JP3761035B2 - Non-reciprocal circuit element - Google Patents

Description

  The present invention relates to a non-reciprocal circuit device that is a microwave nonreciprocal device using a garnet, and more particularly to a reduction in insertion loss and stabilization of temperature characteristics of small lumped constant circulators and isolators.

In recent years, along with the downsizing of passive components such as semiconductor elements such as ICs and transistors, multilayer chip capacitors, multilayer chip inductors, chip resistors, etc., the miniaturization and thinning of microwave devices that have surface-mounted these devices have rapidly progressed. Yes. In such a movement, it is desired to reduce the size and thickness of a nonreciprocal circuit element, which is a microwave nonreciprocal element that is extremely important in configuring a microwave device. In response to these market needs, attempts to reduce the size of lumped constant circulators and isolators, which are nonreciprocal circuit elements, inevitably have increased insertion loss, resulting in deterioration of reflection loss and reverse loss. . In particular, the insertion loss directly affects the duration of the storage battery of the mobile phone, and its reduction is strongly desired.

  FIG. 10 is a schematic structural plan view showing the state of the central conductor of the lumped constant circulator of the prior art. FIG. 11 is a cross-sectional view of the A-A ′ structure of FIG. 10, and also shows a magnetic circuit for applying a DC magnetic field in addition to the central conductor 1 and the garnet 2. Three sets of central conductors 1a, 1b, and 1c are arranged on the disk-like garnet 2 in a state of being radially stacked. Reference numeral 4 denotes an insulating sheet provided so that the central conductors 1a, 1b, and 1c are not short-circuited at the intersection. One of the central conductors 1a, 1b, 1c is an input / output terminal (◯ 1, ○ 2, ○ 3), and the other is connected to the common part 3 and grounded (in this case, a ferromagnetic metal case 6 which is a ground conductor). ing. A load capacitor C is connected between each input / output terminal (◯ 1, ○ 2, ○ 3) and the common portion 3 (ground conductor), and determines the operating frequency of the circulator.

  And in order to implement | achieve a circulator operation | movement with desired impedance, the ferrite magnet 5 which applies a direct-current magnetic field to the garnet 2 is arrange | positioned. The ferrite magnet 5 is inscribed in the upper surface of the ferromagnetic metal case 6. On the other hand, the garnet 2 is inscribed in the lower surface of the ferromagnetic metal case 6 through the common portion 3 of the central conductor. The ferrite magnet 5 is magnetized as shown by an arrow, and the garnet 2 is magnetized as shown by an arrow. In FIG. 11, only the ends 1a and 1b of the central conductor are shown. The 1c and insulating sheet 4 disposed above 1b are omitted. Moreover, in this prior art, as shown with the dotted line in a figure, an isolator can be comprised by connecting the energy absorption resistance Ro between an input-output terminal ((circle) 3) and a ground conductor.

  FIG. 12 is another example of the prior art. This conventional example is a sectional view of a triplate using two garnets 2a and 2b. The conductive common portion 3a covers the upper surface of the garnet 2b. By adopting such a structure, the high frequency magnetic field generated by the current flowing through the center conductor 1a acts on the upper and lower garnets, so that the inductance is increased and the bandwidth and insertion loss are improved. For simplicity, the other ends 1b and 1c of the center conductor and the insulating sheet 4 are omitted.

  As another conventional technique, there is a technique for adjusting a magnetic flux by attaching a magnetic plate to a ferrite magnet. One example thereof is described in JP-A-62-91003. In this prior art, a magnetic plate having a diameter larger than that of a magnet is fixed to a garnet facing surface of a ferrite magnet. As this magnetic plate, permalloy having a high magnetic permeability is used, and the magnetic field applied to the garnet is adjusted by scraping off the periphery of the magnetic plate.

Next, the concept behind the prior art when reducing the insertion loss of a lumped constant circulator will be described. The cause of insertion loss of this lumped constant circulator is divided into 1) electrical loss, 2) magnetic loss, and 3) mismatch loss. The electrical loss is due to the Joule loss due to the electric resistance R of the center conductor or the ground conductor and the dielectric loss tan δ of the load capacitance. The magnetic loss is a garnet magnetic loss. This is due to the ferromagnetic resonance half width ΔH, which is the material constant of garnet, but in practice, it is often affected by the non-uniformity of the DC magnetic field. The mismatch loss is a reflection loss reflected at the input terminal because the impedance of the circulator is not 50Ω and a radiation loss leaking outside because it is not a sealed case.

  Therefore, in order to obtain a low insertion loss, it is necessary to use materials and components having as small electrical resistances R, tan δ, and ΔH as possible. However, it is extremely difficult to realize a uniform magnetic field distribution in terms of a magnetic circuit even if such materials and parts are used. Furthermore, in order to reduce radiation loss, a sealed case may be used. However, since this case structure is also related to the uniformity of the magnetic field, it is not easy to obtain a uniform magnetic field in the sealed case.

  Now, regarding the insertion loss, there is another big problem in practice. Even if the characteristics of each element, magnetic field, etc. are adjusted during assembly to achieve circulator characteristics that are optimal at room temperature, the saturation magnetization 4πMs of the garnet and the DC magnetic field of the permanent magnet change as the ambient temperature changes. . The load capacity also changes. For this reason, there is a problem that the input impedance is greatly shifted at low and high temperatures and the insertion loss is increased. Therefore, it is extremely important in practice to combine these temperature-changing parameters to stabilize the temperature characteristics of the circulator. However, it is difficult to realize the specifics, and the low-loss and temperature characteristics are satisfactory. Realization of a circulator is desired.

  The present invention relates to an invention of a nonreciprocal circuit element that can realize low insertion loss and does not deteriorate temperature characteristics by considering a magnetic field application method of the nonreciprocal circuit element in view of the above-described problems of the prior art. It is.

The present invention provides a first garnet, a plurality of center conductors arranged in an insulated state on the first garnet, one end of each of the center conductors connected to a ground conductor, and the other end of each of the center conductors Are input / output terminals, and load capacitors are connected between the input / output terminals and the ground conductor, respectively, and a ferrite magnet for applying a DC magnetic field to the first garnet is provided, and these are housed in a metal case. In the nonreciprocal circuit device having the structure, a garnet yoke is disposed between the ferrite magnet and the central conductor, and a temperature coefficient of a DC magnetic field applied to the first garnet is increased. It is a non-reciprocal circuit device with excellent temperature characteristics.

In the present invention, the garnet yoke may be disposed so as to be in contact with both the ferrite magnet and the central conductor, or may be joined to the central conductor side of the permanent magnet. You may join on top. When the central conductor and the garnet yoke are joined, an insulator may be interposed between the garnet yoke and the central conductor.

  In the present invention, the diameter of the garnet yoke is preferably in the range of 0.8 to 1.4 times the diameter of the first garnet.

  In the present invention, it is preferable that the thickness of the garnet yoke is in the range of 0.3 to 1.5 times the thickness of the first garnet.

  In the present invention, the saturation magnetization 4πMs of the garnet yoke is preferably in the range of 1 to 1.5 times the saturation magnetization 4πMs of the first garnet.

  In the present invention, the shape of the first garnet and / or the garnet yoke may be a disk shape, and the circumferential end may be rounded with a radius of 0.05 mm or more.

According to the present invention, a garnet yoke is disposed between the ferrite magnet and the central conductor disposed on the first garnet, thereby optimizing the magnetic field distribution and configuring a low-loss nonreciprocal circuit device. be able to. In addition, a non-reciprocal circuit device having stable temperature characteristics can be provided, which is extremely useful in microwave devices such as mobile phones.

  The main object of the present invention is to provide a new magnetic circuit of a nonreciprocal circuit element. This is particularly effective in a small lumped constant circulator / isolator. In addition, as described above, the isolator is configured by connecting one terminal of the circulator to the energy absorption resistor and grounding the energy absorption resistor, and is achieved by the same technology as the circulator. I will explain. Hereinafter, the contents of the present invention will be described in detail using examples. In addition, the code | symbol attaches | subjects the same code | symbol about the member of the same function. However, the same thing is not necessarily shown.

FIG. 1 is a diagram showing a cross-sectional structure of a first embodiment according to the present invention. The structure of this embodiment will be described. The ferrite magnet 5 is inscribed in the upper surface of the ferromagnetic metal case 6. The first garnet 2 is inscribed in the lower surface of the ferromagnetic metal case 6 through the common portion 3 of the central conductor. A garnet yoke 7 according to the present invention is provided on the surface of the ferrite magnet 5 facing the first garnet 2. The ferrite magnet 5 is magnetized as indicated by an arrow, whereby the garnet yoke 7 and the first garnet 2 are magnetized as indicated by an arrow. The center conductor is the same as in the prior art, and only 1a is shown for the end of the center conductor. The upper 1b and 1c, and the insulating sheet 4 are omitted.

  The structure of the present invention is similar at first glance to the prior art triplate structure of FIG. 12, but the operation is quite different. This is because, in the conventional structure of FIG. 12, the garnet 2b acts as a nonreciprocal element as a circulator operation together with the garnet 2a. Therefore, the performance of the circulator is directly affected by the magnetic field distribution of the ferrite magnet 5 and easily causes magnetic loss. On the other hand, the garnet yoke 7 of the present invention does not act directly on the circulator operation, but acts as a yoke of the magnetic circuit. The greatest effect is an action that softens the steep magnetic field distribution by the ferrite magnet 5.

  In addition, the present invention has an effect of increasing the temperature coefficient of the DC magnetic field applied to the first garnet 2 by the ferrite magnet 5. In our research, when the circulator is made thinner, the temperature characteristic of the actual magnetic field strength acting on the garnet becomes smaller than the temperature coefficient of the residual magnetic flux density of the ferrite magnet. From this point of view, the temperature coefficient of saturation magnetization of the garnet is generally larger than the temperature coefficient of the ferrite magnet. Therefore, in the structure of the present invention, the garnet yoke 7 acts in series in a magnetic circuit, and the first garnet 2 has the effect of increasing the temperature coefficient of the DC magnetic field applied to 2 and consequently stabilizing the temperature characteristics of the circulator.

  With the structure of the first embodiment according to the present invention, a 900 MHz band lumped constant isolator was constructed, and the electrical characteristics were measured. This electrical characteristic is shown in FIG. In FIG. 4, B is the embodiment and A is the conventional structure. The upper diagram shows the reflection loss S11, the middle diagram shows the insertion loss S21, and the lower diagram shows the reverse loss S12. Comparing with the peak value of the insertion loss S21, the structure of the prior art is 0.42 dB as shown in FIG. However, in the embodiment of the structure of the present invention, it can be seen that the peak values of the insertion loss are improved by 0.30 dB and 0.12 dB.

  This is because the distribution of the DC magnetic field applied to the first garnet 2 is improved by the presence of the garnet yoke 7. In this embodiment, the first garnet 2 and the garnet yoke 7 are 3.7 mmφ × 0.35 mmt, but the first garnet 2 and the garnet yoke 7 have extremely different diameter relationships. As a result of experiments, it has been found that the combination of the above has little effect of the present invention. That is, when the diameter of the garnet yoke 7 is larger than 1.4 times the diameter of the first garnet, the shielding effect of the garnet yoke is enhanced, and the magnetic force of the ferrite magnet 5 is not easily transmitted to the first garnet. On the other hand, if the diameter of the garnet yoke 7 is less than 0.8 times the diameter of the first garnet, the effect of improving the magnetic field distribution by the garnet yoke is not likely to appear. Therefore, the outer diameter of the garnet yoke 7 is preferably 0.8 to 1.4 times the diameter of the first garnet. More preferably, it is 0.9 times to 1.1 times.

  The same applies to the thickness of the garnet yoke. When the thickness of the garnet yoke is more than 1.5 times the thickness of the first garnet, the shielding effect becomes stronger, so that the first garnet is formed. The applied magnetic field is insufficient. On the contrary, it was confirmed that there was almost no effect when the ratio was less than 0.3 times.

  Furthermore, the same 4πMs for the garnet yoke and the first garnet was used in the first embodiment. However, it can be seen that the 4πMs for the garnet yoke is slightly increased and can be increased by about 1.3 times. It was. However, it was confirmed that when 4πMs of the garnet yoke is larger than 1.5 times, the ferromagnetic resonance absorption in this portion is increased and the circulator performance is remarkably deteriorated.

  FIG. 2 is a view showing a cross-sectional structure of a second embodiment according to the present invention. The difference from FIG. 1 is that the circumferential portion of the first garnet 2 is processed to have a roundness R. FIG. 5 shows the electrical characteristics of the second embodiment when such a structure is used in comparison with the first embodiment. In FIG. 5, B is the first embodiment and C is the second embodiment. Comparing with the peak value of the insertion loss S21, it is 0.30 dB in the first embodiment B. However, in the second embodiment C, it can be seen that the peak values of the insertion loss are improved by 0.25 dB and 0.05 dB. This is because the distribution of the DC magnetic field applied to the first garnet 2 is further improved by rounding around the end of the first garnet 2. In the present embodiment, the first garnet 2 having a diameter of 3.7 mmφ × 0.35 mmt was used, and the radius of roundness at this end was about 0.1 mm. In the experiment, it was confirmed that the effect appeared when the radius was 0.05 mm or more.

  FIG. 3 is a view showing a cross-sectional structure of a third embodiment according to the present invention. The difference from FIG. 2 is that only one side of the circumferential portion of the garnet yoke 7 is rounded and rounded instead of rounding the circumferential portion of the first garnet 2. In the case of using such a structure, the electrical characteristics of this example were almost the same as those of the second example. This is also because the distribution of the DC magnetic field applied to the first garnet 2 is improved by the roundness around the end of the garnet yoke 7.

  FIG. 6 shows the temperature characteristics of the electrical performance of the lumped constant isolator when the structure of FIG. 11 of the prior art is used. The thick solid line is + 25 ° C, the rough dotted line is + 85 ° C, and the fine dotted line is -35 ° C. It can be seen that in the conventional magnetic circuit, the peak value of the insertion loss S21 is not only bad at 0.4 dB, but the center frequency greatly fluctuates with temperature change. Particularly, the characteristic change at high temperature is large. This is because in the small and thin isolator structure, the temperature coefficient of the magnetic field strength applied to the garnet 2 by the ferrite magnet is apparently reduced.

  FIG. 7 shows temperature characteristics of the first embodiment of the present invention when a garnet yoke is used as a yoke of a magnetic circuit. It can be seen that due to the presence of this garnet, the peak value of the insertion loss S21 becomes as small as 0.3 dB and the temperature change of the center frequency becomes extremely small. This is because the garnet yoke acts in series as a magnetic circuit to increase the temperature coefficient of the magnetic field strength applied to the first garnet. This shows that the temperature characteristics of the nonreciprocal circuit device of the present invention are extremely stable.

  A sectional structure of the fourth embodiment according to the present invention is shown in FIG. In this embodiment, a garnet yoke 7 is arranged on three sets of central conductors 1 arranged in an insulated state on one surface of the first garnet 2. Also in this example, the same characteristics as in the first example could be obtained. In this embodiment, an insulator may be interposed between the garnet yoke 7 and the central conductor. The structure of the fourth embodiment is very similar to the conventional structure of FIG. 12, but the garnet yoke 7 has no surrounding conductor, and the conductor 3a does not surround the garnet 2b as shown in FIG. As described above, this difference has a different effect and a completely different structure.

  FIG. 9 shows a sectional structure of the fifth embodiment according to the present invention. In this embodiment, the garnet yoke 7 is in contact with both the ferrite magnet 5 and the central conductor 1. With this structure, it was possible to obtain the same characteristics as in the first embodiment. Also in this embodiment, an interposition such as an insulator may be interposed between the garnet yoke 7 and the central conductor 1 or between the garnet yoke 7 and the ferrite magnet 5.

According to the present invention, a garnet yoke is disposed between the ferrite magnet and the central conductor disposed on the first garnet, thereby optimizing the magnetic field distribution and configuring a low-loss nonreciprocal circuit device. be able to. In addition, a non-reciprocal circuit device having stable temperature characteristics can be provided, which is extremely useful in microwave devices such as mobile phones.

1 is a structural cross-sectional view of a first embodiment according to the present invention. It is a structure sectional view of the 2nd example concerning the present invention. It is a structure sectional view of the 3rd example concerning the present invention. It is an electrical characteristic comparison figure of a prior art and 1st Example of this invention. It is an electrical property figure of the 1st example and the 2nd example of the present invention. It is a temperature characteristic figure of the lumped constant type isolator of a prior art. It is a temperature characteristic figure of the 1st example of the present invention. It is a structure sectional view of the 4th example concerning the present invention. It is structural cross-sectional view of 5th Example based on this invention. It is a plan view of the internal structure of a lumped constant circulator / isolator according to the prior art. It is sectional drawing of the lumped constant type | mold circulator of a prior art. It is a cross-section figure of another lumped constant type circulator of a prior art.

Explanation of symbols

1 central conductor 2 first garnet 3 common part (ground conductor)
4 Insulating sheet 5 Permanent magnet 6 Ferromagnetic metal case 7 Garnet yoke

Claims (9)

A first garnet, a plurality of central conductors arranged in an insulated state on the first garnet, one end of each of the central conductors is connected to a ground conductor, and the other end of each of the central conductors is an input / output terminal And having a ferrite magnet for applying a DC magnetic field to the first garnet, wherein the load capacity is connected between the input / output terminal and the ground conductor, and these are housed in a metal case. In the circuit element, a temperature characteristic of a DC magnetic field applied to the first garnet is increased by arranging a garnet yoke between the ferrite magnet and the central conductor. Excellent nonreciprocal circuit element.   2. The nonreciprocal circuit device with excellent temperature characteristics according to claim 1, wherein the garnet yoke is in contact with both the permanent magnet and the central conductor.   2. The nonreciprocal circuit device with excellent temperature characteristics according to claim 1, wherein the garnet yoke is in contact with a central conductor side of the permanent magnet.   2. The nonreciprocal circuit device with excellent temperature characteristics according to claim 1, wherein the garnet yoke is in contact with the central conductor.   5. The nonreciprocal circuit device having excellent temperature characteristics according to claim 2, wherein the garnet yoke and the central conductor are in contact with each other with an insulator interposed therebetween. 2. The nonreciprocal circuit with excellent temperature characteristics according to claim 1, wherein the diameter of the garnet yoke is in the range of 0.8 to 1.4 times the diameter of the first garnet. element.   2. The non-temperature characteristic superiority according to claim 1, wherein the thickness of the garnet yoke is in the range of 0.3 to 1.5 times the thickness of the first garnet. Reversible circuit element.   2. The non-temperature characteristic excellent non-temperature characteristic according to claim 1, wherein the saturation magnetization 4πMs of the garnet yoke is in the range of 1 to 1.5 times the saturation magnetization 4πMs of the first garnet. Reversible circuit element. The temperature characteristic according to claim 1, wherein the shape of the first garnet or the garnet yoke is a disk shape, and a round end having a radius of 0.05 mm or more is attached to a circumferential end thereof. Excellent nonreciprocal circuit element.

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