MICROWAVE ENGINEERING (2171001) B.E. 7th … · microwave engineering (2171001) b.e. 7 th semester laboratory manual 2016 department of electronics and communication engineering government

MICROWAVE ENGINEERING

(2171001)

B.E. 7th SEMESTER

LABORATORY MANUAL

2016

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

GOVERNMENT ENGINEERING COLLEGE - MODASA

CERTIFICATE

This is to certify that Mr. /Ms.

_____________________________________________ Roll No.

_______________ And Enrolment no._______________________ of seventh

semester of B.E____________________ Class has satisfactorily completed

his/her one full semester in “2171001 MICROWAVE ENGINEERING”

satisfactorily in partial fulfilment of Bachelor of Electronics and communication

Engineering degree to be awarded by Gujarat Technological University.

Nitin J. Bathani

Date: - …. /… /…….

SI-3033 Transmission Line Analysis Software - 1 -

The SI-3033 Software comes with a Hard Lock (HASP)and requires Windows 95/98 for operation. The softwarewill install automatically as soon as the CD is inserted inthe Drive. Enumerated below are the key steps to befollowed for installation of the software.

1. Attach the Hard Lock to the Parallel Port LPT1 of theComputer. The printer can be connected to the hardlock.

2. Put the CD in the CD-Drive

5. The installation window will come on screen. Clickon “Finish”

7. On succesful installation “Installation Sucessful”window will appear, click on “OK”

8. Window stating “Install shield Self-Extracting Exe”will appear; click on “Yes”

9. Window stating “HASP Device Driver Status” willappear, click on “Next”

10. In the next window select “Typical”

11. In the next window select “Next”

12. In the next window select “OK”

13. In the next window select “Finish”

14. A SI-3033 window appears, double click on“SI-3033.exe” to start the software.

Installation of SI-3033 Transmission Line Analysis Software


Establishing the connectivity toPC through RS232


Connecting the PC to the S-18Rand establishing the connectivity

through RS232

RS232 cable8 pin end

RS232 cable 25 pinend connected to

COM2 (or COM1)

Hard Lockconnected toLPT1

Make the connections as shown above. Most PCsuse the COM1 serial port for connection of themouse, hence COM2 serial port is generally usedfor connection to S-18R. However, Laptops mayhave only COM1 available; as they may have abuilt-in mouse or a seperate port.

Stepwise instructions are as follows:1. Put Computer ON and start SI-3033 Software2. Put S-18R ON3. On the SI-3033 Software menu click:

“Connect” then “Connect Receiver”6. A small popup will indicate

“connected succesfully”7. A message on the left upper corner will say

“Receiver Connected”

Operation of the software is intutive and userfriendly. For other connections of the Transmis-sion Line etc, refer to the instrument manual.


C O N T E N T

Chapter 1 Standing WavesExp 1.1 Transmission Line terminated in a SHORT (Z

L= 0)

Exp 1.2 Transmission Line terminated in CHARACTERISTIC IMPEDANCE (ZL= 50)

Exp 1.3 Transmission Line terminated in OPEN (ZL= Infinity)

Exp 1.4 Transmission Line terminated in SHORTED L/8 (ZL= L/8+Short)

Exp 1.5 Transmission Line terminated in OPEN L/8 (ZL= L/8+OPEN)

Exp 1.6 Transmission Line terminated in RESISTIVE LOAD RL

> ZL

(ZL= 100 ohms)

Exp 1.7 Transmission Line terminated in RESISTIVE LOAD RL< Z

L(Z

L= 25 ohms)

Exp 1.8 Transmission Line terminated in RESISTIVE INDUCTIVE LOAD(Z

L= L/8+25E)

Exp 1.9 Transmission Line terminated in RESISTIVE CAPACITIVE LOAD(Z

L= L/8+100E)

Exp 1.10 Transmission Line terminated in Res+Cap as LOAD(Z

L= 27E+10pF in Series)

Exp 1.11 Transmission Line terminated in Res+Inductor as LOAD(Z

L= 27E+2T Coil in Series)

Exp 1.12 IMPEDANCE Measurement along the Transmission Line

Chapter 2 VSWR - SpectrumExp 2.1 Study of Vi (incident voltage) Variation with FrequencyExp 2.2 Study of Vr (Reflected Voltage) Variation with FrequencyExp 2.3 Study of VSWR with FrequencyExp 2.4 Study of DIRECTIONAL COUPLER directivityExp 2.5 Study of Standing Wave Pattern Behaviour at any Distance on the Transmission

Line at different Frequencies

Chapter 3 RF Recorder - Probe PositionExp 3.1 Study of RF Recorder & Probe Position

Chapter 4 SMITH CHARTExp 4.1 Study of SMITH CHART Auto Generation

Chapter 5 Study of Impedance Matching using a Dual Slug Tuner


CHAPTER 1

Standing WavesSoftware Description

& Experiments

This section deals with various experiments on StandingWaves using the software , based on section 10-7 RE-FLECTION COEFFICIENT, SLOTTED LINE ANDSMITH CHART of the text book mentioned below.

Nine case conditions have been discussed by the authorbased on an ideal lossless slotted line. Students will beable to experiment and verify the results, within experi-mental error, for all these nine cases.

Measurements that can be done using the Standing WavePlot are:

1. FREQUENCY2. VSWR3. COMPLEX IMPEDANCE ie: R + jX4. SMITH CHART - manual representation of R+jX

Further, experiments can be conducted to observe theinstantenous relationship between the Voltage and theCurrent on the SWR plots and obtain the IMPEDANCEPlot along the slotted line.

for associated theory refer toELECTROMAGNETICS

John D. Kraus

page nos are mentioned in italicsand in brackets (nnn) where applicable.


Experiment 1.1Transmission Line terminated in a SHORT (Z

L= 0)

(page 409 Case 3)

Trace 1Red Click

DynamicWindow 1

MeasurementWindow 2

TravelDistance

Frequency

Cur1/Cur2 RatioComputed FreqCur1 & Cur2Difference

mV readingBlue Cursor2of Red Plot

NotesmV readingRed Cursor1of Red Plot

Red Cursor 1 Blue Cursor 2

PROCEDUREa. Terminate the Transmission Line with the standard SHORT

The default Travel Distance is set to 590mm and is generally not required to bechanged for these experiments. This is the distance that the carriage will travelfrom the Home position. The Home position is the Input side for the Transmis-sion Line.

The default Frequency is 800MHz, change it to 721MHz* (* see note at end of this exp)

Ensure that the probe is connected to SMA-V output on the Probe Carriage andthat the cable will have no obstruction during the probe travel.

Click on the “Trace 1” button, the Probe measurement commences, the curve isplotted in the “Dynamic Window 1”. On completion, the Standing Wave isplotted in the “Measurement Window 2” in Red Colour.

MEASUREMENTS1. Frequency

Place the Cursor1 and Cursor2 at the minimum points as shown above.The distance between the 2 cursors is the Half Wavelength (L/2) and can be readoff as 206mm; which works out to a Frequency of 728.16MHz (L=300/(freqMHz). This compares, within experimental error, close to the 721MHz fed

Impedance


from the generator.

2. VSWRMove the Cursor1 to the right and place it at the Max Voltage point (223mm)VSWR is the ratio of the maximum to the minimum voltage on the StandingWave Plot. Read off the Cur1/Cur2 Ratio,hence VSWR = 69.419

3. COMPLEX IMPEDANCE - R+jX (page 410,411)Click on the “Impedance” buttonThe “Window 2” will be replaced, wherein you have to enter numerical values.

default - Freq = 721MHz DO NOT change itdefault - VSWR = 2 CHANGE IT to 69.419default - Xvm = 0 DO NOT change it

Click on the “OK” button and observe the Computed Impedance belowR= 0.7 ohms and the value of X is Zero

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 0.7,A RED DOT is plotted corresponding to the Complex Impedance = 0.7+j0

OBSERVATION & CONCLUSION1. In a ideal Lossless Line, all the 3 peaks of the Standing Waves would have had

identical value and Infinite Amplitude.2. Thus the VSWR would ideally be Infinity as against the measured 69.4193. The value of “R” would have been ZERO against the measured 0.7 ohms.4. The RED POINT on the Smith Chart would have shifted to the Left and on the

the Outer Circle of the Smith Chart as depicted by the Ideal Plot above.HENCE it is concluded that the Experimental Results correlate with theory.

Ideal Plot = 0 + j0


IMPORTANT

* NOTE: The 721MHz frequency was derived from the requirement of a smallLine of Lambda/8 for conducting the experiments covering Cases 6,7,8 & 9.

This Line Length is obtained by connecting Two “Female to Male” [F-M] adapt-ers in series. The Physical Length of the combination of these two will differfrom its Electrical Length. (factors like impedance difference of the adapters,variation in propogation velocity etc contribute to this difference).

Eight times the Electrical Length would give us the Lambda of the Frequency atwhich the Two Adapters would act as Lambda/8 Line.

The Electrical Length can be measured as follows.1. Obtain the Trace 1 of the Transmission Line terminated in a SHORT

at say 800MHz which is the default frequency.2. Connect the Line as follows:

Line + [F-M] + [F-M] + SHORT3. Click on “Trace 2” and obtain the Standing Wave Pattern.4. Place Cursor1 and Cursor2 on the Minima of the Red and Blue Plot.5. Let this distance as indicated by the Difference = Xmm6. The Frequency for conducting the experiments for the 9 cases would be

f = 300 / [(Xx8)/1000] MHz

7. During the manual writeup X equalled 52mm, which works out to 721MHz

Hence, it is essential to experiment as above and calculate the Frequency forwhich the Two Adapters used by you would act as Lambda/8 line. Substitutethis Frequency for the 721MHz mentioned, throughout all the 9 cases’ ex-perimentation.


Experiment 1.2Transmission Line terminated in CHARACTERISTIC IMPEDANCE (Z

L= 50)

(page 409 Case 1)

PROCEDUREa. Terminate the Transmission Line with the standard 50E


The default Frequency is 800MHz, change it to 721MHz.


Click on the “Trace 2” button, the Probe measurement commences, the curve isplotted in the “Dynamic Window 1”. On completion, the Standing Wave isplotted in the “Measurement Window 2” in Blue Colour, in addition to theearlier Trace 1 of the Exp1


Frequency is measured with maximum accuracy as in Exp1 wherein you get thesharpest minima.


2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in thecenter of the plot) on the Blue Trace. VSWR is the ratio of the maximum to theminimum voltage on the Standing Wave Plot. Read off the Cur1/Cur2 Ratio ofthe 2nd reading from the top,hence VSWR = 1.135


Freq = 721MHzVSWR = 1.135Xvm = 0 (since the minimas of Shorted & 50E plots are coincident)

Click on the “OK” button and observe the Computed Impedance belowR= 44.1 ohms and the value of X is Zero

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 44.1A RED DOT is plotted corresponding to the Complex Impedance = 44.1+j0

OBSERVATION & CONCLUSION1. In an ideal Lossless Line of 50E terminated in an exact 50E, the plot would

have been a straight line with no undulations.2. Thus the VSWR would ideally be One as against the measured 1.1353. The value of “R” would have been 50 ohms against the measured 44.1 ohms.4. The RED POINT on the Smith Chart would have been on the exact center of

the plot as depicted by the Blue Hexagon aboveHENCE it is concluded that the Experimental Results correlate with theory.

Ideal Plot = 50 + j0


Experiment 1.3Transmission Line terminated in OPEN (Z

L= Infinity)

(page 409 Case 2)

PROCEDUREa. Terminate the Transmission Line with the OPEN






Frequency is measured with maximum accuracy as in Exp1 wherein you get thesharpest minima. The same measurement can be verified with the OPENStanding Wave, because the minima obtained are also sharp in this case.

2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in thecenter of the plot) on the Blue Trace. VSWR is the ratio of the maximum to the


minimum voltage on the Standing Wave Plot. Read off the Cur1/Cur2 Ratio ofthe 2nd reading from the top,hence VSWR = 79.721


Freq = 721MHzVSWR = 79.721Xvm = 110

Click on the “OK” button and observe the Computed Impedance belowR+jX= 75.7 +j541.9 ohms

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 75.7 and X=541.9A RED DOT is plotted for the Complex Impedance = 75.7+j541.9

OBSERVATION & CONCLUSION1. In an ideal Lossless Line of 50E terminated in an exact OPEN, all the 3 peaks

of the Standing Waves would have had identical value and Infinite Amplitude.Further, the Minima of the Trace1 and the Maxima of the Trace2 would havebeen coincident. What is observed is the air impedance.

2. The VSWR would ideally be Infinity as against the measured 79.7213. The value of “R” would have been Infinity against the measured

75.7+j541.9 ohms.4. The RED POINT on the Smith Chart would have been ideally on the centerline

of the outermost circle as depicted by the Blue Hexagon aboveHENCE it is concluded that the Experimental Results correlate with theory.

Ideal Plot = Infinity + j0


Experiment 1.4Transmission Line terminated in SHORTED L/8 (Z

L= L/8+Short)

(page 409 Case 4)

PROCEDUREa. Terminate the Transmission Line with the 2 N Adapters + SHORT

ie: N(F to M) adapter + N(F to M) adapter + SHORT.NOTE: The two N Adapters are equivalent to an electrical Line Length ofLambda/8 at 721MHz. Method of measuring the electrical length is de-

scribed elsewhere in the manual.




Click on the “Trace 2” button, the Probe measurement commences, the curve isplotted in the “Dynamic Window 1”. On completion, the Standing Wave isplotted in the “Measurement Window 2” in Blue Colour, in addition to theearlier Trace 1 of the Exp1. (The above colour may however differ)


Frequency is measured with maximum accuracy as in Exp1 wherein you get thesharpest minima. The same measurement can be verified with the case becausethe minima obtained are also sharp in this case.


2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in the center of theplot) on the Blue Trace. VSWR is the ratio of the maximum to the minimum voltage onthe Standing Wave Plot. Read off the Cur1/Cur2 Ratio of the 2nd reading from the top,hence VSWR = 35.79



Click on the “OK” button and observe the Computed Impedance belowR+jX= 3.3 +j58.1 ohms Theta = 81.3 deg

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 3.3 and X=58.1A RED DOT is plotted for the Complex Impedance = 3.3+j58.1 & Theta = 81.3 deg

OBSERVATION & CONCLUSION1. In an ideal Lossless Line of 50E terminated in an L/8+SHORT all of the

Standing Waves would have had identical value and Infinite Amplitude.2. The VSWR would ideally be Infinity as against the measured 35.793. The value of Impedance would have been j50 against the measured 3.3+j58.1 ohms.4. The RED POINT on the Smith Chart would have been ideally on the Top Center

of the outermost circle as depicted by the Blue Hexagon above at Theta=90 deg insteadof the measured 81.3 deg

HENCE it is concluded that the Experimental Results correlate with theory.

Ideal Plot = 0 + j50Theta = 90 deg


Experiment 1.5Transmission Line terminated in OPEN L/8 (Z

L= L/8+OPEN)

(page 409 Case 5)

PROCEDUREa. Terminate the Transmission Line with the 2 N Adapters + OPEN

ie: N(F to M) adapter + N(F to M) adapter + OPEN.NOTE: The two N Adapters are equivalent to an electrical Line Length ofLambda/8 at 721MHz. Method of measuring the electrical length is described

elsewhere in the manual.




Click on the “Trace 2” button, the Probe measurement commences, the curve isplotted in the “Dynamic Window 1”. On completion, the Standing Wave isplotted in the “Measurement Window 2” in Blue Colour, in addition to the earlierTrace 1 of the Exp1. (The above colour may however differ)


Frequency is measured with maximum accuracy as in Exp1 wherein you get thesharpest minima. The same measurement can be verified with the case becausethe minima obtained are also sharp in this case.


2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in the center of theplot) on the Blue Trace. VSWR is the ratio of the maximum to the minimum voltage on theStanding Wave Plot. Read off the Cur1/Cur2 Ratio of the 2nd reading from the top,hence VSWR = 33.47



Click on the “OK” button and observe the Computed Impedance belowR+jX= 2.9 -j48.4 ohms Theta = -91.7 deg Capacitive Load

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 2.9 and X=-48.4A RED DOT is plotted for the Complex Impedance = 2.9-j48.4 & Theta = -91.7 deg

OBSERVATION & CONCLUSION1. In an ideal Lossless Line of 50E terminated in an L/8+OPEN all of the

Standing Waves would have had identical value and Infinite Amplitude.2. The VSWR would ideally be Infinity as against the measured 33.473. The value of Impedance would have been -j50 against the measured 2.9-j48.4 ohms.4. The RED POINT on the Smith Chart would have been ideally on the Lower Center

of the outermost circle as depicted by the Blue Hexagon above at Theta=-90 deg insteadof the measured -91.7 deg

HENCE it is concluded that the Experimental Results correlate with theory.

Ideal Plot = 0 - j50Theta = -90 deg


Experiment 1.6Transmission Line terminated in RESISTIVE LOAD R

L> Z

L(Z

L= 100 ohms)

(page 409 Case 6)

PROCEDUREa. Terminate the Transmission Line with the 100E Resistive Load







2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in thecenter of the plot) on the Blue Trace. VSWR is the ratio of the maximum to the


minimum voltage on the Standing Wave Plot. Read off the Cur1/Cur2 Ratio ofthe 2nd reading from the top,hence VSWR = 1.840



Click on the “OK” button and observe the Computed Impedance belowR+jX= 92 +j1.8 ohms


OBSERVATION & CONCLUSIONIn an ideal Lossless Line of 50E terminated in 100E, that is double theCharacteristic Impedance1. The VSWR would ideally be 2 as against the measured 1.843. The value of “R” would have been 100E against the measured

92+j1.8 ohms.4. The RED POINT on the Smith Chart would have been ideally on the centerline

of the 100E circle as depicted by the Blue Hexagon aboveHENCE it is concluded that the Experimental Results correlate with theory.



Experiment 1.7Transmission Line terminated in RESISTIVE LOAD R

L< Z

L(Z

L= 25 ohms)

(page 409 Case 7)

PROCEDUREa. Terminate the Transmission Line with the 25E Resistive Load

The default Travel Distance is set to 590mm and is generally not required to bechanged for these experiments. This is the distance that the carriage will travel from theHome position. The Home position is the Input side for the Transmission Line.


Ensure that the probe is connected to SMA-V output on the Probe Carriage and that thecable will have no obstruction during the probe travel.

Click on the “Trace 2” button, the Probe measurement commences, the curve is plottedin the “Dynamic Window 1”. On completion, the Standing Wave is plotted in the“Measurement Window 2” in Blue Colour, in addition to the earlier Trace 1 of the Exp1


Frequency is measured with maximum accuracy as in Exp1 wherein you get the sharp-est minima.

2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in the center ofthe plot) on the Blue Trace. VSWR is the ratio of the maximum to the minimumvoltage on the Standing Wave Plot. Read off the Cur1/Cur2 Ratio of the 2nd readingfrom the top,hence VSWR = 2.213




Click on the “OK” button and observe the Computed Impedance belowR+jX= 22.6 +j0.6 ohms


OBSERVATION & CONCLUSIONIn an ideal Lossless Line of 50E terminated in 25E, that is Half theCharacteristic Impedance1. The VSWR would ideally be 2 as against the measured 2.2133. The value of “R” would have been 25E against the measured

22.6+j0.6 ohms.4. The RED POINT on the Smith Chart would have been ideally on the centerline

of the 25E circle as depicted by the Blue Hexagon aboveHENCE it is concluded that the Experimental Results correlate with theory.



Experiment 1.8Transmission Line terminated in RESISTIVE INDUCTIVE LOAD (Z

L= L/8+25E)

(page 409 Case 8)

PROCEDUREa. Terminate the Transmission Line with the 2 N Adapters + 25E

ie: N(F to M) adapter + N(F to M) adapter + 25E.NOTE: The two N Adapters are equivalent to an electrical Line Length of Lambda/8at 721MHz. Method of measuring the electrical length is described elsewhere in the

manual.

The default Travel Distance is set to 590mm and is generally not required to be changedfor these experiments. This is the distance that the carriage will travel from the Homeposition. The Home position is the Input side for the Transmission Line.



Click on the “Trace 2” button, the Probe measurement commences, the curve is plottedin the “Dynamic Window 1”. On completion, the Standing Wave is plotted in the“Measurement Window 2” in Blue Colour, in addition to the earlier Trace 1 of theExp1. (The above colour may however differ)


Frequency is measured with maximum accuracy as in Exp1 wherein you get the sharp-est minima.





Click on the “OK” button and observe the Computed Impedance belowR+jX= 39.5 +j30.7 ohms Theta = 89.9 deg

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 39.5 and X=30.7A RED DOT is plotted for the Complex Impedance = 39.5+j30.7 & Theta = 89.9 deg

OBSERVATION & CONCLUSIONIn an ideal Lossless Line of 50E terminated in an L/8+25E1. The VSWR would ideally be 2 as against the measured 2.042 (which is very close)2. The value of Impedance would have been 40+j30 against the measured 39.5+j30.7ohms.3. The RED POINT on the Smith Chart is almost at the theoritical point 40+j30HENCE it is concluded that the Experimental Results correlate with theory.


Experiment 1.9Transmission Line terminated in RESISTIVE CAPACITIVE LOAD (Z

L= L/8+100E)

(page 409 Case 9)

PROCEDUREa. Terminate the Transmission Line with the 2 N Adapters + 100E

ie: N(F to M) adapter + N(F to M) adapter + 100E.NOTE: The two N Adapters are equivalent to an electrical Line Length of Lambda/8 at 721MHz. Method of measuring the electrical length is described elsewhere in

the manual.

The default Travel Distance is set to 590mm and is generally not required to bechanged for these experiments. This is the distance that the carriage will travel fromthe Home position. The Home position is the Input side for the Transmission Line.


Ensure that the probe is connected to SMA-V output on the Probe Carriage and thatthe cable will have no obstruction during the probe travel.

Click on the “Trace 2” button, the Probe measurement commences, the curve isplotted in the “Dynamic Window 1”. On completion, the Standing Wave is plotted inthe “Measurement Window 2” in Blue Colour, in addition to the earlier Trace 1 of theExp1. (The above colour may however differ)



2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in the center of


the plot) on the Blue Trace. VSWR is the ratio of the maximum to the minimum voltage onthe Standing Wave Plot. Read off the Cur1/Cur2 Ratio of the 2nd reading from the top,hence VSWR = 2.042



Click on the “OK” button and observe the Computed Impedance belowR+jX= 34.4 +j36.0 ohms Theta = -103.9 deg

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 34.4 and X=36.0A RED DOT is plotted for the Complex Impedance = 34.4+j36.0 & Theta = -103.9 deg

OBSERVATION & CONCLUSIONIn an ideal Lossless Line of 50E terminated in L/8+100E1. The VSWR would ideally be 2 as against the measured 2.0423. The value of “R” would have been 40-j30 against the measured 34-j26 ohms.4. The RED POINT on the Smith Chart would have been ideally on the vertical line

passing thru the centre on the 40 ohms circle as depicted by the Blue Hexagon aboveHENCE it is concluded that the Experimental Results correlate with theory.

Ideal Plot = 40 - j30


Experiment 1.10Transmission Line terminated in Res+Cap as LOAD (Z

L= 27E+10pF in Series)

PROCEDUREa. Terminate the Transmission Line with the 27ohms +10pf Cap in Series

The default Travel Distance is set to 590mm and is generally not required to bechanged for these experiments. This is the distance that the carriage will travel fromthe Home position. The Home position is the Input side for the Transmission Line.


Ensure that the probe is connected to SMA-V output on the Probe Carriage and thatthe cable will have no obstruction during the probe travel.

Click on the “Trace 2” button, the Probe measurement commences, the curve isplotted in the “Dynamic Window 1”. On completion, the Standing Wave is plotted inthe “Measurement Window 2” in Blue Colour, in addition to the earlier Trace 1 of theExp1



2. VSWRMove the Cursor1 and Cursor2 to the Max and Min points (preferably in the center ofthe plot) on the Blue Trace. VSWR is the ratio of the maximum to the minimumvoltage on the Standing Wave Plot. Read off the Cur1/Cur2 Ratio of the 2nd readingfrom the top,hence VSWR = 2.089




Click on the “OK” button and observe the Computed Impedance belowR+jX= 25.3 -j10.6 ohms - Negative implies CAPACITIVE-j10.6 ohms corresponds to a value of 20.915pf at 721MHz

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 25.3 and X=-10.6A RED DOT is plotted for the Complex Impedance = 25.3 - j10.6 & Theta = -148.9 deg

OBSERVATION & CONCLUSIONIt is observed that the components of complex impedance can be measured with StandingWave techniques. At different frequencies, Resistive value is fairly close whereas theCapacitive value will be differ substantially, approaching 10pF at lower frequencies. Thiscan be verified by making measurements at various frequencies.


Experiment 1.11Transmission Line terminated in Res+Inductor as LOAD (Z


PROCEDUREa. Terminate the Transmission Line with the 27ohms + 2T Coil in Series




Click on the “Trace 2” button, the Probe measurement commences, the curve is plotted inthe “Dynamic Window 1”. On completion, the Standing Wave is plotted in the “Mea-surement Window 2” in Blue Colour, in addition to the earlier Trace 1 of the Exp1


Frequency is measured with maximum accuracy as in Exp1 wherein you get the sharpestminima.





Click on the “OK” button and observe the Computed Impedance belowR+jX= 24.4 +j48.4 ohms - Positive implies INDUCTIVEj48.4 ohms corresponds to a value of 0.0106 uH (ie:10.6nH) at 721MHz

4. SMITH CHART - manual representation of R+jXClick on the “Smith Chart” on the main menu andClick again on “Smith - Manual Plot”Enter the value of R = 24.4 and X=-48.4A RED DOT is plotted for the Complex Impedance = 24.4+j48.4 & Theta = 84.8 deg

OBSERVATION & CONCLUSIONIt is observed that the components of complex impedance can be measured withStanding Wave techniques. At different frequencies, Resistive value is fairly closewhereas the Inductive value will be differ with frequency. This can be verified bymaking measurements at various frequencies.


Experiment 1.12Impedance Measurement along the Transmission Line

Transmission Line terminated in Res+Inductor as LOAD (ZL= 27E+2T Coil in Series)

IMPEDANCE SETUPThis routine generates impedance conversion parameters which are saved in afile on the harddisk. This routine will take roughly 5 minutes and may be carriedout every few months or earlier, depending on the severity of use.

Click on the “Impedance Setup” button on the main menu and follow the instruc-tions. You are required to terminate the Line in 50E and switch connections fromSMA-V to SMA-I, instructions are given clearly as the setup proceeds.

Impedance Scale(Scalar Value)

PROCEDUREa. Terminate the Transmission Line with the 27ohms + 2T Coil in Series



Ensure that the probe is connected to SMA-I output on the Probe Carriage and that thecable will have no obstruction during the probe travel.

Click “Trace 1” and select “R+jX:I” and then click on OK. This will generate theStanding Wave Pattern of the CURRENT at every 1mm along the Line and will beplotted in Window 2 as the Red Plot


Now, click “Trace 2” and select “R+jX:V” and then click OK. This will generate theStanding Wave Pattern of the VOLTAGE at every 1mm along the Line and will beplotted in Window 2 as the Blue Plot.

Now, click on “Trace 3” and select “V/I :Imp” and then click OK. A third trace, GreenPlot is generated in the Window 2, which is the IMPEDANCE Plot. This plot is com-puted from dividing instantenous values of V/I and plotting the same as the ImpedancePlot.

On the right hand side a vertical, OHMS scale is generated. This scale auto adjustsitself from the maximum (284.4 ohms) to the minimum (13.8 ohms) values of Imped-ance along the Line.

At the position of the Cursor 1 and Cursor 2 the Green windows (3rd from top) indicatethe value of the IMPEDANCE of the Trace 3.

OBSERVATIONS AND CONCLUSIONS.It is observed that:1. Wherever the Voltage is maximum, the Current is minimum.2. That the Impedance is maximum, wherever the Voltage is maximum.Thus we conclude that the Impedance varies cyclically along the transmission line andcomplies with theory within experimental error.

MULTIPLE TRACES are thus useful for studying the co-relationship between Stand-ing Wave Patterns obtained with different terminations. Many of the previous experi-ments can be conducted showing 4 plots at a time, for better understanding.


CHAPTER 2

VSWR - SpectrumSoftware Description

& Experiments

This section deals with various experiments on VSWR - Spectrumusing this software feature. These experiments use innovative nonconventional software methods for clearer understanding of For-ward Power, Reverse Power, VSWR and Standing Wave Patternbehaviour at different frequencies at different points on the trans-mission line.

Measurements that can be done on a Transmission Line terminatedin a LOAD

1. Study of Vi (incident voltage) variation with Frequency2. Study of Vr (reverse voltage) variation with Frequency3. Study of VSWR variation with Frequency4. Study of Directional Coupler directivity.5. Study of Standing Wave amplitude variation with Frequency

at different distances along the Transmission Line.


Experiment 2.1Study of Vi (incident voltage) Variation with Frequency


Trace Type

Set Parameters

PROCEDUREa) Connect the load 27E+2T Coil at the Arrow Head End of the Directional Coupler.b) Connect this combination at the end of the Transmission Line.c) Connect the SMA Output of the Directional Coupler to the RF INPUT of the Receiver.

The Directional Coupler gives an output voltage proportional to the power flowing in thedirection of the arrow, shown on the device, which in this case would be the Power Incident intothe Load.

Click on “VSWR-Spectrum” on the main menu and obtain the above screen display.Click on “Set Parameters” and change “Start Freq to 450MHz” and “No of Steps to 201”The Stop Freq will change to 850MHz and Step Size to 2000KHz.

From the “Trace Type” click on “Vi ---> Directional Coupler” and press “START”

The Voltage Incident on the Load is measured from 450MHz to 850MHz at every 2MHzinterval and plotted as a Red Trace on the screen. Cursor measurement of Frequency and Vi canbe verified by shifting the cursor.


Experiment 2.2Study of Vr (Reflected Voltage) Variation with Frequency


PROCEDUREThe general setup and procedure is similar to Exp 2.1a) The Directional Coupler has to be reversed. Hence, connect the load 27E+2T Coil at the

Arrow Tail End of the Directional Coupler.b) Connect this combination at the end of the Transmission Line.c) Connect the SMA Output of the Directional Coupler to the RF INPUT of the Receiver.

The Directional Coupler gives an output voltage proportional to the power flowing in thedirection of the arrow, shown on the device, which in this case would be the Power Reflected bythe Load.

Click on “VSWR-Spectrum” on the main menu and obtain the above screen display.Click on “Set Parameters” and change “Start Freq to 450MHz” and “No of Steps to 201”The Stop Freq will change to 850MHz and Step Size to 2000KHz.

From the “Trace Type” click on “Vr <--- Directional Coupler” and press “START”

The Voltage Reflected from the Load is measured from 450MHz to 850MHz at every 2MHzinterval and plotted as a Blue Trace on the screen. Cursor measurement of Frequency and Vrcan be verified by shifting the cursor.


Experiment 2.3Study of VSWR with Frequency


PROCEDUREHaving obtained the Vi and the Vr Plots, the VSWR button is now enabled.Click on “VSWR” button to obtain a Green Plot which shows the variation of VSWR withFrequency.

Set the cursor to 722MHz and read off the values of Vi, Vr and VSWR.

Vi = 12.0 by measurementVr = 6.0 by measurement

& VSWR = 3.0 by computation

The VSWR computation is as follows.

Rho = Vr/Vi ( Rho is the Reflection Coefficient )= 6/12= 0.5

VSWR = (1+Rho)/(1-Rho) = 1.5/0.5 = 3.0

Each point of the VSWR Plot is plotted using the Vi and Vr measured at each Frequency.

VSWR


Experiment 2.4Study of DIRECTIONAL COUPLER directivity

Transmission Line terminated in CHARACTERISTIC IMPEDANCE (ZL= 50E)

PROCEDURETerminate the Transmission Line with 50EObtain the Vi, Vr and VSWR Plot as per Exp 2.1, 2.2 & 2.3

OBSERVATION & CONCLUSIONIt will be observed that since the Line is terminated in its Characteristic Impedance, theReflected Power is very much lower than the Incident or Forward Power. This is as itshould be, because the 50E Load absorbs most of the incident power.

From the VSWR Plot, which is fairly linear, it can be seen that the VSWR is between 1.22to 1.3 over the 450 - 850 MHz range. Ideally the Reflected Power would be zero and theVSWR would be 1.0 throughout.

This is because, even though the Load 50E is fairly accurate, the Directional Coupler picksup some forward power when it is connected for the reverse power measurement.

The Directivity of the coupler is specified as 20dB, which implies that the coupler willcouple and pickup 1/10 th (-20dB) of the incident power.

Based on computations shown in Exp 2.3 for a Directivity of 20dBif Vi = 1.0then Vr = 0.1 (ie: 20dB coupling)then Rho = 0.1and VSWR = 1.1/0.9 = 1.22

It is this factor which gives rise to the VSWR error of 1.22 instead of 1.0Hence, we conclude that using this Directional Coupler any VSWR less than 1.22 will bemeasured as 1.22, thereby the uncertainity of termination is from 61ohms to 40.98ohms.


Experiment 2.5Study of Standing Wave Pattern Behaviourat any Distance on the Transmission Line

at different FrequenciesTransmission Line terminated in Res+Inductor as LOAD (Z


PROCEDURETerminate the Transmission Line with 27E+2T Coil

Set the Frequency Parameters to 450-850MHz and “Distance from Home” to 110mm.The probe carriage will start moving to 110mm position.Select “Spectrum” and press START to obtain the First Plot Plot.

Place the Cursor at the Minimum. The Frequency is 644MHz as read out by the cursor.

Knowing, that along a Transmission Line a minimum would occur at every Lambda/2;we move the Probe Carriage by a further 233mm, ie: to 343mm position and obtain the2nd Plot. ( Lambda = 300/f , hence Lambda = 300/644 meters. therefore Lambda/2 =233 mm )

OBSERVATION & CONCLUSIONIt is observed that the Minimum position almost co-incides for both 110mm and343mm, at 644MHz.

From this we conclude that a Standing Wave Pattern at 644MHz, for the same Loadshould exhibit minima at 110mm and 344mm respectively.

The next page illustrates this verification.


PROCEDURETerminate the Transmission Line with 27E+2T Coil

Click on “Standing Waves” on the main menu.Set the frequency to 644MHz

Click on “Trace 1” and enter “27E+2T” after selecting R+jX

After the Plot is obtained, place the Cursor 1 and Cursor 2 on the first 2 minima as shownabove. Read off the distances as 110mm and 341mm respectively.

OBSERVATION & CONCLUSIONIt is observed that the Cursor 2 distance is slightly in error whereas the Curor 1 is coincidentat 110mm. We conclude that within experimental error the results are confirming.

NOTE: The initial position of the probe at 110mm was arbritary and the Student is encour-aged to try out any initial distance and verify the above.

Cursor 1 Distancefrom Home

Cursor 2 Distancefrom Home


CHAPTER 3

RF Recorder - Probe PositionSoftware Description

This section explains these two features which can be usedfor Measurement and Monitoring the RF Voltage in differ-ent forms and could be used innovatively depending on theingenuity of the user.


Experiment 3.1Study of RF Recorder & Probe Position

Frequency

DigitalMeter

Strip Chart

Distance in mmfrom Home

Click on “RF Monitor” and on “Probe Position” to obtain the above screen dis-play.

The Level can be monitored in different modes.

Precise adjustments and measurements can be made using the DIGITAL MeterMode at any frequency.

The Frequency at which the Level is being monitored can be changed in finesteps or by direct entry.

The Strip Chart gives the history of Level fluctuation, (irrespective of Frequency)

The Probe Position can be directly entered as “Distance from Home” or varied in1mm steps. The “Home” and “End” buttons will move the probe carriage to theHome position (input side) or the End position (termination side) respectively.

VSWRdisplay


CHAPTER 4

SMITH CHARTSoftware Description

& Experiments


Experiment 4.1Study of SMITH CHART Auto Generation

Transmission Line terminated in Res + Ind (ZL=27E+2T Coil)

PROCEDURETerminate the Transmission Line with the 27E+2T Coil

Click on the “SMITH Chart” and further select “Smith - Auto 450 to 850MHz”The software will prompt the user and commence measurements, which will take about30 minutes to complete.

When the first measurement at 450MHz is completed, a CYAN Square is plotted on theSMITH Chart and the R+jX values are listed on the screen.

Measurements are made at 50MHz interval, upto 850MHz. As each subsequent measure-ment is completed it is plotted as a RED Dot on the SMITH Chart and the R+jX valuesare listed. On completion a Line joins all the dots to generate the SMITH Chart.

SMITH Chart - Ref ScanThis routine generates reference parameters used for generation of the SMITH Chartwhich are saved in a file on the harddisk. This routine will take roughly 15 minutes andmay be carried out every few months or earlier, depending on the severity of use.

Click on the “SMITH Chart” button on the main menu and then click on the “ReferenceScan” and follow the instructions. You are required to terminate the Line in SHORT,instructions are given clearly as the scan proceeds. Note, the SHORT has to placed atthe plane of measurement of the Impedance for generation of the Smith Chart.

450MHz 850MHz


CHAPTER 5

Study ofImpedance Matching

using aDual Slug Tuner

Software Description& Experiments


Experiment 5.1Study of IMPEDANCE MATCHING using a Dual Slug Tuner

Transmission Line terminated in a high VSWR Load

METHOD OUTLINEA matching device is interposed between the Transmission Line and the Com-plex Load, and so adjusted that it would match the Transmission Line as closeas possible. There being however a mis-match between the device and theLoad. Broadband matching is difficult to achieve, whereas Narrowband match-ing is relatively easier.

The matching device used is a Dual Slug Tuner. It operates by introducing areflected wave that is adjusted to produce a reflection equal in magnitude andopposite in phase to the reflected wave produced by the Load impedance.

The phase of the reflection so introduced is controlled by moving the slugsalong the line while maintaining the spacing between them constant. Themagnitude of the reflected wave can be controlled with minimum effect on thephase, by moving the two slugs equal amounts in opposite directions.

Slug Tuners are limited in the range of impedances that can be matched. Resis-tive mismatches are easier to match than a complex load. Open circuit, Shortcircuit and pure reactances cannot be matched using this method. In manycases, whilst obtaining a better match for a narrow range of frequencies mayworsen the mismatch at other frequencies.

The STEPS are as follows.1. We will use the method of Exp 2.3 to obtain the VSWR vs FREQUENCY

plot of the Hi VSWR LOAD.

2. Then we will use the method of Exp 4.1 to obtain theSMITH CHART of the Hi VSWR LOAD

3. We will then connect the Dual Slug Tuner, between the Directional Coupleroutput and the Hi VSWR LOAD, and using the method of Exp 2.3; obtain the

ADJUST the Tuner for optimum matching at 600MHz

4. We will then obatin the SMITH CHART of the matched system and observethat the Hi VSWR LOAD is very closely matched at 600MHz

Each step is explained in detail in the next few pages.


STEP 1

Refer to Exp 2.3 for the procedure, and obtain the above VSWR vs PLOT of the HiVSWR LOAD as shown above.Observe that the VSWR varies from 5.66 to about 17. We will match the Imped-ance such that the VSWR at 600MHz approaches 1 from the high value of 7.597

Refer to Exp 4.1 for procedure and obtain the SMITH CHART for the Hi VSWRLOAD as shown below.The 600MHz point is on the VSWR circle of 5.3 on the Smith Chart. (the valuediffers from above due to cumulative/residual errors of the system). For matching,this point would have to move towards the center.

STEP 2

600MHz


STEP 3 Now connect the set up as follows.

Transmission Line + D.Coupler --> + Dual Slug Tuner + Hi VSWR Load

Click on “VSWR-Spectrum” on the main menu.Click on “Set Parameters” and Enter the following:

Start = 450MHzStop = 850MHzFreq Step = 2000KHzNo of Steps = 201

Connect the Directional Coupler for Vi (--> incident voltage) measurement

Click on “Trace Type” and select “Vi --> Directional Coupler”press START and then press STOPPosition the Cursor at 600MHz

Reverse the Directional Coupler for Vr (<-- reflected voltage) measurementTransmission Line + <--D.Coupler + Dual Slug Tuner + Hi VSWR Load

Click on “Trace Type” and select “Vr <-- Directional Coupler”press START (DO NOT press STOP)

To achieve IMPEDANCE MATCHING at 600MHz the 2 Slugs have to be adjustedusing the insulated tool. As the Slugs are adjusted, the REFLECTED curve willkeep changing (allow one full sweep for update for each change). The RED BARindicates the Minimum VSWR value and frequency; the full scale value being 3.0.As you keep adjusting the Slug positions you will observe that the Curve Dips atcertain frequency. Keep moving the Slugs and mutual spacing so that the Dip comesto the 600MHz cursor position. Concurrently note that the RED BAR minimisestowards 1.0. Keep adjusting the Slugs untill you achieve the Lowest VSWR at600MHz.Shown below is after the Slugs were adjusted for a VSWR of 1.15 at 600MHz


STEP 4 To verify the Impedance Matching, connect the set up as follows.

Transmission Line + Dual Slug Tuner + Hi VSWR Load

Obtain the SMITH CHART as per procedure of Exp 4.1The result obtained is shown below.

The 600MHz point has moved towards the center with a VSWR of 1.1 from theearlier circle of 5.3. The other points have changed considerably

600MHz

MICROWAVE ENGINEERING (2171001) B.E. 7th … · microwave engineering (2171001) b.e. 7 th semester laboratory manual 2016 department of electronics and communication engineering government

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