Wave transmission lines and networks – Plural channel systems – Nonreciprocal gyromagnetic type
Reexamination Certificate
1999-09-24
2002-05-28
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Nonreciprocal gyromagnetic type
C333S024200
Reexamination Certificate
active
06396361
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-reciprocal circuit element used for a mobile communication unit including an automobile telephone or a portable telephone mainly used in a microwave band, particularly to an isolator and a circulator. Moreover, the present invention relates to a board on which non-reciprocal circuit elements are mounted.
2. Related Art of the Invention
Because a LUMPED ELEMENT TYPE isolator can be compactly configured as a non-reciprocal element circuit used for a terminal of a mobile communication unit, it has been early used and further compacted and decreased in loss.
Conventionally, an isolator has been set between a power amplifier and an antenna at a transmission stage in order to prevent an unnecessary signal from being returned to the power amplifier and stabilize the impedance at the load side of the power amplifier. Characteristics required for an isolator include a large backward loss required for the above functions and a small forward loss for reducing the power consumption at a transmission stage and lengthening the service life of a battery. Therefore, the improvement of characteristics of an isolator has been concentrated on how to improve the above characteristics in a frequency band used.
Because terminal units have been suddenly downsized recently, it is attempted not only to downsize the parts used but also to reduce the number of parts by using a multifunctional part. In case of an isolator, it is attempted to downsize the single product and moreover, it is attempted to secure the attenuation at a frequency higher than the frequency band used for the isolator and omit an LPF (Low Pass Filter) used for a transmission stage by adding functions of the LPF to the isolator.
However, because it has been difficult so far to add functions of an LPF to an isolator without deteriorating the characteristic of a frequency band used for the isolator, there has been a problem on practical use.
It is an object of the first aspect of the present invention to provide an isolator added with LPF functions without deteriorating the characteristic of a conventional frequency band used for the isolator in order to solve the above conventional problems.
The general configuration of a LUMPED ELEMENT TYPE isolator widely used for terminals of portable telephones at present will be briefly described below by referring to FIG.
31
. Three sets of strip lines
61
A
a
,
61
A
b
,
61
A
c
electrically insulated, crossed at an angle of 120°, and overlapped each other are arranged on a ferrite disk
62
A, and a magnet
63
A for magnetizing the ferrite disk
62
A is set so as to face the ferrite disk
62
A. One ends of the strip lines
61
A
a
and
61
A
b
are connected with input/output terminals
65
A
a
and
65
A
b
and one end of the strip line
61
A
c
is terminated by a predetermined resistance
66
A.
Moreover, capacitors
64
A
a
,
64
A
b
, and
64
A
c
are added to one ends of the strip lines
61
A
a
,
61
A
b
, and
61
A
c
in parallel with the input/output terminals
65
A
a
and
65
A
b
or the resistance
66
A. Moreover, the other ends of the strip lines
61
A
a
,
61
A
b
, and
61
A
c
are respectively grounded. Then, an upper case
67
A and a lower case
68
A are set which serve as a part of a magnetic circuit and contain the ferrite disk
62
A, the magnet
63
A and the strip lines
61
A
a
,
61
A
b
, and
61
A
c.
It is described below that the upper case
67
A and the lower case
68
A serve as a part of the magnetic circuit. If neither upper case
67
A nor lower case
68
A are used, the magnetic flux emitted from one side of the magnet
63
A returns to the other side of the magnet
63
A after passing through an infinite route. However, when forming the upper case
67
A and the lower case
68
A with, for example, a magnetic material such as iron and covering the magnet
63
A with the upper case
67
A and the lower case
68
A, the magnetic flux emitted from one side of the magnet
63
A returns to the other side of the magnet
63
A after passing through the upper case
67
A and lower case
68
A without passing through an infinite route. That is, the fact that the upper case
67
A and lower case
68
A serve as a part of the magnetic circuit represents returning the magnetic flux emitted from one side of the magnet
63
A to the other side of the magnet
63
A after making the magnetic flux pass through the upper case
67
A and lower case
68
A without making it pass through an infinite route.
Characteristics requested as performances of an isolator are a small forward transmission loss (insertion loss) and a large backward transmission loss (isolation). In
FIG. 31
, when assuming that the upper case
67
A-side of the magnet
63
A is N-pole and the lower case
68
A-side of the magnet
68
A is S-pole and most predetermined signals input to the input/output terminal
65
A
a
are output from the input/output terminal
65
A
b
, the direction from the input/output terminal
65
A
a
toward the input/output terminal
65
A
b
, that is, the transmission direction of the signals is the forward direction. That is, it is requested for an isolator that a signal output from the input/output terminal
65
A
a
toward the input/output terminal
65
A
b
has a small transmission loss and a signal output from the input/output terminal
65
A
b
toward the input/output terminal
65
A
a
has a large transmission loss. In practical use, the magnitude of insertion loss or isolation that can be assured in a desired frequency band is a problem. Because various improvements are attempted for an insertion loss and the peak value (minimum value) of the insertion loss is decreased, an insertion loss value that can be assured in a desired frequency band is also considerably lowered. However, because characteristics of an isolation are not adequate, the isolation of 15 dB or more recently required for the design of a portable telephone is not secured in a desired frequency band. That is, a band in which a desired isolation is secured is narrow before and after a desired frequency of a signal.
Moreover, the above conventional LUMPED ELEMENT TYPE isolator has the following problem.
That is, because the interval between the ferrite disk
62
A and the case lower-side
68
A is small, when the magnetic flux emitted from the permanent magnet
63
A passes through the ferrite disk
62
A through the case upper-side
67
A and lower-side
68
A of metallic magnetic materials, the magnetic flux density of the outer periphery of the ferrite disk
62
A becomes higher than that of the central portion of the disk
62
A and thereby, the magnetization distribution in the ferrite disk
62
A is deteriorated.
The third aspect of the present invention is made to solve the problems of the above conventional isolator and its object is to provide a non-reciprocal circuit element having a superior transmission characteristic by improving the magnetization distribution in a ferrite disk and greatly reducing an insertion loss which-is an isolator characteristic.
SUMMARY OF THE INVENTION
To solve the above conventional problems, the first aspect of the present invention uses a non-reciprocal circuit element for transmitting a signal in one direction or cyclically transmitting a signal by using circuit means having at least a ferrite (
34
), transmission lines (
31
,
32
, and
33
), and a capacitor (
21
), comprising:
at least two external input/output terminals (
11
and
12
) for transferring a signal to and from an external unit and at least one of external grounding terminals (
13
,
14
, and
15
) to be grounded; wherein
at least one (
13
) of the external grounding terminals is set between at least one set of external input/output terminals (
11
and
12
).
To solve the above conventional problems, the second aspect of the present invention has an object of providing a LUMPED ELEMENT TYPE isolator having a large isolation band width.
To attain the above object, the second aspect of the present invention uses a LUMPED ELEMENT TYPE isolator comprising:
a ferrite
Hase Hiroyuki
Hattori Masumi
Horio Yasuhiko
Takeuchi Takayuki
Bettendorf Justin P.
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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