Download Home Work-VI SEM-MICROWAVE

MICROWAVE ENGINEERING-II
Unit- I
MICROWAVE MEASUREMENTS
1. Explain microwave power measurement.
2. Why we can not use ordinary diode and transistor in microwave detection and
microwave amplification?
3. Calculate the VSWR of a transmission system operating of 10Ghz .Assume TE10
wave transmission inside a waveguide of dimension a= 4 cm, b=2.5cm. The distance
measured between twice minimum power point =1mm on a slotted line.
4. Explain the frequency measurement of microwave signal.
5. Explain the double minimum method of measuring VSWR and prove that,
VSWR= λg/π∆x
Where
λg =guide wavelength
∆x = distance between twice the minimum power point. Assume perfect square law
detection.
6. Describe the method for measuring high RF microwave power.
7. Write about the following microwave measurement:
(a) VSWR
(b) Wavelength
(c) Unknown impedance
(d) Microwave power measurement, power falls in the range of 1 mw to 10
mw.
8. Explain the impendence measurement using magic tee.
9. Which type of equipments used for measuring the scattering parameter? Explain its
working with suitable block diagram.
10.Explain the method of measuring scattering parameter.
11.Two identical 30 db directional coupler are used to sample incident and reflected power
in a waveguide. VSWR =2 and the output of coupler sampling incident power =4.5 mw.
What is the value of reflected power?
12.Describe two methods for measuring high R.F. power level.
13.How are microwave measurements different from low power measurements?
14.Explain how bolo-meters are used for power measurement.
15.A slotted line is used to measured the frequency and it was found that the distance
between the nulls is 1.95 cm. Given the guide dimensions as 3.5X2 cm. Calculate the
value of frequency.
16.Double minimum method is used to determine the VSWR value on a waveguide. If the
separation between two adjacent nulls is 4cm and that between twice minimum power
points is 3 cm. determine the value of VSWR.
17.Explain the working of thermistor for microwave power measurement. Draw the
complete set-up of a wheat stone bridge method, having its one arm as thermistor, for
microwave power measurement.
18.Draw the variation of resistance of a barratters with temperature. Write the name of
material composition used for it.
19.Write notes on following:
(a) Slotted line
(c) Network Analyzer
(e) Spectrum Analyzer
(b) Bolometer
(d) Wave meter
(f) Reflect meter
UNIT = II
PLANAR TRANSMISSION LINES
1. Explain the losses in micro-strip lines.
2. A shielded strip line has the following parameter, Dielectric constant of insulator
(polystyrene)
єr= 2.56
Strip width w =25mils
Strip thickness t = 14mils
Shield depth d = 70 mils
Calculate the following:
(I)
The K factor
(II) The fringe capacitance
(III) The characteristic impedance of the line
3. Explain parallel, strip line and its distributed parameters, characteristic impendence
attenuation losses.
and
4. A lossless parallel strip line has a conducting strip width w. The substrate dielectric
separating the two conducting strips has a relative dielectric constant Erd of 6.0 and a thickness
d of 4.0 mm.
Calculate:
(I)
The required width w of the conducting strips in order to have characteristic impedance
of 50 ohm.
(II) The strip line capacitance
(III) The phase velocity of the wave in the parallel strip line.
5. Explain the following about micro strip line:
(i) Static parameters and characteristic impedance
(ii) The effective micro strip permittivity and effective relative permittivity
(iii) Losses in a micro strip
(iv)Limitation of micro strip
6. A micro strip line is to be designed on alumina substrate having relative dielectric
constant Er= 8.2. The w/h ratio is 0.95. Compute the effective relative dielectric constant, the
characteristic impedance Zo, the phase velocity and guide wavelength.
7. What do you mean by micro strip line? Define along with neat diagrams. List all the
advantages and disadvantage of micro strip lines over strip lines
8. Explain clearly the structure of field lines in the strip lines and micro strip lines.
9. What are slot lines and how do they differ from micro strip lines?
10. A shield strip line has the following parameters. Relative dielectric constant of the insulator
polyethylene єrd = 2.25
Strip width
w = 2 mm
Strip thickness t = 0.5 mm
Shield depth d = 4 mm
Calculate:
(i) K factor
(ii) Fringe capacitance
(iii) Characteristic impendence.
11. Compare the characteristics of waveguide, strip line and micro strip lines.
12. Explain the application, advantage and structures of fin line.
13. Explain, why fin lines are suitable for millimeter wave frequencies.
14. What do you mean by NRD-guide? List all the merits and limitations of NRD-guide
15. Explain various discontinuities and bends in the planar transmission line.
16. Explain the coaxial to strip line and coaxial to micro strip line transition.
17. What are the coplanar strips? List the advantage and application of the coplanar strip line.
18. A strip line has a ground plane spacing of 2 mm, a strip width of 1 mm and is filled with a
dielectric medium with dielectric constant 2.3. Calculate the characteristic impendence.
20.Calculate the characteristic impendence of a strip line having constants w = 0.14 cm and
h = 0.3 cm if the substrate relative permittivity is 2.3.
UNIT = iii
MICROWAVE NETWORK ANALYSIS
1. Show using S-matrix theory that a lossless non reciprocal two port microwave device cannot
be constructed.
2. Explain the properties of S-matrix.
3. Show that, if a microwave junction satisfies reciprocity condition and if there are no active
devices, then S-parameters are equal to their corresponding transposes.
4. List the advantage of S-parameter.
5. If the impendence matrix of a device is
[3 4
1 2]
Find the scattering matrix.
6. Explain the combination rules of signal flow graph.
7. The two-port devices represented by following matrices are cascaded
[ 0.2 0.3
[0.1
0.2
0.1 0.4 ]
and
0.4
0.5]
Find the scattering matrix of the resulting device. Determine its properties, i.e. symmetry,
reciprocity, lossless and matching.
8. Explain the Mason’s non touching loop rule with example.
9. Explain the properties of reciprocity and lossless networks.
10. For a section of a transmission line, the ABCD parameter is
[ 0.87
25j
0.01j
0.87]
Find the Z-matrix.
11. Explain different types of discontinuities in micro strip and waveguides with equivalent
circuits.
12. Prove that the relation between (S) and (Z) is
[S] = ( [Z] / Zo – [u] ) ( [Z] / Zo +[u]) -1
13. Write the short notes :
(a) Advantages of S-matrix
(b) Signal flow graphs
(c) Discontinuities in micro strip
(d) Equivalent circuit for two port network.
UNIT – IV
MICROWAVE SEMICONDUCTOR DEVICES
1. Explain the construction, operation and practical applications of PIN-diode.
2. Draw the equivalent circuit and characteristic of tunnel diodes and explain parallel and
series loading.
3. Describe the Ridley-Watkins-Hilsum theory and modes of operation of Gunn diodes.
4. Describe the operating principles of IMPATT and TRAPATT diode.
5. Explain tunneling effect by energy band diagram and write application of tunnel diode.
6. Draw equivalent circuit of PIN, Varactor diode.
7. An IMPATT diode has the following parameters.
Carrier drift velocity
= 2*107 Cm/s
Drift region length
= 6 µm
Maximum operating voltage = 100 v
Maximum operating current = 200 mA
Efficiency
= 15 %
Breakdown voltage
= 90 v
Calculate:
(i)
Maximum CW o/p power in watts
(ii) The resonant frequency in GHz
8. Explain the construction, working and equivalent circuit diagram of the following
devices.
(i)
IMPATT
(ii) Tunnel Diode
9. In a two-valley model theory of Gunn diode, prove that,
[ (µl-µu)/ (µl+µu) (-Ednl/nldE) -P] › 1
Where ul and uu are the electron mobility in lower and upper valley respectively,
E is the applied Electric field and n1 is the electron density in power valley, P is a function of
scattering mechanism.
10.For a n-type Ga As Gunn diode
Electron density, n= 1018 cm-3
Electron density at lower valley n1 = 1010 cm-3
Electron density at upper valley nu = 108 cm-3
Temperature T = 300 K
Determine the conductivity of the diode.
11.Draw the voltage versus current characteristic of a tunnel diode, hence explain it
negative resistance characteristic and with the help of energy band diagram, explain
operation of tunnel diode.
12.Write short notes on tunnel diodes.
13.Explain the construction, operation and equivalent circuit, figure of merit and application
of varactor diode.
14.Discuss the difference between Gunn diode and tunnel diode.
15.Explain the Gunn Effect.
16. In certain Gunn diode of active length 10 µm, the drift velocity of electron is
cm/s. Calculate the natural frequency of diode.
2*107
17.A Ku-band IMPATT diode has a pulsed operating voltage of 100 v and a pulsed operating
current of 0.9 A. The efficiency is about 10%.
Calculate: (i) The output power
(ii) The duty cycle if the pulse width is 0.1 ns and the
Frequency is 16 GHz.
18.Describe the modes of operation for Gunn diode and explain characteristic in each
mode of operation. Also draw the equivalent circuit and explain application as an
oscillator.
19. An n-type GaAs Gunn diode has the following parameters.
Electron drift Vd = 2.5*105m/s
Negative electron mobility I µn I = 0.015 m2/Vs
Relative dielectric Constant Er = 13.1
Determine the criterion for classifying the modes of operation.
20. State the condition for stable domain formation in a bulk GaAs semiconductor.
Discuss briefly the modes of operation of the Gunn diode.
21.How are one generate a SPDT switch using PIN diode, explain.
22.Explain why it is possible to have amplification by using a device which exhibits negative
resistance.
23.Draw a schematic diagram of an IMPATT and fully explain the two effect that combine to
produce a 180 degree –phase difference between the applied voltage and the resulting
current.
24.Explain the volt-ampere characteristics of a tunnel diode, with the help of energy band
and Fermi level diagram. What do you mean by quantum mechanical tunneling?
25.Explain the working principle of a TRAPATT .In what way differs from IMPATT diode and
why?
26.Explain construction, principle of operation and application of MESFET.
27.Explain the construction, working and application of charge coupled device (CCD).
28.Explain the construction, working and equivalent circuit diagram of the microwave
transistor.
29.Describe structure, operation and layout of the microwave BJT.
30.A typical GaAs MESFET has the following parameterRg = 2.5 ohm
Ri = 2.2 ohm
Gm = 50 mho
Rd = 42 ohm
Rs = 3.2 ohm
Cgs = 0.66 pf
(1) Determine the cut-off frequency
(2) Find the maximum operating frequency
31.Why GaAs is superior to silicon as a microwave material.
32.Explain working principle and dynamic characteristic of charge coupled devices. Also
draw the energy band diagram of these devices.
33.The n-type three phase surface channel CCD has the following specification:
Electron density Nmax = 2*1012 cm-2
Insulator relative dielectric constant Er = 3.9
Insulator thichness
d = 0.15 µm
Compute the insulator capacitance
34.What are the main characteristic of MESFET which makes it useful for microwave
operation? Explain the working of a simple MESFET.
35.A Silicon JFET has a gate length of 6 um. Calculate the macimum frequency of oscillation
for the device (Given Vs = 2*105 m/s).
36.Calculate the pinch-off voltage for an n-channel JFET which has the following parameterElectron density
Nd = 2*1023 m-3
Channel height
a = 0.6 * 10-6 m
Relative dielectric constant Er = 11.8
37.Compare the performance characteristic of bipolar transistor, MOSFET and MESFET.
38. Write the short notes on following
(1) JFET
(2) MESFET
(3) CCD
38.Give difference between laser and maser in working principle, construction and
application and also explain laser action.
39.Explain the principle and construction of a typical ruby maser cavity amplifier.
40.What is a maser? What does its name signify? What application does it have?
41.Discuss fully the operation of the ruby laser. Show a basic sketch of one.
42.Compare and contrast the operation and application of ammonia maser and ruby maser.
43.What is laser? Explain the working of a non-semiconductor laser.
44.Why maser is such a low noise devices?
45.List the advantage and application of ruby laser.
46.A laser is found to emit 1 micron. If energy of the lower laser energy level is 4 * 10-20
joule. Determine the upper laser level energy level.
Given h =6.63 * 10-34 j/s.
UNIT – V
MONOLITHIC MICROWAVE INTEGRATED CIRCUITS
1. List the basic characteristics required for an ideal substrate material.
2. Describe the MMICs techniques.
3. Describe the basic fabrication process for MOSFET.
4. Explain properties of material in MMIC fabrications.
5. Explain thin film formation in MMIC.
6. List the basic properties provided by ideal dielectric and resistive material used in
MMIC.
7. Explain the MMIC fabrication technique with help of suitable example.
8. Explain the CMOS formation with suitable diagram.
9. Why Ga As is superior to silicon as a microwave semiconductor material.
10.Describe the advantage of microwave integrated circuit over the conventional circuits.
11.Explain the advantage and disadvantage of MMIC over hybrid integrated circuits.
12.A circular spiral inductor has the following parameters
Number of turns
n=5
Separation
s = 100 mils
Film width
w = 50 mils
Compute the inductance.