Wave transmission lines and networks – Plural channel systems – Nonreciprocal gyromagnetic type
Reexamination Certificate
1999-03-30
2001-04-24
Bettendorf, Justin P. (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Nonreciprocal gyromagnetic type
C333S024200
Reexamination Certificate
active
06222425
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonreciprocal circuit device for use in a microwave band such as, for instance, an isolator or a circulator.
2. Description of the Related Art
Generally, a nonreciprocal circuit device, such as a lumped constant isolator or a circulator, has low attenuation of signals in the forward direction and high attenuation of signals in the reverse direction, and is used in a transmission circuit of a communications unit such as, for instance, a mobile telephone.
However, linear distortion in an amplifier integrated into a communications unit causes radiation (spurious emissions, especially at two and three times the fundamental frequency). Since this radiation can cause interference and irregular operation of a power amplifier, it must be kept below a fixed level. Radiation is sometimes prevented by using an amplifier with excellent linearity, or by using an extra filter to attenuate radiated waves.
However, an amplifier with excellent linearity is expensive, and using an extra filter increases the number and cost of components, and in addition, increases the overall size of the communications equipment. For these reasons, these measures cannot easily be used in mobile telephones and the like, where there is a strong demand for smaller and less expensive devices.
On the other hand, a lumped constant isolator functions as a bandpass filter in the forward direction, and consequently it has large attenuation in the forward direction in frequency bands distant from the pass band. It may be envisaged that radiation can be attenuated by utilizing these characteristics to block spurious emissions outside the pass band. However, since conventional isolators were not originally designed to obtain attenuation outside the pass band, their capability for this purpose is limited.
Accordingly, the present applicants devised an experimental isolator (not yet publicly known) which contains a circuit element comprising a low-pass filter. As shown in
FIG. 12
, this isolator includes an inductor L
1
which is a constituent element of a low-pass filter. This inductor L
1
is patterned on a dielectric substrate
18
which is provided between a magnetic assembly
4
and a magnet
6
, and connected between an input port and a matching capacitor Co′.
Consequently, as shown in the equivalent circuit diagrams of FIG.
13
and
FIG. 14
, a &pgr;-type low-pass filter, comprising the connection of C
1
-L
1
-C
2
, is connected to the input port. Here, since C
1
is provided by a part of the capacitance of the matching capacitor Co′ of the isolator, it does not need to be provided separately. C
2
is formed by externally appending a capacitance to the isolator.
According to the above mentioned isolator containing a low-pass filter, attenuation outside the pass band can be increased, and interference and irregular operation caused by radiation can be prevented. The low-pass filter has a simple constitution and is inexpensive, making an expensive amplifier and an extra filter unnecessary, and enables the device to be made small-scale at low cost.
However, when the above low-pass filter is provided on a dielectric substrate, the magnet is in contact with the dielectric substrate, and consequently there is a concern that the high-frequency material characteristics of the magnet, particularly the tangent &dgr; or Dissipation Factor (Dissipation Factor=tangent &dgr;×100[%]), will have an adverse effect on the insertion loss of the isolator.
In general, commercially available mass-produced magnets were not developed for high-frequency components, and they are consequently liable to have a considerable dissipation factor (loss tangent). Therefore, it can be expected that the insertion loss of the isolator will increase when a circuit element on the dielectric substrate is in contact with the magnet. A further problem is that the magnet has a high dielectric constant, making it difficult to form inductance.
SUMMARY OF THE INVENTION
The present invention has been realized in consideration of these problems, and is able to provide a nonreciprocal circuit device which is capable of reducing the insertion loss of an isolator when a circuit element is provided on a dielectric substrate.
The nonreciprocal circuit device of the present invention comprises a magnetic assembly comprising a plurality of central conductors arranged so as to intersect adjacent to a ferrite body, a dielectric substrate disposed between a magnet and said magnetic assembly, said magnet applying a dc magnetic field to said magnetic assembly; wherein a circuit element is provided by patterning on said dielectric substrate, and a dielectric film or layer is disposed at least between said circuit element on said dielectric substrate and said magnet.
Alternatively, the dielectric film may be affixed to the magnet, or to the dielectric substrate.
In other embodiments of the present invention, the circuit element is provided by patterning on a laminated dielectric substrate, and at least one dielectric layer of said laminated substrate is disposed between at least said circuit element and said magnet.
In an alternative arrangement, a circuit element may be provided by patterning on said dielectric substrate, and a dielectric film may cover at least one part of the surface of said circuit element.
Preferably, the circuit element may comprise all or part of an inductor; a &pgr;-type low-pass filter; an LC series bandpass filter comprising an inductor and a capacitor; a phase-shift circuit comprising a micro-stripline; a phase-shift circuit comprising a stripline; a directional coupler; a capacitance coupler comprising a capacitor; or a band-elimination filter. Each of these circuit elements is known to the art. Each is formed by patterning as described herein.
Other features and advantages of the present invention will become apparent from the following description of embodiments of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 3922620 (1975-11-01), Deutsch
patent: 5068629 (1991-11-01), Nishikawa et al.
patent: 5153537 (1992-10-01), Desmarest
patent: 5923224 (1999-07-01), Makino et al.
patent: 5945887 (1999-08-01), Makino et al.
patent: 0779673 (1997-06-01), None
European Search Report dated Jun. 25, 1999.
Hasegawa Takashi
Kawanami Takashi
Makino Toshihiro
Okada Takekazu
Bettendorf Justin P.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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