05-09-2012, 02:32 PM
A NOVEL MICROSTRIP PATCH ANTENNA WITH REDUCED SURFACE WAVE EXCITATION
[attachment=33435]
Abstract
A microstrip circular patch antenna with two shorting pins
is proposed as an antenna with reduced surface wave and lateral wave
excitation. Theoretical analysis of the cavity modes of the patch lead to
a design procedure for the antenna. Simulation results using the IE3DZeland
software support the theory and verify the reduced surface wave
capability. By using four shorting pins instead of two, we demonstrate
the possibility of achieving circular polarization with high polarization
purity in addition to the reduced surface wave. It is demonstrated that
a discrimination against the lateral wave of 30 dB or more is achievable.
Applications include design of large patch arrays with reduced coupling
and GPS receiving antennas that reduce low angle interfering signals.
INTRODUCTION
One of the major concerns in microstrip antenna design is the excited
surface waves. In addition to their contribution to power loss, surface
waves cause undesired coupling between components printed on the
same substrate, such as the case in patch antenna arrays [1]. Several
attempts have been made recently to reduce such coupling [e.g., 2–
5]. Eventually, excited surface waves will be diffracted at the edges
of a finite ground, which causes the radiation pattern to be corrupted
and deviate from its desired shape. Besides, the presence of surface
waves is usually associated with appreciable lateral waves and low angle
radiation. This can introduce interfering signals in receiving antennas
with broadside patterns such as the case with Global positioning
system (GPS) and assisted GPS receiving antennas [6, 7].
CIRCULARLY POLARIZED PATCH ANTENNA
WITH RSW
The patch antenna with two shorting pins considered above can
produce linearly polarized radiation but is not suitable for circular
polarization. This is so since the geometry lacks symmetry about
the y-axis (the H-plane). In many applications, such as the GPS,
circular polarization is the preferred polarization for combating space
propagation effects [16, 17]. To radiate or receive such polarization, we
propose a patch antenna with 4 shorting pins as depicted in Fig. 6.
Here we choose α = 45◦ in order to get the same symmetry about x
and y axes. The patch is fed by two feeds placed at φ = 0◦ and 90◦
and their currents are in phase quadrature.
CONCLUSIONS
A novel patch antenna with reduced surface wave and reduced lateral
wave capability has been introduced. The antenna is composed of
a circular patch with two shorting pins on a grounded dielectric
substrate. By properly adjusting the patch radius, the pins’ positions
and the dielectric constant, one can achieve reduced surface wave at
a prescribed resonant frequency. The idea is also extended to a 4-
pin shorted patch where the pins are located at the angular positions
φ = ±45◦ and ±135◦. While the 2-pin patch can support only linearly
polarized waves.
[attachment=33435]
Abstract
A microstrip circular patch antenna with two shorting pins
is proposed as an antenna with reduced surface wave and lateral wave
excitation. Theoretical analysis of the cavity modes of the patch lead to
a design procedure for the antenna. Simulation results using the IE3DZeland
software support the theory and verify the reduced surface wave
capability. By using four shorting pins instead of two, we demonstrate
the possibility of achieving circular polarization with high polarization
purity in addition to the reduced surface wave. It is demonstrated that
a discrimination against the lateral wave of 30 dB or more is achievable.
Applications include design of large patch arrays with reduced coupling
and GPS receiving antennas that reduce low angle interfering signals.
INTRODUCTION
One of the major concerns in microstrip antenna design is the excited
surface waves. In addition to their contribution to power loss, surface
waves cause undesired coupling between components printed on the
same substrate, such as the case in patch antenna arrays [1]. Several
attempts have been made recently to reduce such coupling [e.g., 2–
5]. Eventually, excited surface waves will be diffracted at the edges
of a finite ground, which causes the radiation pattern to be corrupted
and deviate from its desired shape. Besides, the presence of surface
waves is usually associated with appreciable lateral waves and low angle
radiation. This can introduce interfering signals in receiving antennas
with broadside patterns such as the case with Global positioning
system (GPS) and assisted GPS receiving antennas [6, 7].
CIRCULARLY POLARIZED PATCH ANTENNA
WITH RSW
The patch antenna with two shorting pins considered above can
produce linearly polarized radiation but is not suitable for circular
polarization. This is so since the geometry lacks symmetry about
the y-axis (the H-plane). In many applications, such as the GPS,
circular polarization is the preferred polarization for combating space
propagation effects [16, 17]. To radiate or receive such polarization, we
propose a patch antenna with 4 shorting pins as depicted in Fig. 6.
Here we choose α = 45◦ in order to get the same symmetry about x
and y axes. The patch is fed by two feeds placed at φ = 0◦ and 90◦
and their currents are in phase quadrature.
CONCLUSIONS
A novel patch antenna with reduced surface wave and reduced lateral
wave capability has been introduced. The antenna is composed of
a circular patch with two shorting pins on a grounded dielectric
substrate. By properly adjusting the patch radius, the pins’ positions
and the dielectric constant, one can achieve reduced surface wave at
a prescribed resonant frequency. The idea is also extended to a 4-
pin shorted patch where the pins are located at the angular positions
φ = ±45◦ and ±135◦. While the 2-pin patch can support only linearly
polarized waves.