JPS588762B2 - Circulator and isolator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic field temperature compensation method for stabilizing the temperature of circulators and isolators used in the vHF band, UHF band, and other microwave regions.

Generally, as shown in FIG. 1, the saturation magnetization 4πMs of most ferromagnetic materials including ferrite gradually decreases as the temperature rises, and rapidly reaches zero at a certain temperature.

This temperature is called the Curie temperature Tc. Generally, circulators and isolators have a structure in which a static magnetic field Hext is applied to a ferrite having such characteristics by a permanent magnet or the like.

Therefore, in circulators and isolators that do not perform temperature compensation, their electrical characteristics change extremely sensitively to temperature, so stabilizing the temperature of circulators and isolators to avoid this has been an important research topic.

Conventionally, the first thing considered to improve this instability was to increase the upper limit temperature T2 of the operating temperature range (T1 to T2).
The purpose is to use a ferrite having a Curie temperature as high as possible (for example, 80° C.), and avoid using it near the Curie temperature, where there is a drastic change of 4πMs.

Ferrite used in circulators and isolators used in the microwave region is required not only to have a high Curie temperature Tc but also to have as little absorption of electromagnetic waves as possible in microwaves.

However, in general, a high Curie temperature Tc and a low absorption are in a contradictory relationship, and it is difficult to find a suitable material, which is a major research topic in materials research.

Ca-V garnet was developed for the above purpose.

The cucumber temperature of this garnet is about 200℃,
The temperature coefficient α4πMs of 4πMs in the operating temperature range is −0.3%/° C., and 4πMs decreases linearly as the temperature increases.

However, the temperature coefficient of 4πMs is defined as α4πMS3Δ4πMs/4πMs·ΔT(1).

Here, Δ4πMs is the amount of change of 4πMs in the temperature difference ΔT.

However, even with this amount of change, 4πMs changes by about 30% for a temperature change of 100°C, and some kind of temperature compensation is required.

A temperature compensation method when 4πMs changes with temperature is usually performed by changing the external magnetic field Hext with temperature.

For example, when a ferrite magnet is used as a permanent magnet, the temperature coefficient αHext of the external magnetic field Hext is approximately 0.1
5%/°C, which is smaller than α4πMs.

However, the temperature coefficient of HeXt is defined by aHext3ΔHext/Hext·ΔT (2).

Here, △Hext is the amount of change in Hext due to the temperature difference △T.

Normally, temperature compensation is done by adjusting α4πMs and αHext, so specifically, as shown in Figure 2, the magnetic shunt steel 3 whose Curie temperature is near the upper limit temperature T2 (60 to 100°C) is ferrite magnets 1 and 1a in series to increase αHext.

In FIG. 2, 2 and 2a are iron plates, 4 is a magnetic yoke, and 5 is a garnet disk.

However, such temperature compensation methods naturally have limitations.

This is because there are two things that change as 4πMs changes: the center frequency of the circulator and isolator, and the matching state.

As will be explained later, the temperature compensation method for the center frequency and the temperature compensation method for the matched state are generally different, so the garnet's 4π
If the amount of change in Ms is large, there is a drawback that it is impossible to simultaneously perform temperature compensation under the condition of a constant center frequency and the condition of a constant matching state over a wide temperature range.

In order to eliminate these drawbacks, rare earth element G
A Ca-V garnet containing d was developed.

As shown in Figure 3, this garnet has a working temperature range (
T1 to T2), 4πMs shows a convex temperature change.

The temperature TN of the convex peak is within the operating temperature range (T1 to T2
) (usually between 0 and 40°C).

The temperature coefficient of 4πMs of this garnet is the above-mentioned Ca-
It is not monotonous like V-type garnet, but the sign reverses at temperatures before and after TN.

In some Gd-Ca-V garnets, T
1=-20℃-TN=α4πMs=+0.2% at 20℃
/℃, -0.2%/0C at TN=20℃~T2=60℃
It is.

In such garnets, the absolute value of 4πMs as a differential value at each temperature is not much improved compared to Ca-V garnets, but within the operating temperature range (T1 to T2)
The change in 4πMs in Δ4πMs is the conventional Ca −
It is 1/3 to 1/5 or less compared to V-based garnet, which corresponds to a significantly smaller temperature coefficient.

For example, when T1=-20°C and T2-60°C, the temperature coefficient is 0.07%/°C.

Comparing this temperature coefficient with the temperature coefficient αHext of the external magnetic field using a ferrite magnet = 0.15%/°C, the former force is significantly smaller, so temperature compensation must be performed to reduce αHe x t. No.

In this method, for example, as shown in FIG. 4, a magnetic shunt steel 6 having a Curie temperature of 60 to 100 DEG C. is wound in a ring shape around a ferrite magnet and mounted in parallel in a magnetic circuit.

The other numbers in FIG. 4 have the same meanings as in FIG.

FIG. 5 shows the temperature change of the external magnetic field C when this method is used.

At the same time, the external magnetic field A and Gd when no magnetic shunt steel is installed
- The dotted line indicates the temperature change of 4πMs of the V-based garnet.

As is clear from FIG. 5, although this method significantly improves the temperature characteristics of the circulator and isolator in the vicinity of the TN, it also has the following drawbacks.

(1) The temperature characteristics of the circulator and isolator at low and high temperatures except near TN are not improved.

On the high temperature side, the temperature characteristics are better if the magnetic shunt steel is not installed.

(2) Since a magnetic shunt steel with a high Curie temperature is used, the change in 4πMs of the magnetic shunt steel near TN is small, and the 5th
In order to obtain the flat temperature characteristics of Hext as shown in the figure, a large amount of magnetic shunt steel is required.

In addition, since a large amount of the magnetic lines of force emitted by the permanent magnet penetrate into the magnetic shunt steel, a strong permanent magnet is required to obtain the required external magnetic field to be applied to the garnet.

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a circulator and an isolator with temperature-stable electrical characteristics.

In order to achieve the above object, the present invention provides a saturation magnetization of 4πMs
at least one ferrite plate having a convex temperature characteristic such that the temperature has a maximum at 0 to 40°C, at least one permanent magnet arranged above and below the plane of the ferrite plate, In circulators and isolators formed by applying a static magnetic field perpendicular to the
A magnetic shunt steel having a Curie temperature in the range of ~40°C, and a magnetic shunt steel having a higher Curie temperature and a lower Curie temperature compared to the Curie temperature, are added to the magnetic circuit including the permanent magnet. It is characterized by being mounted in parallel and in series.

Hereinafter, the present invention will be explained using its theoretical basis and examples.

The temperature compensation force method when 4πMs of the ferrite plate changes with temperature differs somewhat depending on the type of circulator and isolator and the concept of temperature compensation.

For the sake of simplicity, a lumped constant circulator with unimodal characteristics using an abacus resonance region will be described.

In this circulator, the center frequency and the matching state with the external circuit change as the temperature changes by 4πMs.

The conditions under which each does not change with temperature are as follows.

However, in this case, it was assumed that the load capacitor did not change due to temperature.

) Condition for constant center frequency αHext=α4πMs(
3) 1 (2) Condition of constant matching state αHext=1/2α4π
Ms(4) As is clear from the above equation, the condition that the center frequency is constant and the condition that the matching state is constant generally do not match.

However, in both cases, αHext is simply proportional to α4πMs, and there is no difference in matching the temperature change in Hex t to the shape of the temperature change in 4πMs.

Although the above discussion has been limited to lumped parameter circulators having unimodal characteristics, this tendency is in principle exactly the same for distributed parameter waveguide type circulators and isolators.

As is clear from the above discussion, when using garnet whose saturation magnetization 4πMs is convex with respect to temperature, the external magnetic field Hext must also be deformed into a convex shape.

In order to obtain such characteristics, it is impossible to obtain a magnetic shunt steel having a high Curie temperature, and it is necessary to use a magnetic shunt steel having a Curie temperature close to the above-mentioned temperature TN.

This is the basic idea of the present invention.

In many cases, as shown in FIG. 1, the change in 4πMs of magnetic shunt steel is large near the Curie temperature Tc, and the change becomes smaller as the temperature moves away from that temperature.

In the magnetic shunt steel mainly composed of Fe-Ni considered in this example, the region where this 4πMs changes significantly is 20~
The temperature was 30°C.

In this region, the effect of magnetic shunt steel is very strong.

FIG. 6 shows a first embodiment of the invention.

This represents the temperature change 2 of the external magnetic field Hext when magnetic shunt steel having a Curie temperature near TNE 20° C. is mounted in parallel in a magnetic circuit by the means shown in FIG.

In the figure, A and B show the temperature change of the external magnetic field when no magnetic steel is mounted, and the temperature change of 4πMs of Gd-Ca-V-based garnet.

As is clear from the figure, D changes along the curve A in the temperature range higher than TN = 20°C, but from TL1 = 0°C to
In the temperature range of TN=20°C, the curve A approaches the curve at the end.

2 approaches a convex curve in the temperature range TL1 to TN.

However, at temperatures below TL1 where the change in 4πMs of the magnetic shunt steel becomes small, the curve 2 deviates from the curve B, and again shows a tendency to be dragged down by the temperature change in A.

As a result of applying this example to a VHF broadband lumped constant type circulator, a circulator that operates stably in the temperature range of 0 to 60°C was realized.

FIG. 8 shows a second embodiment of the invention.

In the embodiment shown in Fig. 6, the external magnetic field Hex represents the temperature change E.

In FIG. 7, 6 and 7 are TN=20℃ and TL1=
These are two types of magnetic shunt steels that have a curie temperature of 0℃,
They are each wound in a ring shape around the ferrite magnets 1a and 1.

As is clear from Fig. 8, this magnetic shunt steel 7 acts in parallel on the magnetic circuit, so that TL1=O℃ - TL2=-20℃
The temperature characteristics of Hext in the region vary along the curve of the convex mouth.

However, at temperatures below TL2, where the change in 4πMs of the magnetic shunt steel becomes small, E departs from the mouth curve and again shows a tendency to be dragged by the temperature change of A.

As a result of applying this example to a VHF band broadband concentrated type circulator, a circulator that operates stably in the temperature range of -20 to 60°C was realized.

It will be clear from the above description that by repeating the above-described method, it is possible to further extend the operating temperature range to the lower temperature side.

However, even if the temperature range is expanded using the method described above, the amount of change in 4πMs will increase, and the matching state will collapse significantly, and the absorption of electromagnetic waves by this type of garnet will increase at low temperatures. It is considered appropriate to install about two to three types of magnetic shunt steel.

Temperature compensation on the low temperature side using TN was possible in the previous two embodiments, but in order to compensate for the characteristics at high temperatures exceeding 60° C., a more fine-grained method is required.

In other words, when the temperature exceeds 60℃, the 4π of certain garnets
The temperature coefficient α4a of Ms is 0.2%/℃ to 0.3%/℃
It gets bigger.

Therefore, in the temperature range exceeding 60℃, the external magnetic field Hex
The temperature coefficient αHext of t must be increased.

FIG. 9 shows a third embodiment of the invention.

In addition to the magnetic shunt steels 6 and 7, a magnetic shunt steel 3 having a higher Curie temperature of 80° C. than TN is installed in series in a magnetic circuit.

As a result of applying this embodiment to a VHF broadband lumped constant type circulator, a circulator that operates stably in the temperature range of -20 to +80°C was realized.

Figure 12 shows the reverse loss (dB) of this circulator.
shows the temperature characteristics of

A is the curve at 20°C, mouth is at 80°C, and c is the curve at -20°C.

FIG. 11 shows a case where the conventional temperature compensation method shown in FIG. 5 is used.

As is clear from comparing FIG. 12 with this, the circulator using the embodiment of the present invention has a reverse loss over a very wide temperature range of -20 to 80°C and a required bandwidth of 88 to 110 MHz. General specifications 20d
B is easily satisfied, and it is clear that the effect of the present invention is significant.

Further, in some Gd-Ca-V garnets, α4πMs on the high temperature side may be smaller than αHext.

As is clear from the above explanation, in this case, magnetic steel having a Curie temperature higher than TN may be mounted in parallel rows in terms of the magnetic circuit.

FIG. 10 shows a fourth embodiment of the invention.

In this case, the magnetic shunt steels 6 and 7 having different Curie temperatures are wound around only one permanent magnet.

With this method, almost the same results as in FIG. 12 were obtained.

Temperature TN at which the saturation magnetization 4πMs of the ferrite plate becomes maximum
The reason for setting the temperature to 0 to 40°C as described in the claims is as follows.

That is, if the temperature is outside this range, the value of Δ4πMs in the working temperature range of -20 to 40°C will not become so small.

For example, at TN=-10℃, α4πMs(-20~6
0℃) is 0.2%/℃, and Ca-V related garnet 0
．． It is not much smaller than 3%/°C.

Similarly, if the temperature exceeds 40° C., α4πMs will increase, which is not preferable, but at the same time, the absorption of electromagnetic waves will increase, making it unusable in many cases.

As explained above using the four embodiments of the present invention,
It will be clear that the effects of the present invention are significant.

[Brief explanation of drawings]

Figure 1 is a diagram showing the temperature change of saturation magnetization of a ferromagnetic material, Figure 2 is a magnetic circuit diagram in which magnetic shunt steel is mounted in series using the conventional technology, and Figure 3 is a diagram showing the temperature change of saturation magnetization of a ferromagnetic material. Figure 4 is a diagram showing the temperature change in saturation magnetization, Figure 4 is a magnetic circuit diagram in which magnetic shunt steel is mounted in parallel using the conventional technology, Figure 5 is a diagram showing the temperature change in the external magnetic field when temperature compensation is performed using the conventional technology, 6 and 8 are diagrams showing temperature changes in the external magnetic field when temperature compensation is performed according to the present invention, FIG. 7 is a magnetic circuit diagram in which two types of magnetic shunt steel are mounted in parallel according to the present invention, and FIG.
Figures 1 and 10 are magnetic circuit diagrams in which two types of magnetic shunt steel are installed in parallel and one type of magnetic steel is installed in series according to the present invention, and Figures 11 and 12 are according to the prior art and the present invention, respectively. FIG. 3 is a diagram showing temperature changes in reverse loss of a lumped constant circulator when temperature compensation is performed.

Claims (1)

[Claims] 1. At least one ferrite plate having a convex temperature characteristic with a maximum saturation magnetization 4πMs in the range of 0 to 40°C, at least one plate above and below the plane of the ferrite plate. In the circulator and isolator in which the above permanent magnets are arranged and a static magnetic field is applied substantially perpendicular to the plane of the ferrite plate, a magnetic shunt steel having a Curie temperature in the range of 0 to 40° C. is used as the permanent magnet. A circulator and an isolator, characterized in that the circulator and isolator are mounted in a magnetic circuit in parallel to a magnetic circuit including the circulator and the isolator. 2. At least one ferrite plate having a convex temperature characteristic with a maximum saturation magnetization 4πMs in the range of 0 to 40°C, and at least one permanent magnet arranged above and below the plane of the ferrite plate. In the circulator and isolator in which a static magnetic field is applied perpendicularly to the plane of the ferrite plate, magnetic shunt steel having a Curie temperature in the range of 0 to 40°C is magnetically applied to the magnetic circuit including the permanent magnet. One or more types of magnetic shunt steel that are installed in parallel in a circuit and have a lower Curie temperature than the magnetic shunt steel,
A circulator and an isolator, characterized in that the circulator and isolator are mounted in parallel in a magnetic circuit to a magnetic circuit including the permanent magnet. 3. At least one ferrite plate having a convex temperature characteristic with a maximum saturation magnetization 4πMS in the range of 0 to 40°C, and at least one permanent magnet arranged above and below the plane of the ferrite plate. In the circulator and isolator in which a static magnetic field is applied substantially perpendicular to the plane of the ferrite plate, magnetic shunt steel having a Curie temperature in the range of 0 to 40°C is magnetically applied to the magnetic circuit including the permanent magnet. A magnetic shunt steel having a higher Curie temperature than the magnetic shunt steel is installed in series or parallel to the magnetic circuit including the permanent magnet. Characteristics of circulator 2 and isolator.