Information
-
Patent Grant
-
6816122
-
Patent Number
6,816,122
-
Date Filed
Tuesday, January 28, 200321 years ago
-
Date Issued
Tuesday, November 9, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Frishauf, Holtz, Goodman & Chick, P.C.
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
In an electromagnetic coupling type four-point feeding loop antenna (10) comprising a tubular body (11), a loop portion (12) having a loop width (W1), four feeders (13) each having a feeder width (W2), and four electromagnetic coupling wires (17) each having a coupling wire width (W3), the loop width, the feeder width, and the coupling wire width are substantially equal to one another. A gap (δ) between the feeder and the electromagnetic coupling wire is laid in a range between 0.2 mm and 0.8 mm, both inclusive, when the electromagnetic coupling type four-point feeding loop antenna has a feeding impedance of a range between 25 Ω and 100 Ω, both inclusive.
Description
This application claims priority to prior application JP 2002-20097, JP 2002-70097, JP 2002-91512, and JP 2002-93843, the disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a digital radio receiver for receiving an electric wave from an artificial satellite (that may be called a “satellite wave”) or an electric wave on the ground (that may be called a “terrestrial wave”) to listen in a digital radio broadcasting and, in particular, to a loop antenna for use in the digital radio receiver.
In recent years, a digital radio receiver, which receives the satellite wave or the terrestrial wave to listen in the digital radio broadcasting, has been developed and is put to practical use in the United States of America. The digital radio receiver is mounted on a mobile station such as an automobile and can receive an electric wave having a frequency of about 2.338 gigaheltz (GHz) to listen in a radio broadcasting. That is, the digital radio receiver is a radio receiver which can listen in a mobile broadcasting. In addition, the terrestrial wave is an electric wave in which a signal where the satellite wave received in an earth station is frequently shifted a little. It is noted that the satellite wave is circular polarization while the terrestrial wave is linear polarization.
In order to receive such an electric wave having the frequency of about 2.338 GHz, it is necessary to set up an antenna outside the automobile. Although such antennas have been proposed those having various structures, the antennas of cylindrical-type are generally used rather than those of planer-type (plane-type). It is possible to obtain a wider directivity by making a shape of the antenna cylindrical.
A loop antenna is known in the art as one of the antennas of the cylindrical-type. The loop antenna has structure where one antenna lead member is wound around a peripheral surface of a hollow or solid cylindrical (which is collectively called “cylindrical”) member in a loop fashion, namely, is an antenna having the form of a loop. The cylindrical member may be merely called a “bobbin” or a “dielectric core” in the art. In addition, the antenna lead member may be merely called a “lead.” It is known in the art that the loop antenna acts as an antenna having a directivity in a longitudinal direction thereof if the antenna lead member has an all around length which is selected to about one wavelength. This is because the antenna lead member has a sinusoidal distribution of a current. The loop antenna is for receiving the circular polarization or the satellite wave. That is, the loop antenna is used as a satellite wave antenna.
Although it is necessary for the loop antenna to feed to it, a four-point feeding is generally adopted to the loop antenna. In order to receive circular polarization, feeding is carried out at four points having a phase difference of 90 degrees. The loop antenna with the four-point feeding is called in the art a four-point feeding loop antenna. In an existing four-point feeding loop antenna, a feeding is directly carried out to a loop portion.
More specifically, the existing four-point feeding loop antenna comprises a cylindrical body formed by rounding a flexible insulation film around a central axis in a cylindrical fashion, a loop portion made of conductor that is formed on the cylindrical body along a peripheral surface thereof around the central axis in a loop fashion, and four feeders formed on the peripheral surface of the cylindrical body to feed the loop portion at four points. The loop portion is directly connected with each of the four feeders. Such a four-point feeding loop antenna is called a directly coupling type four-point feeding loop antenna.
After the electric wave is received by the loop portion as a received wave, the received wave is divided through the four feeders into four partial received waves which are phase shifted and combined by a phase shifter so as to match phases of the four partial received waves to obtain a combined wave, and then the combined wave is amplified by a low-noise amplifier (LNA) to obtain an amplified wave which is delivered to a receiver body. A combination of the four-point feeding loop antenna, the phase shifter, and the low-noise amplifier is called an antenna device.
In the manner which is described above, inasmuch as the existing four-point feeding loop antenna directly feeds the loop portion from the four feeders, the existing four-point feeding loop antenna is disadvantageous in that it has a too high feeding impedance. Thus, the existing four-point feeding loop antenna is disadvantageous in that it is difficult to obtain an impedance match.
In addition, a monopole antenna is for receiving the linear polarization or the terrestrial wave. That is, the monopole antenna is used as a terrestrial wave antenna. A combination of the loop (or satellite wave) antenna and the monopole (or terrestrial wave) antenna is called a composite antenna. In order to receive both of the satellite wave and the terrestrial wave, an antenna unit including the composite antenna is used. The antenna unit further comprises a shield case mounting the loop antenna and the monopole antenna thereon, top and bottom covers for covering the loop antenna, the monopole antenna, and the shield case. In order to connect the antenna unit with a receiver body, a twin cable is used. The twin cable is connected to the shield case through a bushing sandwiched between the top cover and the bottom cover. The twin cable consists of a first cable for the loop antenna or the satellite wave and a second cable for the monopole antenna or the terrestrial wave. The first cable has a first connector at a tip thereof while the second cable has a second connector at a tip thereof.
On the other hands, the receiver body has a first receptacle for the satellite wave and a second receptacle for the terrestrial wave. Accordingly, the first and the second connectors must be connected to the first and the second receptacles, respectively. It is therefore necessary to distinguish between the first cable and the second cable.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a four-point feeding loop antenna which is capable of easily obtaining an impedance match.
It is another object of the present invention to provide a four-point feeding loop antenna which is capable of widening an adjustment range of impedance and a frequency characteristic thereof.
It is still another object of the present invention to provide a four-point feeding loop antenna which has a high antenna gain.
It is yet another object of the present invention to provide an antenna unit comprising a twin cable which is capable of certainly distinguishing between a first cable for a satellite wave and a second cable for a terrestrial wave.
Other objects of this invention will become clear as the description proceeds.
According to a first aspect of this invention, an electromagnetic coupling type four-point feeding loop antenna comprises a tubular body formed by rounding a flexible insulator film member around a central axis in a tubular fashion. The tubular body has a peripheral surface. Made of conductor, a loop portion is formed on the tubular body along the peripheral surface around the central axis in a loop fashion. The loop portion has a loop width. Four feeders are formed on the peripheral surface of the tubular body to feed to the loop portion at four points. Each of the four feeders has a feeder width. Connected to the loop portion, four electromagnetic coupling wires extend on the flexible insulator film member from the loop portion along the four feeders with gaps left between the four feeders and the four electromagnetic coupling wires, respectively. Each of the four electromagnetic coupling wires has a coupling wire width. The loop width, the feeder width, and the coupling wire width are substantially equal to one another. Each of the gaps is laid in a range between 0.2 mm and 0.8 mm, both inclusive, when the electromagnetic coupling type four-point feeding loop antenna has a feeding impedance of a range between 25 Ω and 100 Ω, both inclusive.
According to a second aspect of this invention, an electromagnetic coupling type four-point feeding loop antenna comprises a tubular body formed by rounding a flexible insulator film member around a central axis in a tubular fashion. The tubular body has a peripheral surface. A loop portion made of conductor is formed on the tubular body along the peripheral surface around the central axis in a loop fashion. Four feeders are formed on the peripheral surface of the tubular body to feed to the loop portion at four points. Four pairs of electromagnetic coupling wires are connected to the loop portion. Each pair of electromagnetic coupling wires extends on the flexible insulator film member from the loop portion along one of the four feeders with gaps so as to put the one of the four feeders between the pair of electromagnetic coupling wires.
According to a third aspect of this invention, a four-point feeding loop antenna comprises a tubular body formed by rounding a flexible insulator film member around a central axis in a tubular fashion. The tubular body has a peripheral surface. A loop portion made of conductor is formed on the tubular body along the peripheral surface around the central axis in a loop fashion. The loop portion has four bending portions each of which is bent towards a feeding source. Four feeders are formed on the peripheral surface of the tubular body to feed to the loop portion at four points.
According to a fourth aspect of this invention, an antenna unit comprises a satellite wave antenna for receiving a satellite wave, a terrestrial wave antenna for receiving a terrestrial wave, and a shield case mounting the satellite wave antenna and the terrestrial wave antenna thereon. Top and bottom covers are for covering the satellite wave antenna, the terrestrial wave antenna, and the shield case. A twin cable is connected to the shield case through a bushing sandwiched between the top cover and the bottom cover. The twin cable comprises a first cable for the satellite wave antenna and a second cable for the terrestrial wave antenna. The first and the second cables have first and second outer coats, respectively. At least one of the first and the second outer coats has marking formed thereon to allow to distinguish between the first cable and the second cable.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1A
is a plan view showing an electromagnetic coupling type four-point feeding loop antenna according to a first embodiment of this invention;
FIG. 1B
is a front view of the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIG. 1A
;
FIG. 2
is a perspective view showing an arrangement relationship between a loop portion and four feeders which constitute the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 1A and 1B
;
FIG. 3
is development of the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 1A and 1B
;
FIG. 4A
is a plan view showing a composite antenna including the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 1A and 1B
;
FIG. 4B
is a front view of the composite antenna illustrated in
FIG. 4A
;
FIG. 5A
is a plan view showing a composite antenna including an electromagnetic coupling type four-point feeding loop antenna according to a second embodiment of this invention;
FIG. 5B
is a front view of the composite antenna illustrated in
FIG. 5A
;
FIG. 6
is a perspective view showing an arrangement relationship between a loop portion and four feeders which constitute the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 5A and 5B
;
FIG. 7
is development of the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 5A and 5B
;
FIG. 8A
is a plan view showing a composite antenna including an electromagnetic coupling type four-point feeding loop antenna according to a second embodiment of this invention;
FIG. 8B
is a front view of the composite antenna illustrated in
FIG. 5A
;
FIG. 9
is a perspective view showing an arrangement relationship between a loop portion and four feeders which constitute the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 8A and 8B
;
FIG. 10
is development of the electromagnetic coupling type four-point feeding loop antenna illustrated in
FIGS. 8A and 8B
;
FIG. 11A
is a plan view showing an antenna unit including the composite antenna illustrated in
FIGS. 4A and 4B
;
FIG. 11B
is an longitudinal sectional view of the antenna unit illustrated in
FIG. 11A
;
FIG. 12A
is a plan view of a twin cable for use in the antenna unit illustrated in
FIGS. 11A and 11B
; and
FIG. 12B
is a sectional view taken along a line A—A in FIG.
12
A.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to
FIGS. 1A
,
1
B,
2
, and
3
, the description will proceed to an electromagnetic coupling type four-point feeding loop antenna
10
according to a first embodiment of this invention. The illustrated electromagnetic coupling type four-point feeding loop antenna
10
has a central axis O and comprises a tubular body
11
, a loop portion
12
, four feeders
13
. In the example being illustrated, the tubular body
11
is a cylindrical body.
The tubular body
11
is formed by rounding a flexible insulator film member (which will later be described) around the central axis O in a tubular fashion in the manner which will later be described. The loop portion
12
is made of conductor and is formed on the tubular body
11
along a peripheral surface thereof around the central axis O in a loop fashion. The four feeders
13
are formed on the peripheral surface of the tubular body
11
to feed to the loop portion
12
at four points. As the conductor of the loop portion
12
, for example, copper foil may be used. In addition, as the flexible insulator film member for use in the tubular body
11
, for example, plastic such as polyimide resin is used. In the example being illustrated, the tubular body
11
has a diameter of 20 mm.
According to this invention, the electromagnetic coupling type four-point feeding loop antenna
10
has gaps δ between the loop portion
12
and the four feeders
13
to feed to the loop portion
12
by electromagnetic coupling. In the example being illustrated, each gap δ is equal to, for example, 0.4 mm and preferably may lie in a range of 0.2-0.8 mm.
As shown in
FIGS. 1A and 1B
, the tubular body
11
has a longitudinal lower end which is fixed on a circuit board
14
. The circuit board
14
has a main surface
14
a
on which a phase shifter
15
is formed. The circuit board
14
has a back surface
14
b
on which a ground conductive pattern (not shown) is formed. In addition, the four feeders
13
have four feeding terminals
13
a
(
FIG. 2
) which are electrically and mechanically connected to input terminals of the phase shifter
15
using solder
16
.
Referring to
FIG. 3
, the flexible insulator film member
20
for use in forming the tubular body
11
substantially has a rectangular shape which has an upper side
20
U
, a lower side
20
L
, a first lateral side
20
S1
, and a second lateral side
20
S2
. By connecting the first lateral side
20
S1
with the second lateral side
20
S2
, the tubular body
11
is formed as shown in
FIGS. 1A and 1B
. This connection between the first lateral side
20
S1
and the second lateral side
20
S2
is carried out, for example, by using double-sided adhesive tape or an adhesive agent.
In addition, the loop portion
12
is formed on one surface of the flexible insulator film member
20
in the vicinity of the upper side
20
U
. While the tubular body
11
is formed by rounding the flexible insulator film member
20
, both ends of the loop portion
12
are electrically connected to each other.
In the electromagnetic coupling type four-point feeding loop antenna
10
, each of the four feeders
13
extends in parallel with the central axis O from the lower side
20
L
and the vicinity of the loop portion
12
. In addition, the loop portion
12
is connected with four electromagnetic coupling wires
17
which extend from the loop portion
12
toward the lower side
20
L
along the four feeders
13
with the gaps δ left between the four feeders
13
and the four electromagnetic coupling wires
17
, respectively. By changing a coupling length L between the feeder
13
and the electromagnetic coupling wire
17
which are adjacent to each other, it is possible to change a frequency characteristic of the electromagnetic coupling type four-point feeding loop antenna
10
.
Formed on the one surface of the flexible insulator film member
20
, the loop portion
12
, the four feeders
13
, and the four electromagnetic coupling wires
17
may be made of the conductive material (e.g. copper file).
In general, it is necessary in a four-point feeding loop antenna to make a feeding impedance thereof 50 Ω. In the electromagnetic coupling type four-point feeding loop antenna
10
according to the first embodiment of this invention, it is possible to lower an impedance at each feeding terminal
13
a
up to 25 Ω. Accordingly, it is possible to make an impedance at an output terminal
15
a
of the phase shifter
15
a range between 50 Ω and 100 Ω, both inclusive. That is, by feeding to the loop portion
12
by electromagnetic coupling, it is possible to easily obtain the impedance match. In addition, it is possible to change the impedance at each feeding terminal
13
a
by changing a size of each gap δ.
On the contrary, in an existing four-point feeding loop antenna having structure where each feeder
13
is directly connected to the loop portion
12
, each feeding terminal
13
a
has a too high impedance of a range between 250 Ω and 300 Ω. As a result, it is difficult to obtain impedance match at the output terminal
15
a
of the phase shifter
15
.
Now, the description will proceed to position relationship among the loop portion
12
, the four feeders
13
, the gaps δ, and the four electromagnetic coupling wires
17
with concrete sizes.
Referring to
FIG. 3
, it will be assumed for the
electromagnetic coupling type four-point feeding loop antenna
10
that the tubular body
11
has a diameter of 20 mm, the loop portion
12
has a loop width of W
1
, each feeder
13
has a feeder width of W
2
, and each electromagnetic coupling wire
17
has a coupling wire width of W
3
in which the loop width W
1
, the feeder width W
2
, and the coupling wire width W
3
are equal to one another. In this event, each of gaps δ is laid in a range between 0.2 mm and 0.8 mm, both inclusive when the feeding impedance at the output terminal
15
a
of the phase shifter
15
has a range between 25 Ω and 100 Ω.
More specifically, it will be assumed for the above-mentioned electromagnetic coupling type four-point feeding loop antenna
10
that the feeding impedance has 25 Ω. In this event, each of the loop width W
1
, the feeder width W
2
, and the coupling wire width W
3
is equal to 1 mm, each of the gaps δ is equal to 0.4 mm. In addition, an interval L
1
between the loop portion
12
and the lower side
20
L
is equal to 20 mm, an interval L
2
between the lower side
10
L and a tip of each of the four electromagnetic coupling wires
17
is equal to 9 mm, and each of the four feeders
13
has a length L
3
of 15 mm.
In addition, it will be assumed for the above-mentioned electromagnetic coupling type four-point feeding loop antenna
10
that the feeding impedance has 50 Ω. In this event, each of the loop width W
1
, the feeder width W
2
, and the coupling wire width W
3
is equal to 1 mm, and each of the gaps δ is equal to 0.4 mm. The interval L
1
between the loop portion
12
and the lower side
20
L
is equal to 20 mm, the interval L
2
between the lower side
20
L
and the tip of each of the four electromagnetic coupling wires
17
is equal to 5 mm, and each of the four feeders
13
has the length L
3
of 12 mm.
Furthermore, it will be assumed for the above-mentioned electromagnetic coupling type four-point feeding loop antenna
10
that the feeding impedance has 100 Ω. In this event, each of the loop width W
1
, the feeder width W
2
, and the coupling wire width W
3
is equal to 1 mm and each of the gaps δ is equal to 0.4 mm. The interval L
1
between the loop portion
12
and the lower side
20
L
is equal to 20 mm, the interval L
2
between the lower side
20
L
and a tip of each of the four electromagnetic coupling wires
17
is equal to 3 mm, and each of the four feeders
13
has the length L
3
of 8 mm.
Referring to
FIGS. 4A and 4B
, the description will proceed to a composite antenna including the electromagnetic coupling type four-point feeding loop antenna
10
. The illustrated composite antenna further comprises a monopole antenna
30
. Similar reference symbols are attached to those similar to the electromagnetic coupling type four-point feeding loop antenna
10
in illustrated in
FIGS. 1A
,
1
B,
2
, and
3
and description thereof is omitted to simplify description.
With this structure, the electromagnetic coupling type four-point feeding loop antenna
10
can receive the satellite wave or the circular polarization while the monopole antenna
30
can receive the terrestrial wave or the liner polarization.
In the example being illustrated, the monopole antenna
30
is mounted on the circuit board
14
in a direction of the central axis O of the tubular body
11
. In the example being illustrated, the monopole antenna
30
has an upper projected length of 1.8 mm.
Referring to
FIGS. 5A
,
5
B,
6
, and
7
, the description will proceed to a composite antenna including an electromagnetic coupling type four-point feeding loop antenna
10
A according to a second embodiment of this invention. The illustrated electromagnetic coupling type four-point feeding loop antenna
10
A is similar in structure to that illustrated in
FIGS. 1A
,
1
B,
2
, and
3
except that the number of the electromagnetic coupling wires
17
is different from that illustrated in
FIGS. 1A
,
1
B,
2
, and
3
in the manner which will later become clear. Similar reference symbols are attached to those similar to the electromagnetic coupling type four-point feeding loop antenna
10
in illustrated in
FIGS. 1A
,
1
B,
2
, and
3
and description thereof is omitted to simplify description.
The illustrated electromagnetic coupling type four-point feeding loop antenna
10
A comprises eight electromagnetic coupling wires
17
or four pairs of the electromagnetic coupling wires
17
. Each pair of electromagnetic coupling wires
17
extends on the flexible insulator film member
20
from the loop portion
12
along a particular one of the four feeders
13
with gaps δ so as to put the particular one of the four feeders
13
between the pair of electromagnetic coupling wires
17
in question. That is, in the example being illustrated, the gaps δ have a shape of a comb. By changing a coupling length L between the feeder
13
and the electromagnetic coupling wire
17
which are adjacent to each other, it is possible to change a frequency characteristic of the electromagnetic coupling type four-point feeding loop antenna
10
A. In addition, it is possible to change the impedance at each feeding terminal
13
a
by changing a size of each gap δ.
It is possible for the electromagnetic coupling type four-point feeding loop antenna
10
A to widen the gap δ in comparison with the electromagnetic coupling type four-point feeding loop antenna
10
. It is generally difficult to process (form) the feeders
13
and the electromagnetic coupling wires
17
so as to maintain narrow gaps δ with high precision.
In other words, in the electromagnetic coupling type four-point feeding loop antenna
10
A, it is possible to increase an area of an electromagnetic coupling portion by making the gaps δ comb-shaped and it is possible to widen an adjustment range of the impedance and the frequency characteristic in comparison with the electromagnetic coupling type four-point feeding loop antenna
10
.
Referring to
FIGS. 8A
,
8
B,
9
, and
10
, the description will proceed to a composite antenna including an electromagnetic coupling type four-point feeding loop antenna
10
B according to a third embodiment of this invention. The illustrated electromagnetic coupling type four-point feeding loop antenna
10
B is similar in structure to that illustrated in
FIGS. 1A
,
1
B,
2
, and
3
except that the loop portion is modified from that illustrated in
FIGS. 1A
,
1
B,
2
, and
3
in the manner which will later become clear. The loop portion is therefore depicted at
12
A. Similar reference symbols are attached to those similar to the electromagnetic coupling type four-point feeding loop antenna
10
in illustrated in
FIGS. 1A
,
1
B,
2
, and
3
and description thereof is omitted to simplify description.
The loop portion
12
A has four bending portions
121
each of which is bent towards a feeding source. In the example being illustrated, a space T
1
between the feeder
13
and the bending portion
121
is substantially equal to a space T
2
between the electromagnetic coupling wire
17
as shown in FIG.
10
. In
FIG. 10
, a reference symbol of m indicates a tab for sticking.
The present co-inventors confirmed that the electromagnetic coupling type four-point feeding loop antenna
10
B comprising the tubular body
11
having the diameter of 20 mm has an antenna front gain which is similar to that of the electromagnetic coupling type four-point feeding loop antenna
10
comprising the tubular body
11
having the diameter of 25 mm. It is therefore possible to miniaturize the electromagnetic coupling type four-point feeding loop antenna
10
B.
Although the third embodiment of this invention is applied to the electromagnetic coupling type four-point feeding loop antenna
10
B, the third embodiment of this invention may be applied to a directly coupling type four-point feeding loop antenna. In addition, although the tubular body
11
is the cylindrical body, the tubular body
11
may be a hollow prismatic body.
Referring to
FIGS. 11A and 11B
, the description will proceed to an antenna unit including the composite antenna illustrated in
FIGS. 4A and 4B
.
The illustrated antenna unit further comprises a shield case
42
mounting the loop antenna
10
and the monopole antenna
30
thereon. Low noise amplifiers (not shown) are received in the shield case
42
. A combination of a top cover
44
and a bottom cover
46
is for covering the loop antenna
10
, the monopole antenna
30
, and the shield case
42
. A twin cable
50
is connected to the shielding case
42
through a bushing
48
sandwiched between the top cover
44
and the bottom cover
46
. The twin cable
50
is for connecting the loop antenna
10
and the monopole antenna
30
with a receiver body (not shown).
In the manner which is described above, the loop antenna
10
serves as the satellite wave antenna for receiving the satellite wave while the monopole antenna
30
serves as the terrestrial wave antenna for receiving the terrestrial wave.
As shown in
FIGS. 12A and 12B
, the twin cable
50
comprises a first insulated cable
51
for the loop antenna
10
or the satellite wave and a second insulated cable
52
for the monopole antenna
30
or the terrestrial wave.
As shown in
FIG. 12B
, the first insulated cable
51
comprises a first inner conductor
511
, a first outer conductor
512
, a first insulator
513
between the first inner conductor
511
and the first outer conductor
512
, and a first outer coat
514
for coating the first outer conductor
512
. Likewise, the second insulated cable
52
comprises a second inner conductor
521
, a second outer conductor
522
, a second insulator
523
between the second inner conductor
521
and the second outer conductor
522
, and a second outer coat
524
for coating the second outer conductor
522
. The first and the second insulated cables
51
and
52
are in parallel to each other and united in a body in a state that they can be easily separated from each other by hands (or external force). At any rate, the first and the second cables
51
and
52
have the first and the second outer coats
514
and
524
united in a body at a contact part between them.
As regards one end of the twin cable
50
, the first and the second insulated cables
51
and
52
are separated from each other to easily connect to two terminals (first and second receptacles), which are distant from each other, of the receiver body. The twin cable
50
has first and second connectors
56
and
57
at tips of the first and the second insulated cables
51
and
52
. As shown in
FIG. 12A
, a split-proof bushing
58
for preventing the first and the second insulated cables
51
and
52
from separating from each other is put on the twin cable
50
at a position apart from the first and the second connectors
56
and
57
by about several centimeters. In addition, the bushing
48
for fixing the twin cable
50
in the antenna unit is put on the twin cable
50
near other ends of the twin cable
50
. The split-proof bushing
58
and the bushing
48
may be mounted on the twin cable
50
or may be integrally formed with the first and the second outer coats
514
and
524
of the twin cable
50
.
Marking
61
is formed on the second outer coat
524
of the second insulated cable
52
to allow to distinguish between the first insulated cable
51
and the second insulated cable
52
. In the example being illustrated, the making
61
comprises a solid line extending in a longitudinal direction along the second insulated cable
52
and has a color different from that of the first and the second outer coats
514
and
524
. For example, when the color of the first and the second outer coats
514
and
524
is black, the color of the making
61
may be white.
Although the marking
61
is formed on the second outer coat
524
in the example being illustrated, making may be formed on the first outer coat
514
in lieu of the second outer coat
524
. In addition, another making
62
may be further formed on the first outer coat
514
as shown at a dot-dash line in FIG.
12
A. In this event, the making
62
formed on the first outer coat
514
and the making
61
formed on the second outer coat
524
have different colors. Alternatively, if the making is carried out by printing, characters such as “for satellite wave” and “for terrestrial wave” may be printed on the first and the second outer coats
514
and
524
at regular intervals along the longitudinal direction of the twin cable
50
, respectively.
While this invention has thus far been described in conjunction with a few preferred embodiment thereof, it will now be readily possible for those skilled in the art to put this invention into various other manners. For example, although the feeders
13
and the electromagnetic coupling wires
17
substantially extend a normal direction to the lower side
20
L
of the flexible insulator film member
20
in the above-mentioned embodiments, they may substantially extend in an oblique direction to the lower side
20
L
of the flexible insulator film member
20
.
Claims
- 1. An electromagnetic coupling type four-point feeding loop antenna comprising:a tubular body formed by rounding a flexible insulator film member around a central axis in a tubular fashion, said tubular body having a peripheral surface; a loop portion made of a conductor, said loop portion being formed on said tubular body along said peripheral surface around said central axis in a loop fashion, said loop portion having a loop width; four feeders formed on the peripheral surface of said tubular body to feed to said loop portion at four points, each of said four feeders having a feeder width; and four electromagnetic coupling wires, connected to said loop portion, extending on said flexible insulator film member from said loop portion along said four feeders with gaps left between said four feeders and said four electromagnetic coupling wires, respectively, each of said four electromagnetic coupling wires having a coupling wire width, wherein said loop width, said feeder width, and said coupling wire width are substantially equal to one another and each of said gaps is laid in a range between 0.2 mm and 0.8 mm, both inclusive, when said electromagnetic coupling type four-point feeding loop antenna has a feeding impedance of a range between 25 Ω and 100 Ω, both inclusive.
- 2. An electromagnetic coupling type four-point feeding loop antenna as claimed in claim 1, wherein:said flexible insulator film member has a substantially rectangular shape having an upper side, a lower side, a first lateral side, and a second lateral side, said tubular body is formed by connecting said first lateral side with said second lateral side, said loop portion is formed on one surface of said flexible insulator film member in a vicinity of the upper side, and each of said four feeders extends on said flexible insulator film member from said lower side to a vicinity of said loop portion.
- 3. An electromagnetic coupling type four-point feeding loop antenna as claimed in claim 2, wherein each of said loop width, said feeder width, and said coupling wire width is equal to 1 mm, each of said gaps is equal to 0.4 mm, an interval between said loop portion and said lower side is equal to 20 mm, an interval between said lower side and a tip of each of said four electromagnetic coupling wires is equal to 9 mm, and each of said four feeders has a length of 15 mm when said feeding impedance is equal to 25 Ω.
- 4. An electromagnetic coupling type four-point feeding loop antenna as claimed in claim 2, wherein each of said loop width, said feeder width, and said coupling wire width is equal to 1 mm, each of said gaps is equal to 0.4 mm, an interval between said loop portion and said lower side is equal to 20 mm, an interval between said lower side and a tip of each of said four electromagnetic coupling wires is equal to 5 mm, and each of said four feeders has a length of 12 mm when said feeding impedance is equal to 50 Ω.
- 5. An electromagnetic coupling type four-point feeding loop antenna as claimed in claim 2, wherein each of said loop width, said feeder width, and said coupling wire width is equal to 1 mm, each of said gaps is equal to 0.4 mm, an interval between said loop portion and said lower side is equal to 20 mm, an interval between said lower side and a tip of each of said four electromagnetic coupling wires is equal to 3 mm, and each of said four feeders has a length of 8 mm when said feeding impedance is equal to 100 Ω.
- 6. An antenna unit comprising:a satellite wave antenna for receiving a satellite wave; a terrestrial wave antenna for receiving a terrestrial wave; a shield case on which said satellite wave antenna and said terrestrial wave antenna are mounted; a top cover and a bottom cover for covering said satellite wave antenna, said terrestrial wave antenna, and said shield case; and a twin cable connected to said shield case through a bushing sandwiched between said top cover and said bottom cover, said twin cable comprising a first cable for said satellite wave antenna and a second cable for said terrestrial wave antenna, said first and said second cables having first and second outer coats, respectively, and at least one of said first and said second outer coats having a marking formed thereon to distinguish between said first cable and said second cable.
- 7. An antenna unit as claimed in claim 6, wherein said satellite wave antenna comprises a loop antenna, and said terrestrial wave antenna comprises a monopole antenna.
- 8. An antenna unit as claimed in claim 6, wherein said marking has a color different from a color of said first and said second outer coats.
- 9. An antenna unit as claimed in claim 8, wherein said marking is formed on said first and said second outer coats, and the marking for said first outer coat and the marking for said second outer coat have different colors.
Priority Claims (4)
Number |
Date |
Country |
Kind |
2002-020097 |
Jan 2002 |
JP |
|
2002-070097 |
Mar 2002 |
JP |
|
2002-091512 |
Mar 2002 |
JP |
|
2002-093843 |
Mar 2002 |
JP |
|
US Referenced Citations (7)