CHAPTER 4 EFFECT OF DIELECTRIC COVERS ON THE …shodhganga.inflibnet.ac.in/bitstream/10603/28955/13/13_chapter 4.pdfEFFECT OF DIELECTRIC COVERS ON THE PERFORMANCES OF MICROSTRIP ANTENNAS

83

CHAPTER 4

EFFECT OF DIELECTRIC COVERS ON THE PERFORMANCES OF

MICROSTRIP ANTENNAS

4.1. INTRODUCTION

In the previous chapter we have described effect of dielectric thickness on antenna

performances. As mentioned the main objective of this chapter is to find the environmental

impacts on the various patch antennas such as square and pentagonal patch with various

dielectric covers which is linearly polarized having the resonant frequency of 2.45 GHz

(with 10% bandwidth), using FR4 (epoxy), as the dielectric substrate material of 0.8 mm

thickness. The relative permittivity of the dielectric material is 4.4. The main reason behind

selecting this frequency range is that the antenna is used in WLAN (wireless-LAN)

systems. As there are many environmental factors which affect the normal working of the

microstrip patch antennas.

Hence it is important to study the performance variation of the microstrip patch antenna

due to various climatic conditions such as snow, dust- particles and Plexiglas, NelTec,

Glass PTFE and Rogers. As we know that in rainy conditions the water layer is formed due

to adhesion and surface tension and its actual instantaneous thickness depends upon

number of factors such as, exact orientation of patch surface (if patch surface is slightly

inclined, the gravitational force will play its part accordingly), rate of precipitation, wind

condition, humidity etc.

4.2. DESIGNING OF DIELECTRICS LOADED PATCH ANTENNAS

In order to study the effect of dielectric loading of different dielectric constant on the

performance behavior of square patch antenna, the optimum design parameters are selected

to achieve the compact dimensions as well as the best possible characteristics such as high

radiation efficiency, high gain, directivity and bandwidth. The proposed antenna structure

is fed with 50 ohms coaxial cable for impedance matching and HFSS simulation tool has

been used for the analysis, which offers multiple state-of the-art solver technologies, each

84

based on the finite element method. The obtained results reveal that dielectric loading do

not change only the resonance frequency but also affects the other parameters; gain,

directivity and bandwidth. In particular, the resonance frequency lowers and shift in

resonant frequency increases with the dielectric constant of covers. In addition, it has also

been observed that return loss and VSWR increases, however bandwidth and directivity

decreases with the dielectric constant of dielectrics.

4.2.1. Design of Square Patch Antenna

The patch antenna that introduces here has made of the conduction material copper (Figure

4.1).

Figure 4.1 Structure of square patch antenna

The geometry of square patch antenna having a dielectric cover is shown in Figure 4.2.

Figure 4.2 Structure of antenna with dielectric cover

85

4.2.2. Design Specifications

The proposed square patch antenna was designed using following specifications:

Relative permittivity of the substrate εr = 2.33

Design frequency f0 = 2.4 GHz

Loss tangent of substrate tanδ = 0.001

Height of the substrate h =1.575 mm

Length of patch antenna L= 55.75 mm

Height of the dielectric h =1.575 mm

Relative permittivity of the dielectrics εr = 2.2, 2.5 and 3.02

Dielectric cover materials NelTec, Glass PTFE, Rogers

In reality, the microstrip antenna attached to an electronic device will be protected by a

dielectric cover (dielectric) that acts as a shield against hazardous environmental effects.

These shielding materials normally plastics (lossy dielectric) will decrease the overall

performances of the antenna operating characteristics such as resonant frequency,

impedance bandwidth and radiating efficiency. A transmission line has the line capacitance

C. Suppose all the dielectric layers are removed from this structure. The remaining

conductor system has the line capacitance C0, which is smaller than C. The theory of a

distributed parameter transmission line gives a relation between the wavelength of an

unloaded line λ0 and the guide wavelength of a capacitance-loaded line λ

Similarly, it gives a relation between the characteristic impedance of the unloaded line Z0

and the characteristic impedance of the capacitance-loaded line Z

As is well known in the TEM transmission theory, is identical to the free-space

wavelength, and Z0 is given by

86

Where c is the velocity of light.

Characteristic Impedance and Phase Velocity

The characteristic impedance Z0 and the phase velocity vp of a TEM transmission line can

be written as [1]

Where C and C0 are the capacitances of the transmission line structure with and without

dielectric, respectively, εe is the effective dielectric constant which takes into account the

effect of the fringing fields in the substrate, the sheet material, and the free space, and c is

the velocity of light in free space. The mode considered here is a quasi-TEM mode. The

expression for the capacitance is obtained using the variational method.

For a matched antenna, the change in the fractional resonant frequency relative to the

unloaded case can be calculated using the following expression [2]

The first-order change in the resonant frequency may be expressed as

87

Where εe0 is the effective dielectric constant without cover.

The reason behind alteration of performance of the antenna is that, due to dielectric loading

the characteristic impedance and phase-velocity are modified as mentioned earlier.

4.2.3. Result of Square Patch Antenna with Various Dielectric Covers

In order to observe the effects of dielectric covers on the antenna characteristics, the

proposed antenna has been analyzed using dielectric cover of dielectric constant 2.2, 2.5

and 3.02. The obtained characteristics are shown in Figures 4.3-4.9; however the

corresponding data are tabulated in Table 4.1[3-4].

Figure 4.3 S-parameter of square patch antenna with various dielectric covers

-40

-35

-30

-25

-20

-15

-10

-5

0

1.8 2 2.2 2.4 2.6

Retu

rn

Loss

(d

B)

Frequency (GHz)

Neltec

Glass PTFE

Rogers

88

Figure 4.4 VSWR with various dielectric covers

Figure 4.5 Gain with various dielectric covers

(εr = 2.2) (εr = 2.5) (εr = 3.02)

Figure 4.6 Directivity with various dielectric covers

1

1.5

2

2.5

3

1.8 2.1 2.4

VS

WR

Frequency(GHz)

Neltec

Glass PTFE

Rogers

-10-9-8-7-6-5-4-3-2-10123

-200 -150 -100 -50 0 50 100 150 200

Ga

in(d

B)

Angle,Degree

Neltec

Glass PTFE

Rogers

0

0.2

0.4

0.6

0.8

1

1.2

-200 0 200

Dir

ecti

vit

y

Angle,Degree

0

0.5

1

1.5

2

2.5

-200 0 200

Dir

ecti

vit

y

Angle,Degree

0

0.5

1

1.5

2

-200 0 200

Dir

ecti

vit

y

Angle,Degree

89

(εr = 2.2) (εr = 2.5) (εr = 3.02)

Figure 4.7 Radiation patterns with various dielectric covers

(εr = 2.2) (εr = 2.5) (εr = 3.02)

Figure 4.8 Smith chart with various dielectric cover

(εr = 2.2) (εr = 2.5) (εr = 3.02)

Figure 4.9 Impedance with various dielectric cover

-20

-10

0

10

20

30

40

50

60

1 2 3

Imp

ed

an

ce(O

hm

)

Frequency(GHz) -20

-10

0

10

20

30

40

50

1 2 3Imp

ed

an

ce(O

hm

)

Frequency(GHz)

-10

0

10

20

30

40

50

60

1 2 3

Imp

ed

an

ce(O

hm

)

Frequency(GHz)

90

Table 4.1 Antenna parameters with dielectric loadings

Dielectric

material

Dielectric

constant

(ɛr)

Frequency

(GHz)

Return

loss (dB)

Impedance

(Ω)

Gain

(dB) VSWR

BW

(%)

Directivity

(dB)

NelTec 2.2 2.26 -33.62 51.92 2.0225 1.042 3.62 2.0833

Glass

PTFE 2.5 2.24 -24.12 47.1331 2.52 1.132 3.91 1.8411

Rogers 3.02 2.14 -14.78 37.83 1.0553 1.445 3.49 1.0808

4.3. SQUARE MICROSTRIP PATCH ANTENNA: DESIGN ANALYSIS AND RESULTS


Feeding technique : Coaxial feed

Substrate material : FR-4

Relative permittivity of the substrate ( ) : 4.4

Design frequency : 2.4-2.4835GHz (ISM band)

Thickness of dielectric substrate : 0.8 mm

Elemental side : 28.6139 mm

Feed location : 8.30158 mm

Coaxial cable dimensions

Inner radius a : 0.635 mm

Outer radius b : 2.0445 mm

4.3.2. Simulated Results

In order to present the design procedure of achieving impedance matching for this case,

dimension of sides of square patch is selected initially be 29.187 mm. After optimization

we met the design challenges such as return losses should be less than -10 dB, VSWR< 2

and low spurious feed radiation.

91

Snow as Dielectric Cover

Apart from rain, many other environmental factors also affect the working of the microstrip

patch antenna installed at any working location. The accumulation of these environmental

factors may degrade the performance of the antenna. The other factors may include snow

accumulation, dust particles accumulation etc. Now we use the snow as the dielectric cover

the antenna patch surface with εr = 1.35 and tanδ = 0.0009. We also observed

that at higher substrate thickness, resonance frequency does not shift significantly.

Return Loss

As shown in the Figure 4.10, with the accumulation of the snow over the patch, the

resonance frequency shifts towards lower value and the return loss increases.

Figure 4.10 Return loss variations with accumulation of snow on square patch antenna

Impedance

As shown in the Figure 4.11, with the accumulation of the snow over the patch, the input

impedance of the antenna will shifts towards lower values. Thus the antenna performance

will get disturbed.

-35

-30

-25

-20

-15

-10

-5

0

1.8 2 2.2 2.4 2.6 2.8

Retu

rn

loss

[d

B]

Frequency [GHz]

dB(S11) at t='0.0mm'

dB(S11) at t='0.1mm'

92

Figure 4.11 Input impedance variations with accumulation of snow on square patch antenna

VSWR

As shown in the Figure 4.12, with the accumulation of the snow over the patch, the VSWR

of the antenna will increases. Thus the antenna performance may get disturbed.

Figure 4.12 VSWR variations with accumulation of snow on square patch antenna

Dust Particles as Dielectric Cover

0

10

20

30

40

50

60

1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9

Imp

ed

an

ce [

Ω]

Frequency [GHz]

impedance at t='0.0mm'


0

2

4

6

8

10

1.9 2.1 2.3 2.5 2.7 2.9

VS

WR

Frequency [GHz]

VSWR at t='0.0mm'

VSWR at t='0.1mm'

93

Now we use the dust as the dielectric cover over the antenna patch surface with r = 3.0

and tanδ = 0.0062 and found that, it affects antenna performances.

Return Loss

As shown in the Figure 4.13, with the accumulation of the dust particles over the patch, the


Figure 4.13 Return loss variations with accumulation of dust on square patch antenna

Impedance


input impedance of the antenna will shifts towards lower values. Thus the antenna

performance will get disturbed.

-35

-30

-25

-20

-15

-10

-5

0

2.2 2.3 2.4 2.5 2.6 2.7 2.8

Retu

rn

loss

[d

B]

Frequency [GHz]

(S11) at t='0.0mm'

(S11) at t='0.1mm'

94

Figure 4.14 Input impedance variations with accumulation of dust on square patch antenna

VSWR


VSWR of the antenna will increases. Thus the antenna performance will get disturbed.

Figure 4.15 VSWR variations with accumulation of dust on square patch antenna

Plexiglas as Dielectric Cover

Now we use the Plexiglas as the dielectric cover over the antenna patch surface with εr

= 3.40 and tanδ = 0.001.

0

10

20

30

40

50

60

2.2 2.3 2.4 2.5 2.6 2.7

Imp

ed

an

ce [

Ω]

Frequency [GHz]



0

2

4

6

8

10

2.2 2.3 2.4 2.5 2.6 2.7

VS

WR

Frequency [GHz]

VSWR at t='0.0mm'

VSWR at t='0.1mm'

95

Return Loss

As shown in the Figure 4.16, with the accumulation of the Plexiglas over the patch, the


Figure 4.16 Return loss variations with accumulation of Plexiglas on square patch antenna

Figure 4.17 Input impedance variations with accumulation of Plexiglas on square patch

antenna

Impedance




-35

-30

-25

-20

-15

-10

-5

0

2.2 2.3 2.4 2.5 2.6 2.7 2.8

Retu

rn

loss

[d

B]

Frequency [GHz]

(S11) at t='0.0mm'

(S11) at t='0.1mm'

0

10

20

30

40

50

60

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

Imp

ed

an

ce [

Ω]

Frequency [GHz]

impedance at

t='0.0mm'

impedance at

t='0.1mm'

96

VSWR



Figure 4.18 VSWR variations with accumulation of Plexiglas on square patch antenna

The simulated and measured results have also been tabulated in Table 4.2 and Table 4.3

respectively.

Table 4.2 Antenna performance variation due to accumulation of different materials over

square patch surface

Materials Thickness

(mm)

Resonant

Frequency

(GHz)

% Change

in Resonant

Frequency

Return

Loss

(dB)

Bandwidth (MHz)

VSWR Impedance

(Ω)

Rain Water

0 2.45 0 -31.3528 62.1 0.4702 50.11

0.1 2.175 11.22 -21.1258 49 1.5299 44.42

Snow

0 2.45 0 -31.3528 62.1 0.4702 50.11

0.1 2.3875 2.55 -21.844 58.8 1.408 46.34

Dust Particles

0 2.45 0 -31.3528 62.1 0.4702 50.11

0.1 2.425 1.02 -23.8647 58.8 1.1148 49.5

Plexiglas

0 2.45 0 -31.3528 62.1 0.4702 50.11

0.1 2.4375 0.51 -22.9988 58.7 1.5389 49.33

0

2

4

6

8

10

2.2 2.3 2.4 2.5 2.6 2.7

VS

WR

Frequency [GHz]

VSWR at t='0.0mm'

VSWR at t='0.0mm'

97

4.3.3. Measured Result

Return Loss

Figure 4.19 Return loss variations due to accumulation of water and dust on square patch

antenna

As shown in the Figure 4.19 measured result is in agreement with the simulated results. We

also observed that with accumulation of water and dust particles over the patch the


Table 4.3 Measured parameters of the square patch antenna

Materials Resonant

Frequency

(GHz)

% Change in Resonant

Frequency

Return

Loss (dB)

Bandwidth

(MHz)

Normal antenna 2.39 0 -19.28 45

With dust particle 2.18 8.7 -15.19 35

With water level 2.34 2 -28.45 50

Increased water

level 2.21 7.5 -13.71 35

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

1.9E+09 2.2E+09 2.5E+09 2.8E+09

Retu

rn

Loss

(dB

)

Frequency (Hz)

S11(dB)

S11_Dust Particle

S11_water

S11_Increased Water Level

98

4.4. PENTAGONAL MICROSTRIP PATCH ANTENNA: DESIGN ANALYSIS AND

RESULTS


Feeding technique : Coaxial feed

Substrate material : FR-4

Relative permittivity of the substrate : 4.4

Design frequency : 2.4-2.4835GHz (ISM band)

Thickness of dielectric substrate : 0.8 mm

Elemental side : 19.21 mm

Feed location : 8.21 mm

Coaxial cable dimensions:

Inner radius a : 0.635 mm

Outer radius b : 2.0445 mm

4.4.2. Simulated Results

Initially each side of the pentagonal patch antenna was selected to be equal to 20.23 mm,

which was calculated corresponding to 2.45 GHz (ISM band) but the design challenges

were not met. After optimization and selecting the each side of the pentagon equal to 19.21

mm we met the design challenges such as return loss less than -10 dB, VSWR< 2 and low

spurious feed radiation.

Snow as Dielectric Cover

Now we use the snow as the dielectric cover over the antenna patch surface with εr=

1.35 and tanδ = 0.0009. We observed that at higher substrate thickness, resonance

frequency does not shift significantly.

Return Loss

As shown in the Figure 4.20, with the accumulation of the snow over the patch, the


99

Figure 4.20 Return loss variations with accumulation of snow on pentagonal patch antenna

Impedance

As shown in the Figure 4.21, with the accumulation of the snow over the patch the input

impedance of the antenna will shifts towards lower values. Thus the antenna performance

will get disturbed.

Figure 4.21 Input impedance variations with accumulation of snow on pentagonal patch

antenna

-35

-30

-25

-20

-15

-10

-5

0

2.3 2.35 2.4 2.45 2.5 2.55 2.6

Retu

rn

loss

[d

B]

Frequency [GHz]

(S11) at t='0.0mm'

(S11) at t='0.1mm'

0

10

20

30

40

50

60

2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

Imp

ed

an

ce [

Ω]

Frequency [GHz]



100

VSWR

As shown in the Figure 4.22, with the accumulation of the snow over the patch, the VSWR

of the antenna will increases. Thus the antenna performance will get disturbed.

Figure 4.22 VSWR variations with accumulation of snow on pentagonal patch antenna

Dust Particles as dielectric cover

Now we use the dust as the dielectric cover over the antenna patch surface with εr

= 3.00 and tanδ = 0.0062.

Return Loss



Figure 4.23 Return Loss variations with accumulation of dust on pentagonal patch antenna

0

2

4

6

8

10

2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

VS

WR

Frequency [GHz]

(VSWR at t='0.0mm'

(VSWR at t='0.1mm'

-35

-30

-25

-20

-15

-10

-5

0

1.8 2 2.2 2.4 2.6 2.8

Retu

rn

loss

[d

B]

Frequency [GHz]

(S11) at t='0.0mm'

(S11) at t='0.1mm'

101

Impedance




Figure 4.24 Input Impedance variations with accumulation of dust on pentagonal patch

antenna

VSWR



Figure 4.25 VSWR variations with accumulation of dust on pentagonal patch antenna

0

10

20

30

40

50

60

2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

Imp

ed

an

ce [

Ω]

Frequency [GHz]



0

2

4

6

8

10

2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

VS

WR

Frequency [GHz]

VSWR at t='0.0mm'

VSWR at t='0.1mm'

102

Plexiglas as Dielectric Cover

Now we use the Plexiglas as the dielectric cover over the antenna patch surface with εr

= 3.40 and loss tanδ = 0.001.

Return Loss



Figure 4.26 Return loss variations with accumulation of Plexiglas on pentagonal patch

antenna

Impedance




-35

-30

-25

-20

-15

-10

-5

0

2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

Retu

rn

loss

[d

B]

Frequency [GHz]

(S11) at t='0.0mm'

(S11) at t='0.1mm'

103

Figure 4.27 Input impedance variations with accumulation of Plexiglas on pentagonal patch

antenna

VSWR



Figure 4.28 VSWR variations with accumulation of Plexiglas on pentagonal patch antenna

0

10

20

30

40

50

60

2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

Imp

ed

an

ce [Ω

]

Frequency [GHz]



0

2

4

6

8

10

2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

VS

WR

Frequency [GHz]

VSWR at t='0.0mm'

VSWR at t='0.1mm'

104

The simulated and measured results are tabulated in Tables 4.4 and 4.5 respectively.

Table 4.4 Antenna performance variation due to accumulation of different materials over

pentagonal patch surface

Materials Thickness

(mm)

Resonant Frequency

(GHz)

% Change

in

Resonant Frequency

Return Loss

(dB)

Bandwidth

(MHz) VSWR

Impedance

(Ω)

Rain

Water

0 2.438 0 -28.99 64.1 0.6172 51.95

0.1 2.25 7.69 -23.34 52.2 1.1846 47.42

Snow

0 2.438 0 -28.99 64.1 0.6172 51.95

0.1 2.438 0 -26.3 64.1 0.8418 51.67

Dust Particles

0 2.438 0 -28.99 64.1 0.6172 51.95

0.1 2.413 1.02 -24.84 62 0.9957 51.82

Plexiglas

0 2.438 0 -28.99 64.1 0.6172 51.95

0.1 2.413 1.02 -23.6 58.8 1.1488 51.68

4.4.3. Measured Result

Return loss

Figure 4.29 Return loss variations with accumulation of dust and water on pentagonal patch

antenna

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

2E+09 2.2E+09 2.4E+09 2.6E+09

S11(d

B)

Frequency

S11(dB)

S11(dB)_with Dust

S11(dB)_Water

S11(dB)_Increased

Water Level

105

As shown in the Figure 4.29 measured result is in agreement with the simulated results. We

also observed that with accumulation of water and dust particles over the patch the

resonance frequency shifts towards lower value.

Table 4.5 Measured parameters of the pentagonal patch antenna

Materials

Resonant

Frequency

(GHz)

% Change in

Resonant

Frequency

Return

Loss

(dB)

Bandwidth

(MHz)

Normal antenna 2.34 0 -22.13 40

With dust

particle 2.32 1 -28.34 45

With water level 2.33 0.4 -27.98 40

Increased water

level 2.3 1.7 -29.17 55

4.5. CONCLUSIONS

Therefore, the effect of dielectric loading of different constant on the behavior of square

and pentagonal patch antenna reveals that dielectric loading do not change only the

resonance frequency but also affects its other parameters; VSWR, return loss, gain,

directivity and bandwidth. In particular, the resonance frequency lowers to; 2.26 GHz, 2.24

GHz, and 2.14 GHz for dielectrics of εr= 2.2, 2.5 and 3.02 respectively and corresponding

shift in frequency are found to be 0.24 GHz, 0.26 GHz and 0.36 GHz respectively [5]. That

is dielectric with lowest dielectric constant (εr = 2.2) provide better impedance matching,

hence has nominal effects and do not disturb much the performance characteristics of the

antennas. The obtained results also indicate that return loss and VSWR increases, however

10-dB return loss, BW and directivity decreases with the dielectric constant of dielectrics.

The value of impedance, return loss and VSWR are minimum, whereas BW and directivity

are maximum for dielectric having dielectric constant (εr = 2.2) and vice-versa for εr = 3.02.

The obtained results are found true that low εr material induced less capacitance during

loading on the patch antenna, hence could be preferred to use as protective layers for

106

antenna systems. The antenna performance has also been studied under the different

conditions, accumulating snow, dust, particle and Plexiglas on the antenna and found that:

Accumulation of snow on square microstrip patch antenna reduces the resonant frequency

from 2.45 GHz to 2.3875 GHz. For snow, accumulation is confined to height of 0.1 mm.

This results in 2.55% change in the resonant frequency. Similarly in case of dust particles

and Plexiglas, whereas in dust particle slight change in resonant frequency is observed, it

deviates from 2.45 GHz to 2.425 GHz, with a percentage change of just 1.02%. Plexiglas

affects resonant frequency the most, i.e., from 2.45 GHz to 2.1375 GHz. This leads to a

12.75% change in the resonant frequency. Also, accumulation of snow on pentagonal

microstrip patch antenna doesn‘t affect the resonant frequency. For snow, accumulation is

confined to height of 0.1 mm. Similarly it is considered in case of dust particles and

Plexiglas, where as in dust particle slight change in resonant frequency is observed, it

deviates from 2.4375 GHz to 2.4125 GHz, with a percentage change of just 1.02%.

Plexiglas affects resonant frequency the most, i.e., from 2.4375 GHz to 2.4125 GHz. This

leads to a 1.02 % change in the resonant frequency. The measured results are in agreement

with the simulated results. In order to study the performances of the microstrip antenna

under various temperature variations, the chapter FIVE focuses to describe the effects of

temperature changes on the patch antennas.

107

REFERENCES

1. I. J. Bahl and S. S. Stuchly, ―Analysis of a microstrip covered with a lossy dielectric‖,

IEEE Trans. Microwave Theory Tech. Vol. MTT-28. No.2, pp. 104-109, Feb. 1980.

2. I. J. Bahl, P. Bhartia and S.S. Stuchly, ―Design of a microstrip antenna covered with a

dielectric layer,‖ IEEE Transactions on Antennas and Propagation, Vol. AP-30, No.2, pp.

314-18, March 1982.

3. R. Mittra,Y. Li and K. Yoo, ―A comparative study of directivity enhancement of microstrip

patch antennas with using three different superstrates,‖ Microwave and Optical Technology

Letters, Vol. 52, No. 2 pp. 327-331, February 2010.

4. R. R. Wakodkar, S. Chakraborty and B. Gupta, ―Investigation of water loading effect on

broadband planar array antenna for vehicular communication link,‖ IEMCON 2011, IEM in

collaboration with IEEE on 5th and 6th January, pp.604-607, 2011.

5. R. K. Yadav & R. L. Yadava, "Performance analysis of superstrate loaded patch antenna

and abstain from environmental effects,‖ International Journal of Engineering Science and

Technology (IJEST), Vol. 3 No. 8, pp. 6582-6591, August 2011.

Documents

CHAPTER 4 EFFECT OF DIELECTRIC COVERS ON THE …shodhganga.inflibnet.ac.in/bitstream/10603/28955/13/13_chapter 4.pdfEFFECT OF DIELECTRIC COVERS ON THE PERFORMANCES OF MICROSTRIP ANTENNAS