College : Vardhaman College Of Engineering
Degree : B.Tech
Department : Electronics & Communication Engineering
Semester : VI
Subject : Microwave Engineering
Document type : Question Paper
Website : vardhaman.org
Download Previous / Old Question Papers :
May- 2014 :https://www.pdfquestion.in/uploads/vardhaman.org/6393-BT6RMAY14.pdf
Microwave Engineering Question Paper :
Four Year B. Tech VI Semester Regular Examinations June – 2014
(Regulations: VCE-R11)
(Electronics and Communication Engineering)
All parts of the question must be answered in one place only
Related : Vardhaman College Of Engineering Composite Materials B.Tech Question Paper : www.pdfquestion.in/6391.html
Unit – I :
1. a) Briefly explain the different frequency bands used for Microwave communication. 3M
b) Derive expression for Hz starting from the wave equation for a rectangular wave guide operating in TE mode assuming wave propagation along Z axis. 12M
2. a) The cross section of a rectangular wave guide is 20cmx5cm. Find 6 lowest order modes which will propagate on the waveguide and their cut-off frequencies. 8M
b) Derive the resonant frequency of a rectangular cavity starting from TE and TM fields on the waveguide and forcing the boundary conditions on the end walls of the resonator. 7M
Unit – II :
3. a) With the help of neat constructional details, derive S-matrix for H-plane tee and also prove that H plane is 3 dB splitter. 7M
b) List some important applications of Directional couplers. Explain the working of a multirole directional coupler. 8M
4. a) Explain the working principle of a circulator and derive its S –Matrix. 8M
b) A 3- port device has insertion loss of 1 dB, isolation of 30 dB and VSWR =1.5. Find the S-matrix. 7M
Unit – III :
5. a) With a neat sketch explain the mechanism of oscillations in a reflex klystron. 9M
b) A reflex klystron is operated under the following conditions:
Vo =600 v, L= 1mm,
Rsh =15kO, e/m =1.75×1011
fr =9GHz and n=2 (mode= 1 3/4)
Assuming that the transit time through the gap and the beam loading can be neglected,
Find the value of repeller voltage. 6M
6. a) With the help of neat diagram explain the working principle of a TWT Amplifier. 9M
b) A TWTA operates under the following conditions:
Beam voltage Vo =3Kv
Beam current Io =30 mA
Characteristic impedance Zo=10O
Circuit length N= 50
Frequency f= 10 GHz
Determine
i. The Gain parameter C
ii. The output power gain AP 6M
Unit – IV :
7. a) Briefly explain crossed field devices. Give the different classifications of Magnetron. 9M
b) An X-band pulsed conventional magnetron has the following operating parameter Anode voltage: Vo=5.5KV; Beam current: Io=4.5A. Operating frequency: f=9GHz; Resonator conductance: Gr=2×10-4 mho Loaded conductance: Gl =2.5×10-5 mho; Vane capacitance C=2.5pF. Duty cycle: DC=0.002; power loss: Ploss =18.50kw
Compute:
i. The angular resonant frequency
ii. The unloaded quality factor
iii. The loaded quality factor
iv. The external quality factor
v. The circuit efficiency
vi. The electronic efficiency 6M
8. a) Draw the current – voltage characteristics and energy band diagram of n-type Gallium Arsenide (GaAs) Gunn diode and explain the “negative resistance effect” in these diodes. 8M
b) What are avalanche transit time devices? With neat graphs explain IMPATT diode operation. 7M
Unit – V :
9. a) Explain the measurement of impedance using reflectometer at microwave frequency. 9M
b) Calculate the SWR of a transmission system operating at 10GHz. Assume TE10 wave transmission inside a waveguide of dimensions a=4cm, b=2.5cm. The distance measured between twice minimum power points=1mm on a slotted line. 6M
10. a) Briefly explain the different techniques used to measure frequency at microwave frequencies. 10M
b) You have two directional couplers (20dB) in a guide to sample the incident and reflected powers. The outputs of the two couplers are 3mw and 0.lmw respectively. What is the value of VSWR in the main guide? What is the value of reflected power? 5M