JP7722038B2 - Non-reciprocal circuit elements - Google Patents

Description

This application relates to a non-reciprocal circuit element.

Non-reciprocal circuit elements include isolators and circulators, and are used in the transmission and reception circuits of devices such as mobile phones and their base stations. Non-reciprocal circuit elements are used to prevent amplifier damage and to obtain highly linear and stable output power, and are equipped with functions that minimize insertion loss in the signal transmission direction and increase transmission loss in the reverse direction. For example, Patent Document 1 discloses a non-reciprocal circuit element that can be miniaturized.

Japanese Patent Application Laid-Open No. 2001-267810

As information and communications technology advances, there is a demand for transmitting ever-larger amounts of information, and the electromagnetic waves used in information and communications networks such as mobile phone communications are in the high-frequency band, which allows for the transmission of larger amounts of information. Specifically, there is a demand for non-reciprocal circuit elements that are compatible with frequencies in the 3 GHz to 6 GHz band known as the Sub-6 frequency band.

The purpose of this disclosure is to provide a non-reciprocal circuit element compatible with the 3 GHz to 6 GHz band.

A non-reciprocal circuit element according to one embodiment of the present disclosure comprises a ferrimagnetic material having a main surface, multiple central conductors arranged on the main surface of the ferrimagnetic material in a mutually insulated state, and a laminated magnet formed by stacking a ferrite magnet containing Sr and a rare earth magnet containing Sm, the laminated magnet being arranged opposite the multiple central conductors, and the composite temperature coefficient of the residual magnetic flux density of the laminated magnet is -0.14%/°C or more and -0.06%/°C or less.

The ferrimagnetic material may have a saturation magnetic flux density of 40 mT or more and 80 mT or less, and the temperature coefficient of the saturation magnetic flux density may be -0.45%/°C or more and -0.25%/°C or less.

The ratio of the thickness of the rare earth magnet to the total thickness of the ferrite magnet and the rare earth magnet may be greater than or equal to 1/4 and less than or equal to 3/4.

In the laminated magnet, the ferrite magnet may be closer to the multiple central conductors than the rare earth magnet.

The composite temperature coefficient of the residual magnetic flux density of the laminated magnet may be -0.12%/°C or more and -0.08%/°C or less.

In the frequency characteristics of the insertion loss of the non-reciprocal circuit element, the resonant frequency of the main band and the attenuation pole closest to the resonant frequency may be separated by 200 MHz or more in the temperature range from -40°C to 125°C.

Embodiments of the present disclosure provide a non-reciprocal circuit element compatible with the 3 GHz to 6 GHz band.

FIG. 1 is an exploded perspective view showing one embodiment of the non-reciprocal circuit device of the present embodiment. FIG. 2 shows the magnetic field strength applied to the ferrimagnetic material of the laminated magnet in the temperature range of 5° C. to 125° C. FIG. 3A shows the frequency characteristics of the VSWR and insertion loss of the non-reciprocal circuit device of Example 1. FIG. 3B shows the frequency characteristics of the attenuation of the non-reciprocal circuit device of Example 1. FIG. 4A shows the frequency characteristics of the VSWR and insertion loss of the non-reciprocal circuit device of Comparative Example 1. FIG. 4B shows the attenuation frequency characteristics of the non-reciprocal circuit device of Comparative Example 1. FIG. 5A shows the frequency characteristics of the VSWR and insertion loss of the non-reciprocal circuit device of Comparative Example 2. FIG. 5B shows the attenuation frequency characteristics of the non-reciprocal circuit device of Comparative Example 2. FIG. 6A shows frequency characteristics of the input VSWR and insertion loss of the non-reciprocal circuit device of Example 2. FIG. 6B shows the frequency characteristics of the output VSWR and isolation of the non-reciprocal circuit device of Example 2. FIG. 7A shows the frequency characteristics of the input VSWR and insertion loss of the non-reciprocal circuit device of Comparative Example 3. FIG. 7B shows the frequency characteristics of the output VSWR and isolation of the non-reciprocal circuit device of Comparative Example 3.

Figure 1 is an exploded perspective view of the non-reciprocal circuit element 30 of this embodiment. The non-reciprocal circuit element 30 is compatible with frequencies in the 3 GHz to 6 GHz band, for example, and is used in the transmitting and receiving circuits of mobile phones and mobile phone base stations. The external dimensions of the non-reciprocal circuit element 30 are, for example, approximately 5 mm in length, 5 mm in width, and 2.5 to 4 mm in height, and the non-reciprocal circuit element 30 is a lumped-element non-reciprocal circuit element.

The non-reciprocal circuit element 30 comprises a ferrimagnetic material 3, multiple central conductors, and a laminated magnet 2.

The ferrimagnetic material 3 has, for example, a disk shape with a main surface 3a. For example, the diameter of the main surface 3a is approximately 1.5 mm or more and 2.5 mm or less. The ferrimagnetic material 3 preferably has a low saturation magnetic flux density of, for example, 40 mT or more and 80 mT or less, and a low ferromagnetic resonance half-width (ΔH<2500 A/m). Furthermore, the temperature coefficient (temperature dependence) of the saturation magnetic flux density is preferably approximately -0.45%/°C or more and -0.25%/°C or less. Furthermore, the saturation magnetic flux density is preferably 40 mT or more and 70 mT or less, and the low ferromagnetic resonance half-width is preferably ΔH<2000 A/m. It is even more preferable that the temperature coefficient (temperature dependence) of the saturation magnetic flux density is approximately -0.4%/°C or more and -0.3%/°C or less. The ferrimagnetic material 3 is made of a ferrimagnetic compound, for example, yttrium iron garnet (YIG).

The multiple central conductors are electrically insulated from one another and are arranged on the main surface 3a of the ferrimagnetic material 3 in a crosswise stacked state. In this embodiment, the central conductors 4, 5, and 6 are arranged at an angle of 120°. The ferrimagnetic material 3 and the central conductors 4, 5, and 6 form an assembly 20.

The laminated magnet 2 includes a rare earth magnet 2A and a ferrite magnet 2B. The rare earth magnet 2A includes Sm. The ferrite magnet includes Sr. The rare earth magnet 2A has a plate shape with main surfaces 2An and 2As, with the north pole located on the main surface 2An side and the south pole located on the main surface 2As side. Similarly, the ferrite magnet 2B has a plate shape with main surfaces 2Bn and 2Bs, with the north pole located on the main surface 2Bn side and the south pole located on the main surface 2Bs side.

As shown in FIG. 1, the rare earth magnet 2A and the ferrite magnet 2B are stacked so that the main surface 2An of the rare earth magnet 2A faces the main surface 2Bs of the ferrite magnet 2B. The rare earth magnet 2A and the ferrite magnet 2B need only be stacked close to each other, and may be bonded to each other with an adhesive or the like. The stacked magnet 2 is positioned relative to the assembly 20 so that the main surface 2Bn of the ferrite magnet 2B faces the central conductors 4, 5, and 6.

The magnetic fields generated by the rare earth magnet 2A and the ferrite magnet 2B are oriented in the same direction, and the magnet stack 2 generates a unified magnetic field. The magnet stack 2 applies a magnetic field perpendicular to the main surface 3a of the ferrimagnetic material of the assembly 20.

Specific _examples of rare earth magnets 2A include _SmCo5 (1-5 system), _Sm2Co17 (2-17 system), _and Sm-Fe-N magnets. Ferrite magnets 2B include _SrO.Fe2O3 magnets. Table 1 shows the residual magnetic flux density and temperature coefficient of residual magnetic flux density of rare earth magnets 2A and ferrite magnets 2B.

The residual magnetic flux density of the entire magnet laminate 2 is preferably between approximately 0.55 T and 1.0 T. Furthermore, the temperature coefficient of the residual magnetic flux density of the entire magnet laminate 2 is preferably between -0.14%/°C and -0.06%/°C, and more preferably between -0.12%/°C and -0.08%/°C. Hereinafter, the temperature dependence of the residual magnetic flux density of the entire magnet laminate 2 will be referred to as the composite temperature coefficient.

The remanence (T) and composite temperature coefficient (%/°C) of the entire laminated magnet 2 can be adjusted by changing the materials of the rare earth magnet 2A and ferrite magnet 2B and the ratio of the thicknesses of the respective magnets. For example, if the thickness of the rare earth magnet 2A is Tr and the thickness of the ferrite magnet 2B is Tf, the above-mentioned composite temperature coefficient can be achieved by adjusting the ratio of the thickness of the rare earth magnet 2A (Tr) to the total thickness of the rare earth magnet 2A and ferrite magnet 2B (Tr + Tf) between 1/4 and 3/4.

More specifically, the above-mentioned composite temperature coefficient can be achieved by configuring the magnet laminate 2 with the thickness ratio shown in Table 2. In Table 2, Sm ₂ Co ₁₇ , which has a temperature coefficient of -0.04 to -0.02%/°C, is used as the rare earth magnet 2A, and SrO.Fe ₂ O ₃ , which has a temperature coefficient of -0.20 to -0.18%/°C, is used as the ferrite magnet 2B. The external dimensions of the magnet laminate 2 are, for example, approximately 3 to 5 mm in length, 3 to 5 mm in width, and 0.8 to 1.2 mm in height when the operating frequency band is 3.6 GHz to 4.0 GHz, and approximately 3 to 5 mm in length, 3 to 5 mm in width, and 0.8 to 2.2 mm in height when the operating frequency band is 4.8 GHz to 5.0 GHz.

Figure 2 shows the magnetic field strength applied to the ferrimagnetic material by the laminated magnet 2 over a temperature range of 5°C to 125°C. Experimental results show that the composite temperature coefficient of the residual magnetic flux density Br of this laminated magnet is strongly correlated with the temperature change rate of the applied magnetic field strength. Therefore, in Figure 2, the composite temperature coefficient of the residual magnetic flux density Br is converted into the temperature change rate of the applied magnetic field strength to the ferrimagnetic material and displayed.

For example, the temperature change in remanence can be achieved by adjusting the thickness as described above when Sm ₂ Co ₁₇ is used as rare earth magnet 2A and SrO·Fe ₂ O ₃ is used as ferrite magnet 2B. As described above, laminated magnet 2 has a remanence value (0.55 T or more) that cannot be achieved with ferrite magnet SrO·Fe ₂ O ₃ alone, and a composite temperature coefficient of remanence (-0.14%/°C or more, -0.06%/°C or less) that cannot be achieved with rare earth magnet Sm ₂ Co ₁₇ alone.

The non-reciprocal circuit element 30 further includes capacitance elements 8, 9, and 10 such as flat capacitors, a resistance element 11, and a resin case 7. The resin case 7 has a recess 13a in which the assembly 20 is placed. The capacitance elements 8, 9, and 10 and the resistance element 11 are placed in recesses 13b, 13c, and 13d provided in the resin case 7, with one end electrically connected to one of the center conductors 4, 5, and 6 and an external terminal provided on the resin case 7, and the other end grounded to the bottom surface of the recess 13a provided in the resin case 7. The non-reciprocal circuit element 30 further includes an upper case 1 and a lower case 12, which are arranged above and below the resin case 7, thereby covering the resin case 7.

Next, the magnetic properties of the laminated magnet 2 of the non-reciprocal circuit element 30 will be explained with reference to Figure 2 and Table 3.

As shown in Table 3, conventional non-reciprocal circuit elements operating in the 700 MHz to 2.6 GHz band have been designed to roughly match the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material and the composite temperature coefficient of the magnet's residual magnetic flux density, so that the high-frequency characteristics of the non-reciprocal circuit element, specifically the frequency characteristics of VSWR (voltage standing wave ratio), reverse loss, and insertion loss, do not fluctuate significantly in the operating temperature range of the non-reciprocal circuit element, which is between -40°C and 125°C.

The inventors of this application conducted detailed research into the design of non-reciprocal circuit elements for use in the 3-6 GHz band. They found that in this high-frequency band, the absorption characteristics due to magnetic resonance generated when a DC magnetic field is applied to a ferrimagnetic material by a magnet react more sensitively to magnetic field strength than the resonance peak of the main-band characteristics of the LC resonant circuit formed by the central conductor and capacitive element. Therefore, when the applied magnetic field decreases under high-temperature conditions, the attenuation pole of magnetic resonance shifts significantly toward the lower frequency side. This overlap with the main-band attenuation pole results in increased insertion loss in the transmission direction and a deterioration in the linearity of the power amplifier output, making it difficult to meet IMD (intermodulation distortion) standards (e.g., -50 dBc max).

The non-reciprocal circuit device according to the embodiment of the present application is designed differently from conventional non-reciprocal circuit devices, taking into account the temperature dependence of the resonance peak of the main band characteristics of the LC resonant circuit and the temperature dependence of the attenuation pole of the magnetic resonance, so that the attenuation pole of the magnetic resonance does not overlap with the main band of the LC resonant circuit in the temperature range of -40°C to 125°C. Specifically, the saturation magnetic flux density of the ferrimagnetic material 3 is set to 40 mT to 80 mT, which is lower than the value used in conventional non-reciprocal circuit devices. Furthermore, the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material 3 is set to -0.4%/°C to -0.3%/°C, which is lower than conventional values. Meanwhile, by using the laminated magnet 2, the composite temperature coefficient of the remanence is set to _-0.14 %/°C to -0.06%/°C, which is difficult to achieve with a single _Sm2Co17 magnet. In other words, the slope of the composite temperature coefficient of the residual magnetic flux density of the magnet laminate 2 is half or less compared to the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material 3. As a result, as will be explained in the experimental results below, in the frequency characteristics of the insertion loss of the non-reciprocal circuit device 30, it is possible to separate the resonant frequency of the main band and the attenuation pole closest to the resonant frequency by 200 MHz or more in the temperature range of -40°C to 125°C. Furthermore, the non-reciprocal circuit device 30 can satisfy the required characteristics of an IMD, etc.

Patent Document 1 discloses that a low-profile (low-profile) non-reciprocal circuit element can be achieved by reducing the thickness of the permanent magnet in the non-reciprocal circuit element. It also describes the use of a rare-earth magnet, which has a higher residual magnetic flux density than an Sr ferrite magnet, to reduce the thickness of the permanent magnet. It also describes that the temperature characteristics of the residual magnetic flux density of rare-earth magnets are flat, and that replacing an Sr ferrite magnet with a rare-earth magnet does not eliminate the temperature characteristics of the saturation magnetic flux density of the ferrimagnetic material. For this reason, Patent Document 1 discloses the use of a stacked Sr ferrite magnet and an Nd-Fe-B magnet. Although Patent Document 1 discloses the use of two permanent magnets, the temperature characteristics of the residual magnetic flux density obtained by the two permanent magnets must be similar to the temperature characteristics of the saturation magnetic flux density of the ferrimagnetic material.

In contrast, in the non-reciprocal circuit element 30 of this embodiment, the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material 3 is made smaller than the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material in conventional non-reciprocal circuit elements, while the composite temperature coefficient of the residual magnetic flux density of the laminated magnet 2 is made larger than the temperature coefficient of the residual magnetic flux density of the permanent magnet in conventional non-reciprocal circuit elements. In other words, the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material 3 and the composite temperature coefficient of the residual magnetic flux density of the laminated magnet 2 are set using a different concept from conventional methods.

The non-reciprocal circuit element of this embodiment uses a laminated magnet made up of a ferrite magnet containing Sr and a rare earth magnet containing Sm, allowing the composite temperature coefficient of the residual magnetic flux density to be set to between -0.14%/°C and -0.06%/°C. This makes it possible to realize a non-reciprocal circuit element with excellent high-frequency and temperature characteristics in the 3-6 GHz band.

The following describes the experimental results of the high-frequency and temperature characteristics of the non-reciprocal circuit device of this embodiment.

Figure 3A shows the VSWR and insertion loss frequency characteristics of Example 1, a non-reciprocal circuit device of this embodiment operating in the 4.8 GHz to 5.0 GHz (4.9 GHz band). Figure 3B shows the attenuation frequency characteristics over an enlarged frequency range. The laminated magnet 2 uses a rare earth magnet 2A made of Sm ₂ Co ₁₇ and a ferrite magnet 2B made of SrO.Fe ₂ O ₃ with a thickness ratio of 1:1. The residual magnetic flux density is 0.7 to 0.8 T, and the temperature coefficient of the residual magnetic flux density is -0.12%/°C or more and -0.08%/°C or less.

Figures 3A and 3B show the frequency characteristics obtained at temperatures of -40, 25, 85, 105, 115, and 125°C. The frequency characteristics shift as the temperature rises or falls. However, as shown in Figure 3A, in the range of -40°C to 125°C, the VSWR and insertion loss remain sufficiently low, indicating that good frequency characteristics are obtained. Furthermore, as shown in Figure 3B, as the operating temperature rises, the magnetic resonance attenuation pole A shifts closer to the main band resonance peak P. However, even at 125°C, the main band resonance peak P and the magnetic resonance attenuation pole A are more than 200 MHz apart, so the impact on the main band resonance characteristics is small.

Figure 4A shows the frequency characteristics of VSWR and insertion loss for Comparative Example 1, a non-reciprocal circuit element that uses a rare earth magnet made of Sm ₂ Co ₁₇ instead of laminated magnet 2 in the non-reciprocal circuit element of Example 1. Figure 4B shows the frequency characteristics of attenuation over an expanded frequency range. The rare earth magnet made of Sm ₂ Co ₁₇ has a residual magnetic flux density of 0.9 to 1.2 T and a temperature coefficient of residual magnetic flux density of -0.04 to -0.02%/°C.

As shown in Figure 4A, as the operating temperature rises, the VSWR and insertion loss increase at the lower end of the operating band. On the other hand, as shown in Figure 4B, whether the operating temperature rises or falls, the magnetic resonance attenuation pole A remains 500 MHz or more away from the main band resonance peak P. Therefore, in Comparative Example 1, although the magnetic resonance attenuation pole A can be well controlled, at high temperatures, the VSWR and insertion loss deteriorate, particularly at the lower end of the operating band.

Figure 5A shows the frequency characteristics of VSWR and insertion loss for Comparative Example 2, a non-reciprocal circuit element that uses a ferrite magnet made of _SrO.Fe2O3 instead of laminated magnet ₂ in the non-reciprocal circuit element of Example 1. Figure 5B shows the frequency characteristics of attenuation over an expanded frequency range. The ferrite magnet made _{of SrO.Fe2O3 has} a residual magnetic flux density of 0.33 to 0.45 T and a temperature coefficient of residual magnetic flux density of -0.20 to -0.18%/°C.

As shown in Figure 5A, as the operating temperature rises, the VSWR and insertion loss increase across the entire operating frequency band. Furthermore, as shown in Figure 5B, as the operating temperature rises, the attenuation pole A of the magnetic resonance approaches the resonance peak P of the main frequency band, and at 125°C, it is only about 150 MHz away from the resonance peak P. Therefore, it can be seen that in Comparative Example 2, as the temperature rises, the VSWR and insertion loss deteriorate across the entire operating frequency band, and the influence of the attenuation pole A of the magnetic resonance is apparent in the resonance peak P.

Figure 6A shows the frequency characteristics of the input VSWR and insertion loss of Example 2, a non-reciprocal circuit element of this embodiment operating in the 3.4 GHz to 3.8 GHz (3.6 GHz band). Figure 6B similarly shows the frequency characteristics of the output VSWR and isolation. The magnet laminate 2 is the same as in Example 1. As shown in Figures 6A and 6B, the input VSWR, output VSWR, insertion loss, and isolation characteristics all maintain sufficiently good values in the temperature range of -40°C to 125°C, demonstrating that good frequency characteristics can be obtained.

Figure 7A shows the frequency characteristics of the VSWR and insertion loss on the input side of Comparative Example 3, a non-reciprocal circuit element that uses a ferrite magnet made of _SrO.Fe2O3 instead of the laminated magnet ₂ in the non-reciprocal circuit element of Example 2. Figure 7B similarly shows the frequency characteristics of _the VSWR and isolation on the output side. As with Comparative Example 2, the ferrite magnet made of _SrO.Fe2O3 has a residual magnetic flux density of 0.33 to 0.45 T and a temperature coefficient of residual magnetic flux density of -0.20 to -0.18%/°C. Figures 7A and 7B show the frequency characteristics obtained at temperatures of -40, 25, 85, and 125°C.

As shown in Figure 7A, as the operating temperature rises or falls, the input VSWR or insertion loss increases across the entire operating band. Furthermore, as shown in Figure 7B, as the operating temperature rises or falls, the output VSWR increases across the entire operating band, and isolation deteriorates. Therefore, it can be seen that in Comparative Example 3, the input VSWR, output VSWR, insertion loss, and isolation all deteriorate across the entire operating band as the temperature rises or falls.

When a non-reciprocal circuit element according to an embodiment of the present disclosure was fabricated, it was possible to achieve characteristics of insertion loss of 1 dB (typical), isolation of 10 dB (typical), and intermodulation distortion of -60 dBc or less (with 5 W x 2 wave input) in a product operating in the typical frequency range of 3.4 to 3.8 GHz/400 MHz included in 5G band n78.

Furthermore, as can be seen from the above experiments, even when manufacturing non-reciprocal circuit elements for use in frequency bands other than the 3.4-3.8 GHz band, between 3 GHz and 6 GHz, the configuration of this embodiment is an extremely effective technology that exhibits little change in characteristics from low to high temperatures, and can achieve low insertion loss, low IMD, and high isolation.

The non-reciprocal circuit element disclosed herein can be used in a variety of frequency bands, and is particularly suitable for use in the 3 to 6 GHz band.

REFERENCE SIGNS LIST 1 Upper case 2 Laminated magnet 2A Rare earth magnets 2An, 2As, 2Bn, 2Bs, 3a Main surface 2B Ferrite magnet 3 Ferrimagnetic material 4, 5, 6 Center conductor 7 Resin case 8, 9, 10 Capacitor element 12 Lower case 13a to 13d Recess 20 Assembly 30 Non-reciprocal circuit element

Claims (5)

a ferrimagnetic body having a main surface;
a plurality of central conductors arranged on a main surface of the ferrimagnetic material in a mutually insulated state;
a laminated magnet in which a ferrite magnet containing Sr and a rare earth magnet containing Sm are stacked, the laminated magnet being disposed opposite the plurality of central conductors;
A non-reciprocal circuit element comprising :
The composite temperature coefficient of the residual magnetic flux density of the laminated magnet is -0.14%/°C or more and -0.06%/°C or less, and the slope is half or less of the temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material,
The frequency characteristics of the insertion loss of the non-reciprocal circuit element are such that, in a temperature range of −40° C. to 125° C., the resonance frequency of the main band and the attenuation pole closest to the resonance frequency are separated by 200 MHz or more.
Non-reciprocal circuit element. The temperature coefficient of the saturation magnetic flux density of the ferrimagnetic material is -0.45%/°C or more and -0.25%/°C or less ,
The saturation magnetic flux density of the ferrimagnetic material is 40 mT or more and 80 mT or less.
The non-reciprocal circuit device according to claim 1 . the ratio of the thickness of the rare earth magnet to the total thickness of the ferrite magnet and the rare earth magnet is 1/4 or more and 3/4 or less;
The non-reciprocal circuit device according to claim 1 or 2. In the laminated magnet,
the ferrite magnet is closer to the plurality of central conductors than the rare earth magnets ;
The non-reciprocal circuit device according to claim 1 . The composite temperature coefficient of the residual magnetic flux density of the laminated magnet is -0.12%/°C or more and -0.08%/°C or less.
The non-reciprocal circuit device according to claim 1 .