# RTU Previous Question Papers BE EC 6 th Semester

# Microwave Engineering May 2012

**Unit -1**

1. (a) Discuss the Network analyser setup for the measurement of Scattering parameters.

(b) In a SWR measurement at 10 GH_{3}, the distance between the successive minima is 0.1cm. Inside dimension of waveguides are 4cm and 2cm respectively.TE_{|0} mode is propagating through the waveguide. Calculate the VSWR.

**Or**

1. (a) How can we measure power of micro wave signals using —

(i) Bolo meter

(ii) Thermocouple

(b) In a Calorimeter – Wattmeter power measurement system, mas§ of , water taken is 1000 gm and rise in temperature is 100°c. Calculate the amount of incident microwave power.

2 . (a) .-Discuss different type of losses occurred in Micrortrip lines, along with necessary relation.

(b) A certain micro strip line has the following parameters-

Er = 5.23 t = 2.8 mils

h = 7 mils w = 10 mils

calculate the characteristic Impedance (Zo) of the line.

**Or**

2. (a) What do you mean by parallel strip lines. Explain.

(b) Derive the relation for character Impedance and attenuation losses of a parallel strip line.

(c) A shielded strip line has the following parameters –

Er = 2.56 *

w =25mils (strip width)

t= 14 mils (strip thickness)

4=70 mils (shield depth)

Calculate – (i) k factor

(i) Frindge capacitance

(iii) Characteristic Impedance of the line

**Unit-Ill**

3. (a) Discuss ABCD matrix analysis of two port networks .

(b) Briefly explain , all possible dis continuaties , which can occur in waveguides.

**Or**

3. (a) What are Reciprocal Networks ? Explain.

(b) How can we say, Directional Coupler is a reciprocal multipart junction. Explain its construction and Working.

**Unit-IV**

4. (a) Define the term Negative Resistance . Name the diode which works on the principle of Negative resistance.

(b) Discuss TRAPATT diodes on the basis of following points –

(i) Physical structure

(ii) Principle of operation

(ii) Power output & Efficiency

**Or**

4. (a) Explain the working of Tunnel diode. Draw the energy band diagram under different bias conditions.

(b) A Silicon IFET at 300°K has the following parameters –

Electron density (Nd) = 1 x 10^{17} cm

Hole density (Na)=lxl0^{19} cm^{-3}

Relative dielectric constant (Er) =11.8

Channel height (a) = 0. 2x 10″^{4} cm

Channel length (L) = 8×10^{-4} cm

Channel Width (z) = 5 Ox 10″^{4} cm

Electron Mobility (|i_{n}) = 800 cm^{2} /v.s

Drain Voltage (Vd)=10V

Gate Voltage (Vg) – -1.5 V

Calculate

(i) Pinch off Voltage (ii) Pinch off current

(iii) Built in Voltage (iv) Drain current

(v)Saturation drain current at Vg = 0 (iv) Cut off frequency

**Unit-V**

5. (a) Discuss different type of MMIC fabrication techniques .

(b) Categories the materials available for MMIC and give their characteristics.

**Or**

5. (a) What is the use of planar inductor films in their film formation.

(b) Explain different type of Inductor film available, along with required expressions.

(c) An Interdigitated capacitor fabricated on a GaAs substrate has the following parameters –

Number of fingers (N) = 8

Relative dielectric constants of GaAs (Er) = 13.10

Substrate height (h) = 0.254 cm

Finger Length (1) = 0.00254 cm

Finger base width (w) =0.051 cm

Compute the capacitance.