JP2010147853A - Non-reciprocal circuit element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a 2-port type non-reciprocal circuit element capable of improving the heat dissipation of a termination resistor and suppressing the degradation of electrical characteristics. <P>SOLUTION: The non-reciprocal circuit element (2-port type isolator) includes ferrite 32 to which a DC magnetic field is applied by a permanent magnet 41, a first center electrode and a second center electrode arranged at the ferrite 32, and a circuit board 20. Further, matching capacitors and the termination resistor R are provided to the non-reciprocal circuit elemen. The termination resistor R is a chip type in which a resistor film is formed on at least one surface of an insulating substrate, and is mounted on the circuit board 20 making the resistor film face the surface of the circuit board 20. The generated heat of the termination resistor R is radiated via the circuit board 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nonreciprocal circuit device, and more particularly to a nonreciprocal circuit device such as an isolator or a circulator used in a microwave band.

  Conventionally, nonreciprocal circuit elements such as isolators and circulators have a characteristic of transmitting a signal only in a predetermined specific 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.

  As this type of non-reciprocal circuit device, a 3-port isolator described in Patent Document 1 and a 2-port isolator described in Patent Document 2 are known. In this type of isolator, the high-frequency signal input in the reverse direction is diffused by the terminal resistor. If the heat dissipation of the termination resistor is poor, the electrical characteristics of the isolator deteriorate with increasing temperature. Therefore, it is necessary for the termination resistor to ensure good heat dissipation in order to avoid excessive heat generation.

  Therefore, in the isolator described in Patent Document 1, the heat dissipation of the termination resistor is improved by increasing the electrode area on the ground side of the chip resistor. The ground side electrode is soldered to a ground terminal electrode provided on the surface of the circuit board, and the resistor film is disposed on the side opposite to the mounting surface. However, this isolator uses a dedicated product with a larger ground-side electrode as a termination resistor rather than a general-purpose product, so that the cost is high and the design change cannot be flexibly handled.

In the three-port isolator described in Patent Document 1, since the termination resistor is connected to the ground electrode, it is not necessary to consider the heat dissipation so severely. On the other hand, the two-port type isolator described in Patent Document 2 is obtained by winding the first and second center electrodes around a ferrite so as to cross each other in an insulated state in order to achieve a low insertion loss. . Since the termination resistor is connected in parallel with the first center electrode between the input and output ports, the termination resistor is not connected to the ground electrode. Will deteriorate.
Japanese Patent No. 36829797 International Publication No. 2007/046299 Pamphlet

  Accordingly, an object of the present invention is to provide a two-port nonreciprocal circuit device that can improve the heat dissipation of a termination resistor and suppress deterioration of electrical characteristics.

In order to achieve the above object, a non-reciprocal circuit device according to one aspect of the present invention comprises:
With permanent magnets,
A ferrite to which a DC magnetic field is applied by the permanent magnet;
A first center electrode and a second center electrode arranged to intersect the ferrite in an electrically insulated state from each other;
A circuit board for mounting the permanent magnet and the ferrite;
With
The first center electrode has one end electrically connected to the input port and the other end electrically connected to the output port;
The second center electrode has one end electrically connected to the output port and the other end electrically connected to the ground port.
A first matching capacitor is electrically connected between the input port and the output port;
A second matching capacitor is electrically connected between the output port and the ground port;
A termination resistor is electrically connected between the input port and the output port,
The termination resistor is a chip type in which a resistor film is formed on at least one surface of an insulating substrate, and is mounted on the circuit board with the resistor film facing the surface of the circuit board.
It is characterized by.

  In the nonreciprocal circuit device, when a reverse signal is input, the power is consumed by the terminating resistor. Since the resistor film is mounted so that the resistor film faces the surface of the circuit board, the heat generated by the resistor film is dissipated through the circuit board, improving the withstand voltage characteristics and causing failure such as burnout of the terminal resistor. Can be prevented. The termination resistor does not require any special processing or processing, and a general-purpose product can be used. Further, the nonreciprocal circuit element itself can be reduced in size by increasing the heat dissipation path. Furthermore, since the temperature rise of the termination resistor is suppressed, the variation of the resistance value due to the heat generation of the termination resistor is reduced, and the deterioration of the isolation characteristic is avoided. In particular, in a two-port isolator in which the second center electrode is wound around a ferrite a plurality of times in order to reduce the insertion loss, a terminal resistor having a high resistance value of about 100 to 500Ω is used. In this isolator, it is possible to maintain preferable electrical characteristics by improving the heat dissipation of the terminating resistor, and the power consumption of the high-frequency signal in the reverse direction is effective.

  In addition, by making the resistor film face the surface of the circuit board, the equivalent series inductance component parasitic to the terminal resistance is reduced compared to the case where the resistor film is disposed on the side opposite to the surface of the circuit board as in the prior art. The isolation band can be widened.

  According to the present invention, the heat dissipation of the termination resistor can be improved, and in the two-port isolator, the heat generation of the termination resistor that has a high resistance value and is not connected to the ground electrode is alleviated, and the electrical characteristics are deteriorated. Can be suppressed and contributes to miniaturization.

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

(Refer 1st Example and FIGS. 1-9)
FIG. 1 shows an exploded perspective view of a 2-port isolator which is a first embodiment of a 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 element 30 including a ferrite 32 and a permanent magnet 41.

  As shown in FIG. 2, the ferrite 32 is formed with a first center electrode 35 and a second center electrode 36 which are electrically insulated from each other on the front and back main surfaces 32a and 32b. Here, the ferrite 32 has a rectangular parallelepiped shape having a first main surface 32a and a second main surface 32b which are parallel to each other.

  The permanent magnet 41 is bonded to the main surfaces 32a and 32b via, for example, an epoxy adhesive 42 so that a DC magnetic field is applied to the ferrite 32 in a direction substantially perpendicular to the main surfaces 32a and 32b. (See FIG. 4), the ferrite-magnet element 30 is formed. The main surface 41a of the permanent magnet 41 has the same dimensions as the main surfaces 32a and 32b of the ferrite 32, and is arranged with the main surfaces 32a and 41a and the main surfaces 32b and 41a facing each other so that their external shapes coincide with each other. Yes.

  The first center electrode 35 is formed of a conductor film. That is, as shown in FIG. 2, the first center electrode 35 rises from the lower right on the first main surface 32a of the ferrite 32 and branches into two at the upper left at a relatively small angle with respect to the long side. It is inclined and rises to the upper left, wraps around the second main surface 32b via the relay electrode 35a on the upper surface, and branches into two so as to overlap the first main surface 32a in a transparent state on the second main surface 32b One end thereof is connected to a connection electrode 35b formed on the lower surface. The other end of the first center electrode 35 is connected to a connection electrode 35c formed on the lower surface. Thus, the first center electrode 35 is wound around the ferrite 32 for one turn. And the 1st center electrode 35 and the 2nd center electrode 36 demonstrated below cross | intersect in the state insulated by mutually forming the insulating film.

  The second center electrode 36 is formed of a conductor film. In the second center electrode 36, first, the 0.5th turn 36a is inclined at a relatively large angle with respect to the long side from the lower right to the upper left on the first main surface 32a and intersects the first center electrode 35. The first turn 36c is formed so as to intersect the first central electrode 35 substantially perpendicularly on the second main surface 32b via the relay electrode 36b on the upper surface. . The lower end portion of the first turn 36c goes around the first main surface 32a via the relay electrode 36d on the lower surface, and the 1.5th turn 36e is the first main surface 32a in parallel with the 0.5th turn 36a. It is formed so as to intersect with the center electrode 35 and wraps around the second main surface 32b via the relay electrode 36f on the upper surface. 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 35 c and 36 p formed on the lower surface of the ferrite 32, 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.

  Further, the connection electrodes 35b, 35c, 36p and the relay electrodes 35a, 36b, 36d, 36f, 36h, 36j, 36l, 36n are silver or silver in a recess 37 (see FIG. 3) formed on the upper and lower surfaces of the ferrite 32. It is formed by applying or filling an electrode conductor such as an alloy, copper, or copper alloy. In addition, dummy recesses 38 are formed on the upper and lower surfaces 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 the mother ferrite substrate in advance, 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 ferrite 32, YIG ferrite or the like is used. The first and second center electrodes 35 and 36 and various electrodes can be formed as a thick film or thin film of silver or a silver alloy by a method such as printing, transfer, or photolithography. As the insulating film of the center electrodes 35 and 36, a dielectric thick film such as glass or alumina, a resin film such as polyimide, or the like can be used. These can also be formed by methods such as printing, transfer, and photolithography.

  The ferrite 32 can be integrally fired with a magnetic material including an insulating film and various electrodes. In this case, Cu, Ag, Pd, or Pd / Ag that can withstand high temperature firing of various electrodes is used.

  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 substrate obtained by forming predetermined electrodes on a plurality of dielectric sheets, laminating them, and sintering them. The circuit board 20 includes an equivalent circuit shown in FIGS. 5 and 6 and an internal configuration diagram. As shown in FIG. 7, matching capacitors C1, C2, CS1, CS2, and CP1 are incorporated, and a termination resistor R (see FIG. 1) that is a chip-type element is externally attached on the circuit board 20. 5 shows a first circuit example, FIG. 6 shows a second circuit example, and FIG. 7 corresponds to the circuit configuration of FIG. Terminal electrodes 25a to 25e are formed on the front surface, and external connection terminal electrodes 26, 27, and 28 are formed on the back surface (mounting surface).

  The ferrite / magnet element 30 is placed on the circuit board 20, and the connection electrodes 35b, 35c, 36p on the lower surface of the ferrite 32 are reflow soldered to the terminal electrodes 25a, 25b, 25c on the circuit board 20 to be integrated. And 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 disposed immediately above the ferrite / magnet element 30. As shown in FIG. 1, the resin material 11 is filled between the circuit board 20 and the yoke 10 and around the ferrite / magnet element 30. The terminal resistance R is also covered with the resin material 11. The resin material 11 is, for example, a resin in which silica, phenol resin, and epoxy resin are mixed as main components.

  The connection relationship between the matching circuit element and the first and second center electrodes 35 and 36 is, for example, as shown in FIG. 5 as the first circuit example and FIG. 6 as the second circuit example. Here, a description will be given with reference to FIG. 7 based on the second circuit example shown in FIG.

  The external connection terminal electrode 26 formed on the back surface of the circuit board 20 is connected to the terminal electrode 25a (input port A) via the matching capacitor CS1, and is connected to the matching capacitor C1 and the termination resistor R. Yes. The terminal electrode 25 a is connected to one end of the first center electrode 35 through a connection electrode 35 b formed on the lower surface of the ferrite 32.

  The other end of the first center electrode 35 and one end of the second center electrode 36 are connected via a connection electrode 35 c formed on the lower surface of the ferrite 32 and a terminal electrode 25 b (output port B) formed on the surface of the circuit board 20. The terminal resistor R and the capacitors C1 and C2 are connected to each other and to the external connection terminal electrode 27 formed on the back surface of the circuit board 20 via the capacitor CS2. In addition, the termination resistor R is connected to terminal electrodes 25d and 25e formed on the surface of the circuit board 20.

  The other end of the second center electrode 36 is connected to the capacitor C2 and the circuit board 20 via the connection electrode 36p formed on the lower surface of the ferrite 32 and the terminal electrode 25c (ground port C) formed on the surface of the circuit board 20. It is connected to an external connection terminal electrode 28 formed on the back surface. Further, a grounded impedance adjusting capacitor CP1 is connected to a connection point between the input side terminal electrode 25a (input port A) and the capacitor CS1.

  The first circuit example shown in FIG. 5 is a basic type in which some elements (capacitors CS1, CS2, CP1) in the second circuit example shown in FIGS. 6 and 7 are omitted.

  In the two-port isolator configured as described above, one end of the first center electrode 35 is connected to the input port A, the other end is connected to the output port B, and one end of the second center electrode 36 is connected to the output port B. Since the other end is connected to the ground port C, 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 during operation. Therefore, a 2-port lumped constant isolator with low insertion loss can be obtained.

  Further, since the second center electrode 36 is wound around the ferrite 32 by two turns or more, the second center electrode 36 has a high inductance value and Q value, and the characteristics as an isolator are improved.

  When a high-frequency signal in the reverse direction is input from the external connection terminal electrode 27, most of the power is consumed by the termination resistor R, and the termination resistor R generates excessive heat as it is. Therefore, in the first embodiment, as shown in FIG. 8A, the chip-type termination resistor R is mounted with the resistor film facing the surface of the circuit board 20.

  The terminating resistor R is formed by forming electrodes 62 on both ends of the alumina substrate 61 and forming a resistor film 63 on one surface, and covering the resistor film 63 with a protective layer 64. For example, the electrode 62 is a thick film made of silver added with glass, the resistor film 63 is a thick film made of a dielectric material containing metal oxide as a main component and added with glass, and the protective layer 64 is made of glass. Become. The electrode 62 is joined to the terminal electrodes 25 d and 25 e on the circuit board 20 with solder 65.

  In the two-port isolator, when a reverse signal is input, the power is consumed by the termination resistor R, and the termination resistor R generates heat. Since the resistor film 63 is mounted with the resistor film 63 facing the surface of the circuit board 20, the heat generated by the resistor film 63 is dissipated through the circuit board 20, and the withstand voltage characteristics are improved. Failure such as burning can be prevented. In particular, the effect is great when the circuit board 20 is made of a material having good heat conduction, such as ceramic or glass ceramic composite material, as compared with the resin material. Moreover, the termination resistor R does not require special processing or processing, and a general-purpose product can be used. Further, the nonreciprocal circuit element itself can be reduced in size by increasing the heat dissipation path.

  Further, since the temperature rise of the termination resistor R is suppressed, the resistance value fluctuation due to the heat generated by the termination resistor R is reduced, and the deterioration of the isolation characteristic is avoided. In particular, in a two-port isolator in which the second center electrode 36 is wound around the ferrite 32 a plurality of times in order to reduce the insertion loss, a terminal resistor having a high resistance value of about 100 to 500Ω is used. . In this isolator, it is possible to maintain preferable electrical characteristics by improving the heat dissipation of the termination resistor R, which is effective.

  The resistance value of the termination resistor R has a predetermined temperature characteristic and varies depending on the temperature. Isolation decreases when the resistance value changes from a predetermined value. Further, when the termination resistor R is repeatedly exposed to a high temperature state, the resistance value increases and the isolation decreases. However, in the first embodiment, since the heat generation of the termination resistor R can be reduced, there is no decrease in isolation during operation of the communication device equipped with the isolator, and it is not easily affected by the operation status of the communication device. The characteristic is stabilized.

  On the other hand, as shown in FIG. 8B, when the resistor film 63 is disposed on the opposite side of the surface of the circuit board 20 as in the prior art, an equivalent series is provided between the resistor film 63 and the terminal electrodes 25d and 25e. Inductance components LS1 and LS2 are parasitic. FIG. 9 shows the inductance components LS1 and LS2 as an equivalent circuit. In the first embodiment, since the resistor film 63 is opposed to the surface of the circuit board 20, the equivalent series inductance component parasitic on the termination resistor R is reduced, and the isolation band can be widened. Specifically, in the first embodiment, the equivalent series inductance value is reduced by about 1 nH, and the bandwidth where the isolation is 20 dB or more is increased by 0.6%.

The circuit constants in the second circuit example of FIG. 6 are shown below.
First center electrode 35: Inductance value 1.7 nH
Second center electrode 36: inductance value 22nH
Capacitor C1: 4 pF, has a role of determining the frequency of isolation. It is preferable to have a value that maximizes isolation in the operating frequency band.
Capacitor C2: 0.3 pF, has a role of determining the pass frequency. It is preferable to set a value that minimizes the insertion loss in the operating frequency band.
Capacitor CS1: 2.5 pF, and has a role of matching the isolator to a characteristic impedance of 50Ω. It is preferable to set a value that minimizes the insertion loss in the operating frequency band.
Capacitor CS2: 3.5 pF, and has a role of matching the isolator to a characteristic impedance of 50Ω. It is preferable to set a value that minimizes the insertion loss in the operating frequency band.
Termination resistor R: 390Ω, which plays the role of absorbing reverse power as the termination resistor of the isolator. It is preferable to have a value that maximizes isolation in the operating frequency band.
Capacitor CP1: 0.05 pF, and has a role of matching the isolator to a characteristic impedance of 50Ω. It is preferable that the input return loss is maximized and the insertion loss is minimized in the operating frequency band.

(Modification, see FIG. 10)
FIG. 10 shows a modified example of the termination resistor mounting form. Here, before the termination resistance R is sealed with the resin material 11, the soldered portion of the termination resistance R is covered with the resin material 12. The resin material 12 is obtained by adding ceramic such as alumina, aluminum nitride, glass, silicon oxide or the like to an epoxy resin, and has thermal conductivity.

  The resin material 12 is usually called an underfill resin, and a resin having high adhesion and high permeability is used to improve the bonding strength between the substrate and the component. By using the resin material 12 having thermal conductivity as the underfill resin, the resin material 12 is filled between the resistor film 63 and the surface of the circuit board 20, so that the thermal coupling between the two becomes high and the resistance is increased. The heat dissipation of the body film 63 is further improved.

(Refer to the second embodiment, FIG. 11)
As shown in FIG. 11, the two-port type isolator which is the second embodiment of the nonreciprocal circuit device according to the present invention is a lumped constant type isolator, which roughly includes the upper yoke 70, the circuit board 80, the permanent magnet 90, The ferrite 91 is provided with the first and second center electrodes 95 and 96 and the lower yoke 100.

  A resin case portion 101 is integrally formed on the lower yoke 100, and an external connection terminal (IN) 102, an external connection terminal (OUT) 103, and an external connection terminal (GND) 104 are formed on the resin case portion 101. Is attached. The functions of the upper yoke 70, the circuit board 80, the permanent magnet 90, the ferrite 91, and the first and second center electrodes 95 and 96 are the same as those of the flat yoke 10, the circuit board 20, the permanent magnet 41, and the ferrite shown in the first embodiment. 32, and basically the same as the action of the first and second center electrodes 35 and 36. The circuit configuration is the same as that of the first circuit example or the second circuit example shown in FIG. 5 or FIG. 6, and the internal configuration of the circuit board 80 is basically the same as that shown in FIG. In the second embodiment, the principal surfaces of the permanent magnet 90 and the ferrite 91 are arranged parallel to the surface of the circuit board 80, so-called horizontally.

  Also in the second embodiment, the termination resistor R is mounted with its resistor film facing the surface of the circuit board 80. Therefore, the effect is the same as that of the first embodiment.

(Refer to the third embodiment, FIG. 12)
As shown in FIG. 12, the isolator according to the third embodiment of the non-reciprocal circuit device according to the present invention communicates the modularized ferrite / magnet device 30, the terminating resistor R, and the capacitors C1, C2, CS1, CS2, CP1. Solder mounted on terminal electrodes 51a, 51b, 51c, 51d, 51e, 52a, 52b, 53a, 53b, 54a, 54b, 55a, 55b, 56a, 56b formed on the wiring circuit board 50 of the machine It is. The circuit configuration is as shown in FIG. 6, and the connection relationship in the printed circuit board 50 is basically the same as that in FIG.

  Also in the third embodiment, the terminating resistor R is mounted with its resistor film facing the surface of the printed circuit board 50. Therefore, the operation and effect are the same as in the first embodiment.

(Other examples)
The non-reciprocal circuit device according to the present invention is not limited to the above-described embodiments, 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 are reversed, the input port and the output port are switched. Further, the configuration of the matching circuit is arbitrary, and circuit configurations other than the equivalent circuits of FIGS. 5 and 6 are possible. Further, the configurations of the first and second center electrodes and the number of windings with respect to the ferrite are arbitrary.

It is a disassembled perspective view which shows the nonreciprocal circuit device (2 port type isolator) which is 1st Example. It is a perspective view which shows the ferrite with a center electrode. It is a perspective view which shows the said ferrite. It is a disassembled perspective view which shows a ferrite magnet element. 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 block diagram which shows the internal structure of the circuit board in the said 2nd circuit example. (A) is sectional drawing which shows the mounting state of the termination resistance in 1st Example, (B) is sectional drawing which shows the mounting state of the termination resistance in a prior art example. It is an equivalent circuit diagram which shows the equivalent series inductance component which generate | occur | produces parasitically in termination resistance. It is sectional drawing which shows the modification of the mounting state of termination resistance. It is a disassembled perspective view which shows the nonreciprocal circuit device (2 port type isolator) which is 2nd Example. It is a disassembled perspective view which shows the nonreciprocal circuit device (2 port type isolator) which is 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... Underfill resin 20, 80 ... Circuit board 30 ... Ferrite magnet element 32, 91 ... Ferrite 35, 95 ... 1st center electrode 36, 96 ... 2nd center electrode 41, 90 ... Permanent magnet 50 ... Wiring circuit board 61 ... Insulating substrate 63 ... Resistor film C1, C2 ... Matching capacitor R ... Terminating resistor A ... Input port B ... Output port C ... Ground port

Claims (4)

With permanent magnets,
A ferrite to which a DC magnetic field is applied by the permanent magnet;
A first center electrode and a second center electrode arranged to intersect the ferrite in an electrically insulated state from each other;
A circuit board for mounting the permanent magnet and the ferrite;
With
The first center electrode has one end electrically connected to the input port and the other end electrically connected to the output port;
The second center electrode has one end electrically connected to the output port and the other end electrically connected to the ground port.
A first matching capacitor is electrically connected between the input port and the output port;
A second matching capacitor is electrically connected between the output port and the ground port;
A termination resistor is electrically connected between the input port and the output port,
The termination resistor is a chip type in which a resistor film is formed on at least one surface of an insulating substrate, and is mounted on the circuit board with the resistor film facing the surface of the circuit board.
A nonreciprocal circuit device characterized by the above.   The nonreciprocal circuit device according to claim 1, wherein the second center electrode is wound around the ferrite by two or more turns.   The termination resistor is soldered to a terminal electrode whose electrode is formed on the surface of the circuit board, and a resin material having thermal conductivity is filled between the resistor film and the surface of the circuit board. The nonreciprocal circuit device according to claim 1, wherein   4. The nonreciprocal circuit device according to claim 1, wherein the circuit board is a wired circuit board of a communication device.

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