Isolator with capacitors and chip resistors located outside...

Details Isolator with capacitors and chip resistors located outside... Isolator with capacitors and chip resistors located outside...

2000-12-08

2002-11-19

Bettendorf, Justin P. (Department: 2817)

Wave transmission lines and networks

Coupling networks

Nonreciprocal gyromagnetic type

C333S001100

Reexamination Certificate

active

06483394

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an isolator used in the microwave apparatuses. More specifically, the present invention relates to an isolator in which a ferromagnetic sheet (Sr-ferrite) together with an internal terminal sheet (with strip lines extending therefrom) and a garnet ferrite is inserted into a shielding case; dielectric devices and a chip resistor are installed on a PCB and around the shielding case; a connecting terminal sheet is formed; and thus the ferromagnetic sheet is securely placed by means of the strip lines of the internal terminal sheet and the garnet ferrite of the shielding case, so that the leakage magnetic flux shielding effect can be reinforced, that the bulk of the isolator can be made compact, that the assemblability can be improved, and that the manufacturing process can be simplified.
BACKGROUND OF THE INVENTION
The generally known conventional isolator is inserted to between an antenna switch and a power amplifier module of a wireless apparatus, so that the signals reflected from the antenna switch are absorbed, thereby protecting the power amplifier module.
FIG. 1
is a block diagram of a system involving the isolator. As shown in this drawing, transmission signals Tx are amplified by a power amplifier module
15
, are filtered by a low pass filter
14
, and are sent through an antenna switch
12
to an antenna
11
, so that the signals can be transmitted from the antenna
11
.
Meanwhile, reception signals Rx are received by the antenna
11
, and are sent through the antenna switch
12
to a band pas filter
16
so as to be filtered. Generally, an isolator
13
is disposed between the antenna switch
12
and the power amplifier module
15
of the wireless apparatus, so that the signals reflected from the antenna switch
12
can be absorbed, thereby protecting the power amplifier module
15
.
FIG. 2
illustrates the basic equivalent circuit for the isolator. As shown in this drawing, an input terminal is coupled to an output part of the power amplifier module
15
of the transmitting part so as to receive the transmission signals Tx. Further, the input terminal block is connected an internal terminal block
22
, and thus, the high frequency transmission signals Tx are transferred to the internal terminal block
22
. An input capacitor C
1
is connected between the input terminal block and the ground.
Further, an output terminal block is connected to the internal terminal block
22
, while the other end of the output terminal block is connected to the antenna switch
12
, so that the high frequency signals can be finally transmitted from the antenna
11
.
An output capacitor C
2
is connected between the output terminal block and the ground. A ground capacitor C
3
and a longitudinal resistor R (50&OHgr;) are connected in parallel between the internal terminal block
22
and the ground. The signals which have been transferred from the power amplifier module
15
through the input terminal block and the internal block to the output terminal block can reversely flow partly from the antenna switch
12
. These returned signals are sunk into the ground from the internal block
22
through the longitudinal resistor R.
Therefore, the isolator
13
removes the power of the returning signals so as to ultimately prevent the power amplifier module
15
from being damaged by the power of the returning signals, thereby protecting the power amplifier module
15
.
FIG. 3
is an exploded perspective view showing the constitution of the conventional isolator. As shown in this drawing, the isolator includes: an upper case
31
; a ferromagnetic sheet (Sr-ferrite)
32
for generating a constant magnetic field; an internal terminal block
33
disposed under the ferromagnetic sheet
32
, for generating an induced magnetic field, and including a garnet ferrite
42
and three strip lines
33
′ connected to the input and output terminal blocks and to the ground; dielectric devices
35
a-
35
c
and a chip resistor
34
respectively connected to the three strip lines
33
′ of the internal terminal block
33
; an injection-molded case
36
having through holes
41
for fastening the internal terminal block
33
, and having spaces for receiving the chip resistor
34
and the three dielectric devices
35
a
-
35
c
, with input/output electrodes
38
and
39
and a ground electrode
37
being accommodated therein; and a lower case
40
.
In this conventional isolator, the arrangement of the components is as follows. That is, the ferromagnetic sheet
32
and the garnet ferrite
42
are accommodated into the separate injection-molded case
36
. Further, the three dielectric devices
35
a
-
35
c
, the input/output electrodes
38
and
39
, and the ground electrode
37
are horizontally arranged, and they are connected through the strip lines of the internal terminal block
33
. Accordingly, the sizes of the dielectric devices, the chip resistor and the garnet ferrite are increased, and therefore, the overall bulk of the isolator is expanded.
Further, when the strip lines
33
′ of the internal terminal block
33
are soldered to the dielectric devices
35
a
-
35
c
and to the input/output electrodes
38
and
39
, soldering defects are apt to occur due to the narrow space within the injection-molded case
36
, as well as degrading the workability and the assemblability of the isolator, and making it impossible to obtain uniform products.
SUMMARY OF THE INVENTION
The present invention is intended to overcome the above described disadvantages of the conventional technique.
Therefore it is an object of the present invention to provide an isolator in which a ferromagnetic sheet is securely placed by means of strip lines of an internal terminal sheet and a garnet ferrite, thereby improving the shielding of the leakage magnetic flux to the degree of maximizing the shielding effect.
It is another object of the present invention to provide an isolator in which dielectric devices and a chip resistor are installed on a circuit board of the shielding case, thereby making the bulk of the isolator compact, making the response to the frequency easy, and making the characteristics of the product stable.
It is still another object of the present invention to provide an isolator in which the isolator can be easily installed on a circuit board, thereby improving the assemblability, and simplifying the manufacturing process.
In achieving the above objects, the isolator according to the present invention includes: upper and lower cases; a ferromagnetic sheet disposed within a shielding case, for generating a constant magnetic field; an internal terminal sheet having a plurality of strip lines for being connected to input/output electrode terminals and aground terminal and disposed under the ferromagnetic sheet and a garnet ferrite, the garnet ferrite being for generating an induced magnetic field; and the input/output electrode terminals and a chip resistor and three dielectric devices for being connected to the three strip lines of the internal terminal sheet, wherein the ferromagnetic sheet is inserted into the shielding case together with the garnet ferrite and the internal terminal sheet (with the strip lines extending therefrom), the shielding case is inserted into a lower metal case, the three dielectric devices and the chip resistor are installed on a circuit board and around the lower metal case, and a connecting terminal part having the input/output electrode terminals is formed.
In another aspect of the present invention, the isolator according to the present invention includes: upper and lower cases; a ferromagnetic sheet disposed within a shielding case, for generating a constant magnetic field owing to an input current; an internal terminal sheet having a plurality of strip lines for being connected to input/output electrode terminals and a ground terminal and disposed under the ferromagnetic sheet and a garnet ferrite, the garnet ferrite being for generating an induced magnetic field; and the input/output electrode terminals and a chip resistor

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