__FREE PDF AMW-ANTENNAS AND MICROWAVE ENGINEERING Unit Wise 16 Marks Important Questions__

ANTENNAS AND MICROWAVE ENGINEERING Unit Wise 16 Marks Important Questions |

## UNIT-I

1. Explain in detail, the physical concept of radiation. Illustrate with necessary diagrams, how the electromagnetic fields guided within the transmission line and antenna, finally get “detached” from the antenna to form a free-space wave.

2. Explain in detail the field regions of antenna. What is the significance of Fraunhofer zone?

3. Define and explain in detail the terms Gain, Directivity, beam width, Bandwidth and Polarization of an antenna.

4. Define and describe the following parameters of an antenna:

(i)Radiation Pattern (ii)Radiation intensity (iii)Directivity (iv)Effective aperture

5. Define and explain the significance of the following antenna parameters:

(i) Antenna brightness temperature (ii) Antenna noise temperature

(iii) Antenna Efficiency (iv)Half Power Beam width

6. (i)How are antennas classified based on radiation characterstics? Explain with an example, the radiation pattern characteristics of omnidirectional antenna.

(ii)Explain in detail about:1)Radiation pattern lobes 2) Aperture efficiency 3) Beam solid angle

7. (i)Derive FRIIS transmission formula.

(ii) A radio link has a 20 W transmitter connected to an antenna of 2.5 m2

effective aperture at 5 GHz. The receiving antenna has an effective aperture of 0.5m2

and is located at a 15 Km line of sight distance from the transmitting antenna. Assuming lossless, matched antennas, find the power delivered to the receiver. (Nov 2019)

8. Explain the various loss and gain terms considered in the microwave link budget. Also discuss on the significance of link margin and fade margin of a communication system.

9. Define and explain the various parameters used to analyse the noise characteristics of a microwave receiver.

10. Discuss on the noise analysis of a Microwave receiver front end, including antenna and transmission line contributions.

11. Obtain expression for the field and power radiated by an oscillating dipole and calculate the radiation resistance. (Nov 2020)

12. i) What is impedance matching ? Explain about the techniques used to solve the impedance matching problems.

ii) Using Friss transmission formula find the maximum power received at a distance of 1 Km over a free space. A 100 MHz circuit consisting of a transmitting antenna of 30 dB gain and a receiving antenna with a 25 dB gain is used. The power input to the transmitting antenna is 150 W. (Nov 2020)

13. (i)Define and explain the significance of the following antenna parameters:

a. Radiation resistance b. Antenna temperature

(ii)How are antennas classified based on radiation characteristics? Illustrate with

examples.(NOV/DEC 2021)

14. Examine the Noise Characterization of a microwave receiver.(NOV /DEC 2021)

**ANTENNAS AND MICROWAVE ENGINEERING-AMW Question Bank with Answers Pdf**

## UNIT-II

1. Derive the expression for the field quantities radiated from a / 2 dipole and prove that the radiation resistance to be 73 Ohms.

2. (i) Compare uniform and tapered aperture antennas. Give examples.

(ii)With neat diagrams, explain parabolic reflector antenna and its Cassegrain feeding system.

3. Discuss the principle working of Parabolic reflectors. Explain the various feed techniques their relative merits and demerits. Discuss the role of f/d ratio in the parabolic reflectors (f- focal length,D – diameter of reflector). (May 2019)

4. (i) Explain the radiation mechanism of Microstrip antenna. (ii) Write short notes on Slot antenna. (Nov 2019) (Nov 17)

5. Design a 50 to 200 MHz log periodic dipole antenna for gain corresponds to scale factor 0.8 and space factor 0.15. Assume the gap spacing at the smallest dipole is 3.6 mm. (May 18)

6. Explain in detail about log periodic antennas. What is the need for feeding from end with shorter dipoles and the need for transposing the lines? Also discuss the effects of decreasing Î±. (Nov/Dec 2016)

7. Design a Log-Periodic dipole array with 7 dBi gain and a 4 to 1 bandwidth. Specify apex angle Î±, scale constant k and the number of elements. (Nov/Dec 2015)

8. Explain the design procedure for the construction of log periodic antenna. (May 2016)

9. Explain the principle of operation of Log periodic antenna with neat schematic diagram. (Nov/Dec 2016) (May 2019)

10. Discuss in detail how a spiral antenna behaves as a frequency independent antenna. (May 2014)

11. (i) What is Log periodic antenna? Explain the principle of Log periodic antenna. (ii) Design a 50 – 200 MHz log – periodic antenna to obtain a gain corresponds to scale factor 0.8 and space factor 0.15(Nov 2019)

12. Explain in detail the radiation from a slot antenna and their feed systems. (Nov/Dec 2016)

13. (i) Explain the principle of parabolic reflector antenna and discuss on different types of feed used with neat diagram.

(ii) The diameter of a parabolic reflector is 2m. For operation at 6GHz, find the beam width between first nulls and the gain. (Nov 17)

14. Explain the principles of operation of Horn antenna and discuss the various forms of Horn antenna. Obtain the design equations of Horn antenna. (May 18) (May 2019)

15. Explain the radiation mechanism of a microstrip antenna with suitable illustrations. With suitable figures explain the various feed techniques. (May 18)

16. Explain the principle of operation and applications of loop antenna.

17. i) Explain in detail about Loop antenna. Derive the expression for fields at Far region. ii) Explain how a Loop antenna is utilized for determining the direction of an incoming radio signal. (Nov 2020)

18. i) With neat necessary diagrams, explain parabolic reflector antenna and its different types of feeding system. ii) Briefly explain about frequency independent planar Log spiral antenna. (Nov 2020)

19. Discuss the parabola geometry that makes it suitable for antenna reflectors. Develop an antenna employing a parabolic reflector that is likely to be a highly directive receiving antenna.(NOV/DEC 2021)

20. Illustrate the radiation characteristics of microstrip antenna with different types of feeding structures and mention its applications.(NOV/DEC 2021)

21. Explain in detail about Loop antenna. Derive the expression for fields at Far region.(NOV/DEC 2021)

### EC8701 ANTENNAS AND MICROWAVE ENGINEERING- AMW Syllabus

## UNIT-III

1. (i) Write a note on binomial array? (ii) Draw the pattern of 10 element binomial array with spacing between the elements of 3Î» / 4 and Î» / 2 .

2. Derive the expressions for field pattern of broad side array of n point sources.(May 2013)(Nov 2019)

3. Two identical radiators are spaced d = 3Î» / 4 meters apart and fed with currents of equal magnitude but with 1800 phase difference. Evaluate the resultant radiation and identify the direction of maximum & minimum radiation. (May 2015)

4. For a 2 element linear antenna array separated by a distance d = 3Î» / 4 , derive the field quantities and draw its radiation pattern for the phase difference of 450. (Dec 2012)

5. Derive the expressions for field pattern of end-fire array of n sources of equal amplitude and spacing. (May 2012)

6. An antenna array consists of two identical isotropic radiators spaced by a distance of d= Î» / 4 meters and fed with currents of equal magnitude but with a phase difference Î» . Evaluate the resultant radiation for Î» = 0 0 and thereby identify the direction of maximum radiation. (Dec 2011)

7. Describe a broadside array. Deduce an expression for the radiation pattern of a broadside array with two point sources.

8. Plot the radiation pattern of a linear array of 4 isotropic elements spaced Î»/2 apart and fed out of phase with equal currents.

9. (i) Derive Array factor of an Uniform linear array of n sources. Explain the significance of array factor. (Dec 2013)

(ii) Compare End fire and Broadside array. (May 2014)

10. Explain in detail about: 1) adaptive arrays 2) Phased arrays.(Nov 2019)

11. Obtain the expression for the field and the radiation pattern produced by a N element array of infinitesimal with distance of separation Î» / 2 and currents of unequal magnitude and phase shift 180 degree. (May 2016)

12. (i)Using pattern multiplication determine the radiation pattern for 8 element array separated by the distance Î» / 2 .

(ii) Write short notes on tapered array and phased array. (May 2016)

13. Develop a treatise on the following forms of arrays: (Nov/Dec 2015)

(i)Linear array (ii)Two-element array (iii)Uniform array (iv)Binomial array

14. Derive and draw the radiation pattern of 4 isotropic sources of equal amplitude and same phase. (April/May 2017)

15. (i) Describe the principle of phased arrays and explain how it is used in beam forming. (April/May 2017)(Nov/Dec 2016)

(ii) Write short notes on binomial arrays. (April/May 2017)(Nov/Dec 2016)

16. Derive the expression for the array factor of a linear array of four isotropic element spaced Î»/2 apart fed with signals of equal amplitude and phase. Obtain the directions of maxima and minima.(Nov17)

17. (i) Explain in detail the Binomial array and derive the expression for the array factor. Also obtain the excitation coefficients of a seven element binomial array.

(ii)What is phased array?(Nov 17)

18. Derive the expression for the array factor of a linear array of four isotropic element spaced Î»/2 apart fed with signals of equal amplitude and phase. Obtain the directions of maxima and minima. (May 18)

19. Design a broadside Dolph-Tschebyscheff array of 10 elements with spacing‘d’ between the elements and with a major-to-minor lobe ratio of 26 dB. Find the excitation coefficients and form the array factor. (May 18)

20. i) What is broad side array ? Deduce the expression for the Radiation pattern of a broadside array with n- vertical dipoles.

ii) Design a 4 element broadside array of Î»/2 spacing between elements.(Nov 20)

21. i) What is non-uniform excitation amplitudes ? Draw the pattern of 10 elements binomial array with spacing’s between the elements of Î»/2.

ii) Write short notes about Active antenna.(Nov 20)

22. i) A broad casting station (500 to 1000 KHz band) requires a pattern in the horizontal plane fulfilling the conditions as given below. The max. field intensity with as little variation as possible, is to be radiated in the 90° sector between NE and WE. No nulls in the pattern can occur in this sector. The nulls must be present in the due east and due SW directions in order to prevent interference with other stations in these directions. ii) What is the need of smart antennas ? Briefly explain about Adaptive arrays.(Nov 20)

23. Determine the field pattern of an array of n-elements characterized by in-phase sources. (NOV/DEC 2021)

24. Describe in detail about smart antennas and its applications. (NOV/DEC 2021)

25. A uniform linear array consists of 16 isotropic point sources with a spacing of Î»/4. If the phase difference is -90o . Determine the directivity, HPBW, beam solid angle and effective apertures.(NOV/DEC 2021)

### ANTENNAS AND MICROWAVE ENGINEERING-AMW LAB VIVA

## UNIT-IV / PART-B

1. Explain how Directional coupler can be used to measure reflected power. Also Derive scattering Matrix for Two hole Directional coupler. (Nov2012) (May 2013 & 2015) (Nov 2019)

2. Derive and explain the properties of H-plane tee and give reasons why it is called shunt Tee. (Nov 2012) (May 2017)

3. Derive and explain the properties of E-plane tee and give reasons why it is called series Tee. (Nov 2014) (Dec 2015) (May 2013) (May 2017)

4. (i)Derive the equation for scattering matrix of magic Tee.(Nov 2013) (Nov 2017)

(ii) Find the directivity in db for a coupler if the same power is applied in turn to input and output of the coupler with output terminated in each case in matched impedance. The auxiliary output readings are 450mW and 0.710ÂµW. (May 2014)

5. Explain the working of Attenuators with neat diagram. (May 2014)(Dec 2015)

6. Explain Physical structure, negative resistance, power output & efficiency of IMPATT Diode.(Nov 2013) (May 2013) (Dec 2015) (May 2015)

7. Briefly Explain Gunn Effect & modes of operation of the Gunn Diode. Explain the working

principle of Gunn diode with two valley model and plot its characteristics. (Dec 2015) (May

2015) (Nov 2019)

8. Derive the S matrix for a directional coupler and also verifying the properties of it (May 2018)

9. (i)Derive the S matrix H plane TEE.

(ii)Explain the mode of oscillation of gunn diode. (May 2018)

10. (i)Explain the construction of Magic Tee and derive its S-matrix.(Nov 2019)

(ii) Derive the scattering matrix for a directional coupler. (Nov 2018)

11. Describe the Gunn effect with the aid of two valley model theory

12. Explain the working principle and operation of multi-cavity Klystron amplifier and derive the expression for its output power. (Nov 2016)

13. Explain the working principle of Reflex klystron oscillator and derive output power & Efficiency. (Nov 2013) (Dec 2015) (Nov 2017)

14. Explain the operation of TWT Amplifier & write its characteristics. (Dec 2015) (Nov & May 2017)

15. Explain Ï€ mode of operation of Magnetron Oscillators mention few high frequency limitations. (May 2015)

16. A Reflex klystron is to be operated at frequency of 10 GHz, with dc beam voltage 300V, repeller 3 space 0.1 cm for 1 mode. Calculate PRFmax and corresponding repeller voltage for a beam 4 current of 20 mA.

17. A Reflex klystron is to be operated at frequency of 9 GHz, with dc beam voltage 600V, repeller 3 space 1 cm for 1 mode. Calculate electronic efficiency, output power and corresponding 4 repeller voltage for a beam current of 10 mA. The beam coupling coefficient is assumed to be 1.

18. A two-cavity klystron amplifier is tuned at 3 GHz. The drift space length is 2cm and beam current is 25mA. The catcher voltage is 0.3 times the beam voltage. It is assumed that the gap length of the cavity << the drift space so that the input and output voltages are in phase (Î² = 1). Compute (a) 1 Power output and efficiency for N= 5 (b) Beam voltage, input voltage and output voltage for 41 maximum power output of N= 5 mode.4

19. A two-cavity klystron amplifier operates at 5GHz with a dc beam voltage of 10KV and a 2 mm cavity gap. For a given input RF voltage, the magnitude of the gap voltage is 100 volts. Calculate the transit time at the cavity gap, the transit angle, and the velocity of the electrons leaving the gap.

20. An X- band pulsed conventional magnetron has the following operating parameters: Anode Voltage Vo = 5.5 KV, Beam current is 4.5 mA, Operating frequency 9GHz, Resonator conductance 2×10-4 mho, Loaded conductance 2.5 ×10-4 mho, Vane capacitance is 2.5 PF, Duty cycle 0.002, Power loss is 18.5 KW. Compute 1) Angular resonant frequency, 2) Unloaded quality factor 3) loaded quality factor, 4) external quality factor 5) circuit efficiency 6) electronic efficiency

21. A 250kw pulsed cylindrical magnetron has the following parameters. Anode voltage = 25Kv, peak anode current = 25 A, Magnetic field = 0.35Wb/m2 , Radius of the cathode = 4CM, Radius of the Anode = 8CM, Calculate efficiency of the magnetron, cyclotron angular frequency, Cutoff magnetic field. (May 2013) (Nov 2013) (May 2013) (Dec 2015) (May 2015)

22. Write a detailed note on cylindrical magnetron (Nov 2013) (Nov 2017)(Nov 2019)

23. A traveling wave tube (TWT) operates under the following parameters: Beam Voltage V0=3Kv; Beam Current I0=30ma; Characteristics impedance of helix =Z0=10â„¦; Circuit length =N=50m; Frequency f=10GHz. Determine: (i) gain parameters C (ii) Output power gain Ap in decibels. (iii) All four propagation constants. (Nov 2016)

24. With neat diagram explain the operation of two cavity Klystron amplifier and derive the equations for velocity modulation process. (May 2017)(Nov 2019)

25. (i) Draw a neat sketch showing the constructional features of a cavity magnetron and explain why magnetron is called as crossed field device.

(ii) Derive an expression for cut off magnetic field for a cylindrical magnetron. (Nov 2019)

26. A reflex klystron is operated at 8 GHz with dc beam voltage of 600 V for 1.75 mode, repeller space length of 1mm, and dc beam current of 9 mA. The beam coupling coefficient assumed to be 1. Calculate the repeller voltage, electronic efficiency and output power. Vo =600 V, L= 1mm,IO =9mA Î’0 = 1, f=8 GHz, n =2 or 1 3/4 mode. (May 2018)

27. (i) Draw the schematic of two cavity Klystron amplifier and explain the process of velocity modulation and bunching .Also derive the equation of velocity modulation.

(ii) With neat diagram, explain how amplification of RF wave is accomplished in Helix type TWT. (Nov 2018)

28. (i)Draw the cross sectional view of Magnetron tube and explain the process of bunching. Derive the expression for Hull cut off voltage. (ii) Compare TWT and Klystron(Nov 2018)

29. A two cavity Klystron amplifier has the following specifications. Beam Voltage Vo= 900V;Beam current Io=30mA;Frequency f= 8 GHz. Gap spacing in either cavity d= 1mm ;Spacing between center of cavities L= 4cm Effective shunt impedance Rth = 49kâ„¦. Determine (i)Electron velocity(ii) Dc transit time of electron (iii)Maximum input voltage (iv)Voltage gain(Nov 2018)

30. Write short notes on the following Microwave passive devices along with S parameters. i) Directional Couplers. ii) Attenuator. (Nov 20)

31. i) With the help of two valley theory, explain how negative resistance is created in Gunn diodes. ii) Describe the construction and operation of a basic magnetron. (Nov 20)

32. i) Describe with neat sketch the construction details and principle of operation of Klystron amplifier and derive the expression for its optimum bunching distance Lopt. (Nov 20)

33. Discuss the working principle of Gunn diode as a transferred electron device with two valley model. Also draw the structure, equivalent circuit and V-I characteristics of Gunn diode.(NOV/DEC 2021)

34. Illustrate the operation and properties of power divider; also derive the S-parameters.(NOV 2021)

### EC8701 ANTENNAS AND MICROWAVE ENGINEERING- AMW Notes

## UNIT-V / PART-B

1. What is a matching network? Why is this required? Briefly explain T &Ï€ matching networks. (Nov 2012& 2013)

2. Explain in detail about Microstrip line matching network with neat diagram. (May 2017)

3. Discuss the smith chart approach to design the L section and T section matching networks

4. i)Explain the significance of impedance matching and tuning.

ii) What are the design issues in T and Pi matching network and explain. (Nov 2019)

5. Design an L-section matching network to match a series RC load with an impedance ZL= (200- j100) Î© to 100Î© line at frequency of 500 MHz. (use smith chart).

6. Design a matching network to match a ZL= (10+j10) Î© to 50Î© line. Specify the values of L and C at frequency of 1GHz. (use smith chart). (May 2014)

7. Using smith chart design any two possible configurations of discrete two element matching networks to match the source impedance Zs= (50+j25) â„¦ to the load ZL = (25-j50) â„¦. Assume Zo= 50â„¦, f=2GHz. (May 2015)

8. Design a T-type matching network that transforms a load impedance into a input impedance and that has a maximum nodal quality factor of 3. Compute the values for the matching network components, assuming that matching is required at GHz.

9. Discuss in detail the steps involved in microwave filter design.

10. (i)Write mathematical analysis of amplifier stability (Nov/Dec 2018, April/May 2019)

(ii)A microwave amplifier is characterized by its S parameters. Derive equations for power gain, available gain and transducer gain. (May 2018) ( May 2019) (Nov 2019)

11. An RF Amplifier has the following S-parameters: . Furthermore, the input side of the amplifier is connected to a voltage source with and source impedance . The output is utilized to drive an antenna which has an impedance of . Assuming that the S-parameters of the amplifier are measured with reference to a characteristic impedance, find the following quantities: (a) Transducer gain , Unilateral transducer gain , available gain , operating power gain G and (b) Power delivered to the load , available power and incident power to the amplifier . (Nov 2017) (Nov 2019)

12. Investigate the stability regions of a transistor whose S-parameters are recorded as follows: S12=0.2 ∟-10˚;S11=0.7∟ -70 ˚;S21=5.5 ∟85 ˚;S22=0.7∟ -45 ˚; at 750 MHz. (Nov 2016)

13. Explain in detail noise figure in an amplifier.

14. Discuss in brief steps involved in the design of Low Noise Amplifiers.

15. Elaborate on Microwave Power amplifiers and their efficiencies.

16. Explain in detail the types of mixers in microwave circuits.

17. Write a detailed note on microwave oscillator design.

18. i) Write the mathematical analysis of amplifier stability.

ii) Design a microwave amplifier for maximum transducer power gain. (Nov 20)

19. Discuss various aspects of amplifier power relation for RF transistor amplifier design. (NOV/DEC 2021)

20. Explain the various stabilization methods and stability considerations for RF transistor amplifier design.(NOV/DEC 2021)