Important Questions in
**Transmission **

Lines and Wave guides

** **EC2305

EC 2305 subject for NOV/DEC 2011 ANNA UNIVERSITY EXAMINATIONS FOR III YEAR ECE Students

**EC2305 Transmission Lines & WG**

**UNIT I**

1. Derive Characteristic Impedance, Inductance, Capacitance & Cutoff frequency for constant K low pass filter.

2. Draw a constant K T-section band pass filter and explain the operation with necessary design equations.

3. Design a m-derived T section low pass filter having a cutoff frequency of 5000 hz and a design impedance of 600 ohms. The frequency of infinite attenuation is 1.5f_{c }

4. Design prototype T section band pass filter having cut-off frequency of 1 khz and 4khz and impedance of 600 ohms. Find resonant frequency.

UNIT II

1. Discuss in detail inductance loading of telephone cables and derive the attenuation constant and phase constant and velocity of signal transmission for the uniformly loaded cable?

2. A line has R = 8.4 ohm/km, L = 2.67 mH/km, G = 1.8 Âµ mho/km and C = .00835ÂµF/km. Determine Z_{o}, Î³, V for f = 1000 Hz. Vs = 4.0 volts and length = 100 km.

3. What is Waveform distortion? Explain its types with equations. Derive the condition for a distortion less line?

4. A telephone cable 34 km long has a R = 23 ohm/km and C = 0.008 ÂµF/km. Calculate attenuation constant, velocity and wavelength of line at 2000 Hz

5. Derive the two Standard forms for Voltage and Current of a line terminated by an impedance of the transmission line.

UNIT III

1. Explain single stub matching on a transmission line and derive an expression to find the length & location of the stub used for matching on a line?

2. Determine the stub length and distance from load. Given that a complex load 50+j100 is to be matched to a 75 ohms transmission line using short circuited stub.

3. Derive the expression for the field strength for the TE waves between parallel plates propagating in z direction.

4. Determine the lengths of the two stubs terminated by a load impedance of 23.23 + 18.25 ohms with Zo= 40 ohms assuming a quarter wave spacing is achieved between the stubs.

5. Derive the expression for the input impedance of the dissipationless line and the expression for the input impedance of a quarter wave line. Also discuss its applications

UNIT IV

1. Derive the expression for the field strength for the TM waves between parallel plates propagating in z direction.

2. Derive the characteristics of TE, TM and TEM waves for parallel plates

3. A parallel plane waveguide with plate separation of 20 cm with the TE10 mode excited at 1 Ghz. Find the propagation constant.

4. A Waveguide formed by two parallel copper sheets Ïƒ=5.8*10^{7} s/m separated by a 5 cm thick lossy dielectric Îµr=2.25, Î¼r=1, Ïƒ=10^{-10}s/m. For an operating frequency of 10 Ghz, find Î², Î±_{d}, Î±_{v}, V_{g}, V_{p} & Î»_{g} for TE_{1}, TM_{2} and TEM modes.

UNIT V

1. Using Bessel function derive the TE wave components in circular waveguide.

2. The cutoff wavelengths of rectangular waveguide are measured to be 8 cm and 3.6cm for TE_{10 }mode and TE_{11} mode respectively. Determine waveguide dimensions.

3. Determine the solution of electric and magnetic fields of TE waves guided along rectangular waveguide

4. What are the dimensions of a waveguide with a frequency of 0050.5 Mhz, the guide wavelength for TE_{10 }mode is 87.57% of the cut off wavelength.

5. Explain the various excitation methods of Rectangular waveguides.