Progress In Electromagnetics Research Symposium Proceedings, Moscow, Russia, August 18–21, 2009
Small Size and Multiband Monopole F-shaped Antenna
Configuration for Wireless Communications Applications
Fawwaz J. Jibrael and Majd F. Yuhanna
Electrical and Electronic Engineering Department, University of Technology, Baghdad, Iraq
Abstract— The performance and analysis of a small size and multiband monopole F-antenna
(MFA) are introduced. The proposed antenna design, analysis and characterization are per-
formed using the Method of Moments (MoM) technique. The radiation characteristics, VSWR,
reflection coefficient, input impedance, gain, and polarization of the proposed antenna are de-
scribed and simulated using 4NEC2 software package. The proposed antenna operates at higher
than frequency band (3 or 4 bands) depending on dimensions of the antenna.
In today’s world of expanding wireless communications, there is increasing need for more compact,
multiband, and moderate gain antennas for portable communication systems to respond to the
great demand for both military and commercial communication systems. Multi-band and wideband
antennas are desirable in personal communication systems, small satellite communication terminals,
and other wireless applications. Wideband antennas also find applications in Unmanned Aerial
Vehicles (UAVs), Counter Camouflage, Concealment and Deception (CC&D), Synthetic Aperture
Radar (SAR), and Ground Moving Target Indicators (GMTI). Some of these applications also
require an antenna be embedded into the airframe structure. Monopole F-Antenna (MFA) designs
can assist in meeting these design requirements.
The designed antenna operates at more than one frequency, characterized by its small size,
whose design depends on variable dimensions, and is not printed antenna [1–3]. It offers high gain
ranging between 4-to-10dB.
2. PROPOSED ANTENNA GEOMETRY AND DESIGN
Figure 1 depicts the proposed antenna, known as monopole F-antenna (MFA), placed in Y Z-plane.
This antenna is divided into three parts: L1, L2, and L3, as shown in Figure 1 with relevant
dimensions. This antenna is simulated using commercial numerical modeling software 4NEC2,
a Method of Moment-based software. The Method of Moment (MoM) is used to calculate the
current distribution along the monopole F-antenna, and hence the radiation characteristics of the
antenna . The 4NEC2 program is used in all simulations. This is very effective in analyzing
antennas that can be modeled with wire segments, such as the one under consideration here. To
suit the requirements, the antenna is modeled with no dielectric present, although some of the
practical implementations do require dielectric support . The modeling process is simply done
by dividing all straight wires into short segments where the current in one segment is considered
constant along the length of the short segment. It is important to make each wire segment as short
as possible without violating computational restrictions maximum segment length to radius ratio.
In NEC, to model wire structures, the segments should follow the paths of conductor as closely as
Feed source of this antenna is set at 1 volt and the design frequency is chosen as 750MHz, which
gives design wavelength λ of 0.4m (40cm), giving length (L1) of the corresponding λ/4 monopole
antenna length of 10cm and the wire conductor radius of 1mm, as shown in Figure 1.
Figure 1 consists of two ((a) and (b)) different shapes of the proposed antenna, differing only in
dimension (L3). The effect of dimensions’ variation can be seen on input impedance, gain, VSWR,
and frequency bands in the results subsection later.
3. ANTENNAS SIMULATIONS AND RESULTS
From the results of Method of Moment simulation code (NEC), used to perform detailed study of
VSWR, reflection coefficient, gain, input impedance, polarization and radiation pattern character-
istics of the monopole F-antenna.
The real and imaginary parts of the input impedance of these proposed antennas (Figure 1(a) and
1(b)) are shown in Table 1. It shows the multiple resonance characteristics of the antenna together