JP4793350B2 - 2-port nonreciprocal circuit device - Google Patents

Description

  The present invention relates to a two-port nonreciprocal circuit device, and more particularly to a two-port nonreciprocal circuit device used as an isolator in a microwave band.

  Conventionally, nonreciprocal circuit elements such as isolators have a characteristic of transmitting a signal only in a predetermined direction and not transmitting in a reverse direction. Utilizing this characteristic, for example, an isolator is used in a transmission circuit unit of a mobile communication device such as a car phone or a mobile phone.

  This type of non-reciprocal circuit element includes a ferrite having a central electrode disposed thereon, a permanent magnet that applies a DC magnetic field thereto, a matching capacitor, a resistance, and the like. Patent Documents 1 and 2 describe a three-port nonreciprocal circuit device in which a ferrite having a central electrode formed of an Ag / Pd alloy is sintered and integrated. The reason why the center electrode is formed of an Ag / Pd alloy is that the firing temperature of ferrite is as high as about 1350 ° C., and therefore Cu, Ag, etc. having a sintering temperature lower than that cannot be used.

However, Pd or Ag / Pd has a low conductivity of about 10 × 10 ⁶ S. In particular, the first and second center electrodes are arranged in ferrite, and the other end of the second center electrode connected to the ground port is connected to the ground. In a two-port isolator with a low insertion loss provided with a matching capacitor between the ports, a large current flows through the second center electrode. Therefore, if the second center electrode is formed of Pd or Ag / Pd having a low conductivity, Q However, there was a problem that the value was lowered and the insertion loss was increased.

On the other hand, in order to maintain low insertion loss, the center electrode may be formed of Cu, Ag or the like having high conductivity. However, since this cannot be simultaneously fired with ferrite, it is fired separately, increasing the firing process. However, this leads to a significant cost increase.
Japanese Patent Laid-Open No. 06-343005 JP-A-10-270911

  Accordingly, an object of the present invention is to provide a two-port nonreciprocal circuit device having a small insertion loss without increasing the firing process.

In order to achieve the above object, a two-port non-reciprocal circuit device according to the present invention includes:
With permanent magnets,
A ferrite to which a DC magnetic field is applied by the permanent magnet;
A first central electrode made of a conductor film disposed on the ferrite, having one end electrically connected to the input port and the other end electrically connected to the output port;
A second conductive film that intersects the first center electrode in an electrically insulated state and is disposed on the ferrite, having one end electrically connected to the output port and the other end electrically connected to the ground port; A center electrode;
A first matching capacitor electrically connected between the input port and the output port;
A second matching capacitor electrically connected between the output port and the ground port;
A resistor electrically connected between the input port and the output port;
With
The ferrite and the permanent magnet constitute a ferrite / magnet assembly sandwiched by permanent magnets from both sides in parallel with the surface on which the first and second center electrodes are disposed,
The ferrite is composed of a center layer and an outer layer that ensures insulation between the first center electrode and the second center electrode, and the first center electrode is formed of Pd or Ag / Pd on the center layer. The second center electrode is formed of Pd or Ag / Pd on the outer surface of the outer layer, and the center layer, the outer layer, the first and second center electrodes are integrally sintered,
A plating film made of a metal material having a conductivity of 40 × 10 ⁶ S or more is formed on the surface of the second center electrode;
It is characterized by.

In the two-port nonreciprocal circuit device according to the present invention, since the plating film made of a metal material having a conductivity of 40 × 10 ⁶ S or more is formed on the surface of the second center electrode, the Q value of the second center electrode is large. During operation, a large current easily flows through the second center electrode, and the insertion loss is further reduced. In addition, the ferrite center layer, outer layer, and first and second center electrodes can be simultaneously and integrally fired, simplifying the manufacturing process. In addition, since the second center electrode is disposed outside the first center electrode, the cross-sectional area of the coil of the second center electrode is increased, the inductance is increased, and the insertion loss is further decreased.

  In the two-port nonreciprocal circuit device according to the present invention, the plating film can be formed of Cu or Ag. Further, it is preferable that the saturation magnetization differs between the ferrite central layer and the outer layer. Either the case where the saturation magnetization of the outer layer is small or the case where it is large relative to the central layer may be used. Even if the same ferrite (magnetic material for microwaves) is used, the saturation magnetization differs between the central layer and the outer layer, so that the magnetic permeability differs between the central layer and the outer layer, and the device operates as an isolator.

  The thickness of the outer layer is preferably smaller than the thickness of the center layer. The coupling between the first and second center electrodes is strengthened.

  According to the present invention, the ferrite central layer, outer layer, and first and second central electrodes can be integrally fired at the same time, so that the number of firing steps can be reduced and manufacturing can be performed at low cost, and Pd or Ag / Pd Since a plating film made of a metal material having a high conductivity is formed on the surface of the second center electrode made of, the Q value of the second center electrode is increased and the insertion loss is reduced.

  Embodiments of a two-port nonreciprocal circuit device according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an exploded perspective view of a 2-port isolator which is an embodiment of a 2-port nonreciprocal circuit device according to the present invention. This 2-port type isolator is a lumped constant type isolator, and generally includes a flat yoke 10, a circuit board 20, and a ferrite / magnet assembly 30 including a ferrite 32 and a permanent magnet 41. In FIG. 1, the hatched portion is a conductor.

  As shown in FIG. 2, the ferrite 32 is composed of a center layer 33 and two outer layers 34A and 34B, each of which uses a magnetic material for microwaves. The outer layers 34A and 34B are made of a material whose saturation magnetization (Ms) is smaller or larger than the saturation magnetization of the center layer 33, and functions as an insulating layer for ensuring the first and second center electrodes 35 and 36 in an insulated state. ing. The materials of the center layer 33 and the outer layers 34A and 34B will be described in detail later.

  The center layer 33 of the ferrite 32 has a rectangular parallelepiped shape, the first main surface is indicated by reference numeral 32a, the second main surface is indicated by reference numeral 32b, and the upper and lower surfaces are indicated by reference numerals 32c and 32d.

  Further, the permanent magnet 41 opposes the main surfaces 32a and 32b so as to apply a magnetic field to the ferrite 32 in a direction perpendicular to the main surfaces 32a and 32b, for example, an epoxy-based adhesive 42 (see FIG. 1). To form a ferrite / magnet assembly 30. The main surface of the permanent magnet 41 has the same dimensions as the main surfaces 32a and 32b, and is arranged with the main surfaces facing each other so that their external shapes match.

  The first center electrode 35 is formed of a conductor film on the first and second main surfaces 32 a and 32 b of the center layer 33. That is, on the first main surface 32a, the first center electrode 35 rises from the lower right and is inclined at a relatively small angle with respect to the long side at the upper left, rises at the upper left, and is a relay electrode on the upper surface 32c. It goes around to the 2nd main surface 32b via 35a. The first central electrode 35 is formed on the second main surface 32b so as to substantially overlap the first main surface 32a in a see-through state, and one end thereof is connected to the connection electrode 35b formed on the lower surface 32d. The other end of the first center electrode 35 is connected to a connection electrode 35c formed on the lower surface 32d. Thus, the first center electrode 35 is wound around the ferrite 32 for one turn. Outer layers (insulating layers) 34A and 34B are provided on the main surfaces 32a and 32b on which the first center electrode 35 is formed, and insulation with the second center electrode 36 described below is ensured.

  The second center electrode 36 is formed of a conductor film on the outer layers 34A and 34B. First, in the outer layer 34A, the 0.5th turn 36a is formed in a state of being inclined at a relatively large angle with respect to the long side from the lower right to the upper left and intersecting the first center electrode 35, and for the relay on the upper surface 32c. The first turn 36c is formed in the outer layer 34B so as to cross the first center electrode 35 substantially vertically in the outer layer 34B through the electrode 36b. The lower end of the first turn 36c goes around the outer layer 34A via the relay electrode 36d on the lower surface 32d, and the 1.5th turn 36e is parallel to the 0.5th turn 36a in the outer layer 34A. It is formed in an intersecting state and wraps around the outer layer 34B via the relay electrode 36f on the upper surface 32c. Similarly, the second turn 36g, the relay electrode 36h, the 2.5th turn 36i, the relay electrode 36j, the third turn 36k, the relay electrode 36l, the 3.5th turn 36m, the relay electrode 36n, the fourth turn The eyes 36o are formed on the surface of the ferrite 32, respectively. Further, both ends of the second center electrode 36 are connected to connection electrodes 35c and 36p formed on the lower surface 32d, respectively. The connection electrode 35 c is shared as a connection electrode at each end of the first center electrode 35 and the second center electrode 36.

  That is, the second center electrode 36 is wound around the ferrite 32 in a spiral manner for four turns. Here, the number of turns is calculated by assuming that the state in which the center electrode 36 crosses the first or second main surface 32a, 32b once each is 0.5 turns. The crossing angle of the center electrodes 35 and 36 is set as necessary, and the input impedance and insertion loss are adjusted.

  The connection electrodes 35b, 35c, 36p and the relay electrodes 35a, 36b, 36d, 36f, 36h, 36j, 36l, 36n are electrode conductors in recesses 37 (see FIG. 3) formed on the upper and lower surfaces 32c, 32d. It is formed by coating or filling. In addition, dummy recesses 38 are formed on the upper and lower surfaces 32c and 32d in parallel with various electrodes, and dummy electrodes 39a, 39b, and 39c are formed. This type of electrode is formed by forming a through hole in advance in a mother ferrite substrate serving as the center layer 33, filling the through hole with an electrode conductor, and then cutting at a position where the through hole is divided. Various electrodes may be formed as conductor films in the recesses 37 and 38.

  As the permanent magnet 41, a strontium-based, barium-based, or lanthanum-cobalt-based ferrite magnet is usually used. As the adhesive 42 for adhering the permanent magnet 41 and the ferrite 32, it is optimal to use a one-component thermosetting epoxy adhesive.

  The circuit board 20 is a laminated board obtained by forming predetermined electrodes on a plurality of dielectric sheets, laminating them, and sintering them. As shown in FIGS. , Matching capacitors C1, C2, Cs1, Cs2, Cp1, Cp2 and a terminating resistor R are incorporated. Terminal electrodes 25a, 25b, and 25c are formed on the upper surface, and external connection terminal electrodes 26, 27, and 28 are formed on the lower surface, respectively.

  The connection relationship between these matching circuit elements and the first and second center electrodes 35 and 36 is, for example, as shown in FIG. 4 as a first circuit example and FIG. 5 as a second circuit example. Here, the connection relationship will be described based on the first circuit example shown in FIG.

  The external connection terminal electrode 26 formed on the lower surface of the circuit board 20 functions as the input port P1, and this terminal electrode 26 is connected to the matching capacitor C1 and the termination resistor R. The electrode 26 is connected to one end of the first center electrode 35 via a terminal electrode 25 a formed on the upper surface of the circuit board 20 and a connection electrode 35 b formed on the lower surface 32 d of the ferrite 32.

  The other end of the first center electrode 35 and one end of the second center electrode 36 are connected to a termination resistor R via a connection electrode 35 c formed on the lower surface 32 d of the ferrite 32 and a terminal electrode 25 b formed on the upper surface of the circuit board 20. And connected to capacitors C 1 and C 2 and to an external connection terminal electrode 27 formed on the lower surface of the circuit board 20. This electrode 27 functions as the output port P2.

  The other end of the second center electrode 36 is formed on the lower surface of the capacitor C2 and the circuit board 20 via the connection electrode 36p formed on the lower surface 32d of the ferrite 32 and the terminal electrode 25c formed on the upper surface of the circuit board 20. The external connection terminal electrode 28 is connected. This electrode 28 functions as a ground port P3.

  In the second circuit example shown in FIG. 5, capacitors Cs1 and Cp1 are connected to the input port P1 side, and capacitors Cs2 and Cp2 are connected to the output port P2 side. These capacitors are used for impedance adjustment. ing.

  The ferrite / magnet assembly 30 is placed on the circuit board 20, and various electrodes on the lower surface 32d of the ferrite 32 are integrated with the terminal electrodes 25a, 25b, 25c on the circuit board 20 by reflow soldering or the like. The lower surface of the permanent magnet 41 is integrated on the circuit board 20 with an adhesive.

  The flat yoke 10 has an electromagnetic shielding function, and is fixed to the upper surface of the ferrite / magnet assembly 30 via a dielectric layer (adhesive layer) 15. The functions of the flat yoke 10 are to suppress magnetic leakage from the ferrite / magnet assembly 30 and leakage of high-frequency electromagnetic fields, to suppress the influence of external magnetism, and this isolator is mounted on a substrate (not shown) using a chip mounter. It is to provide a place to pick up with a vacuum nozzle when mounting. The flat yoke 10 does not necessarily need to be grounded, but may be grounded by soldering or conductive adhesive, and the effect of the high frequency shield is improved when grounded.

  In the two-port isolator having the above configuration, one end of the first center electrode 35 is connected to the input port P1, the other end is connected to the output port P2, and one end of the second center electrode 36 is connected to the output port P2. Since the other end is connected to the ground port P3, a two-port lumped constant isolator with low insertion loss can be obtained. Further, during operation, a large high-frequency current flows through the second center electrode 36 and almost no high-frequency current flows through the first center electrode 35. Therefore, the direction of the high-frequency magnetic field generated by the first center electrode 35 and the second center electrode 36 is determined by the arrangement of the second center electrode 36. By determining the direction of the high-frequency magnetic field, a measure for further reducing the insertion loss is facilitated.

  Further, the ferrite / magnet assembly 30 is mechanically stable because the ferrite 32 and the pair of permanent magnets 41 are integrated with the adhesive 42, and becomes a robust isolator that is not deformed or damaged by vibration or impact. .

  In this isolator, the circuit board 20 is a multilayer dielectric substrate. As a result, a circuit network such as a capacitor and a resistor can be built inside, and the miniaturization and thinning of the isolator can be achieved, and the connection between the circuit elements is performed within the substrate, so that improvement in reliability is expected. it can. Of course, the circuit board 20 does not necessarily have to be a multilayer, and may be a single layer, and a matching capacitor or the like may be externally attached as a chip type.

  Here, materials and manufacturing methods of the ferrite 32, the first and second center electrodes 35 and 36 will be described.

First, a magnetic powder for microwaves mainly composed of yttrium oxide (Y ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) and a polyvinyl alcohol organic binder are dispersed in an organic solvent, and a first slurry is prepared. Get. Instead of the magnetic powder for microwaves, magnetic material powders such as manganese magnesium ferrite, nickel zinc ferrite, and calcium vanadium garnet may be used as appropriate.

  Next, a microwave magnetic material green sheet having a uniform thickness of several tens of μm is formed from the microwave magnetic material slurry (first slurry) obtained as described above, for example, by a doctor blade method. , Punched into a rectangular shape having dimensions of 100 mm × 100 mm.

  On the other hand, as the second slurry, a microwave magnetic slurry is prepared with the same composition system as the first slurry so that the saturation magnetization is decreased or the composition is adjusted so that the saturation magnetization is increased. A green sheet is formed from the second slurry by the same forming method as described above and punched into a rectangular shape having a predetermined size. The green sheet may be formed by extrusion. Further, in a magnetic material for microwaves, it is well known that the saturation magnetization (Ms) is changed by adjusting the composition itself.

  A plurality of green sheets made of the first slurry are laminated to form the center layer 33, and the recesses 37 and 38 are formed to fill the conductor paste. A first center electrode 35 is formed on the main surfaces 32a and 32b of the center layer 33 by a screen printing method using a conductive paste. On the other hand, the second center electrode 36 is formed on the outer layers 34A and 34B by a screen printing method using a conductive paste. The outer layers 34A and 34B are formed with notches for electrical connection with the electrodes provided on the upper and lower surfaces 32c and 32d, and the notches are filled with a conductive paste. Here, as the conductor paste for forming various electrodes, a conductor paste formed by mixing palladium or palladium, silver powder, and an organic solvent is used. The center electrodes 35 and 36 may be formed by a gravure transfer method or the like.

Palladium or silver-palladium alloy is used as the conductive paste because it can withstand a firing temperature of about 1350 ° C. when simultaneously fired with ferrite 32 (center layer 33 and outer layers 34A, 34B made of a magnetic material for microwaves). It is. However, the conductivity of palladium or silver palladium alloy is as low as about 10 × 10 ⁶ S. Therefore, it is difficult for the large current originally required to flow through the second center electrode 36 when the isolator is operated as it is. Therefore, in this embodiment, after sintering described below, the surface of the second center electrode 36 formed on the outside is thick with a metal material having high conductivity (40 × 10 ⁶ S or more) such as Cu and Ag. A plating film with a thickness of about 3 to 5 μm is formed.

  Next, the center layer 33 on which the first center electrode 35 is formed and the outer layers 34A and 34B on which the second center electrode 36 is formed are stacked and pressed to obtain a stacked body. And this laminated body is baked at the temperature of 1300-1400 degreeC, and a sintered compact is obtained. A substrate to be the permanent magnet 41 is bonded to the front and back surfaces of the sintered body to obtain a mother substrate. Next, this mother substrate is cut so as to become one unit of ferrite / magnet assembly 30 (see FIG. 1).

  When the ferrite / magnet assembly 30 is manufactured, the center layer 33 and the outer layers 34A and 34B are made of the magnetic material for microwaves as described above. Sintering temperature and aberration behavior are almost the same, and a sintered body free from warpage and cracks can be obtained, increasing the reliability as an isolator. The simultaneous firing not only simplifies the manufacturing process but also eliminates the need to use expensive materials such as glass as the outer layers (insulating layers) 34A and 34B, thereby reducing the manufacturing cost.

  Furthermore, in this embodiment, the saturation magnetization of the outer layers 34A and 34B is made smaller than the saturation magnetization of the center layer 33. When an external magnetic field is applied to the ferrite 32 in a direction perpendicular to the main surfaces 32a and 32b by the permanent magnet 41, the magnetic material of the central layer 33 contributes to the isolator operation, and the internal magnetic field matched to the central layer 33 An external magnetic field is applied so that Since the outer layers 34A and 34B have a small saturation magnetization, the internal magnetic field is larger than that of the center layer 33 as shown in the following formula (1). As a result, the outer layers 34A and 34B are magnetically saturated as compared with the central layer 33, the magnetic permeability is reduced, and act as a simple insulating layer.

Hin = Hex−N · Ms (1)
Hin: Internal magnetic field Hex: External magnetic field N: Demagnetizing field coefficient Ms: Saturation magnetization

As an example, the external magnetic field Hex is 91500 A / m, the demagnetizing factor N is 0.6, the saturation magnetization Ms of the center layer 33 is 0.10 T (79600 A / m), and the saturation magnetization Ms of the outer layers 34 A and 34 B is 0.04 T. (31800A / m)
Central layer Hin = 91500−0.6 × 79600 = 43740 A / m
Outer layer Hin = 91500−0.6 × 31800 = 72220 A / m
It becomes.

  FIG. 6 shows the insertion loss of the isolator with respect to frequency (see the left vertical axis) and isolation (see the right vertical axis). Solid lines Aa and Ab show the isolation characteristics and insertion loss characteristics of Comparative Example 1 separately fired using a magnetic material for the center layer and a non-magnetic material for the outer layer, and these characteristics are used as a reference. Comparative Example 2 using a magnetic material (saturation magnetization is the same) for the center layer and the outer layer and using palladium for the first and second center electrodes 35 and 36 showed the isolation characteristics equivalent to the solid line Aa. However, the insertion loss characteristic is deteriorated as shown by the thin line Bb.

  On the other hand, as shown in the above embodiment, although magnetic materials are used for the center layer and the outer layer, the saturation magnetization of the outer layer is changed from the saturation magnetization of the center layer as shown in the numerical example. When palladium is used for the first and second center electrodes 35 and 36 and electroless copper plating is applied to the second center electrode 36, the isolation characteristic is the isolation characteristic of the first comparative example. It was equivalent to Aa (characteristic curve overlapped with solid line Aa). Further, the insertion loss characteristic was substantially equal to the insertion loss characteristic Ab of Comparative Example 1, as indicated by a dotted line Cb in FIG.

  That is, according to the present embodiment, the center layer 33, the outer layers 34A and 34B, and the electrode can be fired at the same time, the firing process is reduced, and the insertion loss characteristic is almost equivalent to that of the comparative example 1 (corresponding to the conventional product). And isolation characteristics can be obtained.

  In addition, since the second center electrode 36 is disposed outside the first center electrode 35, the cross-sectional area of the coil of the second center electrode 36 is increased, the inductance is increased, and the insertion loss is further decreased. That is, the insertion loss becomes better as the value of the ratio of the inductance value L1 of the first center electrode 35 to the inductance value L2 of the second center electrode 36 becomes smaller.

  In addition, the thickness of the outer layers 34 </ b> A and 34 </ b> B is preferably smaller than the thickness of the center layer 33. When the outer layers 34A and 34B are thin, the first and second center electrodes 35 and 36 are strongly coupled.

(Other examples)
The two-port nonreciprocal circuit device according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  For example, if the N pole and S pole of the permanent magnet 41 are reversed, the input port P1 and the output port P2 are switched. In the above embodiment, the matching circuit elements are all built in the circuit board. However, a chip type inductor or capacitor may be externally attached to the circuit board. Alternatively, the circuit element can be incorporated in the ferrite 32.

  Further, the shapes of the first and second center electrodes 35 and 36 can be variously changed. For example, the first center electrode 35 may be branched into two on the main surfaces 32a and 32b. Moreover, the 2nd center electrode 36 should just be wound 1 turn or more.

It is a disassembled perspective view which shows one Example of the nonreciprocal circuit device (2 port type isolator) based on this invention. It is a disassembled perspective view which shows the ferrite with a center electrode. It is a perspective view which shows the center layer of a ferrite. It is an equivalent circuit diagram showing a first circuit example of a 2-port isolator. It is an equivalent circuit diagram showing a second circuit example of a 2-port isolator. It is a graph which shows an insertion loss characteristic and an isolation characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Circuit board 30 ... Ferrite magnet assembly 32 ... Ferrite 33 ... Center layer 34A, 34B ... Outer layer 35 ... 1st center electrode 36 ... 2nd center electrode 41 ... Permanent magnet P1 ... Input port P2 ... Output port P3 ... Grand Port

Claims (5)

With permanent magnets,
A ferrite to which a DC magnetic field is applied by the permanent magnet;
A first central electrode made of a conductor film disposed on the ferrite, having one end electrically connected to the input port and the other end electrically connected to the output port;
A second conductive film that intersects the first center electrode in an electrically insulated state and is disposed on the ferrite, having one end electrically connected to the output port and the other end electrically connected to the ground port; A center electrode;
A first matching capacitor electrically connected between the input port and the output port;
A second matching capacitor electrically connected between the output port and the ground port;
A resistor electrically connected between the input port and the output port;
With
The ferrite and the permanent magnet constitute a ferrite / magnet assembly sandwiched by permanent magnets from both sides in parallel with the surface on which the first and second center electrodes are disposed,
The ferrite is composed of a center layer and an outer layer that ensures insulation between the first center electrode and the second center electrode, and the first center electrode is formed of Pd or Ag / Pd on the center layer. The second center electrode is formed of Pd or Ag / Pd on the outer surface of the outer layer, and the center layer, the outer layer, the first and second center electrodes are integrally sintered,
A plating film made of a metal material having a conductivity of 40 × 10 ⁶ S or more is formed on the surface of the second center electrode;
A two-port nonreciprocal circuit device characterized by the above.   The two-port nonreciprocal circuit device according to claim 1, wherein the plating film is made of Cu or Ag.   The two-port nonreciprocal circuit device according to claim 1 or 2, wherein the central layer and the outer layer have different saturation magnetizations.   4. The two-port nonreciprocal circuit device according to claim 1, wherein a thickness of the outer layer is smaller than a thickness of the center layer. 5. A circuit board having terminal electrodes formed on the surface,
The ferrite magnet assembly has a surface on which the first and second center electrodes are disposed on the circuit board in a direction perpendicular to the surface of the circuit board;
The two-port nonreciprocal circuit device according to any one of claims 1 to 4, wherein:

Images