This document describes the design and simulation of a trapezoidal microstrip patch antenna for ultra-wideband applications from 3-10 GHz. The antenna has a trapezoidal patch connected to a microstrip feedline on an FR4 substrate. A slot is etched in the ground plane to increase the impedance bandwidth. Simulations show the antenna achieves over 107% fractional bandwidth with return loss over 10 dB and VSWR less than 2 across the band. Radiation patterns are omnidirectional in the H-plane and bidirectional in the E-plane. The antenna realizes an average gain of 4.569 dB and is presented as a candidate for UWB applications.

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Substrate
Antenna Parameters
L W
Length (in mm) 29 34
DESIGN OF MICROSTRIP PATCH ANTENNA
FOR ULTRA WIDE BAND APPLICATIONS
Kumari Manisha1
, B. Ravinder2
Department of Electronics and Communication
CVR College of Engineering, JNTU Hyderabad
Hyderabad, India
ABSTRACT
This paper presents a planar trapezoidal patch antenna connected to a microstrip feedline, for ultra wideband (UWB)
applications with a wide usable fractional bandwidth of more than 107 %( 3 to 10 GHz) and impedance bandwidth of (1:3.4). The
proposed antenna has dimension of 34 × 29 × 1.6mm3
and has a wide slot etched to the ground plane which increases the
impedance bandwidth of the antenna. It has VSWR < 2 along with good radiation characteristics and return loss of more
than 10 DB.
Keywords—Trapezoidal patch, impedance bandwidth, UWB
I. INTRODUCTION
Microstrip antennas offer the advantages of thin profile, light weight, low cost, and conformability to the host surface and
compatibility with integrated circuitry. In addition to military applications, they have become attractive candidates in a variety of
commercial applications such as mobile satellite communications, the direct broadcast (DBS) system, global positioning system
(GPS), remote sensing and hyperthermia. This led to an extensive research aimed at improving the impedance bandwidth of
microstrip antennas in the last several years.
Since the Federal Communications Commission (FCC) opened the permit of 3.1–10.6 GHz frequency band for commercial
use, ultra wideband (UWB) systems have attracted huge attention in the past decade [1]. As a key component of the UWB system,
the UWB antenna has been studied and researched widely in the academia and industry.Good UWB antennas should have low
return loss, omni-directional or directional radiation pattern and high efficiency over the ultra-wide bandwidth. There are several
ways to widen the impedance bandwidth to design an UWB antenna. In [2], a rectangular patch antenna with tapered transition to
its feedline is designed which provides a high impedance bandwidth and stable radiation pattern. In [3],a knight’s helm shape
antenna with dual slots on rectangular patch is presented which provides a considerable amount of return loss and good
impedance matching for more bandwidth. In [4-7] different antennas with microstrip line feeding for wideband applications are
presented.
The proposed antenna is successfully designed and the simulated results show reasonable agreement with the bandwidth
requirement. In this design, a 3-10 GHz frequency range with impedance bandwidth (1:3.4) for VSWR < 2 and return loss more
than 10 dB is obtained. The radiation patterns and gain are also examined.
II. ANTENNA DESIGN AND IMPLEMENTATION
The proposed antenna consists of a trapezoidal patch connected to the feedline as shown in Fig 1(a) and Fig 1(b). The
photograph of the fabricated antenna is shown in Fig 1(c). The ground plane has a slot etched to it. Variation in the slot dimension
leads to different return loss values.The antenna has dimensions of 34 × 29 mm2
, which is printed on a FR4 substrate of thickness
1.6 mm, relative permittivity, r = 4.4 and loss tangent,tan =0.025.
The excitation is a 50Ω microstrip line. The antenna parameters i.e substrate, front patch and back patch are shown in Table I,
Table II and Table III respectively:
TABLE I. SUBSTRATE PARAMETERS
sub sub

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TABLE II. FRONT PATCH PARAMETERS
Front
Patch
Antenna Parameters
Wa Wb Lf Wf Lt
Length
(in mm) 15 10 12 3 4.716
TABLE III. BACK PATCH PARAMETERS
Back
Patch
Antenna Parameters
Ws Wb La Ls Lg
Length
(in mm) 23 5.5 6 12.85 10.15
(c)
Fig 1. Configuration of the proposed antenna (a) front view (b) back view and (c) fabricated antenna

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III. SIMULATION RESULTS AND DISCUSSIONS
The presented antenna is simulated with CST microwave studio 2011. Fig 2 shows the simulated S-parameter of the
antenna.There are three resonance peaks in the low, mid and high frequency range viz 3.5, 6.15 and 9.5GHz which are obtained due
to modification in ground plane. At these frequencies the antenna is radiating more as shown from the graph.
Fig 2. Simulated S-Parameter
The S-parameter of the proposed antenna is measured by the Rohde and Schwarz vector network analyzer. To be convenient
for comparison, measured and simulated S-parameter curves are shown in Fig 3.
Fig 3. Measured and Simulated S-Parameter
Simulated S-parameter results with varying port dimensions are shown in Fig 4. The best result is obtained with port
dimension of 8 × 6mm2
.
Fig 4. Simulated S-Parameter with varying port dimensions

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The simulated surface currents at 3.5,6 and 9.5 GHz are shown in Fig 5. For 3.5 GHz frequency, current is concentrated more
near the etched slot and less near the trapezoidal patch. For 6.15 GHz frequency, current concentration is more near the
trapezoidal patch whereas for 9.5 GHz frequency, current concentration is near the corners of the slot etched in the ground plane.
(a)
(b)
(c)
Fig 5. Simulated current distribution (a) 3.5 GHz, (b) 6 GHz and (c) 9.5 GHz
The simulated VSWR is less than 2 in the entire frequency range of 3 to 10 GHz as shown in Fig 5. For UWB applications,
VSWR < 2 is desired.

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Fig 6. Simulated VSWR
The simulated E-plane radiation pattern of the antenna is shown in Fig 7. The E-plane radiation pattern looks like a dumbbell
shaped structure because the alternating electric current enters the antenna through the feed line-patch junction and leaves the
antenna through the radiating edge of the patch and hence they form an electric field pattern having field maxima at the radiating
edges in the direction of radiation and field minima at the center of the patch hence a dumbbell shaped radiation pattern is formed
(i.e. bi-directional in nature).
(a) (b)
(c)
Fig 7. Simulated E-plane radiation pattern (a) 3.5 GHz, (b) 6 GHz and (c) 9.5 GHz
The simulated H- plane radiation pattern of the antenna is shown in Fig 8. The magnetic field that is induced due to the electric
field is perpendicular to the electric field lines and hence surrounds the entire electric field lines, thus generating a complete
sphericalshaped radiation pattern. Therefore the radiation pattern of the H-Plane is circular in shape (i.e. omnidirectional in nature).

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(a) (b)
(c)
Fig 8. Simulated H-plane radiation pattern (a) 9.5 GHz, (b) 6 GHz and (c) 3.5 GHz
The 3D radiation pattern of the antenna at 6 GHz is shown in Fig 9.
Fig 9. 3D Radiation Pattern of the antenna at 6 GHz
The realized gain vs frequency of the antennais shown in Fig 10. The gain has an average value of 4.569 dB.

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Fig 10. Realized Gain of the proposed antenna
IV. CONCLUSION
The proposed antenna has a trapezoidal patch which enhances its bandwidth and more resonance peaks are excited byetching a
slot in the ground plane. There is an enhancement in bandwidth by 107% and the impedance bandwidth of (1:3.4) is obtained.The
S-Parameter is more than 10DB throughout the frequency range and the VSWR < 2. Thus the proposed antenna can be a good
candidate for ultra wideband applications.
REFERENCES
[1] Federal Communications Commission (FCC), Washington, DC, “First report and order in the matter of revision of part 15 of the commission’s rules
regarding ultra-wideband transmission systems, ”ET-Docket 98-153, 2002.
[2] Design of a microstrip-fed tap monopole antenna with an ultra wide bandwidth by Z. N. Low, Student member, IEEE, J. H. Cheong, and C. L. Law,
Senior member, IEEE
[3] “Low-cost PCB antenna for UWB applications”, IEEE Antennas and Wireless Propagation Letters, Vol. 4, 2005
[4] R. Zaker, Ch. Ghobadi, and J. Nourinia, “A modified microstrip-fed two-step tapered monopole antenna for UWB and WLAN applications “,progress
in electromagnetics research, PIER 77, 137–148, 2007
[5] Dang Trang Nguyen, Dong Hyun Lee, and Hyun Chang Park,’’ Very compact printed triple band-notched UWB antenna with quarter-wavelength
slots”, IEEE Antennas and Wireless Propagation Letters, Vol. 11, 2012.
[6] Effect of slots in ground plane and patch on microstrip antenna performance by Raj Kumar, J. P. Shinde and M. D. Uplane
[7] R. M. Vane aet.al,”A shorted rectangular microstrip antenna with slots in ground plane”, IE (I), Journal- ET, Vol. 87, July 2006, pp. 19-20.
[8] Garg, R., Bhartia, P., Bahl, I., Ittipiboon, “A., microstrip antenna design handbook”, Artech House, Inc, 2001.
[9] Constantine Balanis, Antenna theory, analysis and design, 2nd ED., 2009, p.727-730