supply. The network analyzer is used to measure the S parameters as it has an inbuilt S-parameter test set. Pre Laboratory: 1) Read sections 1.4, 1.6, 1.9, 1.10, 1.11 in chapter 1 and 3.1, 3.2, 3.3 in chapter 3 from your textbook Microwave Transistor Amplifiers analysis and design by Guillermo Gonzalez. 2) For measuring S parameters of a transistor, both reflection and transmission measurements of traveling waves at both ports have to be performed. And for this, the transistor must be properly biased at the desired Q point, which is essential for proper linear operation of an amplifier. 3) Base bias is used for biasing the transistor. Calculate the values of Base resistor R B and Collector resistor Rc and base current I B for the test conditions Vcc = 3.3V, Ic = 5.5mA, V CE = 3.0V and β DC =

27 Procedure: 1) Design Matching lines using Math CAD and Corel Draw: (Performed by lab instructor) a) Design a 50-ohm stripline transmission line that is 11mm long at 1 GHz. b) Produce 8 masks of stripline in Corel Draw using the above length and calculated width for the 50-ohm transmission line. c) The connectors connected to both transmission and reflection ports are not connected directly to the base and collector pins of transistor, but instead they are connected to the 50-ohm transmission lines on which the base and collector pins are placed. d) Hence, it is required to calibrate the network analyzer with connectors connected to the 50-ohm transmission line. e) Then design a high impedance line, which effectively isolates the dc bias circuit from high frequency signal coming from the network analyzer. f) The high impedance line should be a quarter wavelength long, as a short on one side appears as an open on other side thereby isolating the dc bias circuit. g) Produce 3 masks of the stripline in Corel Draw using the above length and calculated width for high impedance transmission line. h) The final mask pattern in the Corel Draw should look like the figure below: Figure 1 : PCB layout for S parameter measurement i) The four 50 ohm lines in the bottom left to right are for the calibration purposes each corresponding to open, thru, short and load respectively. j) And the high impedance line with 50 ohm line at its end on the bottom right of the figure 1 is for testing purpose. 2) Fabrication of PC boards: (Performed by lab instructor) a) Print the layout designed using Math CAD and Corel Draw on a specially made transfer paper known as the Toner Transfer System. It s a 5 mil, loose-rag, light 27

28 basis weight paper that has a special coating of Dextrin applied by a very large and expensive knife coater which applies a very thin and uniform coat. b) You will be provided with double-sided copper boards of size inches (64mils) and relative permittivity of 4.7. c) The copper board is packaged with a inches copper protective carrier over the base lamination. d) Remove the carrier copper sheet on one side of the board by lifting up a corner and ripping it off. e) Cut the transfer paper to appropriate size such that it has all the layouts in it and place this paper on the side of the copper board where there is no protective layer and tape it. f) Now send the board through the Toner image applicator, which transfers the image from the paper to the copper board. g) Once the board comes out of the TIA, place it in water till the paper gets peeled off leaving the ink on the board. h) Place a piece of Green TRF paper over the board covering all the layouts and tape it to the board i) Send the board through TIA once again. Peel the Green TRF once the board comes out of the TIA. You will find that the Green TRF sticks only over the toner image. j) This forms a double protective layer on the copper below the ink. k) Place the copper board in the beaker containing etching solution prepared by the lab instructor. Leave it until the entire copper except for the layouts, is etched off. l) Wash this board with acetone to remove the black ink thereby leaving copper layouts on the board. m) Finally, remove the carrier copper sheet on the other side of the board by again lifting up one corner and ripping off. This side acts as the ground. n) The PC board is ready for soldering of components now. 3) Soldering various components to the board: (Performed by lab instructor) a) Now that the PC board is ready with the required design on it, you are all set to solder all the components to it. b) First start with the calibration part, which constitutes the four 50 ohm lines in the bottom from left to right. c) Drill 4 small holes at the end of line 3. Use drill press for this purpose. d) Solder small wires onto the end of line 3, pass them through the holes and solder its other end to the groundside. This acts as a Short line. e) Now follow the same step c with line 4. And this time connect 100-ohm resistors between the line and the 2 ground pads. This acts as a Load line. f) Line 1 would act as Open line and line 2 will be the Through line. g) Then drill a small hole at the end of high impedance line 3. This would allow for both open and short tests of the line. h) We won t solder the transistor to lines 5 and 6, connecting base to one and collector to other. Instead we will tape the transistor to the board such that the respective pins land on the respective pads. 28

29 i) And for giving the required pressure so that there is perfect contact between the transistors and lines, we use a high pressure generating equipment called a clothes pin. j) Drill holes near the ground pads for emitter and solder emitter pins to the pads. k) Connect small wires from both emitter pads to ground thereby shorting them. l) Next, drill small holes in the ground pads near the other end of high impedance lines 1 and 2. m) Solder the calculated resistors R B and R C to their corresponding high impedance lines on which the base and collector pins of transistor are soldered respectively. n) Connect RF chokes to the resistors. These act as high impedance to AC thereby avoiding the RF signal to pass through to the DC power supply. o) Solder both RF chokes together and connect two coiled wires to it. This goes to the DC power supply. p) Connect 0.1 µf and 12 pf capacitors to the ends of high impedance lines where resistors are connected. The other end of the capacitors can be soldered to the ground pads. At high frequencies this would act as a short to ground. And at DC it would be open. q) Drill 8 holes in the middle square section of the board and ground it by connecting wires in between the square section and the ground. r) The entire PC board is now ready for calibration and testing. Figure 2 : S parameter test board Capacitor C1 : 12 pf used for RF bypass / RF block Capacitor C2 : 0.1 µf used as low frequency ground at Base Capacitor C3 : 12 pf used as RF bypass / RF block / influences stability Capacitor C4 : 0.1 µf bypass / block, some IP3 improvement 29

30 Figure 3 : another view of S parameter board Figure 4 : Base DC bias circuit 4) Power Up: Turn the Network Analyzer ON using the button LINE which is on the left side of the Analyzer, and if its already ON, then press PRESET. 5) Calibration: a) The first step after you switch on the analyzer is to calibrate it. This will automatically subtract most parasitic effects of the measuring system in the frequency range of interest. b) Input the frequency range 600MHz to 1.2 GHz with 1601 points. Also set the input power source to -20 dbm. For this follow the same steps as you did in your first experiment. Now we start the actual calibration of the analyzer. Press Cal Calibrate Menu Full 2 Port Reflection 30

31 c) Before we start the calibration, it s important to note that the transistor is connected to SMA connectors through a 50-ohm transmission line, which offers considerable impedance at high frequencies. d) Hence, the network analyzer should be calibrated with the SMA connector connected to the 50-ohm line to eliminate its effect on the measurements. e) Connect the SMA cable coming out from PORT 1 to the connector connected to line 3 in Fig. 1 and press Open under the Forward option. The analyzer will now prompt for the short. f) Remove the connector and connect it to line 4 in Fig.1, which is shorted on its other end, and repeat the above procedure. g) Do the same for the 50-ohm load connected to line 5. After this, PORT 1 is calibrated. h) Perform the steps e g for PORT 2. With this step, PORT 2 is also calibrated for reflection measurements. i) Now press Standards Done option to come out of reflection calibration. j) You will be directed to the Calibrate Menu screen. Press Transmission option there. k) Connect both cables coming from both the ports having connectors at their ends to line 6-7 and press the Do Both Fwd + Rev. l) You will be directed to the Calibrate Menu screen once again as the Transmission calibration is done. Press Isolation Omit Isolation m) You will be directed back to the Calibrate Menu screen. Press Done 2-port Cal And you are done with 2 port Calibration. You are now all set to record the data of the transistor. 6) Measurements using the ANA: a) Measure S11 for the high impedance ¼ wavelength transmission line with an open first and with a capacitor at the other end next. Store the results. b) Place the board onto the analyzer with the base side connected to the transmission port. c) Connect the wires to DC power supply and increase voltage to 3.3 V. d) Measure all S parameters of the transistor. Store the results. e) Record the gain of the transistor, i.e., S21. 31

32 Laboratory Report: 1) Present all the pre-laboratory design results. 2) Using MathCAD plot all the S parameters ( in db ) over the full frequency range. 3) Identify the gain of the mismatched transistor at 1 GHz. Also calculate VSWR in and VSWR out 4) Plot the input impedance and the output impedance versus frequency of the transistor. What are their values at 1 GHz? 5) Using MathCAD, plot S11 and S22 in a Smith Chart and compare it with the one you got from the network analyzer. 6) Plot and K over full the frequency range and determine the stability of the transistor at 1 GHz. 7) If the transistor is potentially unstable at 1 GHz, draw the input and output stability circles in the Smith Chart. 32

33 Experiment # 6 Design, Fabrication, Measurement, and Analysis of 1 GHz Amplifier Objective: The objective of this experiment is to design, build and test a common emitter amplifier for the maximum transducer gain at 1 GHz using a Infineon BFP640 Bipolar Junction Transistor. Equipment: 1) Agilent 8753ES Network Analyzer 2) BFP640 BJT 3) Voltage supply 4) Standards Open, Short, 50 ohms load 5) SMA connectors 6) Resistors 68 K Ω, 55 Ω 7) RFC s 8) Capacitors 0.1 µf, 15pF 9) Printed Circuit Boards 10) Fabrication Kit 11) Soldering Iron Kit Pre-Laboratory: 1) Use the S-parameter data obtained from Experiment # 5 to draw the stability circles at 1GHz. 2) Determine the stable portion of the Smith Chart at this frequency. 3) Determine the value of maximum stable gain. 4) Follow the Operating Power-Gain Circles design procedure for Potentially unstable bilateral case to design an amplifier at 1 GHz. (Note ~ You have to select a value of ГL that is away from the output stability circle and on the gain circle. Also perform conjugate match at the input.) 5) Using Г s, Г L, and Г b obtained from the above design procedure, design the input and output single stub matching networks using the Smith Chart at 1GHz. Use 50-ohm characteristic impedance for all transmission lines. Procedure: 1) Draw the amplifier circuit design with the input and output matching lines in Corel Draw. Also draw the necessary calibration lines which are 11mm long having 50 ohms characteristic impedance. The design should look as in figure 1. 33