Microstrip Patch Antenna Cst

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  1. Microstrip Patch Antenna Cst Review
  2. Microstrip Patch Antenna Bandwidth

Sep 16, 2016  How to find impedance at edge of a microstrip patch in CST? I would like to know how to compute the impedance at the edge of a microstrip patch in CST. Apparently it. CST - input impedance of a patch antenna inset fed with microstrip (self.rfelectronics) submitted 3 years ago by nhremna I am trying to design a patch antenna (for 20GHz). Microstrip Patch Antenna Design 1. Study & Design of Micro- strip Patch AntennaPRESENTED BY:-Diptajit Biswas(EC/08/50)Amit Samanta (EC/08/49)Saikat Mandal(EC/08/66)Under the kind guidance of,Mr. Asim Biswas 2. IntroductionO Need of AntennaO Progress of Communication system 3. Simple microstrip patch antenna is designed in CST Microwave Studio at a resonant frequency of 2.4 GHz. The gain of the designed antenna is 8.27 dB and VSWR of 1.18.

Microstrip Patch Antennas. Click here to go to our main antenna page. For a microstrip antenna to work, you want to think the opposite thoughts that you might want to think if you were designing a microstrip MMIC. You want the thing to radiate! The path toward this is threefold. First, the structure needs to be a half-wavelength resonator. Microstrip Patch Array Design Antenna arrays offer improved directivity compared to a single-radiator antenna. The directivity of an array is due to interference effects between the individual elements of the array, which means that the spatial distribution of the elements as well as phases and magnitudes at each element need to be tuned for.

Journal of Electromagnetic Analysis and Applications
 Vol.6 No.3(2014), Article ID:43230,4 pages DOI:10.4236/jemaa.2014.63006

Rectangular Microstrip Patch Antenna Using Air as Substrate for S-Band Communication

1Department of EECE, ITM University, Gurgaon, India, 2Departmentof Electrical and Electronics Engineering, ITM University, Gurgaon & Raipur, India, 3Departmentof Mechanical Engineering, Shinas College of Technology, Shinas, Oman.

Email: manish911989@gmail.com, saurabhsachdeva@itmindia.edu, nkumarswamy15@gmail.com, ipsinghphys@gmail.com

Copyright © 2014 Manish Gupta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accordance of the Creative Commons Attribution License all Copyrights © 2014 are reserved for SCIRP and the owner of the intellectual property Manish Gupta et al. All Copyright © 2014 are guarded by law and by SCIRP as a guardian.

Received April 21st, 2013; revised December 21st, 2013; accepted January 10th, 2014

Microstrip Patch Antenna Cst Review

Keywords: Rectangular Microstrip Patch Antenna; Air Substrate; Directivity

ABSTRACT

A Rectangular Microstrip Patch Antenna model is proposed using air as a substrate to study the characteristics of designed antenna. The dimensions of designed antenna are 17 mm × 16.66 mm with substrate at frequency 3.525 GHz. In this paper, the simulation is performed by using software Computer Simulation Technology (CST) Microwave studio based on finite difference time domain technique. The characterization of the designed antenna was analyzed in terms of return loss, bandwidth, directivity, gain, radiation pattern, VSWR.

1. Introduction

Due to attractive and unique properties (e.g. low profile, conformal nature, and high speed), microstrip antennas are finding many applications in various fields like Microwave Engineering, Mobile Communication, Satellite Communication and aircraft systems. As a result, in recent years a considerable attention has been paid by many antenna designers to enhance the characteristics of these antennas. Microstrip patch antenna is special class of microstrip antennas. It consists of a patch on one side of a dielectric substrate and ground plane on the other side of the substrate [1]. The patch may be of any geometry like circular, triangular, rectangular, elliptical, square, and ring.

To meet the requirement of low profiling, conformal nature there are numerous materials used as a substrate like RT Duriod 5880, FR4, Alumina, Honeycomb, etc. [2].

Chandra et al. [3] proposed rectangular patch antenna using air as substrate for X-band. They used Agilent’s E8363B network analyzer to obtain simulation results; from simulation results they observed 2 - 3 dB improvement in peak gain. Recently Ali et al. [4] designed the microstrip antenna using the same above substrate at 5.8 GHz frequency; results obtained by them strongly match with Chandra et al. [3].

In this paper a sincere attempt is made to design, model, optimize, and analysis rectangular microstrip patch antenna taking air as a substrate at 3.525 GHz with the help of CST microwave [5] electromagnetic simulator.

2. Antenna Design

The selected dielectric materials for the antenna is air which has a dielectric constant of 1 and the height of dielectric substrate is 1.5 mm (h). We use CST microwave studio for design, modeling of proposed antenna. Microstrip feed line of 50 is used to feed the antenna.

The physical dimensions of the patch are based on the following formulae.

(1)

(2)

where L is the length, W is the width and is frequency of the proposed antenna. is the space speed of light and is relative permitivity of substrate. The physical dimensions of the ground plane are based on the following formulae.

(3)

(4)

where Lg and Wg are the length and width of the ground plane and h is the thickness of substrate. The geometry of proposed antenna is shown in Figure 1. The dimension is taken in millimeters (mm) and numbers of used mesh cells are 28,899.

3. Optimized Antenna Design

The dimensions of the metallic patch were slightly changed in order to improve the antenna performance parameters. A systematic study of thickness of the substrate is optimized from 0.2 mm to 4.4 mm in 0.1 mm increments. Finally the dimension of ground plane is mm and dimension of the patch is 17 mm × 16.66 mm.

4. Simulation Results

The measured and simulated results obtained for proposed antenna are presented graphically and numerically. CST microwave studio [5] electromagnetic simulator has been used to obtain these results.

Microstrip Patch Antenna Bandwidth

4.1. Return Loss

Microstrip patch antenna cst

Return Loss is a measurement from which we can judge how much amount of power is reflected back by the antenna.

The numerical value of the S11 parameter from the Figure 2 is −40.9638 dB. There is one sharp narrow deep at 3.525 GHz which shows that proposed antenna is a single band antenna. The bandwidth of the proposed antenna is found to be 140.6 MHz from Figure 2.

4.2. Radiation Pattern

It is a graphical representation of the radiation properties of the antenna as a function of space coordinates [2]. Here the radiation pattern is determined in the far field region.

In this paper we only discuss two radiation properties namely directivity and polarization. Figures 3(a)-(d), are the 3D, 2D, polar and Cartesian graphs of the radiation pattern respectively. Figure 3(a) shows that the directivity of the proposed antenna is 6.68 dBi, radiation efficiency is −25.33% and total efficiency is −25.33%. It is also observed that maximum radiation is emitting from the center of the top the patch. This shows that the proposed antenna is feasible for S-band communication. From Figure3(c) an angular width (3dB) of antenna is 71.0 deg.

4.3. VSWR

VSWR is the way to see how much system is matched. It is the ratio between the maximum voltage and minimum voltage in the transmission line. For the best value of antenna it should be equal to 1.

Figure 1. Geometry of proposed antenna operating at 3.525 GHz.

Figure 2. Return loss of purposed antenna at 3.525 GHz.

(a)(b)(c)(d)

Figure 3. (a) 3D-Radiation pattern of proposed antenna at 3.525 GHz. (b) 2D-Radiation pattern of proposed antenna at 3.525 GHz. (c) Polar plot of proposed antenna operating at 3.525 GHz. (d) Cartesian plot of proposed antenna operating at 3.525 GHz .

Figure 4. VSWR plot of proposed antenna operating at 3.52 GHz.

Looking at Figure 4, it can be observed that the measured value of VSWR is 1.0328.

5. Conclusion

This paper has successfully designed a rectangular patch antenna operating at 3.525 GHz. It is found that using air as a substrate has been an improvement in return loss of −40.965 dB. The antenna also is capable of functioning at 3.525 GHz with a gain of 6.68 dBi. This antenna has a big potential for a Microwave application.

Acknowledgements

Microstrip patch antenna bandwidth

Authors are thankful to reviewer for their helpful comments.

REFERENCES

  1. K. F. Lee and K. M. Luk, “Microstrip Patch Antennas,” Imperial College Press, London, 2011.
  2. C. A. Balanis, “Antenna Theory,” 2nd Edition, John Wiley & Sons, Inc., 1997.
  3. C. Chandan, A Ghosh, S. K. Ghosh and S. Chattopadhyay, “Radiation Characteristics of Rectangular Patch Antenna Using Air Substrates,” 2009 International Conference on Emerging Trends in Electronic and Photonic Devices & Systems, Varanasi, 22-24 December 2009, pp. 346-348.
  4. M. T. Ali, “Gain Enhancement of Air Substrates at 5.8 GHz for Microstrip Antenna Array,” Microwave Technology Centre (MTC), Univ. Teknol. MARA (UiTM), Shah Alam, 2012, pp.477-480.
  5. CST Microwave Studio, “CSTGmbh-Computer Simulation Technology,” 2012.

Journal Menu >>

1. Introduction, Parameters and Fields of Microstrip Antennas

2. Bandwidth and Fringing Fields

3. Feeding Methods for Patch Antennas

4. Tradeoffs and Design Parameters of Microstrip Antennas

5. Video Simulation of Transient Fields Under a Microstrip Antenna

6. Planar Inverted-F Antennas (PIFAs)

7. Video Introduction and Analysis of Patch/Microstrip Antennas

In this section, we'll discuss the microstrip antenna, which is also commonly referred to as the patch antenna. [Note: I'll use the terms microstrip antenna and patch antenna interchangeably.]The rectangular patch antenna is analyzed, and what is learned here will be applied to understanding PIFAs (Planar Inverted-F Antennas).

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Rectangular Microstrip Antenna

Introduction to Patch Antennas

Microstrip or patch antennas are becoming increasingly useful because they can be printed directly onto a circuit board. Microstrip antennas are becoming very widespread within the mobile phone market. Patch antennas are low cost, have a low profile and are easily fabricated.

Consider the microstrip antenna shown in Figure 1, fed by a microstrip transmission line. The patch antenna, microstrip transmission line and ground plane are made of high conductivity metal (typically copper). The patch is of length L, width W, and sitting on top of a substrate (some dielectric circuit board) of thickness h with permittivity . The thickness of the ground plane or of the microstrip is not critically important.Typically the height h is much smaller than the wavelength of operation, but should not be much smaller than 0.025 of a wavelength (1/40th of a wavelength)or the antenna efficiency will be degraded.

(a) Top View of Patch Antenna

(b) Side View of Microstrip Antenna

Figure 1. Geometry of Microstrip (Patch) Antenna.

The frequency of operation of the patch antenna of Figure 1 is determined by the length L. The center frequency will be approximately given by:

The above equation says that the microstrip antenna should have a length equal to one half of a wavelength within the dielectric (substrate)medium.

The width W of the microstrip antenna controls the input impedance. Larger widths also can increase the bandwidth.For a square patch antenna fed in the manner above, the input impedance will be on the order of 300 Ohms. By increasing the width, the impedance can be reduced. However, to decrease the input impedance to 50 Ohms often requires a very wide patch antenna, which takes up a lot of valuable space. The width further controls the radiation pattern.The normalized radiation pattern is approximately given by:

In the above, k is the free-space wavenumber, given by . The magnitude of the fields, given by:

The fields of the microstrip antenna are plotted in Figure 2 for W=L=0.5.

Figure 2. Normalized Radiation Pattern for Microstrip (Patch) Antenna.

The directivity of patch antennas is approximately 5-7 dB. The fields are linearly polarized, and in the horizontal direction when viewing the microstrip antenna as in Figure 1a (we'll see why in the next section). Next we'll consider more aspects involved in Patch (Microstrip) antennas.

Fringing Fields for Microstrip Antennas

Consider a square patch antenna fed at the end as before in Figure 1a. Assume the substrate is air (or styrofoam, with a permittivity equal to 1), and that L=W=1.5 meters, so that the patch is to resonate at 100 MHz. The height h is taken to be 3 cm. Note that microstrips are usually made for higher frequencies, so that they are much smaller in practice.When matched to a 200 Ohm load, the magnitude of S11 is shown in Figure 3.

Figure 3. Magnitude of S11 versus Frequency for Square Patch Antenna.

Some noteworthy observations are apparent from Figure 3. First, the bandwidth of the patch antenna is very small. Rectangular patch antennas are notoriously narrowband; the bandwidth of rectangular microstrip antennas are typically 3%. Secondly, the microstrip antenna was designed to operate at 100 MHz, but it is resonant at approximately 96 MHz. This shift is due to fringing fields around the antenna, which makes the patch seem longer. Hence, when designing a patch antenna it is typically trimmed by 2-4% to achieve resonance at the desired frequency.

The fringing fields around the antenna can help explain why the microstrip antenna radiates. Consider the side view of a patch antenna, shown in Figure 4. Note that since the current at the end of the patch is zero (open circuit end), the current is maximum at the center of the half-wave patch and (theoretically) zero at the beginning of the patch. This low current value at the feed explains in part why the impedance is high when fed at the end (we'll address this again later).

Since the patch antenna can be viewed as an open circuited transmission line, the voltage reflection coefficient will be 1 (see thetransmission line tutorial for more information). When this occurs, the voltage and current are out of phase. Hence, at the end of the patch the voltage is at a maximum (say +V volts). At the start of the patch antenna (a half-wavelength away), the voltage must be at minimum (-V Volts). Hence, the fields underneath the patch will resemble that of Figure 4, which roughly displays the fringing of the fields around the edges.

Figure 4. Side view of patch antenna with E-fields shown underneath.

It is the fringing fields that are responsible for the radiation. Note that the fringing fields near the surface of the patch antenna are both in the +y direction. Hence, the fringing E-fields on the edge of the microstrip antenna add up in phase and produce the radiation of the microstrip antenna. This paragraph is critical to understanding the patch antenna. The current adds up in phase on the patch antenna as well; however, an equal current but with opposite direction is on the ground plane, which cancels the radiation. This also explains why the microstrip antenna radiates but the microstrip transmission line does not. The microstrip antenna's radiation arises from the fringing fields, which are due to the advantageous voltage distribution; hence the radiation arises due to the voltage and not the current. The patch antenna is therefore a 'voltage radiator', as opposed to the wire antennas, which radiate because the currents add up in phase and are therefore 'current radiators'.

As a side note, the smaller is, the more 'bowed' the fringing fields become; they extend farther away from the patch. Therefore, using a smaller permittivity for the substrate yields better radiation. In contrast, when making a microstrip transmission line (where no power is to be radiated), a high value of is desired, so that the fields are more tightly contained (less fringing), resulting in less radiation. This is one of the trade-offs in patch antenna design. There have been research papers written were distinct dielectrics (different permittivities) are used under the patch antenna and transmission line sections, to circumvent this issue.

Next, we'll look at alternative methods of feeding the microstrip antenna (connecting the antenna to the receiver or transmitter).

Next: Feeding Methods for Patch Antennas

Top: Introduction to Microstrip Antennas

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