**EC2305:**

**TRANSMISSION LINES & WAVE GUIDES SEM / YEAR:**

**V / III**

**(REGULATION 2004)**

**DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING**

**QUESTION BANK**

**SUBJECT NAME : TRANSMISSION LINES & WAVE GUIDES**

**UNIT I - TRANSMISSION LINE THEORY**

**PART – A**

**All questions – Two Marks:**

- What is group velocity?
- What is patch loading?
- What do you understand by loading of transmission lines?
- Define Characteristic impedance?
- What is frequency distortion?
- Calculate the load reflection coefficient of open and short circuited lines?
- Calculate the characteristic impedance for the following line parameters
- R = 10.4 ohms /km L = 0.00367 H/km
- C = 0.00835μf /km G = 10.8x10-6 mhos /km
- Define phase distortion?
- Write the equation for the input impedance of a TL?
- Define propagation constant?
- Define wavelength?
- Give the input impedance of a open and short circuit line?
- Define reflection factor?
- Define reflection loss?
- What is meant by reflection co – efficient?
- State the properties of infinite line?
- Write the condition for a distortion less line?
- When does reflection take place on a TL?
- What is transfer impedance? State its expression?
- What is difference between lumped and distributed parameters?
- Draw the equivalent circuit of a TL?
- Write the Campbell’s formula for propagation constant of a loaded line?
- What is the need for loading?

**PART – B**

- Obtain the general solution of Transmission line?
**(16)** - Explain about waveform distortion and distortion less line condition?
**(16)** - Explain about reflection loss?
**(16)** - Discuss in details about inductance loading of telephone cables and derive theattenuation constant (_) and phase constant (_) and velocity of signal transmission(v) for the uniformly loaded cable?
**(16)** - Derive the equation of attenuation constant and phase constant of TL in terms of R,L, C, G?
**(16)** - Explain in details about the reflection on a line not terminated in its

characteristic impedance (z0)?

**(16)**- Explain in following terms
**(16)** - Reflection factor (ii) Reflection loss
- Return loss
- Explain about physical significance of TL?
**(16)** - Derive the equation for transfer impedance?
**(16)** - Derive the expression for input impedance of lossless line?
**(16)** - Explain about telephone cable?
**(16)** - Explain about different type of TL?
**(16)**

**UNIT II - THE LINE AT RADIO FREQUENCIES**

**PART – A**

**All questions – Two Marks:**

- Name few applications of half – wave line?
- Find the VSWR and reflection co – efficient of a perfectly matched line with no reflection from load?
- Explain the use of quarter wave line for impedance matching?
- What is the need for stub matching in transmission lines?
- Why do standing waves exist on TL?
- Define Node and antinodes?
- What are constant S circles?
- What are the advantages of double stub matching over single stub matching?
- Derive the relationship between standing wave ratio and reflection co – efficient?
- Write the expression for the characteristic impedance Ro’ of the matching quarter –wave section of the line?
- Give the applications of smith chart?
- Define standing wave ratio?
- Give the analytical expression for input impedance of dissipation less line?
- Design a quarter wave transformers to match a load of 200 _ to a source resistance of 500 _. The operating frequency is 200 MHz?
- Define skin effect?
- What is zero dissipation line?
- Mention the assumptions of radio frequency lines?
- Distinguish between single stub matching and double stub matching?
- Write down the expression to determine the length of the stub?
- Write down the expression to determine the position of the stub?

**PART – B**

- Explain about half wave transformer?
**(8)** - Application of smith chart?
**(8)** - Explain about voltage and current waveform of dissipation less line?
**(16)** - Derive the expression for the input impedance of the dissipation less line and theexpression for the input impedance of a quarter wave line. Also discuss the applicationof quarter wave line?
**(16)**

- Explain single stub matching on a transmission line and derive the expression and the length of the stub used for matching on a line?
**(16)** - Design a single stub match for a load of 150+j225 ohms for a 75 ohms line at 500 MHz using smith chart?
**(16)** - A 30 m long lossless transmission line with characteristic impedance (zo) of 50 ohm is terminated by a load impedance (ZL) = 60 + j40 ohm. The operating wavelength is 90m. find the input impedance and SWR using smith chart?
**(16)** - Explain double stub matching on a transmission line and derive the expression and thelength of the stub used for matching on a line?
**(16)**

9. Explain about _ / 8 wave transformer?

**(16)** 10. explain about properties of smith chart?

**(16)****UNIT III - GUIDED WAVES**

**Part-A**

**All questions – Two Marks:**

- Define group velocity?
- What are the characteristics of TEM waves?
- What is the cut off frequency of TEM wave?
- Give the expression that relates phase velocity (Vp), Group velocity (Vg) and free space velocity?
- What are TE waves or H waves?
- What are TM waves or E waves?
- What are guided waves?
- What is dominant mode? Give examples?
- Write down the expression for cut off wavelength and cut off frequency?
- Write down the expression for velocity of propagation?
- Define attenuation factor?
- Define wave impedance?
- Distinguish between TE and TM waves?
- Write down the relation between guide wavelengths and cut off wavelength?
- Give the expression for the guide wavelength when the wave transmitted in between two parallel plates?
- Find the frequency of minimum attenuation foe TM waves?
- Give relation between the attenuation factor for TE and TM waves?
- Draw a neat sketch showing the variation in the value of attenuation with frequency for TE, TM, and TEM mode between two parallel plates?
- Draw a neat sketch showing the variation in the value of wave impedance with frequency for TE, TM, and TEM mode between two parallel plates?

**Part-B**

- Discuss the characteristics of TE and TM waves and also derive the cut off

frequency and phase velocity from the propagation constant?

**(16)**- Derive the expression for the field strength for TE waves between parallel plates propagating in Z direction?
**(16)** - Derive the expression for attenuation of TM waves in between parallel plates?
**(16)** - Derive the expression for attenuation of TE waves in between parallel

- Plates?
**(16)**

- Derive the expression for the field strength for TM waves between

- Parallel plates propagating in Z direction?
**(16)**

- Obtain the expression for the field components of an electromagnetic wave propagating between a pair of perfectly conducting planes?
**(16)** - Derive the expression for wave impedance of TE, TM and TEM wave between a pair of perfectly conducting planes?
**(16)** - Explain about transverse electromagnetic waves between a pair of perfectly conducting planes?
**(16)** - Prove that the velocity of propagation?
**(16)**

**UNIT IV - RECTANGULAR WAVEGUIDES**

**Part-A**

**All questions – Two Marks:**

- What are the dominant mode and degenerate modes in rectangular wave – guides?
- A rectangular wave – guides has the following values l=2.54 cm, b= 1.27 cm waveguide thickness = .0127. Calculate the cut off frequency?
- Define wave impedance?
- Why TEM mode is not possible for rectangular wave – guides?
- Define characteristic impedance?
- Define attenuation factor?
- Draw a neat sketch showing the variation in the value of attenuation with frequency for TE, TM, and TEM mode for rectangular wave guide?

- Draw a neat sketch showing the variation in the value of wave impedance with frequency for TE, TM, and TEM mode for rectangular wave guide?
- Write down the expression for cut off wavelength and cut off frequency for rectangular wave guide?
- Write down the expression for cut off wavelength and cut off frequency for TE 10 mode?

- Write down the expression for guide wavelength and velocity of propagation for rectangular wave guide?
- Write down the expression for attenuation constant for TE 10 mode?
- Write down the expression for attenuation constant for TM 11 mode?
- What is cut off frequency?
- What is dominant mode? Name the dominant mode in TE and TM waves?

**Part-B**

- Derive the field configuration, cut off frequency and velocity of propagation for TM waves in rectangular wave – guides?
**(16)** - Determine the solution of electric and magnetic fields of TE waves guided along rectangular wave – guides? `
**(16)** - Explain the wave impedance of a rectangular wave – guide and derive the expression for the wave impedance of TE,TM, and TEM mode?
**(16)** - Discuss the characteristics of TE and TM waves and also derive the cut off frequency and phase velocity from the propagation constant?
**(16)** - Derive the expression for attenuation of TE10 waves in rectangular wave guide?
**(16)** - Derive the expression for attenuation of TM 11 waves in rectangular wave guide?
**(16)** - Explain about excitation modes in rectangular wave guide?
**(16)** - Explain about dominant mode in rectangular wave guide?
**` 16)** - Determine the solution of electric and magnetic fields of TM waves guided along rectangular wave – guides?
**(16)** - Explain about characteristic impedance in rectangular wave guide?
**(16)** - Explain about degenerate mode in rectangular wave guide?
**(16)**

**UNIT V - CIRCULAR WAVE GUIDES AND RESONATORS**

**Part-A**

**All questions – Two Marks:**

- What is cavity resonator?
- Define the quality factor of the cavity resonator?
- Define loaded and un loaded Q cavity resonator?
- Give the application of circular wave guide?
- Why rectangular or circular cavities can be used as microwave resonators?
- Define Bessel’s function?
- What is Eigen value?
- What is dominant mode of TM and TE waves in circular waveguide?
- Write expressions for the Eigen value and cut off wave number for the TE mode?
- Write expressions for the Eigen value and cut off wave number for the TM mode?
- Expression for the resonant frequency of the rectangular cavity resonator?
- Expression for the resonant frequency of the circular cavity resonator?
- Expression for the quality factor of the circular cavity resonator?
- Expression for the quality factor of the rectangular cavity resonator?
- Define cavity tuning?
- Define resonant cavity?
- Give the application of microwave resonator?

**Part-B**

- Derive the Q-factor of a rectangular cavity resonator?
**(16)** - Derive the TM wave components in circular wave guides using Bessel functions?
**(16)** - What is meant by cavity resonator? Derive the expression for the resonant frequency of the rectangular cavity resonator?
**(16)** - Derive the expression for cut off frequency, phase constant and phase velocity of wave in a circular wave guide?
**(16)** - Derive the expression for the resonant frequency of the circular cavity resonator?
**(16)** - Derive the expression for the resonant frequency of the semi circular cavity resonator?
**(16)** - Derive the TE wave components in circular wave guides using Bessel functions?
**(16)** - Derive the expression for the wave impedance in circular wave guide?
**(16)** - Derive the field strength or equation in cylindrical co – ordinates systems?

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