Communications: radio wave antennas – Antennas – High frequency type loops
Reexamination Certificate
2002-10-12
2004-01-20
Nguyen, Hoang V. (Department: 2821)
Communications: radio wave antennas
Antennas
High frequency type loops
C343S866000, C343S702000
Reexamination Certificate
active
06680708
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a loop-shaped antenna and a surface-mounted antenna to be mounted on a circuit board of communication equipment, for example, and the communication equipment having such an antenna.
2. Description of the Related Art
A conventional antenna of this type includes a plurality of radiant electrodes. Each of the radiant electrodes has a resonance frequency band that is different from each other so as to transmit or receive each of a plurality of signals having different resonance frequency bands. As a result, one antenna having a plurality of radiant electrodes can transmit or receive signals with a plurality of frequency bands.
However, in such an antenna, miniaturizing of the antenna is difficult because of the need to have a plurality of radiant electrodes.
FIG. 6
is a schematic perspective view of an example of a surface-mounted antenna. In a surface-mounted antenna
20
, a base member
21
made of a dielectric substance is provided with a feeding radiant electrode
22
arranged to extend from a bottom surface
21
a
toward a side surface
21
d
via a side surface
21
b
and a top surface
21
c
. A metallic plate
24
is attached to the base member
21
with one end connected to the feeding radiant electrode
22
. The other end of the metallic plate
24
is an open end. In the surface-mounted antenna
20
, one radiant electrode is defined by the feeding radiant electrode
22
and the metallic plate
24
.
Such a surface-mounted antenna
20
is connected on a substrate
25
of an object to be mounted (a circuit board of communication equipment, for example) by soldering using the bottom surface
21
a
of the base member
21
as a mounting surface. The base member
21
is provided with a fixing electrode
23
, which is to be a base electrode for soldering. The fixing electrode
26
may be grounded or may not be grounded on the substrate
25
of the object to be mounted (mounting substrate) depending on a circuit of the mounting substrate
25
.
The feeding radiant electrode
22
is connected to a signal supply source
27
via a matching circuit
26
by mounting the surface-mounted antenna
20
on the mounting substrate
25
exactly as designed. Supplying a signal from the signal supply source
27
to the feeding radiant electrode
22
via the matching circuit
26
transmits the signal to the metallic plate
24
via the feeding radiant electrode
22
. By the signal supply, the feeding radiant electrode
22
and the metallic plate
24
produce resonance so as to perform an antenna operation (that is, transmitting or receiving of a signal).
As noted above, the radiant electrode has a plurality of resonant frequencies that are different from each other so as to be able to produce resonance at each of the frequencies. Accordingly, in order to make an antenna applicable to a plurality of communication systems, it is under consideration that one radiant electrode is made to perform a higher-order-mode antenna operation with a frequency higher than that of a basic-mode as well as perform the basic-mode antenna operation (that is, operation of transmitting or receiving of a signal), by utilizing not only the resonance with the basic lowest resonance frequency of the radiant electrode but also the resonance with a higher-order-mode resonance frequency higher than that.
However, in the structure of the surface-mounted antenna
20
, it has been difficult to satisfactorily perform the higher-order mode antenna operation because of insufficiency in a gain.
Since the mounting substrate is assumed to be a grounded plane, in the structure of the surface-mounted antenna
20
, an unnecessary capacitance is produced between the metallic plate
24
and the mounting substrate
25
. There is a problem that the antenna gain is liable to deteriorate because of the unnecessary capacitance between the metallic plate
24
and the mounting substrate
25
.
SUMMARY OF THE INVENTION
In order to solve the above-described problems, preferred embodiments of the present invention provide a miniaturized loop antenna having only one radiant electrode that is capable of transmitting or receiving signals with a plurality of frequency bands that are different from each other so as to perform a basic-order-mode antenna operation and a higher-order-mode antenna operation and a communication apparatus including such a novel antenna.
According to one preferred embodiment of the present invention, a loop antenna includes a linear radiant electrode for performing an antenna operation, one end of the radiant electrode being a feeding end for receiving a signal from a signal supply source and the other end being an open end, wherein the radiant electrode has a substantially loop shape, in which a feeding-end portion and an open-end portion are arranged adjacent to each other with a spaced defined therebetween, and wherein the radiant electrode is provided with a short-cut electrode short-cutting a loop of the radiant electrode.
Preferably, the loop of the radiant electrode extending from the feeding end toward the open end has an electrical length corresponding to a predetermined basic-mode resonance frequency while a short loop extending from the feeding end of the radiant electrode toward the open end via the short-cut electrode has an electrical length corresponding to a higher-order-mode resonance frequency higher than the basic-mode resonance frequency, such that the radiant electrode performs a basic-mode antenna operation and a higher-order-mode antenna operation.
Preferably, the radiant electrode is narrow plate-shaped instead of being linear shaped.
According to this preferred embodiment of the present invention, the wire or narrow plate-shaped radiant electrode is formed to have a substantially loop shape by arranging a feeding-end portion and an open-end portion adjacent to each other with a space provided therebetween. The radiant electrode is provided with the short-cut electrode short-cutting the loop of the radiant electrode. The loop extending from the feeding end of the radiant electrode toward the open end has an electrical length corresponding to the established basic-mode resonance frequency while the short loop extending from the feeding end of the radiant electrode toward the open end via the short-cut electrode has an electrical length corresponding to the established higher-order-mode resonance frequency, so that the radiant electrode can perform predetermined basic-mode and higher-order-mode antenna operations.
That is, signals with predetermined plural frequency bands can be transmitted or received by providing only one radiant electrode, so that the miniaturizing of the antennal can be facilitated in comparison with an antenna having plural radiant electrodes.
In the loop antenna according to this preferred embodiment of the present invention, an electrical length of the loop (basic loop) extending from the feeding end of the radiant electrode toward the open end determines the basic-mode resonance frequency of the radiant electrode while the short loop extending from the feeding end of the radiant electrode toward the open end via the short-cut electrode determines the higher-order-mode resonance frequency of the radiant electrode. The electrical length of the short loop can be changed and set by adjusting the arrangement and length of the short-cut electrode independently of the electrical length of the basic loop. That is, the electrical length of the basic loop and the electrical length of the short loop can be changed and set separately from each other. Therefore, the basic-mode resonance frequency of the radiant electrode and the higher-order-mode resonance frequency can be adjusted and set to independently have the respective established frequencies. Thereby, the design of the radiant electrode is extremely flexible and easy so as to easily allow for and accommodate many design changes.
In contrast, in a conventional antenna, when the radiant electrode is to perform an antenna operation by using higher-order-m
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Hoang V.
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