Wave transmission lines and networks – Plural channel systems – Nonreciprocal gyromagnetic type
Reexamination Certificate
1999-10-13
2003-06-24
Donovan, Lincoln (Department: 2832)
Wave transmission lines and networks
Plural channel systems
Nonreciprocal gyromagnetic type
C333S024200
Reexamination Certificate
active
06583680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to nonreciprocal circuit devices and communications devices used for high-frequency bands, particularly in submillimeter-wave bands.
2. Description of the Related Art
A known example of a nonreciprocal circuit device will be illustrated with reference to FIG.
10
.
FIG. 10
shows an exploded perspective view of a nonreciprocal circuit device, which is commonly referred to as a “lumped-constant nonreciprocal circuit device”.
As shown in
FIG. 10
, a nonreciprocal circuit device
110
comprises an upper yoke
111
and a lower yoke
112
for forming a closed magnetic circuit, three central conductors
121
,
122
, and
123
, a ferrite member
120
having the central conductors thereon, a magnet
113
for applying a DC magnetic field to the ferrite member
120
having the central conductors, and a resin case
130
. The three central conductors
121
,
122
, and
123
formed on the ferrite member
120
mutually intersect at an angle of 120° via an insulation film (not shown). One of the ends of each central conductor is an input/output terminal. The other ends thereof are ground terminals and they are all disposed on the lower surface of the ferrite member
120
. In the resin case
130
, a hole
131
for receiving the ferrite member
120
having the central conductors
121
,
122
, and
123
, recesses
132
and
136
for receiving capacitors
115
and a resistor
114
, and input/output connection electrodes
133
for connecting to input/output terminals are formed. In addition, the input/output connection electrodes
133
are connected to respective terminal electrodes
135
on an outer surface of the resin case
130
, and an electrode connected to an end of the resistor
114
and the back of the capacitor
115
is connected to another terminal electrode
135
on the outer surface of the resin case
130
.
The input/output terminal P
1
′ of the central conductor
121
and the input/output terminal P
2
′ of the central conductor
122
are connected to respective input/output connection electrodes
133
formed in the resin case
130
and the top electrodes of two of the capacitors
115
, respectively, whereas the input/output terminal P
3
′ of the central conductor
123
is connected to the top electrode of the third capacitor
115
and an electrode of the resistor
114
.
FIG. 11
shows an equivalent circuit diagram of the nonreciprocal circuit device
110
having the above structure. The central conductors
121
,
122
, and
123
formed on the ferrite member
120
serve as inductors, and in order to match the impedance thereof to that of an external circuit, the capacitors
115
are additionally disposed in parallel. The resistor
114
is provided in addition to the central conductor
123
so as to permit the nonreciprocal circuit device
110
to act as an isolator allowing only the signals sent from the input/output terminal P
1
′ to the input/output terminal P
2
′ to pass.
Recently, with the demand for miniaturization of communication equipment, reduction in size of a nonreciprocal circuit device as one of the essential components incorporated therein has also been required.
In the lumped-constant nonreciprocal circuit device
110
described above, however, as shown in the equivalent circuit diagram of
FIG. 11
, each inductor and each capacitor constitutes a parallel-resonance circuit. Since the resonance frequency f of the circuit is substantially given by the formula f=1/{2&pgr;·(LC)
½
}, the higher the frequency of the nonreciprocal circuit device, the smaller the value of LC. As a result, the size of the nonreciprocal circuit device is reduced. For example, in the case of 2 GHz, the size of the nonreciprocal circuit device is approximately 7×7 mm.
In this case, the higher the usable frequency, the smaller the nonreciprocal circuit device, with the result that the requirement for miniaturizing the device as a component used in communication equipment is satisfied. However, there is a problem in the manufacturing of the device. In other words, reduction in size of the nonreciprocal circuit device makes formation and connection of the central conductors complicated, leading to occurrences of variations in the manufacturing process among nonreciprocal circuit devices. Furthermore, the higher the frequency and the smaller the value of LC, the greater the influence of variations in manufacturing on characteristics of the nonreciprocal circuit devices. For instance, assuming that an error of 1 nH of inductance occurs in the manufacturing process, consider the degree of the influence on the nonreciprocal circuit device in the cases in which the initial inductances are 10 nH and 1 nH. That is, if the error in the manufacturing process is equal to 1 nH in both cases, when the initial inductance is 10 nH, the change ratio in the inductance is 10%, whereas when the initial inductance is 1 nH, the change ratio is 100%. Therefore, the smaller the initial inductance, the greater the influence on the resonance frequency, leading to occurrence of greater variations in the frequency characteristics of the nonreciprocal circuit device.
For such a reason, there is a limitation on the frequencies usable with a lumped-constant nonreciprocal circuit device. Consequently, from the manufacturing point of view, approximately 2 GHz is the maximum frequency usable with the lumped-constant nonreciprocal circuit device at present.
On the other hand, a nonreciprocal circuit device usable even in frequency bands above approximately 2 GHz is the distributed-constant nonreciprocal circuit device. As an example of this, a description will be given of a known conventional nonreciprocal circuit device referring to FIG.
12
.
FIG. 12
shows an exploded perspective view of the conventional nonreciprocal circuit device, which is ordinarily referred to as a “Y-shaped distributed-constant nonreciprocal circuit device”.
As shown in
FIG. 12
, a conventional nonreciprocal circuit device
140
comprises a ferrite member
120
a
, an electrode
150
formed on a surface thereof, a ground electrode formed on a back thereof, and an upper magnet and a lower magnet
142
. The electrode
150
formed on the ferrite member
120
a
comprises a resonator
151
resonating in the TM
110
mode at the center, and input/output connection electrodes
152
,
153
, and
154
formed in each of the three different directions from the resonator
151
. Between the resonator
151
and the input/output connection electrodes
152
,
153
, and
154
are formed impedance converters
152
a
,
153
a
, and
154
a
having length of &lgr;/4 for the purpose of impedance matching. Additionally, the input/output connection electrodes
152
,
153
, and
154
are provided for being connected to an external circuit.
By applying a DC magnetic field with the upper and lower magnets
142
, the nonreciprocal circuit device
140
functions as a circulator, in which signals from an input/output terminal P
4
′ pass through an input/output terminal P
5
′, signals from P
5
′ pass through an input/output terminal P
6
′, and signals from P
6
′ pass through P
4
′.
In the conventional nonreciprocal circuit device, the resonator formed on the surface of the ferrite member has a substantially circular shape. As a result, at the junction of the input/output connection electrode and the resonator, the electrode width is greatly increased to provide the impedance converter. Impedance matching would be impossible between the input/output connection electrode and the resonator, if they were connected directly without the impedance converter. Thus, in the conventional art, as shown in
FIG. 12
, in order to achieve impedance matching, the impedance converter must be connected to the input/output connection electrode near the resonator. Consequently, this leads to an increase in size of the nonreciprocal circuit device.
SUMMARY OF THE INVENTION
The above-described problems are solved by the present inv
Ohira Katsuyuki
Tokudera Hiromu
Donovan Lincoln
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
LandOfFree
Nonreciprocal circuit device and communications device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Nonreciprocal circuit device and communications device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonreciprocal circuit device and communications device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3136419