UNIT I

ANTENNA BASICS & DIPOLE ANTENNAS

1. Effective length of receiving antenna is………. [ ]

(a)-Voc/E (b)Voc/E (c)VocE (d)None

2. For s Hertz dipole antenna, the half power beam width (HPBW) in the E- plane is [ ]

(a) 360 degree (b) 180 degree

(c) 90 degree (d) 45 degree

3. What is the polarization of a discone antenna? [ ]

(a) Vertical (b) Horizontal

(c) Circular (d) Spiral

4. The radiation fields are nothing but far fields____ [ ]

(a)True (b) false (c) either true or false (d) none

5. The impedance of an isolated antenna when used for receiving is………….when use for

transmitting [ ]

(a)different (b)same

(c) complex (d)none

6. The following terms spell the same meaning in reference to an antenna (GATE 2014) [ ]

(a) near field & principal zone (b)near field & Fresnel zone

(c) near field & fraunhofer (d)far field & Fresnel none

7. Sometimes antennas are terminated to make them ……….. [ ]

(a)operate (b)non resonant

(c)both a&b (d)none

8. The polarization of a wave with electric field vector = (𝑎 𝑥 + 𝑎 𝑦) [ ]

a) Linear (b) Elliptical

(c) Left hand circular (d) Right hand circular

9. Power radiated per unit area in any direction is given by the pointing vector…….. [ ]

(a)P=E*H (b)P=

(c)P=

(d)none

10. Maximum effective aperture is given by the relation….. [ ]

(a)V2/2RrP (b)V

2/4RrP

(c)V/4RrP (d)none

11. Relation betwe en maximum aperture and directive is….. [ ]

(a)D=

Aem (b)D=

Aem (c)Aem=4π (d)none

12. The reciprocity theorem can be used to drive the following…. [ ]

(a)equal of effective length (b)equality of directive pattern

(c)equal of directives (d)all of the above

13. …….defined as 2π*

[ ]

(a) Q of antenna (b)Q of resonant circuit

(b) band width (d)none

14. Beam efficiency εM= [ ]

(a)

(b)

(c)

(d)none

15. Directivity _ Beam area relation…… [ ]

(a)

(b)

(c)

(d) none

16. Relation between Gp & Gd in VHF and UHF range [ ]

(a) Gp=-Gd (b) Gp=Gd (c)both a &b (d)none

17. Scattering ratio β=_____ [ ]

(a)

(b)

(c)

(d)none

18. Equivalent noise temperature is given by the relation [ ]

(a)F=1+

(b) F=1-

(c) F=

(d)none

19. Beam area in terms of half power points is ΩA= [ ]

(a) ѲHP (b)ǾHP (c) ѲHP ǾHP (d)none

20. Solid angle dΩ is__________ [ ]

(a) sinѲdѲdǾ (b) cosѲdѲdǾ (c) sin2ѲdѲdǾ (d)none

21. A straight dipole radiator fed in the centre will cause max. radiation (GATE 2014) [ ]

(a)in the plane // to its axis (b) in the plane normal to its axis

(c)at the plane of feed (d)at its extreme ends

22. The radiation resistance of half wave dipole is___ Ω. [ ]

(a)100 (b)73 (c)150 (d)none

23. The radiation resistance of quarter wave monopole is____ Ω. [ ]

(a)73 (b)36.5 (c)40 (d) none

24. The current distribution in a half wave dipole is___ [ ]

(a) non-sinusoidal (b) sinusoidal (c)in-phase (d)none

25. The current distribution in an alternating current element is____ [ ]

(a) non-sinusoidal (b) sinusoidal (c)constant (d)none

26. Current distribution in very short dipole is____ [ ]

(a) triangular (b) sinusoidal (c)constant (d)none

27. Radiation resistance of current element is____ [ ]

(a)100(

)

2 (b) 200(

)

2 (c)80π

2(

)

2 (d) none

28. Radiation pattern of a short dipole in horizontal plane is a ______ [ ]

(a)rectangle (b)triangle (c)circle (d)none

29. Directional pattern of horizontal half wave dipole is_____ [ ]

(a)figure of eight (b)circle (c)oval (d)none

30. The radiation pattern for a one half wavelength dipole is____ [ ]

(a) figure of six (b) figure of eight (c)only main lobe (d)none

31. The measure of solid angle is a _______ [ ]

(a)steradian(Sr) (b)radian (c)degrees (d)none

32. The measure of plane angle is_____ [ ]

(a)steradian(Sr) (b)radian (c)degrees (d)none

33. Steradian=__________________ degrees [ ]

(a)3282 (b)41253 (c)2134 (d)none

34. The resolution of an antenna=_______________ [ ]

(a)HPBW/2 (b)FNBW/2 (c) FNBW/4 (d)none

35. The resolution of an antenna=_______________ [ ]

(a)HPBW/2 (b)FNBW/2 (c) FNBW/4 (d)none

36. An antenna or aerial is a means of ____________ or receiving radio waves [ ]

(a) transforming(b) coupling (c) radiating (d)none

37. An antenna can be defined as ________ of EM waves [ ]

(a) sensor (b) guiding (c) controlling (d)none

38. The radiation pattern of an antenna is ________ pattern [ ]

(a) 2D (b) 3D (c) 1D (d) none

39. The field radiation pattern is f(θ,φ)=sinθ, then the power radiation pattern is _____ [ ]

(a) Pd (θ,φ)= sinθ (b) Pd (θ,φ)= sin3θ (c) Pd (θ,φ)= sin

2θ (d) none

40. The bandwidth of the antenna is inversely proportional to _________ of antenna [ ]

(a) Q-factor(b) S-factor (c) F-factor (d) none

2 MARK QUESTIONS

1. Define an antenna.

2. What is meant by radiation pattern?

3. Formulate Radiation intensity?

4. Calculate the radiation resistance of a dipole antenna of the length

m.

5. Define Beam efficiency?

6. Define Directivity?

7. What are the different types of aperture?

8. Calculate front to back ratio (FBR) of an antenna expressed in decibels if the antenna radiates

3KW in its optimum direction while 300W in opposite direction.

9. Define Aperture efficiency?

10. What is meant by effective height?

11. What are the field zones?

12. Find the length of half wave dipole at 30MHz.

13. What is meant by Polarization?

14. What is meant by front to back ratio?

15. The radiation efficiency of a certain antenna is 95%, and the input power given to that Antenna is

0.4W.Then how much power is radiated?

16. What is radiation resistance?

17. What is meant by antenna beam width?

18. Define reciprocity Theorem?

19. What is meant by isotropic radiator?

20. A radio link has a 50W transmitted connected to an antenna of 2.5 effective aperture at 5 GHz.

The receiving antenna has an effective aperture of 0.5 and it’s located at a 15 km line of sight

distance from the transmitting antenna. Assuming lossless, match antennas, find the power

delivered to the receiver.

10 MARK QUESTIONS

1. Explain the following

i) Antenna gain ii) Antenna temperature iii) Retarded potential.

2. Explain the following

i) Antenna field zones ii) Antenna radiation pattern iii) Radiation intensity iv) Beam efficiency

3. (a) Define isotropic radiator, gain & beam width of an antenna

(b) Discuss the shape impedance considerations.

4. (a) Explain basic Maxwell’s equations.

(b) The radiation resistance of an antenna is 72Ω and loss resistance is 8Ω. What is the directivity

if the power gain is 16.

5. (a) Explain radiation and Beam efficiency

(b) An antenna has a field pattern given by

E(Ө)=cosӨcos2Ө for 0≤Ө≤

Find i) The half power beam width (HPBW) , ii) Beam width between first nulls (FNBW).

6. (a) Derive the expression for radiation resistance Rr=80π2(dl/λ)

2.

(b) Write about Effective area and Beam width.

7. (a) Show that radiation resistance of half wave dipole is 73Ω.

(b) Explain the terms i)Effective aperture area ii) Directivity iii) Polarization

8. (a) Explain about thin linear wire antennas.

(b) Determine the expression for radiation resistance for a monopole antenna

9. (a) Derive the Field expression for an oscillating current element.

(b) Explain beam width and directivity

10. (a) Explain about radiation power & effective height

(b) Explain the radiation characteristics of dipoles

11. Show that maximum effective aperture of a short dipole is 0.119 and also that

directivity is 1.5.

12. A grounded vertical antenna has an effective height of 113.3m and operates at a

wavelength of 18.8 km with RMS value of base current 725 A. Find E & H fields at a distance of

75 km and its power radiated.

UNIT II

VHF, UHF AND MICROWAVE ANTENNAS – I

1. One of the following is very useful as a multiband HF receiving antenna. This is

the [ ]

(a) Conical Horn (b) Folded Dipole (c) Log-Periodic

(d) Square Loop

2. Loops are extensively used in_____ [ ]

(a)radio receivers (b)aircraft receivers (c)UHF Transmitters (d)all

3. The far field components of loop antennas is Eφ=______ [ ]

(a) [ ]

(b) [ ]

(c)

[ ]

(d)none

4. Radiation resistance of small loop Rr is______ [ ]

(a)197(

)

4 (b) 200(

)

4 (c) 400(

)

4 (d)none

5. Radiation resistance of large loop Rr is______ [ ]

(a)592(

)

(b) 700(

) (c) 3720(

)

(d)none

6. Directivity of small loop is_____ [ ]

(a)D=1/2 (b)D=4/2 (c)D=3/2 (d)none

7. Directivity of large loop is_____ [ ]

(a)D=0.682(

)

(b) 26(

)

(c)0.054(

)

(d)none

8. The magnetic component of loop antenna in θ direction Hθ is ________ [ ]

(a) [ ]

(b) [ ]

(c)

[ ]

(d)none

9. VHF band is______________ [ ]

(a) 3-30KHz (b)30-300MHz (c)3-30MHz (d)none

10. SHF band is ____________ [ ]

(a)3000-30000MHz (b)3-30MHz (c) 300-3000MHz (d)none

11. Antennas operating over 3000 MHz are called _________________ antennas [ ]

(a)HF (b)VHF (c) UHF (d)Microwave

12. Typical antennas used in SHF band are _______________ [ ]

(a)parabolic reflectors (b)lens (c) yagi (d) both a & b

13. An antenna that is circularly polarized is (GATE 2011) [ ]

(a) Helical (b) Small circular loop (c) Parabolic reflector (d) Yagi-Uda

14. The parasitic element whose length is less than the driven element then it is called_ [ ]

(a)reflector (b)director (c)dipole (d)none

15 Which antenna has high input impedance & greater bandwidth_____________ [ ]

(a)horn (b)helical (c)yagi (d)folded dipole

16. Which antenna is used for space communaction systems_____________ [ ]

(a)horn (b)helical (c)yagi (d)folded dipole

17. Lens antennas used for microwaves are usually made of [ ]

a) (Polystrone b) Glass of low refractive index c) Paraboloid surfaces

d) Dielctric media having large refractive index

18. Yagi antenna produces _________ pattern [ ]

(a) bidirectional (b) unidirectional (c) multidirectional (d)none

19. Disadvantage of Yagi antenna is _______________ [ ]

(a)gain is limited (b) BW is limited (c) both a & b (d)none

20. The radiation resistance of tripole is __________________ [ ]

(a)93Ω (b)6 93Ω (c) 657Ω (d)none

21. When an antenna has a gain of 44db then assuming that the main beam of the

antenna is circular in cross section the beam width will be (GATE 2008) [ ]

a) 0.44560 b) 1.44560 c) 2.44560 d) 3.44560

22. The horn antenna is used with __________ & is used as a radiator [ ]

(a)EM wave (b) wave guide (c)UHF waves (d)none

23. A short parabolic right cylinder enclosed by parallel plates is called______ antenna [ ]

(a)pill box (b) cheese (c) pill box or cheese (d)none

24. HF band is____ [ ]

(a) 3-30KHz (b)30-300KHz (c)3-30MHz (d)none

25. UHF band is ____________ [ ]

(a)30-300MHz (b)3-30MHz (c) 300-3000MHz (d)none

26. Microwave band is ____ [ ]

(a)above 30KHz (b)above 30MHz (c)above 30GHz (d)none

27. Tower antenna is a ____antenna [ ]

(a)HF (b)LF (c)MF (d)VHF

28. One application of VLF is___ [ ]

(a) telegraphy (b)mobile (c)point to point communication (d)none

29. Radiation resistance of two wire folded dipole is_____ [ ]

(a)292Ω (b)657Ω (c)400Ω (d)none

30. Folded dipole has ___input impedance [ ]

(a)low (b)high (c)moderate (d)none

31. Yagi-Uda array consists ____ [ ]

(a)one reflector (b)one driven element (c)one or more directors (d)all the above

32. Parasitic elements are___ [ ]

(a)reflector (b)director (c)driven element (d)both a&b

33. The parasitic element whose length is greater than the driven element then it is called_ [ ]

(a)reflector (b)director (c)dipole (d)none

34. The parasitic element whose length is less than driven element then it behaves like ___in nature.

[ ]

(a) inductive (b)capacitive (c)resistive (d)none

35. A simple broad band VHF & UHF antenna is _____ [ ]

(a)helical antenna (b)horn antenna (c)yagi antenna (d)none

36. Helical antenna provides _______polarization characteristics [ ]

(a)circular (b)linear (c)vertical (d)horizontal

37. Pitch angle α=____ [ ]

(a)cos-1

(s/πd) (b) cos-1

(πd /s) (c) tan-1

(s/πd) (d) tan-1

(πd /s)

38. ____ antenna may be regarded as a flared out or opened out wave guide. [ ]

(a)horn (b)helical (c)yagi (d)folded dipole

39. The principle of equality of path length is known as___ [ ]

(a)hygens principle (b)fermats principle (c)Helmholtz (d)none

40. Directivity of pyramidal horn antenna D=_____ [ ]

(a)

(b)

(c)

(d)

2 MARK QUESTIONS

1. What is a dipole antenna?

2. What is a half wave dipole?

3. What is the radiation resistance of a half wave dipole?

4. Find the radiation resistance of a circular loop antenna of radius 0.3183 m operating at 1 MHz.

The radius of wire used is 0.4m, conductivity of wire is 57 mS/m .

5. Give an expression of radiation resistance of a small loop

6. Determine the directivity of loop antenna having radius of 1m when it is operated at 0.9 MHz.

7. What are Electrically Small loop antennas?

8. What are electrically large loop antennas?

9. List out the uses of loop antenna?

10. Calculate the directivity of pyramidal horn antenna with an aperture of size 12 cm x 12 cm

operating with 3.2 cm wavelength.

11. What are the types of radiation modes of operation for an helical antenna?

12. Which antenna will produce circularly polarized waves?

13. List the applications of helical antenna?

14. What is parasitic array?

15. Define axial ratio.

16. What is a loop antenna?

17. What are the parameters to be considered for the design of a helical antenna?

18. How to increase the radiation resistance of a loop antenna?

19. Calculate the directivity of 20 turn helics with α = and circumference equals to one

wavelength.

20. Calculate the power gain of an optimum horn antenna approximately with a square aperture of

10 on a side.

10 MARK QUESTIONS

1. (a) Discuss directivity of small and large loop.

(b) Compare fields of small loop and short dipole.

2. (a) Explain about the construction and characteristics of helical antenna

(b) Discuss about the horn antenna types & its characteristics

3. (a) Explain about construction and operation of Yagi-Uda antenna.

(b) What are the practical design considerations for Monofilar helical antenna in normal mode?

4. (a)Discuss about the helical antenna geometry, axial mode of radiation and its applications.

(b) Discuss the design considerations of pyramidal horn antenna.

5. (a) Discuss the types of horn antennas.

(b) What are parasitic elements &where they are used?

6. (a) Derive the expression for radiation resistance of small loop antenna

(b)Write short notes on i) folded dipole antenna ii) Yagi-Uda array iii) Horn antenna

7. (a)Give the applications of helical antennas

(b)Discuss the types of horn antennas

8. (a).State and Explain Fermat’s principle

(b).What is parasitic elements and where they are used & discuss features of optimum horns

9. Design Yagi-Uda antenna of six elements to provide a gain of 12db if the operating frequency is

200 MHz.

10 Design 10 turns helix to operate in axial mode for optimum design,

a. Determine the circumference ( , pitch angle ( in decrease) separation between turns

( .

b. Determine the Relative wave velocity (free space) Along the wire of helix for ordinary

end- fire design, Hansen-woodyard end –fire design.

c. Find Half power beam width of the main lobe (in decrease)

d. Find the axial ratio (in decibels)

UNIT III

VHF, UHF AND MICROWAVE ANTENNAS – II

1. Microstrip antenna is a------------------- antenna [ ]

(a)low profile (b)high profile (c)medium profile (d)none

2. Patch antennas used at frequency’s above………………… [ ]

(a)50mhz (b)10mhz (c)100mhz (d)10000mhz

3. The frequency of operation of patch antenna is [ ]

(a)

√ (b)

(c)

√ (d)none

4. Microstrip antenna is also known as [ ]

(a)patch (b)slot (c)printed (d) both a &b

5. The f/d ratio of parabolic reflector is lies between

(a)1 to 5 (b)0.5 to 0.7 (c) 0.25 to 0.50 (d) 0.1 to 0.5 [ ]

6. Patch antennas have ……………………….. bandwidth [ ]

(a)Narrow (b)Wide (c) Medium (d)High

7. The characteristic impedence of patch antenna is [ ]

(a) √

(b) ) =

√ (c) =

√ (d) )

8. The directivity of patch antenna is ……………………….. ]

(a)4 (b) 3 (c) 2 (d) 1

9. The size of the patch antenna is …………………………….. [ ]

(a)small (b) large (c)very large (d)none

10. The limitations of patch antennas are [ ]

(a)narrow bandwidth (b) inefficiency (c)both (a) & (b) (d)none

11. A rectangular patch antenna produces …………………..pattern [ ]

(a)pencil beam (b) fan beam (c)wide beam (d) none

12. The important application of patch antenna is [ ]

(a)mobile phone market (b)telemetry (c)telegraphy (d)none

13. One of the practical antennas in µw frequency ranges are [ ]

(a) yagi antenna (b)parabolic reflector (c) helical (d)none

14. The equivalent circuit of earth is [ ]

(a) Series RC circuit (b) Series RL circuits

(c) Series RLC circuit (d) a capacitance in shunt with a resistance

15. Ground wave field strength depends on [ ]

(a) The height of transmitting antenna (b) The height of receiving antenna

(c) the heights of both antennas (d) none

16. The equation of paraboloid will be given as [ ]

(a)𝑥 𝑧 𝑦 (b)𝑦 𝑧 (c)y=mx+c (d) none

17. Advantage of cassegrain feed is [ ]

(a)reduction in spill over (b)reduction in monor lobes

(c)both (a) & (b) (d)none

18. In parabolic reflector, some of the desired rays are not captured by the reflector [ ]

(a) spill over (b)focal length (c) illumination (d) none

19. The power gain of paraboloid reflector is given by [ ]

(a) (

)2

(b) ) (

)2

(c) ) (

)2

(d)none

20. Typical bandwidth of stepped lens antenna is (GATE 2010) [ ]

(a) 12% (b) 10% (c) 5% (d)6%

21. Earth is considered to be smooth if the roughness is………………………… [ ]

(a)<0.1 (b)>0.1 (c)=0.1 (d)none

22. Wavelength in free space & wavelength in a waveguide are the same [ ]

(a)true (b)false (c)neither true nor false (d)none

23. Field strength pattern is the variation of [ ]

(a)|E|vs θ (b)E2

vs θ (c)P vs θ (d)none

24. Power pattern is the variation of [ ]

(a)|E| vs θ (b)|E|3 vs θ (c)P vs θ (d)none

25. For far-field antenna measurement, R must be [ ]

(a)>=

(b)

(c) =

(d) =2(

2

26. At X-band , the size of patch antenna is of order of ………………… [ ]

(a)1 cm (b) 1m (c) 10cm (d)10m

27. A rectangular patch antenna produces …………………..pattern [ ]

(a)pencil beam (b) fan beam (c)wide beam (d) none

28. The important application of patch antenna is [ ]

(a)mobile phone market (b)telemetry (c)telegraphy (d)none

29. One of the practical antennas in µw frequency ranges are [ ]

(a) yagi antenna (b)parabolic reflector (c) helical (d)none

30. The equivalent circuit of earth is [ ]

(a) Series RC circuit (b) Series RL circuits

(c) Series RLC circuit (d) a capacitance in shunt with a resistance

31. VSWR is given by [ ]

(a)

(b) )

(c)

(d)

32. Absolute gain measurement method is also known as [ ]

(a) two identical antenna method (b)3-antenna method

(c) comparison method (d)none

33. The gain of antenna over an isotropic lossless antenna is given by [ ]

(a) =KD (b) =

(c) G=

(d)G=0

34. The disadvantage of lens antenna at low frequency’s is [ ]

(a) less weight (b) heavy &bulky (c) medium weight (d)none

35. When frequency < 10,000MHz, lens antenna as have excessive thickness which is

undesirable, this is over come by [ ]

(a)zoning (b)unzoning (c)dielectric lens (d)none.

36. The thickness of zoned dielectric lens is given by [ ]

(a) t=

(b)

(c)

(d)

37. Lens antenna uses the geometric optics principle known as [ ]

(a)fremat’s principle (b)hygun’s principle

(c)helrn-holtz principle (d)none

38. Lens antenna are used at frequency of above (GATE 2008) [ ]

(a)3000MHz (b)1000MHz (c)10,000MHz (d)none

39. Typical bandwidth of unstepped lens antenna is [ ]

(a) 12% (b) 10% (c) 5% (d)6%

40. Dielectric lens is also known as [ ]

(a)delay lens (b)E-plane lens (c)metallic lens (d)none

41. The thickness of un zoned dielectric lens is given by [ ]

(a) t=

(b)

(c)

(d)none

42. When comparing the gain & beam-width of lens antenna with reflectors the cost of lens

antenna is [ ]

(a)high (b)low (c)medium (d)none

2 MARK QUESTIONS

1. What is a patch antenna?

2. What are the limitations of MSA?

3. What are the advantages of MSA?

4. A parabolic reflector of 1.8m diameter is used at 6 GHz. Calculate beam width between first

nulls.

5. What is rectangular patch antenna?

6. What are the applications of MSA?

7. What is zoning?

8. A parabolic reflector having the diameter of 2.1 m and used at 9GHz. Calculate the gain.

9. Define H-plane metal lens antenna.

10. What is corner reflector?

11. What are the types of reflectors?

12. Mention Different methods of feeds of parabolic reflector antennas.

13. For what mouth parameter a parabolic reflector is a beam width between first nulls (BWFN) of

obtained when it is operated at 2.5GHz.

14. A parabolic reflector of diameter 1.4 m and its BWFN of which is operated at 2.5GHz, find

the reflector capture area.

15. Draw the curved surface of zoning and plane surface zoning.

16. List the applications of Lens antenna.

17. Differentiate between curved surface of zoning and plane surface zoning.

18. What is tolerance?

19. List out the advantages and disadvantages of lens antenna

20. Mention Different methods of feeds of microstrip antenna

10 MARK QUESTIONS

1. (a) Give the advantages and limitations of micro strip antennas

(b) Explain about micro strip antennas with neat diagrams.

2. (a) Write short notes on flare sheet & corner reflector.

(b) Explain the features of parabolic reflectors and what a reflector is & what are the types of

reflectors.

3. (a) Discuss the construction of rectangular patch antenna.

(b) What are the different parameters effects the characteristics of micro strip antenna explain?

4. (a) Explain about flare sheet, corner & paraboloidal reflectors.

(b) Discuss the application of image antenna concept to the 90o corner reflector.

5. (a) Explain about Zoned Lens antenna

(b) A parabolic reflector antenna with diameter 20 m is designed to operate at frequency of 6

GHz and illumination efficiency of 0.54.Calculate antenna gain and decibels.

6. (a) Explain the features of corner reflectors

(b) Explain the principle of operation of dielectric lens antenna.

7. (a) Explain the different tolerances in the lens antenna.

(b) Write short notes on non-metallic dielectric lenses.

8. (a). Explain the basic principle of operation in lens antenna & distinguish between different

types of lens antenna used in practice

(b).With a neat sketch explains the constructional features of parabolic reflector and obtain

expression for its curved profile.

9. A parabolic dish provides a power gain of 50 dB at 10 GHz with 70% efficiency find out

i) HPBW ii) BWFN iii) Diameter

10. (a). A parabolic dish provides a gain of 75db at a frequency of 15 GHz calculate capture area

of the antenna, it’s 3db and null beam widths.

(b). Explain about H-plane metal lens antenna.

UNIT IV

ANTENNA ARRAYS & MEASUREMENTS

1. Directivity of EFA is D=___________ [ ]

(a)2(L/λ) (b) 4(L/λ) (c) 8(L/λ) (d)none

2. Directivity of EFA with increased directivity is D=________- [ ]

(a)1.789[4

] (b) 11.4[2

] (c) 11.4[

] (d)none

3. The technique used in reduction of side lobe level is called_____ [ ]

(a) Tapering (b) Reduction (c) Minimization (d)none

4. The advantage of binomial array is___ [ ]

(a) Beamwidth (b)Gain (c)no side lobes (d)none

5. The beamwidth of binomial array is_________ [ ]

(a) large (b)small (c)moderate (d)none

6. Array factor or secondary pattern=_________ [ ]

(a)

(b)

(c)

(d)none

7. In broad side case θmax=__________ [ ]

(a)900 & 270

0 (b)60

0&120

0 (c)0

0 & 180

0 (d)none

8 . HPBW of broad side array is HPBW=______________ [ ]

(a)

(b)

(c)

(d)none

9. HPBW of End fire array is HPBW=_________ [ ]

(a)

√

(b)

√

(c)

√

(d)none

10. Directivity of BSA is D=___________ [ ]

(a)2(L/λ) (b) 4(L/λ) (c) 8(L/λ) (d)none

11. Phase angle ψ=________ [ ]

(a) βdcosθ (b) βdsinθ (c) βdtanθ (d)none

12. Antenna arrays are used to increase______ [ ]

(a)gain (b)directivity (c)both (d)none

13. Side lobe ratio (SLR)=__________ [ ]

(a)

(b)

(c)

(d)none

14. SLR is ______for a binomial array [ ]

(a)1 (b)0 (c)1.5 (d)none

15. The simplest type of broad side array is also known as__________ [ ]

(a)end fire couplet (b)collinear couplet (c)broad side couplet (d)none

16. .___________is a system of similar antennas oriented similarly to get greater directivity in a

desired direction. [ ]

(a) antenna gain (b)antenna array (c) directivity d)none

17. If the individual antennas of the array are equally spaced along a straight line then it is said to be

[ ]

(a)linear (b)collinear (c) non-linear (d)none

18. A broadside array consisting of 200 cm wavelength with 10 half-wave dipole spacing

10 cm. And if each array element feeding with 1 amp. current and operating at same

frequency then find the half power beamwidth___ (GATE 2010) [ ]

(a) 4 degree (b) 2 degree (c) 10 degree (d) 15 degree

19. An arrangement in which the principle direction radiation is perpendicular to the

array axis & also to the plane containing the array element is called _____________ [ ]

(a)end fire array (b)collinear array (c)broadside array (d)none

20. the arrangement in which the principal directive of radiation consider with the direction of array

axis called_______ [ ]

(a)end fire array (b)broad side array (c)collinear array (d)none

21. Rhombic antenna is _____antenna [ ]

(a)resonant (b) non-resonant (c)used in LF bands (d)none

22. Resonant antenna has a length in exact multiples of (GATE 2013) [ ]

(a)

(b)

(c)

(d)none

23. A broadside array operating at 100 cm wavelength consist of 4 half-wave dipoles

spaced 50 cm apart. Each element carries radio frequency current in the same phase

and of magnitude 0.5 A. The radiated power will be [ ]

(a)196W (b)73W (c) 36.5W (d)18.25W

24. In general , the element of the antenna array is a___________ dipole [ ]

(a)

(b)

(c)

(d)none

25. Unidirectional cosine power pattern has directivity of ___________ [ ]

(a)2 (b)4 (c) 6 (d)none

26. In BSA ,all the elements are placed parallel to each other & the direction of max.radiation is

always ______ to the axis of array [ ]

(a)parallel (b)mutual (c) perpendicular (d)none

27. In ESA ,all the elements are placed equally along a line & the direction of max.radiation is

______ with the direction of the axis of array [ ]

(a)parallel (b)mutual (c) coincides (d)none

28. Path difference= _______________ [ ]

(a) dcosθ (b) dsinθ (c) d2cosθ (d)none

29. Path difference interms of wavelength =________________ [ ]

(a) d/λcosθ (b) d/λsinθ (c) d.λcosθ (d)none

30. All the antennas are arranged co-axially i.e arranged end to end along a single line is called

___________________ array [ ]

(a)BSA (b)EFA (c) collinear (d)none

31. The common example of parasitic array with linear half wave dipoles as elements of array is

_______________________ [ ]

(a)EFA (b)Yagi-Uda array (c) collinear array (d)none

32 If the elements in the array are fed with currents of equal magnitude & phase along the line is

Called ______________ array [ ]

(a)linear (b)collinear (c) non-linear (d)uniform

33. In end fire case θmax=__________ [ ]

(a)900 & 270

0 (b)60

0&120

0 (c)0

0 & 180

0 (d)none

34. Directivity of EFA is D=___________ [ ]

(a)2(L/λ) (b) 4(L/λ) (c) 8(L/λ) (d)none

35. The condition for EFA with increased directivity is based on _____ conditions [ ]

(a)Hansen Woodyard (b) null (c) both a & b (d)none

36. Directivity of EFA with increased directivity is D=___________ [ ]

(a)2.14[6(L/λ)] (b) 4.24[2(L/λ)] (c) 1.789[4(L/λ)] (d)none

37. An Antenna under measurement, the distance between primary &secondary antenna should be

_________________ [ ]

(a) r≥2d2/λ (b) r≥4d

2/λ l (c) r≥d

2/λ (d)none

38. Measurement of gain is done by ___________ methods [ ]

(a)direct comparison (b) absolute (c) both a & b (d)none

39. In the absolute method of gain Measurement, G0= ___________________ [ ]

(a)4πr/λ[√Wr/Wt] (b) 2πr/λ[√Wr/Wt] (c) 8πr/λ[√Wr/Wt] (d)none

40. Measurement of antenna radiation efficiency ηR = _________________ [ ]

(a) G0/D (b) D/G0 (c) Pr/Pt (d)none

2 MARK QUESTIONS

1. What is point source?

2. What is meant by array?

3. What is meant by uniform linear array?

4. What are the types of array?

5. What is Broad side array?

6. Define End fire array?

7. What is collinear array?

8. Differentiate broad side and End fire array?

9. What is the principle of the pattern multiplication?

10. Calculate the directivity of given linear end fire array with improved directivity Hansen-

Woodyard uniform array of 10 elements with a separation of

between the elements.

11. What is tapering of arrays?

12. What is a binomial array?

13. What are the advantages of binomial array?

14. Distinguish between the isotropic and non-isotropic source?

15. Define Side Lobe Ratio.

16. Mention the methods of directivity measurements.

17. What are the sources of error while measuring the antenna parameters?

18. What is antenna measurement?

19. Find the minimum spacing between the elements in a broadside array of 10 isotropic radiators to

a have directivity of 7db

20. What is the advantage of pattern multiplication?

10 MARK QUESTIONS

1. (a) What is antenna array? Define point sources and uniform linear array.

(b) Write short notes on broad side and end fire arrays

2. (a) Two identical point sources separated by a distance ‘d’. Each source having a field pattern

given by = sinӨ. If d=

and the phase angle α=0. Derive an expression for total field and

also plot the pattern.

(b) Derive the expression for far field pattern of an array of two isotropic point sources at equal

amplitude & opposite phase.

2. (a) Write short notes on i)Array of two point sources ii) uniform linear array.

(b) A linear broad side array consists of four equal isotropic in phase point sources with

spacing

(overall length of array= .Find the directivity and the beam width.

3. (a) Explain pattern multiplication with appropriate examples.

(b) Derive the expression for far field pattern of an array of two isotropic point sources at

unequal amplitude & any phase

4. (a) write short notes on broad side and end fire arrays

(b) A broad side array operating at 10cm wavelength consists of 4 half wave dipole spaced 50 cm

each element carries radio frequency current in the same phase and of magnitude 0.5 amps.

Calculate the radiated power, half width of major lobe.

5. (a) Explain any two techniques for antenna gain measurement.

(b) Show that Directivity of BSA,L>>d is D0=2(d/λ)

6. Write short notes on i) Linear array ii) binomial Array iii) EFA with increased directivity

7. Explain the following antenna measurement techniques

i) Directivity ii) Pattern Measurement

8. (a) Explain near & far fields with respect to antenna measurements

(b) Define directivity. Give the procedure for the measurement of directivity.

9. (a). Explain the gain measurement using absolute & comparison methods.

(b). What is principle of pattern multiplication? List the advantages and disadvantages.

10. a). For end fire array consists of several half wave length long isotropic radiators is to have a

directive gain of 30. Find the array length and width of major lobe. What will be theses values for

broad side array.

b). Discuss the features of binomial arrays

UNIT V

WAVE PROPAGATION

1. Troposcatter propagation is related to [ ]

(a) SIDS (b) Faraday rotation (c) fading (d) atmospheric stroms

2. Short waves for long distance communication depends on [ ]

(a) Ionospheric waves (b)ground waves (c) direct waves (d) space waves

3. Attenuation in atmosphere is inversely proportional to the square of the frequency[ ]

(a) Yes (b) No (c) neither true nor false (d)none

4. When an EM wave whose MUF is 25MHz is incident at 40o , then fc is (GATE 2012)

[ ]

(a) 19.15MHz (b) 1.915MHz (c) 2MHz (d) 30MHz

5. The Optimun frequency is ___________ of MUF. [ ]

(a) 85% (b)70% (c) 30% (d) 15%

6. For Satellite tracking at VHF, helical antenna is often used because of [ ]

(a) Super refraction (b) Ionospheric refraction

(c) Faraday effect (d) troposcatter

7. Fading is nothing but [ ]

(a) Amplification of field (b) multiplication of field

(c) Subtraction of two fields (d) Change of field strength

8. The factor A depends on d as [ ]

(a)α

(b) α

(3)α

(d)αd

9. Roughness of earth depends upon [ ]

(a)angle of incidence only (b)frequency if only

(c)standard deviation of earth’s irregularities only (d) , &

10. Impedence measurement by slotted line method is better suited at [ ]

(a)VHF (b)VLF (c)HF (d)UHF & µw frequency’s

11.Which of the wave remains unaffected whether it is a day or night [ ]

(a) tropospheric wave (b)sky wave (c) ground wave (d)none

12. D-layer extends approximately from [ ]

(a) 50 to 90 Km (b) 20-50Km (c) 90-110 Km (d) upto 50Km

13.Microwave signals follow the curvature of the earth & phenomenon is known as [ ]

(a) tropospheric scatter (b) Duct propagation (c) Faraday effect (d) none

14. During day which layer doesn’t exist [ ]

(a) D-layer (b) F1-layer (c) F2-layer (d) F-layer

16.Wave unaffected by day or night is [ ]

(a) ground wave (b)sky wave (c) space wave (d) Tropospheric wave

17. When EM wave propagates from air into ionosphere, its velocity [ ]

(a) Decreases (b) Increases (c) remains the same (d) reduces to zero

18.Los distance is affected by atmospheric refraction [ ]

(a) Yes (b)No

19. Ground wave is affective when the transmitting & receiving antennas are [ ]

(a) Vertically polarized (b) Horizontally polarized

(c) Circularly polarized (d) elliptically polarized

20. Duct propagation takes place when

=…………………….. [ ]

a)+ve (b)_ve (c)0 (d)none

21.Television broadcast generally uses [ ]

(a) Line of sight propagation (c) Ionospheric propagation

(b) Ground wave propagation (d) none

22.Long distance short wave radio broadcasting uses [ ]

(a) Ground wave (c)direct wave

(b) Ionospheric wave (d)none

23.The relative permittivity of the Ionosphere at RF is… [ ]

(a) >1 (b) <1 (c) =1 (d) none

24.Critical frequency of a layer is given by [ ]

(a) fc=81Nm (b) fc=81Nm2 (c) fc=9√ (d)none

25. During day time ionosphere consists of [ ]

(a) D,E,F layers (b) D,E,F2 layers (c) D,E,F1,F2 layers (d) none

26.The absorption of EM waves by the atmosphere depends on [ ]

(a) the frequency in use (b) the polarization of the waves

(c) distance from the transmitter (d) none

27. Skip distance [ ]

(a) increases with increase of frequency (b) increases with decrease of frequency

(c) decreases with increase of frequency (d) decreases with decrease of frequency

28. VLF waves are used for some type of service because [ ]

(a) Penetrate the ionosphere easily (b) transmitting antennas are convenient size

(c) Low power is required (d) they are very reliable

29. Broadcasting antennas are generally [ ]

(a) Omni-directional type (b) vertical type

(c) Horizontal type (d) none

30. In order to receive vertically polarized wave, the conductor of the dipole should be mounted

(á) Horizontal (b) vertical (c) at an angle of 45o (d)none [ ]

31.Scatter transmission is used at frequencies ….. [ ]

(a) UHF & VHF (b) UHF only (c) VLF only (d) none

32.The velocity of the wave when it passes from air into ionosphere [ ]

(a)decreases (b) increases (c)same (d)none

33. The formula for refractive index for ionized layers is [ ]

(a) µ=√

(b) √

(c) √

(d) √

34. MUF is given by [ ]

(a) MUF = fccosθ (b) MUF = fcsecθ (c) MUF =

(d)none

35. If a wave of critical frequency 30MHz is departing at an 60o, then MUF is [ ]

(a) 60MHz (b) 15MHz (c) 10MHz (d) 30MHz

36. Troposcatter propagation is related to [ ]

(a) SIDS (b) Faraday rotation (c) fading (d) atmospheric stroms

37. Short waves for long distance communication depends on [ ]

(a) Ionospheric waves (b)ground waves (c) direct waves (d) space waves

38. Attenuation in atmosphere is inversely proportional to the square of the frequency[ ]

(a) Yes (b) No (c) neither true nor false (d)none

39. When an EM wave whose MUF is 25MHz is incident at 40o , then fc is [ ]

(a) 19.15MHz (b) 1.915MHz (c) 2MHz (d) 30MHz

40. The Optimun frequency is ___________ of MUF. [ ]

(a) 85% (b)70% (c) 30% (d) 15%

41. Atmosphere is said to be standard atmosphere when

=_______ [ ]

(a) 0.036 units/ft (b) 0.06 units/ft

(c) 0.04 units/ft (d) none

2 MARK QUESTIONS

1. Define Sky wave.

2. Determine the maximum usable frequency for a critical frequency of 20MHz and an angle of

incidence of

3. Define Ground wave.

4. What are the types of Ground waves?

5. What is meant by Space Wave?

6. Two aircrafts are flying at altitudes of 3000 m and 5000 m respectively. What is the minimum

possible distance along the surface of the earth over which they can have effective point to point

microwave communication

7. What is meant by fading?

8. What are the types of fading?

9. What are inverse and multi path fading?

10. What is meant by diversity reception?

11. Determine the height of the transmitting antenna to obtain a maximum distance of transmission

upto 38km from a 24 meter high receiving antenna

12. Define Space diversity Reception.

13. Define frequency diversity Reception.

14. Define polarization diversity reception.

15. What is the critical frequency of radio receiver for reflection at vertical incidence if the maximum

value of electron density is 1.26X

16. What is meant by Faraday’s rotation?

17. What are the factors that affect the propagation of radio waves?

18. Define gyro frequency.

19. Define critical frequency.

20. Define Magneto-Ions Splitting.

10 MARK QUESTIONS

1. (a) Discuss the field strength variation with distance & height.

(b) Discuss the atmospheric effects in space wave propagation

2. (a) Explain ground wave propagation.

(b) A radio transmitted operating at a frequency 1.69 MHz is required to provide a ground wave

having strength of 0.5 mv/m at a distance of 16 km. The transmitting antenna with an efficiency

of 50% produces a radiating field proportional to cosӨ. The ground wave has σ = 5x ʊ/cm

and = 15.Calculate the power transmitted.

3. (a) Explain about scattering phenomenon & Super refraction.

(b) Explain about plane earth reflections in ground wave propagation.

4. (a)Explain the different modes of wave propagation.

(b) It is required to establish a short wave communication between two points in earth’s surface

separated by 1200 km. Calculate the and angle of take off the transmitted wave from the

following data. Highest signal frequency return to earth after vertically upward propagation is

7.2MHz and virtual height of ionized layer is 200 km. Assume surface of earth to be flat.

5. (a) Explain the terms

i). Critical frequency ii) Ray path iii) draw the structure of ionosphere; how it varies with weather

6. Explain the structure of Ionosphere.

7. a). VHF Communication is to be established with 50W transmitted at 100MHz. Calculate the

LOS distance if the heights of transmitting and receiving antennas are respectively 50 m and

10m.Assuming the capture area of transmitting antenna is 25 , calculate the field strength at

the receiving antenna end neglecting ground reflected wave.

(b) What is fading & list different types of fading and explain.

8. (a) Explain the refraction and reflection mechanisms in sky wave propagation

(b) Explain the terms i) Critical frequency ii) MUF.

9. (a). Explain the following

i) Virtual height ii)Skip distance iii)Multi-hop propagation

(b). Draw the structure of Ionosphere; how it varies with weather explain.

10. a) In Ionospheric propagation, consider that reflection takes place at height of 300 km and that

the maximum density in ionosphere corresponds to refractive index of 0.8 at 15 MHz frequency.

Determine ground range for curved earth for which given frequency is MUF.

b) Discuss the effects of earth’s curvature.