JP2012105050A - Non-reciprocal circuit element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-reciprocal circuit element of concentrated constant type capable of providing both smaller size and lower loss.SOLUTION: In the non-reciprocal circuit element, a first central electrode 21 and a second central electrode 22 are arranged to cross each other in insulated manner on a ferrite 23 to which an AC magnetic field is applied from a permanent magnet. Here, one end of the first central electrode 21 works as a first port P1, other ends of the first central electrode 21 and the second central electrode 22 work as a second port P2, and one end of the second central electrode 22 works as a third port P3. A resistive element R and a first capacitive element C1 are connected in parallel between an input terminal 41 connected to the first port P1 and an output terminal 42 connected to the second port P2. Between the output terminal 42 and a ground terminal 43 connected to the third port P3, a second capacitive element C2 is connected in series. The following formula is met, where γ: magnetic rotation ratio, μo: vacuum permeability, Hin: internal magnetic field, Ms: saturation magnetization, and ω: angular frequency.

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 mobile phone.

  As this type of non-reciprocal circuit device, ones described in Patent Documents 1 and 2 are known which operate in a magnetic field lower than the magnetic resonance point. The non-reciprocal circuit element described in Patent Document 1 uses a region where the magnetic permeability μ + ′ is negative, which increases the insertion loss. The non-reciprocal circuit element described in Non-Patent Document 1 uses a positive region of magnetic permeability μ + ′, but is a waveguide type. The waveguide type isolator is increased in size because the ferrite is composed of 1/2 the frequency λ. In addition, when operating in a low magnetic field, a phase difference between positive and negative circularly polarized waves is generated with a small magnetic permeability, so that a line length of about ½ of the frequency λ is required, which increases the size and is mounted on a mobile phone or the like. I can't.

  The nonreciprocal circuit element described in Patent Document 2 is a lumped constant type and can reduce the size of the ferrite. However, since it operates with a high magnetic field, the operating magnetic field increases as the frequency increases, and the magnetic circuit There is a problem of increasing the size. In particular, mobile communication devices are required to be small and have low loss in the 3.5 GHz band and the 5 GHz band.

JP-A-10-284909 Japanese Patent Application Laid-Open No. 09-232818

TDK Tech-Mag with ferrite (http://www.tdk.co.jp/techmag/ferrite/grain_54/flame54.htm)

  Accordingly, an object of the present invention is to provide a lumped-constant nonreciprocal circuit device capable of achieving both a reduction in size and a low loss.

γ：磁気回転比
μｏ：真空透磁率
Ｈｉｎ：内部磁界
Ｍｓ：飽和磁化
ω：角周波数
を特徴とする。 The non-reciprocal circuit device according to one aspect of the present invention is
A ferrite core to which a DC magnetic field is applied by a permanent magnet is disposed so that the first center electrode and the second center electrode intersect each other in an insulated state;
One end of the first center electrode is a first port, the other end of each of the first center electrode and the second center electrode is a second port, and one end of the second center electrode is a third port,
A resistor element and a first capacitor element are connected in parallel between an input terminal connected to the first port and an output terminal connected to the second port,
A second capacitive element is connected in series between the ground terminal connected to the third port and the output terminal;
Satisfying the following formula,

γ: magnetic rotation ratio μo: vacuum permeability Hin: internal magnetic field Ms: saturation magnetization ω: angular frequency

  The nonreciprocal circuit element is a lumped constant type, and when a high frequency signal is input from an input terminal, it is output in phase to an output terminal. Therefore, no current flows through the resistance element and there is almost no loss. On the other hand, when a high-frequency signal is input from the output terminal, it is output in reverse phase (180 ° phase inversion) to the input terminal. That is, in the reverse direction, a potential difference is generated between the input and output, current flows through the resistance element and power is consumed, so that output from the input terminal is suppressed. When the internal magnetic field Hin and the saturation magnetization Ms of the ferrite satisfy the above formula, the nonreciprocal circuit element operates in a lumped constant type, a low magnetic field and a permeability μ + ′ in a positive region, thereby reducing the size of the magnetic circuit. And miniaturization of ferrite are compatible. Moreover, since it operates at a position away from the magnetic resonance point, magnetic loss is reduced.

  According to the present invention, it is possible to achieve both reduction in size and low loss in a lumped constant type nonreciprocal circuit device.

It is an equivalent circuit diagram which shows the nonreciprocal circuit element (2 port type isolator) which is one Example. It is a disassembled perspective view which shows the said nonreciprocal circuit element. It is a disassembled plan view which shows the structure of the circuit board which comprises the said nonreciprocal circuit element. It is a graph which shows the circularly polarized magnetic permeability with respect to the magnetic field in a ferrite. It is a graph which shows the insertion loss characteristic of the said nonreciprocal circuit element. It is a graph which shows the isolation characteristic of the said nonreciprocal circuit element. It is a graph which shows the input return loss characteristic of the said nonreciprocal circuit element. It is a graph which shows the output return loss characteristic of the said nonreciprocal circuit element.

  Embodiments of non-reciprocal circuit devices according to the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same member in each figure, and the overlapping description is abbreviate | omitted.

  The nonreciprocal circuit device according to one embodiment is a lumped constant type two-port isolator having the equivalent circuit shown in FIG. That is, the first center electrode 21 and the second center electrode 22 are arranged so as to cross each other in an insulated state on a ferrite 23 to which a DC magnetic field is applied from behind the paper of FIG. An input terminal connected to the first port P1, the other end of each of the first port P1, the first center electrode 21 and the second center electrode 22 as the second port P2, and one end of the second center electrode 22 as the third port P3. The resistor element R and the first capacitor element C1 are connected in parallel between the output terminal 42 connected to the first port 41 and the second port P2, and the output terminal 42 is connected between the ground terminal 43 connected to the third port P3 and the output terminal 42. Two capacitive elements C2 are connected in series.

  Specifically, as shown in FIG. 2, the above two-port isolator is composed of a circuit board 30, a center electrode assembly 20, a permanent magnet 25, an upper yoke 45, and a lower yoke 40. Yes. The upper yoke 45 and the lower yoke 40 are integrally coupled in a state where the circuit board 30, the center electrode assembly 20, and the permanent magnet 25 are accommodated, and function as an electromagnetic shield and a ground conductor. A resin member 44 is integrally molded on the lower yoke 40, and an input terminal 41, an output terminal 42, and a ground terminal 43 for external connection are provided.

  In the center electrode assembly 20, a first center electrode 21 and a second center electrode 22 are arranged on an upper surface of a rectangular microwave ferrite 23 so as to intersect at a predetermined angle with an insulating material (not shown) interposed therebetween. . The center electrode is formed on the ferrite 23 as a thin film conductor, a thick film conductor, or a conductor foil. 2 and 3, the hatched portion is a conductor.

  As shown in FIG. 3, the circuit board 30 is formed by laminating four layers of ceramic sheets 31 a to 31 d, and electrodes 32 a, 33 a, and 33 b are formed on the first layer sheet 31 a (upper surface of the laminate) Electrodes 32b and 32c are formed on the second and third layer sheets 31b and 31c, respectively, and electrodes 32d, 34a and 34b are formed on the back surface (lower surface of the laminate) of the fourth layer sheet 31d. . By laminating these sheets 31a to 31d, the capacitive element C1 is formed between the electrodes 32a, 32b, and 32c, and the capacitive element C2 is formed between the electrodes 32c and 32d.

  Further, the lower electrode 34a is connected to the electrodes 32b and 33a via the via-hole conductor 35b. The lower electrode 34b is connected to the electrodes 32c and 32a via the via-hole conductor 35a. The lower electrode 32d is connected to the electrode 33b through a via-hole conductor 35c.

  The resistance element R is mounted on the circuit board 30 between the electrodes 32a and 33a. The electrode 34 a is connected to the input terminal 41 provided on the lower yoke 40, the electrode 34 b is connected to the output terminal 42, and the electrode 32 d is connected to the ground terminal 43.

  In the non-reciprocal circuit element, the high frequency signal input from the input terminal 41 is output in phase from the output terminal 42. On the other hand, the high-frequency signal input from the output terminal 42 is output to the input terminal in reverse phase, but since power is consumed by the resistance element R, it is rarely output from the input terminal 41. That is, this nonreciprocal circuit device is configured by adding a resistor to a gyrator. In the gyrator, signals in the forward direction are output in phase, and signals in the reverse direction are output in reverse phase (180 ° phase inversion). When the resistance element R is connected in parallel to such a gyrator, the electric potential is the same between the input and the output in the forward direction, so that no current flows through the resistance element R and a signal is output without power consumption. On the other hand, in the reverse direction, a potential difference occurs between the input and the output, and current flows through the resistance element R, so that power is consumed. This is isolation.

  Hereinafter, the operation characteristics in the present embodiment will be described with reference to FIG. FIG. 4 shows the permeability μ ± with respect to the magnetic field (A / m). First, the admittance matrix of the isolator shown by the equivalent circuit in FIG.

Here, Zo is a normalized impedance, K ₁ and K ₂ are air-core inductors, and μ and κ are Polder tensors. An ideal isolator satisfies the above formula (2), and a conditional expression of circuit constants is set to formula (3). However, in reality, there is a possibility of the equation (4), and this is a low magnetic field operation as will be described later. Then, when an admittance matrix is obtained from Equation (4), Equation (5) is obtained.

Conditional expressions of circuit constants are determined from the above expressions (1) and (5), and are expressed as the following expressions (6) to (9). In Expression (8), the sign on the right side is-. That is, since R, √K ₁ K ₂ , and ω are positive, κ / Δ needs to be negative in order to satisfy Equation (8).

  On the other hand, the Polder tensor is expressed by the following equations (10) and (11) using the circularly polarized magnetic permeability.

  From the formulas (1), (10), and (11), κ / Δ is negative when the magnetic permeability is (A) μ +> μ and μ + μ− <0, and (B) μ + <μ. -And [mu] + [mu]-> 0. The actual circular polarization permeability is as shown in FIG. 4, and there is no region in the case of (A). On the other hand, as shown in FIG. 4, there is a low magnetic field operation region in the case of (B).

  Similarly, the permeability conditions for satisfying the expression (3) are (C) μ +> μ− and (B) μ + μ−> 0, and (D) μ + <μ− and μ + μ−. <0. That is, as shown in FIG. 4, there are two operation areas. Lumped constant type isolators are generally operated with a high magnetic field (C) with little loss of magnetic material.

  The circularly polarized magnetic permeability is expressed by the following equation (12).

  Now, ignoring the loss term, the region satisfying the condition (B) (μ +> 0 in the low magnetic field) is derived from the equation (12), and becomes the following equation (13).

  Therefore, by setting the internal magnetic field Hin and the saturation magnetization Ms so as to satisfy the expression (13), a lumped constant type isolator that operates in a low magnetic field can be realized. By operating with a low magnetic field, the magnetic field applied by the permanent magnet is small, the magnet is downsized in size, and the magnetic circuit is downsized. In other words, this lumped constant isolator is compatible with both the miniaturization of the magnetic circuit and the miniaturization of the ferrite. Moreover, since it operates at a position away from the magnetic resonance point, magnetic loss is reduced.

  In contrast to the conventional waveguide type, which requires a λ / 2 size, the ferrite size is sufficiently smaller than λ / 2 because a lumped constant type has only to form a necessary inductance. . For example, if the dielectric constant of ferrite is 14, it is about 4 cm square at λ / 2 at 1 GHz, whereas it can be reduced to 1 mm square size if it is a lumped constant type.

  In the two-port isolator, simulation was performed with a ferrite saturation magnetization of 100 mT, ΔH of 1580 A / m, and an internal magnetic field of 5000 A / m. At this time, the circularly polarized magnetic permeability is μ +: 0.16-0.01j and μ-: 1.76-0.01j at 3.5 GHz. The circuit constants are C1: 3.4 pF, C2: 2.3 pF, and R: 64Ω. The simulation results are shown in FIGS. As is apparent from FIG. 5, the insertion loss is 0.66 dB at 3400 to 3600 MHz, and the isolation is 15.6 dB in the same frequency band as is apparent from FIG.

  As described above, it was confirmed that the nonreciprocal circuit element of 3.5 GHz can operate with an internal magnetic field of 5 kA / m. In order to operate at a high magnetic field, an internal magnetic field higher than at least the magnetic resonance point is required, and in order to operate at 3.5 GHz from μoγHin ≧ ω, 100 kA / m or more is required. Thus, the internal magnetic field can be greatly reduced in the above embodiment.

  The direction of the magnetic field applied from the permanent magnet 25 to the ferrite 23 is directed from the lower surface to the upper surface of the ferrite 23 as shown in FIG. 1, and is opposite to the conventional lumped constant isolator. When the application direction of the magnetic field is reversed, the transmission path of the high-frequency signal is switched. In other words, the insertion loss characteristic and the isolation characteristic are interchanged.

  In the above embodiment, ferrite with saturation magnetization of 100 mT is used. However, the low loss used for high frequency in the GHz band is about 50 mT as the lower limit of saturation magnetization in the case of YIG and CVG ferrite. In this case, when the internal magnetic field is 0 A / m and the lowest frequency is calculated from the above equation (13), it becomes 1.4 GHz. That is, at present, it is a nonreciprocal circuit device capable of realizing 1.4 GHz or higher.

  The 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, the configuration and shape of the center electrode are arbitrary. Further, the capacitive element may be mounted on the circuit board as a chip type in addition to being built in the circuit board.

DESCRIPTION OF SYMBOLS 20 ... Center electrode assembly 21 ... 1st center electrode 22 ... 2nd center electrode 23 ... Ferrite 25 ... Permanent magnet 41 ... Input terminal 42 ... Output terminal 43 ... Ground terminal P1 ... 1st port P2 ... 2nd port P3 ... 1st 3 port R ... resistance element C1, C2 ... capacitance element

Claims (1)

A ferrite core to which a DC magnetic field is applied by a permanent magnet is disposed so that the first center electrode and the second center electrode intersect each other in an insulated state;
One end of the first center electrode is a first port, the other end of each of the first center electrode and the second center electrode is a second port, and one end of the second center electrode is a third port,
A resistor element and a first capacitor element are connected in parallel between an input terminal connected to the first port and an output terminal connected to the second port,
A second capacitive element is connected in series between the ground terminal connected to the third port and the output terminal;
Satisfying the following formula,

γ: Gyromagnetic ratio μo: Vacuum permeability Hin: Internal magnetic field Ms: Saturation magnetization ω: Angular frequency

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