JP3651137B2 - Non-reciprocal circuit element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-reciprocal circuit element used in a high-frequency band such as a microwave band, for example, an isolator, a circulator, and more particularly to a non-reciprocal circuit element that can be reduced in size and price when used in a mobile communication device. .
[0002]
[Prior art]
In general, nonreciprocal circuit elements such as lumped constant type isolators and circulators have extremely small attenuation in the signal transmission direction and extremely large characteristics in the reverse direction. As this type of isolator, there is a conventional one having a structure as shown in FIG.
[0003]
This isolator includes a permanent magnet 3, a magnetic assembly 5 including three central conductors 51, 52, 53 and a ferrite 54 in a magnetic closed circuit mainly composed of an upper yoke 2 and a lower yoke 8, and a resin. The case 7 has a structure. The port portions P1 and P2 of the center conductors 51 and 52 are connected to input / output terminals 71 and 72 and matching capacitors Co and Co formed in the resin case 7, and the port portion P3 of the center conductor 53 is a matching capacitor. Co and terminal resistor R are connected, and one end of each capacitor Co and terminal resistor R is connected to ground terminals 73 and 73.
[0004]
FIG. 9 is an equivalent circuit diagram of this isolator. As shown in FIG. 9, in the conventional isolator, matching capacitors Co are connected as matching circuits to the ports P1, P2, and P3 corresponding to the tips of the center conductors 51, 52, and 53, respectively, and a termination resistor R is connected to one port P3. Connected and configured. Each inductance L is an equivalent inductance formed by the ferrite 54 and the central conductors 51, 52, 53.
[0005]
This isolator is employed in a transmission / reception circuit section of an antenna sharing circuit of a mobile communication device such as a mobile phone or a car phone, and an input / output transmission line and a ground electrode are formed on the front surface, and a ground electrode is formed on substantially the entire back surface. Is used by being surface-mounted on a mounting substrate on which is formed.
[0006]
[Problems to be solved by the invention]
In general, amplifiers incorporated in such communication devices have non-linearity, which is a cause of unnecessary radiation, that is, spurious (integer multiple of fundamental wave, especially second harmonic, third harmonic). It has become. Since this unnecessary radiation causes interference and abnormal operation of the power amplifying unit of other communication devices, it is standardized to be below a certain level.
[0007]
In addition, the isolator also has a function of a band pass filter as a characteristic in the transmission direction. For this reason, the isolator has a characteristic that the attenuation amount is large in the transmission direction in a frequency band far from the pass band. However, the isolator is not originally intended to obtain attenuation outside the band, and the conventional isolator described above obtains the desired attenuation in the frequency band of unnecessary radiation (especially the second harmonic and the third harmonic). I can't. For this reason, in this type of conventional communication equipment, a method of attenuating unnecessary radiation using a separate filter or the like is employed.
[0008]
That is, when the conventional isolator is used, a filter for preventing unnecessary radiation is required as described above, and there is a problem that the component cost increases and the size of the filter increases by the amount of the filter. There was a problem that it was not possible to respond to the request for conversion.
[0009]
Accordingly, an object of the present invention is to provide a non-reciprocal circuit device that can greatly reduce the occurrence of unnecessary radiation by increasing the amount of attenuation outside the band, thereby contributing to downsizing and cost reduction. It is in.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 is a non-reciprocal circuit in which a plurality of center conductors are arranged so as to intersect each other on a magnetic body to which a DC magnetic field is applied, and a matching capacitor is connected between the port portion of each center conductor and ground. In the element
The plurality of center conductors are formed of a single metal plate, and the tip of at least one center conductor connected to the input / output terminal of the center conductors is formed to have a predetermined value of inductance. The inductance is connected between the port portion and the input / output terminal , and occurs in the soldering land of the input / output transmission line of the mounting board on which the inductance, the matching capacitor, and the nonreciprocal circuit element are mounted. A π-type low-pass filter is formed by the electrode distributed capacitance.
[0012]
The invention according to claim 2 is the non-reciprocal circuit device according to claim 1, the distal end portion of the center conductor so as to have the inductance and is characterized in that it is formed by bending.
[0013]
According to a third aspect of the present invention, in the nonreciprocal circuit element according to the first or second aspect , the tip of the central conductor is narrower or thicker than other parts so as to have the inductance. Is formed thinly.
[0014]
According to said structure, a low-pass filter can be formed with the inductance formed in the front-end | tip part of a center conductor, matching capacity | capacitance, and external capacity | capacitances, such as electrode distribution capacity | capacitance of the input / output transmission line of a mounting board | substrate. Therefore, the attenuation amount outside the band can be greatly improved.
[0015]
That is, it is possible to form inductances and capacitors constituting the low-pass filter in the non-reciprocal circuit element without changing the external dimensions, and these inductances and capacitors and external capacitors such as electrode distributed capacitors formed on the mounting substrate. Therefore, if the nonreciprocal circuit device according to the present invention is used, unnecessary radiation can be greatly reduced without using another filter for preventing unnecessary radiation that has been required in the past. can do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
[0017]
The structure and configuration of an isolator according to an embodiment of the present invention are shown in FIGS. 1 is an exploded perspective view of the isolator, FIG. 2 is a plan view in a state where the permanent magnet and the upper yoke are removed, and FIG. 3 is an equivalent circuit diagram. The capacitors and the inductances shown in FIGS. 1 and 2 correspond to the matching capacitance and the inductance shown in FIG. 3, respectively, and are denoted by the same reference numerals.
[0018]
As shown in FIGS. 1 and 2, the isolator of the present embodiment has a disk-shaped permanent magnet 3 disposed on the inner surface of a box-shaped upper yoke 2 made of a magnetic metal, and the upper yoke 2 is also magnetic. A substantially U-shaped lower yoke 8 made of a body metal is attached to form a magnetic closed circuit, and a resin case 7 is disposed on a bottom surface 8 a in the lower yoke 8. A solid 5, matching capacitors C <b> 1 to C <b> 3, and a terminating resistor R are disposed, and a DC magnetic field is applied to the magnetic assembly 5 by the permanent magnet 3. In the magnetic assembly 5, the ground portions of the three central conductors 51 to 53 made of a thin metal plate are in contact with the lower surface of the disk-shaped ferrite 54, and the three central conductors 51 to 53 are in contact with the upper surface of the ferrite 54. 53 has a structure in which an insulating sheet (not shown) is interposed and bent so as to form an angle of 120 degrees with each other, and the tip portions of the center conductors 51 and 52 have a predetermined inductance value. The center conductors 51 and 52 are respectively formed with inductances Lf at the end portions thereof.
[0019]
That is, in the isolator of the present embodiment, the tip portions of the two central conductors 51 and 52 on the signal input / output side are processed into a shape suitable for inductance formation, and the port portions P1 and P2 of the central conductors 51 and 52 and the central conductor are formed. A predetermined value of inductance Lf is formed between the tips 51a and 52a of 51 and 52, respectively.
[0020]
The resin case 7 is made of an electrically insulating member and has a structure in which a bottom wall 7b is integrally formed with a rectangular frame-shaped side wall 7a. The input / output terminals 71 and 72 and the ground terminals 73 and 73 are partly made of resin. An insertion hole 7c is formed in a substantially central portion of the bottom wall 7b. The input / output terminals 71 and 72 are disposed at both corners of the resin case 7, and one end side of each of the input / output terminals 71 and 72 is exposed on the upper surface of the bottom wall 7b. It is provided to be exposed. Further, the ground terminals 73 and 73 are arranged on the other side of the resin case 7, and one end side of each of the ground terminals 73 and 73 is exposed in a predetermined shape at a portion where the capacitors C1 to C3 and the terminating resistor R are arranged on the bottom wall 7b. The other end side is provided so as to be exposed on the lower surface of the bottom wall 7b and the outer surface of the side wall 7a.
[0021]
The magnetic assembly 5 is inserted and disposed in the insertion hole 7 c, and the ground portions of the center conductors 51 to 53 on the lower surface of the magnetic assembly 5 are connected to the bottom surface 8 a of the lower yoke 8.
[0022]
Matching chip capacitors C <b> 1 to C <b> 3 and a chip termination resistor R are arranged on the periphery of the insertion hole 7 c. The lower surface electrodes of the capacitors C1 to C3 and the electrode on one end side of the termination resistor R are connected to the ground terminals 73 and 73, respectively. Port portions P1 to P3 of the respective center conductors 51 to 53 are connected to the upper surface electrodes of the capacitors C1 to C3, respectively, and the other end side of the termination resistor R is connected to the port portion P3.
[0023]
The tips 51a and 52a of the central conductors 51 and 52 are connected to the exposed portions at the left and right upper ends of the bottom wall 7b, which is one end side of the input / output terminals 71 and 72, respectively. That is, the port portions P1, P2 of the central conductors 51, 52 are connected to the input / output terminals 71, 72 via the inductance Lf, respectively.
[0024]
That is, in the isolator of this embodiment, as shown in the equivalent circuit diagram of FIG. 3, the matching capacitors C1 to C3 are connected to the ports P1 to P3 corresponding to the tips of the center conductors 51, 52, and 53, and one port P3 is connected. The terminal resistor R is connected, and an inductance Lf is connected between the two ports P1 and P2 and the input / output terminals 71 and 72 which are signal input / output terminals.
[0025]
As shown in FIG. 4, this isolator is surface-mounted on a mounting substrate 10 in which input / output transmission lines 11 and 12 and a ground electrode 13 are formed on the front surface, and a ground electrode is formed on substantially the entire back surface. Used. Specifically, the input / output terminals 71 and 72 of the isolator are mounted by being soldered to the solder lands 11a and 12a of the transmission lines 11 and 12, and the ground terminals 73 and 73 are soldered to the ground electrodes 13 and 13, respectively.
[0026]
The soldering lands 11a and 12a to which the input / output terminals 71 and 72 of the isolator are soldered are formed wider than other portions in order to obtain sufficient mounting strength (soldering strength). Electrode distributed capacitance Cp inevitably occurs between 11a, 12a and the ground electrode formed on the back surface.
[0027]
Next, the effect of the isolator of a present Example is demonstrated. 5 and 6 are equivalent circuit diagrams in a state where the above-described isolator is mounted on the mounting substrate 10, and FIG. 6 is an equivalent circuit diagram for explaining an operation (operation principle) in the mounting state.
[0028]
As shown in FIG. 5, when the isolator of the present embodiment is mounted on the mounting substrate 10 (see FIG. 4), electrodes that are parasitically generated on the soldering lands 11a and 12a of the transmission lines 11 and 12 of the mounting substrate 10. The distributed capacitors Cp and Cp are connected to the input / output terminals 71 and 72 of the isolator. As shown in FIG. 6, the signal input / output unit (ports P1 and P2 side) of the isolator has an inductance Lf, a capacitance Cf that is a part of the matching capacitances C1 and C2, and an electrode of the mounting substrate 10 that is an external capacitance. A π-type low-pass filter LPF composed of the distributed capacitance Cp is formed.
[0029]
That is, the matching capacitors C1 and C2 of the isolator of the present embodiment are configured by a parallel capacitor of a capacitor Co that functions as an isolator matching circuit and a capacitor Cf that forms the π-type low-pass filter LPF. That is, the matching capacitors C1 and C2 of the isolator of this embodiment are set to values obtained by adding the capacitor Cf to the matching capacitor Co of the conventional isolator. For example, in the 1.5 GHz band, the capacitance Co is set to about 5 pF and the capacitance Cf is set to about 2 pF. In the 900 MHz band, the capacitance Co is set to about 10 pF, the capacitance Cf is set to about 3 pF, and the inductance Lf is 2 nH to 3 nH. Set to degree.
[0030]
The capacitance Cf is normally set to be the same value as the capacitance value of the electrode distribution capacitance Cp so that the input / output impedance (usually 50Ω) of the isolator does not change, but the capacitance Cf is different from the electrode distribution capacitance Cp. By setting the value, the input / output impedance of the isolator can be changed.
[0031]
The inductance Lf is set to a desired value by changing the width, shape, bending method, and the like of the tip portions of the center conductors 51 and 52.
[0032]
The values of the capacitance Cf, the electrode distribution capacitance Cp, and the inductance Lf are appropriately set in consideration of the thickness of the mounting substrate, the used frequency band, the electrical characteristics, the mounting strength, and the like.
[0033]
FIG. 7 is a diagram showing the frequency characteristics in a state where the isolator of this embodiment and the conventional isolator are mounted on a mounting substrate. The solid line shows the characteristics according to this embodiment, and the broken line shows the conventional characteristics. As shown in FIG. 7, it can be seen that the use of the isolator of the present embodiment greatly increases the amount of attenuation on the high frequency band side as compared with the conventional one.
[0034]
As described above, in the isolator according to the present embodiment, the inductance Lf is formed at each of the tip ends of the two central conductors 51 and 52 on the signal input / output side. Since the low-pass filter LPF is formed by the inductance Lf, the matching capacitance C1 (or C2), and the electrode distribution capacitance Cp of the mounting substrate 10 in the signal input / output unit, as shown in FIG. The amount is greatly improved compared to the conventional one.
[0035]
That is, the isolator of the present embodiment incorporates the inductance Lf and the capacitance Cf that constitute the low-pass filter LPF without changing the external dimensions, and the mounting substrate 10 has a low-frequency band on the solder lands 11a and 12a. The electrode distributed capacitance Cp constituting the pass filter LPF is inevitably formed, and if the isolator of this embodiment is used, unnecessary radiation can be greatly increased without using another filter for preventing unnecessary radiation that has been necessary in the past. Therefore, the communication device can be reduced in size and price.
[0036]
In the above-described embodiment, the leading end portions of the center conductors 51 and 52 are bent in a V shape to form the inductance Lf. However, the shape for forming the inductance Lf is not limited to this. It may be bent into a U-shape or a U-shape, or may be bent multiple times in a meander shape.
[0037]
In the above embodiment, the electrode distributed capacity formed on the soldering land portion of the mounting substrate is used as the external capacity. However, the external capacity is not limited to this, and a chip capacitor or the like is used as the external capacity. You may make it use.
[0038]
Further, in the above-described embodiment, the description has been given of the case where the inductance Lf constituting the low-pass filter LPF is formed at the distal ends of the central conductors 51 and 52 on the signal input / output side of the isolator. However, the present invention is not limited to this. The inductance Lf may be formed only on one of the central conductors 51 and 52.
[0039]
In the above embodiment, the isolator has been described as an example. However, the present invention can also be applied to a circulator in which the port P3 is configured as the third input / output unit without connecting the termination resistor R to the port P3.
[0040]
Also, the overall structure is not limited to that shown in FIGS. 1 and 2 of the above embodiment. For example, the plurality of central conductors may be arranged on different layers of a multilayer substrate made of a dielectric material or a magnetic material. May be formed by a method such as printing or vapor deposition. Also in this case, the inductance Lf can be easily formed by forming the tip of the central conductor in a shape suitable for inductance formation.
[0041]
In short, the present invention is characterized in that an inductance constituting a low-pass filter is formed at the tip of the central conductor of at least one signal input / output unit, and other configurations are particularly limited. is not.
[0042]
【The invention's effect】
As described above, according to the non-reciprocal circuit device according to the present invention, the tip of the center conductor is formed to have a predetermined value of inductance, and matching with the inductance formed at the tip of the center conductor is performed. Since the low-pass filter can be formed by the capacitance and the external capacitance such as the electrode distribution capacitance of the mounting substrate, the attenuation amount outside the band can be greatly improved.
[0043]
That is, it is possible to form inductances and capacitors constituting the low-pass filter in the non-reciprocal circuit element without changing the external dimensions, and these inductances and capacitors and external capacitors such as electrode distributed capacitors formed on the mounting substrate. Thus, a low-pass filter can be configured. Therefore, if the non-reciprocal circuit device according to the present invention is used, another filter for preventing unnecessary radiation can be dispensed with, and the communication device and the like can be reduced in size and price.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of an isolator according to an embodiment of the present invention.
FIG. 2 is a plan view of an isolator according to an embodiment of the present invention.
FIG. 3 is an equivalent circuit diagram of an isolator according to the present invention.
FIG. 4 is a perspective view showing a mounted state of an isolator according to an embodiment of the present invention.
FIG. 5 is an equivalent circuit diagram in the mounted state of the isolator according to the present invention.
FIG. 6 is an equivalent circuit diagram for explaining the operation in the mounted state of the isolator according to the present invention.
FIG. 7 is a frequency characteristic diagram of the present invention and a conventional isolator.
FIG. 8 is an exploded perspective view of a conventional isolator.
FIG. 9 is an equivalent circuit diagram of a conventional isolator.
[Explanation of symbols]
2 Upper yoke 3 Permanent magnet 5 Magnetic assembly 51-53 Center conductor 54 Ferrite 7 Resin case 71, 72 Input / output terminal 73 Ground terminal 8 Lower yoke 10 Mounting substrate 11, 12 Transmission line 11a, 12a Soldering land C1-C3 Alignment Capacity (capacitor)
R Terminal resistance Lf Inductance Cp Electrode distribution capacitance P1 to P3 Port (port portion)

Claims (3)

In a non-reciprocal circuit device in which a plurality of center conductors are arranged to cross each other in a magnetic body to which a DC magnetic field is applied, and a matching capacitor is connected between the port portion of each center conductor and the ground,
The plurality of center conductors are formed of a single metal plate, and the tip of at least one center conductor connected to the input / output terminal of the center conductors is formed to have a predetermined value of inductance. The inductance is connected between the port portion and the input / output terminal , and occurs in the soldering land of the input / output transmission line of the mounting board on which the inductance, the matching capacitor, and the nonreciprocal circuit element are mounted. A non-reciprocal circuit device, wherein a π-type low-pass filter is formed with an electrode distributed capacitance. The nonreciprocal circuit device according to claim 1, wherein a distal end portion of the center conductor is formed by bending so as to have the inductance. 3. The nonreciprocal circuit according to claim 1, wherein a tip end portion of the center conductor is formed narrower or thinner than other portions so as to have the inductance. 4. element.

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