Design & Analysis of C shape Microstrip Antenna

Design & Analysis of C shape Microstrip Antenna

1Vishal Upmanu, 2 Dr.D.B.Ojha, 3 Ajay kumar Yadav,

ABSTRACT

Mewar University, Chittorgarh(Raj.)

shapes such as the square, circular, triangular, semicircular, sectoral, and annular ring shapes shown in Figure are also used. Radiation from

the microstrip antenna can occur

The design and analysis of c shaped micro strip patch antenna is presented. A computer simulation using the IE3D software was performed and the s parameters of the antenna were measured. By using only single patch a high impedance bandwidth is achieved .In this thesis MATALAB program for the design and analysis of all the parameters and for different patches have made. These results obtained through MATALAB program yields results compatible with the theoretical analysis of MSA.

1. INTRODUCTION

Deschamps first proposed the concept of the microstrip antenna in 1953. However, practical antennas were developed by Munson and in the 1970s. The numerous advantages of microstrip antenna, such as its low weight, small volume, and ease of fabrication using printed-circuit technology, led to the design of several configurations for various applications. With increasing requirements for personal and mobile communications, the demand for smaller and low profile antennas has brought the microstrip antenna to the forefront.

A microstrip antenna in its simplest form consists of a radiating patch on one side of a dielectric substrate and a ground plane on the other side. The top and side views of a rectangular microstrip antenna are shown in Figure. However other

from the fringing fields between the periphery of the patch and ground plane. The length L of the rectangular patch for the fundamental TM01 mode excitation is slightly smaller than /2, where is the wavelength in the dielectric medium, which in terms of free space wavelength 0 is given as 0/e, where e is the effective dielectric constant of a microstrip line of width W. The value of e is slightly less than the dielectric constant r of the substrate because the fringing fields from the patch to the ground plane are not confined in the dielectric only, but are also spread in the air.

To enhance the fringing fields from the patch, which account for the radiation, the width W of the patch is increased. The fringing fields are also enhanced by decreasing the r or by increasing the substrate thickness h. Therefore, unlike the microwave integrated circuit applications, microstrip antenna uses microstrip patches with larger width and subtrates with lower r and thickness h. For microstrip antenna applications in the microwave frequency band, generally h is taken greater than or equal to 1/16th of an inch. There are many configurations that can be used to feed antennas. The four most popular configurations are .

1 Microstrip line

The microstrip line is also a conduction strip usually much smaller width compared to the patch. The microstrip line is easy to fabricate, simple to match by controlling position and rather simple to model. However as the substrate thickness increased surface waves and spurious feed radiation increases. Which for practical designs limit the bandwidth (typically 2-5%)

Figure:Line

feed achieve different benefits. The most important is higher network capacity, i.e. the ability to serve more user per base station, thus increasing revenues of network operators, and giving customers less probability of blocked or dropped calls. Also, the transmission quality can be improved by increasing desired signal power and reducing interference.

1. Coaxial probe

   The coaxial or probe feed arrangement is shown in Figure. The center conductor of the coaxial connector is soldered to the patch. The main advantage of this feed is that it can be placed at any desire location inside the patch to match with its input impedance. The disadvantages are that the whole has to be drilled in the substrate and that the connector protrudes outside the bottom ground plane, so that it is not completely planar. Also, this feeding arrangement makes the configuration asymmetrical

   Figure: coaxial feed

2. Aperture coupling

   This is most difficult to fabricate and it also has narrow bandwidth. However it is somewhat easier to model and has moderate spurious radiation. Another method for indirectly exciting a patch employs aperture coupling. In the aperture coupled microstrip antennas patch through an electrically small aperture or slot cut in the ground plane, as shown in Figure. The coupling aperture is usually centered under the patch, leading to lower cross polarization due to symmetry of configuration. The shape, size and location of the aperture decide the amount of coupling from the feedline to the patch. The slot aperture can be either resonant or nonresonant.

   Figure: Aperture coupling

3. Proximity coupling

   The electromagnetic coupling is also known as proximity coupling. The feed line is placed between the patch an ground plane, which is separated by two dielectric media, one for patch and other for feed line to optimize the individual performances, and an increase in the BW due to overall substrate thickness of microstrip antennas. The disadvantages are that the two layers need to be aligned properly and that the overall thickness of the antennas increases.

   height of the dielectric substrate is selected as 0.8mm.

   Hence the essential parameters for the design are:

   fo= 1.5GHz er= 4.2

   h=2 mm

   Designed parameters for C shaped patch:

   C e 0 LW cos2 y0

   1 2h

   Where

   L

   Figure: Proximity coupling

   ANALYSIS AND DESIGN

   Design parameter for rectangular patch:

   L= length of the patch W= width of the patch

   h= thickness of the substance

   e = effective dielectric constant

   1

   r 1 r 1 1 12h 2

   The three essential parameters for the design of a rectangular microstrip patch antenna are:

   Frequency of operation (fo) :

   The resonant frequency of the antenna must be selected appropriately .The resonant frequency selected for my design is 900 MHz

   e 2 2 W

   r = relative dielectric constant of the substance

   y0 =feed point location along the y-axis i.e., alog the lrngth of the patch

   Also

   Dielectric constant of the substrate(er):

   The dielectric material selected for

   L1

   1

   C 2

   my design is quartz which has a dielectric constant of 4.2. a substrate with high dielectric constant has been selected since it reduces the dimensions of the antenna .

   Height of the dielectric substrate (h):

   For the microstrip patch antenna to be used in cellular phones, it is essential that the antenna should not be bulky .Hence the

   and

   1. r

Qr

R1 C

C p

1

Q Q

r 1 1 2

Where

Qr =quality factor of the patch

where Q1 = quality factor of the resonant circuit due to normal current = L1

r =resonance frequency of the patch

r

Q c e

R1

and Q2 = quality factor of the resonant circuit due to notch effect = L2

4 f r h

Where

c=velocity of light in free space

The input impedance of the resonant circuit

R1

The mutual inductance = Lm

The mutual capacitance = Cm

C 2 L L C 2 L L 2 4C 2 1 C 2 L L

L p 1 2

p 1 2

p p 1 2

Z 1

m 21 C 2

atch

1

R1

h

• jc1

  1

  jL1

  p

  Cm

  C1

  C2

  C1

• C2

  p

  1

  2

  2 4C C

  1 C 2

  L 0 l

  8

  L2 2

  0

  Where 4107

  and l = equivalent

  The input impedance of the notched rectangular microstrip patch antenna

  length of the notch

  l

  Z patch Zin

  C C

  Z

  • Z

  Zin Z notch

  L s

  patch

  in

  Cs =gap capacitance

  Where

  1

  Z patch

  Zin

  jLm

  1

  jCm

  1

  R1

  jC 1

  2

  2 jL

  Z Z

  C C

  Reflection coefficient = 0 in

  Z 0 Zin

  where C

  1

  2

  C1 C

  Where Z0 = characteristic impedance of the

  L2 L1

• L

co-axial feed 50

The coupling coefficient between these two resonators

1

VSWR = S

1

S 1

Bandwidth =

Q S

And Return loss = 20log

Designed parameters

For designing the notched rectangular microstrip patch antenna, following parameters were used

Design frequency = 1.5GHz Free space wavelength = 100mm

Dilectric constant (R-T duriod) =4.2 Loss tangent (tan) =0.2

The thickness of the substrate (h) =.02 Length of the patch (L) =0.5 Width of the patch (W) =0.4

figure: frequency vs return loss for single notch

IE3D SIMULATION FOR C SHAPED MICROSTRIP PATCH

Various results taken by the IE3D for c shaped microstrip patch antenna are represented by the graphs given below

RESULT ANALYSIS

CONCLUSION

From the work conducted on the micro strip patch antenna ,it can be concluded that micro strip antennas are low profile ,simple and inexpensive to manufacture using modern printed circuit board technology ,mechanically robust when mounted on rigid surfaces .and when the particular patch shape and mode are selected they are very versatile in term of resonant frequency, polarization ,pattern and impedance. in addition by adding loads b/w the patch and the ground plane. such as pins. shorting posts and varactor diodes adaptive elements with variable resonant frequencies. impedance, polarization and pattern can be

designed..in this project we have made a MATLAB program for the design and analysis of all the antenna parameters ,and various patch of different dimensions, the latter being dependent on the substrate permittivity and the resonant frequercy as required by the user.All the polar plots and the graphs of variations in the results with respect to frequency have also been plotted in the report.

REFERENCES

1. K. R. Carver and j. W. Mink, Microstrip antenna technology, IEEE Trans . Antenna Propag. Vol. AP- 29,pp.1-24,1981.

2. Ballanis C A, Antenna Theory and design New York, 1980.

3. Wong B F & Lo Y T, Microstrip antenna for dual frequency operations, IEEE Trans. Antenna Propag.1984.

4. Pandey V. K. & Vishvakarma B R, Theoretical analysis of linear array antenna of Stacked Patches, Indian J Radio & Space Physics, 2005.