Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2002-01-23
2003-07-01
Ham, Seungsook (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C343S702000, C343S846000
Reexamination Certificate
active
06587015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission/reception unit suitable for use in a portable telephone, etc.
2. Description of Related Art
Referring to
FIGS. 10 and 11
, a conventional transmission/reception unit has a wiring pattern
52
and ground patterns
53
a
and
53
b
on a circuit board
51
constituting a printed circuit board, etc, where an antenna
54
as a conductor is formed on this circuit board
51
.
The antenna
54
comprises a linear belt antenna element
55
, and transmission and reception terminals
56
and
57
and a ground terminal
58
which are located on one end of the antenna element
55
.
Various electric components (not shown) which make up transmission and reception circuitry are connected to the wiring pattern
52
on the circuit board
51
, and the transmission and reception terminals
56
and
57
of the antenna
54
are connected through the wiring pattern
52
to the transmission and reception circuitry and the ground terminal
58
is grounded via the ground pattern
53
a.
The ground patterns
53
a
and
53
b
are connected via a ground pattern (not shown) formed virtually on the whole lower surface of the circuit board
51
, though not shown in these figures.
A hexahedral box type cover
59
is made of sheet metal. It has a square top wall
60
, a first side wall
61
, a second side wall
62
, a third side wall
63
and a fourth side wall
64
, a notch
61
a
made at the bottom of the first side wall
61
, and four corners
65
a
,
65
b
,
65
c
and
65
d
(first, second, third and fourth corners, respectively), where the side walls are formed by bending down the four sides of the top wall
60
, and the corners are defined by the side walls.
The cover
59
rests on the circuit board
51
in a way that it covers the electric components disposed on the circuit board
51
except the antenna
54
, and the first, second, third and fourth side walls (
61
,
62
,
63
,
64
) are fixed to the circuit board
51
by soldering their bottoms to the ground pattern
53
b.
The position of the cover
59
on the circuit board
51
is determined by mounting legs (not shown) provided at the bottom of the first and third side walls
61
and
63
which are inserted into holes (not shown) in the circuit board
51
. With the cover
59
in place, the antenna element
55
of the antenna
54
lies along the first side wall
61
.
Also, with the cover
59
in place, the transmission and reception terminals
56
and
57
and the ground terminal
58
are located in the vicinity of the first corner
65
a
, and there is a notch
61
a
above the wiring pattern
52
connected with the transmission and reception terminals
56
and
57
of the antenna
54
and the ground pattern
53
a
so that the wiring pattern
52
and the ground pattern
53
a
are electrically isolated from the first side wall
61
.
The ground pattern
53
a
connected with the ground terminal
58
of the antenna
54
is connected to the ground pattern
53
b
through the ground pattern provided on the rear face of the circuit board
51
. The conventional transmission/reception unit is structured as mentioned above.
FIG. 11
illustrates the electrical length of the ground conductor connected with the ground terminal
58
of the antenna
54
in the conventional transmission/reception unit. As shown in the figure, the electrical length L of the ground conductor in the conventional unit is the sum of the following lengths: a length L
31
of the ground pattern
53
a
between the ground terminal
58
and the ground pattern on the rear face of the circuit board
51
; a length L
32
of the ground pattern on the rear face of the circuit board
51
which lies in the area corresponding to the area between the ground pattern
53
a
and the first corner
65
a
of the cover
59
; a length L
33
as the distance from the bottom of the first or second side wall to its top; and a length L
34
as the distance from the first corner
65
a
to the fourth corner
65
d
on the top wall
60
.
Namely, the electrical length L of the conventional ground conductor is expressed by L
31
+L
32
+L
33
+L
34
. It is desirable that this electrical length L be equal to the length &lgr;/4 of the antenna element
55
of the antenna
54
. However, as demand for a more compact transmission/reception unit is growing, there is a tendency to reduce the size of the cover
59
, resulting in a decrease in the lengths L
31
, L
32
, L
33
and L
34
. As a consequence, the electrical length L tends to be shorter than the length &lgr;/4.
Regarding the length &lgr;/4 of the antenna element
55
, as the frequency becomes lower, the wavelength becomes longer (i.e. &lgr;/4 increases); however, in the conventional unit, a sufficient electrical length L could not be obtained at high frequencies and low frequencies.
When the antenna
54
is formed on the circuit board
51
, if it has a linear antenna element
55
having the required length, the circuit board
51
must be large enough to accommodate it, so the circuit board
51
cannot be compact enough. In addition, the circuit board
51
is on the reverse of the side on which the antenna element
55
is exposed, resulting in a larger loss in radio wave radiation and radio wave reception at the antenna element
55
.
Therefore, the problem of the conventional transmission/reception unit is summarized as follows: the electrical length L of the ground conductor connected with the ground terminal
58
of the antenna
54
(L
31
+L
32
+L
33
+L
34
) is shorter than &lgr;/4; as the cover
59
becomes smaller, the electrical length L becomes shorter, namely its difference from the length &lgr;/4 becomes larger, which leads to a decrease in the gain of the antenna
54
and thus a decrease in its transmission/reception sensitivity.
SUMMARY OF THE INVENTION
In view of the above circumstances, an object of the present invention is to provide a transmission/reception unit in which an electrical length of the ground conductor connected with the ground terminal of the antenna is sufficiently long and the antenna gain is improved.
As a first solution to the above problem, the invention provides a transmission/reception unit comprising:
a circuit board having a wiring pattern including various electric components;
a cubic or hexahedral box type cover made of sheet metal which is mounted in such a manner as to cover the electric components; and
an antenna mounted on the circuit board, the cover having:
a top wall;
a first, a second, a third and a fourth side walls which are formed by bending four sides of the top wall;
a first corner defined by the neighboring first and second side walls;
a second corner defined by the first side wall and the neighboring third side wall;
a third corner defined by the second side wall and the neighboring fourth side wall; and
a fourth corner defined by the neighboring third and fourth side walls,
the antenna having:
an antenna element as a conductor laid along the first side wall of the cover; and
transmission and reception terminals and a ground terminal which are provided in the vicinity of the first corner and located at one end of the antenna element, wherein the ground terminal is connected to a ground pattern provided on the circuit board, the first corner of the cover or its vicinity is soldered to the non-ground wiring pattern, and the ground pattern is connected with the second corner or its vicinity, or the third corner or its vicinity, or the fourth corner (located diagonally to the first corner) or its vicinity, or part of the third or fourth side wall.
As a second solution, the fourth corner or its vicinity is connected to the ground pattern, and an electrical length of the ground conductor connected to the ground terminal of the antenna consists of: a length of the ground pattern extending from the ground terminal to the fourth corner or its vicinity; a length as a distance from a point of connection with the ground pattern to a top of the third or fourth side wall; a length as a distance on the top wal
Alps Electric Co. ,Ltd.
Ham Seungsook
LandOfFree
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