Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1999-07-28
2001-01-30
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S770000
Reexamination Certificate
active
06181280
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to microstrip antennas and, in particular, to a method of enhancing the bandwidth of a microstrip antenna without increasing the size or weight of the antenna.
2. Description of the Related Art
Microstrip antennas have many interesting properties such as low profile and lightweight. However, the inherent narrow bandwidth of a microstrip antenna is one of its serious disadvantages. The conventional microstrip antenna typically exhibits a bandwidth of only 1-2% of the resonant frequency. The narrow bandwidth of the microstrip antenna is often inadequate to meet the requirements for practical applications. The development of techniques for the enhancement of the bandwidth of microstrip antenna has been a topic of special emphasis for several years.
A conventional microstrip antenna is shown in
FIGS. 17A and 17B
. The microstrip antenna
170
illustrated in
FIGS. 17A and 17B
consists of a dielectric substrate
101
, a radiating element
102
constructed on the top surface of the substrate
101
and a ground plane
103
constructed on the bottom surface of the substrate
101
. A power feed hole
104
is provided at a point corresponding to the radiating element
102
on the substrate
101
. A connector
105
, used for feeding radio frequency (RF) power to the radiating element
102
, is inserted through the feed hole
104
from the bottom surface of the substrate
101
. The connector
105
is electrically connected to the radiating element
102
with solder
106
a
and is fixed to the ground plane
103
by solder
106
b.
The techniques currently available for enhancing the bandwidth of microstrip antennas (MSA) include use of a thicker substrate, multi-layer stacked microstrip antennas, electromagnetically coupled (EMC) microstrip antennas, microstrip antennas with parasitic elements, aperture coupled microstrip antennas, and use of external matching circuits. As will be clear from the explanations to be provided, some of the above techniques result in an increase in size and weight of the microstrip antenna while some others suffer from the lack in the structural simplicity usually associated with conventional microstrip antennas.
The prior art structural configurations of microstrip antenna for the improvement of bandwidth using the above mentioned techniques are described below. The elements of new microstrip antennas which are similar to that of the conventional microstrip antenna
170
will have same reference numbers as in
FIGS. 17A and 17B
and additional reference explanations will be omitted.
The prior art microstrip antenna
120
with thick substrate material shown in
FIGS. 12A and 12B
has the undesirable characteristics of increased height and weight of the antenna. The thick substrate of the microstrip antenna shown in
FIGS. 12A and 12B
increases the dielectric loss and also increases the cost of the antenna. The thick substrate of the antenna of
FIGS. 12A and 12B
also causes the generation of surface waves and hence degrades the radiation pattern, which is not desirable.
The prior art microstrip antenna
130
with parasitic elements illustrated in
FIG. 13
has two additional parasitic elements
107
adjacent to the radiating element
102
. A narrow gap separates these parasitic elements
107
from the main radiating element
102
. The microstrip antenna
130
has the disadvantages of increased length and weight.
FIG. 14
illustrates the configuration of a prior art electromagnetically coupled microstrip antenna
140
. Antenna
140
has two substrates
101
placed one above the other. The bottom surface of the top substrate
101
does not have conductive film. There is a radiating element
102
on the top surface of the upper substrate
101
and a narrow microstrip line
108
on the top surface of the lower substrate
101
acts as a feed for the radiating element
102
. The microstrip antenna
140
has the disadvantages of increased height, increased weight and higher cost.
A prior art microstrip antenna
150
with multi-layer stacked elements is illustrated in FIG.
15
. Antenna
150
has two radiating microstrip elements
102
, one on the top surface of upper substrate
101
and the other on the top surface of the middle substrate
101
. The radiating elements
102
are stacked one above the other. A narrow microstrip line
108
is positioned on the top surface of bottom substrate
101
. Microstrip line
108
serves as a common feed for the two radiating elements
102
. As in microstrip antenna
140
, there is no conductive film on the bottom surfaces of the upper and middle substrates
101
. The disadvantages of microstrip antenna
150
are increased height, weight, complexity of design, and higher cost.
A prior art aperture coupled microstrip antenna
160
is shown in FIG.
16
and comprises a radiating element
102
on the top surface of upper substrate
101
and a conductive ground plane
103
with an opening or aperture
109
. A narrow microstrip feed line
108
positioned on the top surface of bottom substrate
101
serves as a feed to the aperture
109
. Power is coupled to the radiating element
102
through the aperture
109
. The disadvantages of microstrip antenna
160
are structural complexity, design complexity, increased height, increased weight, and higher cost.
The prior art microstrip antenna with external matching circuit involving inductors and capacitors does not increase the height and or linear dimensions of the antenna. The inductors and capacitors are used near the feed point of the microstrip antenna and provide a better impedance match, hence an improvement in bandwidth results. The disadvantage is that increased bandwidth is at the expense of an undesirable loss in gain of the antenna. Although the matching circuit components are part of the device to which the microstrip antenna is attached and technically are not part of the antenna, they do add to the total cost of the device.
In the past, shorting pins or slots have been used in microstrip antennas to reduce the resonant frequency or to achieve a dual frequency mode of operation. In the prior art, slots or shorting pins have been used separately to achieve dual frequency performance of the antenna. See, for example, S. C. Pan and K. L. Wong “Design of Dual Frequency Microstrip Antennas using shorting pin loading”, IEEE-APS Symposium, Atlanta, June 1998, pp. 312-315; K. L. Wong and W. S. Chen, “Compact microstrip antenna with dual-frequency operation”, Electronics Letters, Apr. 10th 1997, Vol. 33, No. 8, pp. 646-647; S. Maci, Biffi Gentili, P. Piazzesi and C. Salvador, “Dual band slot-loaded patch antenna”, IEE Proc.-Microw. Antennas Propag., Vol. 142, No. 3, June 1995, pp. 225-232; and S. Maci, G. Biffi Gentili and G. Avitabile, “Single-Layer Dual Frequency Patch Antenna”, Electronics Letters, Aug. 5th 1993, Vol. 29, No. 16, pp. 1441-1443, hereinafter referred to as Pan et al., Wong et al., Maci et al., and Maci et al. (II), respectively.
B. F. Wang and Y. T. Lo, “Microstrip Antennas for Dual-Frequency Operation”, IEEE Transactions on Antennas and Propagation, Vol. AP-32, No. 9, September 1984, pp. 938-943, describes the dual frequency operation of a microstrip antenna using a combination of slots and shorting pins. In the above-cited references, the obtained bandwidths centered around the dual resonant frequencies have been relatively narrow (1-2% of resonant frequencies). There is also a practical lower limit for ratio of (f
u
/f
L
) (f
u
and f
L
being the upper and lower resonant frequencies, respectively). As a consequence of the lower ratio of (f
u
/f
L
), the resonant bands centered around the dual resonant frequencies are rather widely separated. Therefore, combining the two narrow resonant bands to improve the overall bandwidth is very difficult using the previously used configurations that have been illustrated in the above references.
To circumvent the existing disadvantages of the available microstrip antenna bandwidth enhancing techniques, it is the objective of the present inv
Kadambi Govind R.
Masek Thomas F.
Centurion Intl., Inc.
Ho Tan
Thomte Dennis L.
Zarley McKee Thomte Voorhees & Sease
LandOfFree
Single substrate wide bandwidth microstrip antenna does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Single substrate wide bandwidth microstrip antenna, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Single substrate wide bandwidth microstrip antenna will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2537838