Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1999-07-26
2002-07-02
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S895000
Reexamination Certificate
active
06414638
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna for a radio telephone, and more particularly to an antenna for a radio telephone for use in a cellular, PHS (Personal Handy Phone System), or other mobile phone system.
2. Description of the Related Art
Today, cellular, PHS, and other mobile phone systems enjoy widespread use. The radio telephones (telephones) used in such systems have in recent years become increasingly more compact and lightweight, creating a need to make the antennas used therefor smaller in association with the smaller size and lighter weight of the radio telephones.
An extendible/retractable antenna used by extending a rod-shaped antenna from the case of the radio telephone to communicate in locations where electric field strength is weak, and retracting the rod-shaped antenna into the case of the radio telephone to make it convenient to hold and walk when being carried about, and that stands by to receive calls with a helical antenna alone is commonly known as a conventional radio telephone antenna of this type.
For example, there is known an antenna of the kind depicted in
FIG. 11
, wherein a conductor
71
constituting the main body of a rod-shaped antenna
70
is provided at the distal end thereof via an insulating connecting member
72
and a conducting connector
82
with a helical coil
81
constituting the main body of a helical antenna
80
(hereinafter termed “antenna of Conventional Art Example 1”). Where &lgr; represents the wavelength of the service frequency, the electrical length of the rod-shaped antenna
70
is established in the vicinity of &lgr;/4 and the electrical length of the helical antenna
80
is established at &lgr;/4. When the antenna of Conventional Art Example 1 is extended from the case
50
of the radio telephone (
FIG. 11
a
), a high-frequency electric current from a power supply point
41
provided to the circuit board
40
of the radio telephone is supplied through a connecting lead
42
and via a metal retaining member
91
and a fastener
92
so as to excite the antenna
70
. The helical coil
81
provided to the distal end of the conductor
71
is insulated by means of the connecting member
72
, so the high-frequency electric current supplied by the power supply point
41
is obstructed by the connecting member
72
and does not excite the helical antenna
80
. That is, in the state of the antenna being extended from the case
50
, radio waves are emitted from the rod-shaped antenna
70
exclusively, and radio waves are not emitted from the helical antenna
80
.
Meanwhile, when the rod-shaped antenna
70
is retracted within the case
50
(
FIG. 11
b
), high-frequency electric current supplied by the power supply point
41
of the radio telephone through the connecting lead
42
and via the conducting connector
82
excites the helical antenna
80
. The rod-shaped antenna
70
retracted within the case
50
is not excited since the high-frequency electric current is obstructed by the connecting member
72
.
That is, as shown in
FIG. 12
the antenna of Conventional Art Example 1 is such that when the rod-shaped antenna
70
is extended from the case
50
for use, sending and reception are carried out exclusively by the rod-shaped antenna
70
of electrical length in the proximity of &lgr;/4, and where the rod-shaped antenna
70
is retracted within the case
50
for use, sending and reception are carried out exclusively by the helical antenna
80
of electrical length of &lgr;/4.
Also known is an antenna like that depicted in
FIG. 12
, wherein a helical coil
81
is arranged at the distal end of a conductor
11
via a conducting connector
73
only (hereinafter termed “antenna of Conventional Art Example 2”). A rod-shaped antenna
74
comprises a conductor
71
and a connector
73
, the electrical length thereof being established at &lgr;/2, including the conductor
71
and the connector
73
. The electrical length of a helical antenna
80
comprising a helical coil
81
is established at &lgr;/4.
The conductor
71
and the helical coil
81
are electrically connected by means of the connector
73
, and thus when the antenna of Conventional Art Example 2 is in a state extended from the case
50
(
FIG. 12
a
), high-frequency electric current from a power supply point
41
supplied through a connecting lead
42
and via a metal retaining member
91
and a fastener
92
excites the rod-shaped antenna
74
as well as exciting the helical antenna
80
. The electrical length of the rod-shaped antenna
74
is &lgr;/2 and the electrical length of the helical antenna
80
is &lgr;/4, so in a state with the rod-shaped antenna
74
extended from the case
50
, the total electrical length of the rod-shaped antenna
74
and the helical antenna
80
is 3&lgr;/4.
Meanwhile, in a state with this antenna retracted within the case
50
(
FIG. 12
b
), high-frequency electric current from the power supply point
41
of the radio telephone supplied through the connecting lead
42
and via the connector
73
excites not only the helical antenna
80
but also the rod-shaped antenna
74
retracted within the case
50
.
That is, this antenna of Conventional Art Example 2 is such that, in the event that the rod-shaped antenna
72
is extended from the case
50
, the rod-shaped antenna
3
of electrical length of &lgr;/2 and the helical antenna
4
of electrical length of &lgr;/4 are simultaneously excited to carry out sending and reception as an antenna of electrical length of 3&lgr;/4, and in the event of use with the rod-shaped antenna
74
retracted within the case
50
, sending and reception are carried out through parallel operation of the rod-shaped antenna
74
of electrical length of &lgr;/2 and the helical antenna
80
of electrical length of &lgr;/4.
As is well known, emission within a vertical plane by a rod-shaped antenna of electrical length of &lgr;/4 is directed downward with respect to the horizontal direction,. which is a cause of lowered sensitivity in the horizontal direction. Accordingly, the antenna of Conventional Art Example 1 having a rod-shaped antenna
70
of electrical length of &lgr;/4 has this problem of lowered sensitivity. Since the rod-shaped antenna
70
is a grounded type antenna, when the radio telephone is used by pressing against the ear, there is the problem of the impedance characteristic, etc., fluctuating due to the effects of the human body.
Further, in the antenna of Conventional Art Example 1, in the state with the rod-shaped antenna
70
extended from the case
50
, the helical antenna
80
functions merely as a grip for extending and retracting the rod-shaped antenna
70
with respect to the case
50
, and efficiency is poor given the size of the antenna.
Since it is common to manufacture the conductor
71
using a member of small diameter having good elasticity, the arrangement of a helical coil
81
having large mass at the distal end thereof creates susceptibility to vibration due to external pressure, the amplitude thereof being large, creating susceptibility to mechanical or electrical noise and posing the risk that the retaining power of the retaining member
91
may deteriorate.
Further, the connecting member
72
of this antenna of Conventional Art Example 1 has a problem in terms of flexural strength, and depending on the length thereof breakage may occur with repeated flexing. Improving the flexural durability requires means such as lengthening the length, etc., but by so doing the total length of the rod-shaped antenna
70
will become physically long, creating the problem of not being retractable into the case at the time of retraction.
Meanwhile, as is well known, emission within a vertical plane by an antenna of electrical length of 3&lgr;/4 is split into two directions with respect to the horizontal direction, with the main emission being upward-directed, and remains slightly in the horizontal direction as sub-emission. Accordingly, in the antenna of Conventional Art Example 2, wherein transmission and reception are carried out as a
Houkou Electric Corporation
Nixon & Peabody LLP
Studebaker Donald R.
Wimer Michael C.
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