JPH07202517A - Variable band pass filter - Google Patents

Abstract

PURPOSE:To reduce the temperature characteristic or resonance elements to suppress the phase drift value and to suppress self-heating to reduce the temperature drift by providing a permanent magnet in the magnetic field generating part which applies a magnetic field to resonance elements of magnetic resonance. CONSTITUTION:This variable band pass filter is provided with an element yoke 1 provided with resonance elements and the magnetic field generating part which applies a magnetic field to the resonance element. The element yoke 1 forms a close magnetic path together with a magnetic yoke 2. Resonance elements 3 ana 4 consist of, for example, YIG crystal, and a permanent magnet 12 is provided which applies a bias magnetic field to them. A tuning coil 14 is provided in the outside periphery of a pole piece 11 in the exciting yoke 2. In this constitution, the magnetic field is applied to resonance elements 3 and 4 by power supply to the tuning coil 14 to vary the resonance frequency in the range of 0.4 to 3.6GHz. At this time, the variable frequency can be set to 0.4GHz as the lower limit by the bias magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable bandpass filter which is useful when incorporated in a standard signal generator such as a mobile phone.

[0002]

2. Description of the Related Art For example, a thin band YIG (yttrium, iron, and garnet) is used for a resonance element as a variable bandpass filter in which a resonance frequency is varied in a certain range and only a specific frequency within a frequency band within the range is passed. A device using a resonant element made of a crystal has been proposed.
A tuning filter using YIG has both excellent blocking characteristics and wide tuning characteristics in the microwave band.

In order to resonate the resonant element, it is necessary to apply a magnetic field to the resonant element. The magnetic field is generally applied to the resonance element by using an electromagnet by passing a direct current through the coil. The resonance frequency is changed by changing the magnitude of the current supplied to the coil.

For example, as shown in FIG. 4, when the resonance frequency is varied from 0.4 GHz (gigahertz) to 3.6 GHz, it is 200 to tune to 0.4 GHz.
It is necessary to apply a current of mA to apply a magnetic field to the resonance element, and for tuning to 3.6 GHz, for example, 360 mA.
It is necessary to apply the current.

When the resonance frequency is changed by using the electromagnet as described above, a large current is passed through the coil, which causes self-heating. Since YIG has a temperature characteristic, it is easily affected by the heat generated by energizing the coil.

Therefore, conventionally, a temperature compensation circuit has been devised so that the temperature characteristic of YIG is corrected by an electronic circuit to apparently make the temperature characteristic of YIG always zero.

[0007]

However, even when the temperature compensating circuit is used, since the temperature characteristic itself is large, the phase fluctuation (phase drift) also changes abruptly, and the correction cycle is short. turn into. Also, in view of the capacity of the microcomputer used in the temperature compensation circuit, it is inevitable to increase the value of the phase to be corrected at once. For this reason, the temperature characteristics of YIG have not reached zero.

Further, since the lower limit range of the tuning frequency, more specifically, the applied magnetic field in the hatched portion in FIG. 4, is also obtained from the tuning coil, the tuning current is required for that amount, and self-heating becomes large. Then, the self-heating at the time of rising has a great influence on the temperature drift.

Therefore, the present invention has been proposed in view of the above-mentioned conventional technical problems, and the temperature characteristic of the resonant element is reduced to obtain an absolute phase drift within the operation compensation temperature range. An object of the present invention is to provide a variable bandpass filter that can suppress the value and suppress self-heating to reduce temperature drift.

[0010]

According to the present invention, a resonance element that magnetically resonates, a magnetic field generator that applies a magnetic field to the resonance element, and a permanent magnet provided in the magnetic field generator are provided. , To solve the above problems.

Further, according to the present invention, an element yoke made of a magnetic material, an exciting yoke made of a magnetic material which is in contact with the element yoke and forms a closed magnetic path by the element yoke, and the element yoke are provided, and magnetic resonance occurs. A resonance element, a magnetic field generating section composed of a tuning coil provided around the pole piece of the excitation yoke so as to surround the pole piece, and the pole piece around the pole piece of the excitation yoke. Provided on the tuning coil and connected to a temperature compensation circuit for controlling the temperature characteristic of the resonance element to zero, and a pole piece of the excitation yoke so as to face the resonance element. By providing a permanent magnet, the above-mentioned subject is solved.

The permanent magnet provided in the magnetic field generator is provided as close as possible to the resonant element. In addition, the permanent magnet,
A rare earth magnet that is stable in manufacturing is used. On the other hand, a YIG crystal is used for the resonance element.

[0013]

In the present invention, since the YIG crystal is used for the resonance element and the permanent magnet is provided in the magnetic field generating portion for applying a magnetic field to the YIG crystal, the positive temperature characteristic of the YIG crystal is improved. This is offset by the negative temperature characteristic of the permanent magnet, and the temperature characteristic during use of the YIG crystal is reduced. Therefore, the absolute phase drift value in the operation compensation temperature range is suppressed, and the phase correction period becomes long and the phase drift amount becomes small even when the temperature compensation circuit is used.

Further, in the present invention, since the permanent magnet is provided in the magnetic field generator, the permanent magnet can be used as a bias applied magnetic field up to a frequency slightly lower than the lower limit range of the variable tuning frequency. In other words, the permanent magnet can cover the shaded region up to the lower limit of 0.4 GHz of the variable tuning frequency shown in FIG. Therefore, it is not necessary to energize the tuning coil that is the magnetic field generating portion in that range, and as a result, the occurrence of self-heating is suppressed and the temperature drift is small.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. In this embodiment, for example, the resonance frequency is varied in the range of 0.4 GHz to 3.6 GHz, and 25 M is set in a certain frequency band within the range.
This is an example of a variable band-pass filter that allows only frequencies having a width of Hz to pass. For example, in the frequency band of 1 GHz, only frequencies having a width of 25 MHz are passed.

As shown in FIGS. 1 and 2, the variable band-pass filter mainly comprises an element yoke 1 provided with a resonance element, and the element yoke 1 constitutes a closed magnetic path, and a magnetic field is applied to the resonance element. The excitation yoke 2 is provided with a magnetic field generator for application.

The element yoke 1 constitutes a closed magnetic circuit with an exciting yoke 2 which will be described later, and is formed in a flat plate shape with a magnetic material such as permalloy. A pair of resonance elements 3 and 4 that magnetically resonate are provided on one main surface 1a of the element yoke 1.

The resonant elements 3 and 4 are made of, for example, a YIG crystal. A device using these resonant elements 3 and 4 is
It utilizes the mode of uniform precession in magnetic resonance of magnetic garnet, which is a type of free magnetic material. The resonance frequency of the YIG crystal body changes in direct proportion to the strength of the magnetic field applied to the YIG crystal body. Also, YIG
The crystal has the property of having excellent blocking characteristics and a wide range of tuning characteristics in the microwave band.

The YIG crystal has a positive temperature characteristic, a value of 4πMs, a coercive force of 1780 Oe, a crystal direction of <111>, and a temperature characteristic of 8.36 MHz / ° C. In the present embodiment, the YIG crystal has a diameter of 2.5.
It was formed in a disk shape having a thickness of 40 mm and a thickness of 40 mm.

Resonant elements 3 and 4 made of this YIG crystal
Is a pillar 5 made of brass on one main surface 1a of the element yoke 1.
6 are provided, and are provided at predetermined intervals on a micro IC substrate 7 made of a dielectric ceramic provided on the columns 5 and 6. In addition, these resonance elements 3 and 4
Are provided on the surface of the micro IC substrate 7 facing the element yoke 1.

One of the resonance elements 3 is a micro IC substrate 7
It is provided on the input line formed above. Similarly, the other resonance element 4 is also provided on the output line formed on the micro IC substrate 7. A predetermined air gap is provided between the resonance elements 3 and 4 and the element yoke 1 due to the influence of the characteristics.

A top plate 8 is provided so as to further cover the resonance elements 3 and 4. The top plate 8 is
A pillar 9 made of brass on one main surface 1a of the element yoke 1,
10 is provided, and is provided on the columns 9 and 10 at a predetermined distance from the micro IC substrate 7.

On the other hand, the excitation yoke 2 is the element yoke 1 described above.
And constitute a closed magnetic circuit, and are made of a magnetic material such as permalloy as in the element yoke 1. The excitation yoke 2 is formed as a rectangular parallelepiped whose side facing the element yoke 1 is open, and a pole piece 11 having a cylindrical shape, for example, protruding from the bottom surface toward the opening side is integrally formed in the central portion of the excitation yoke 2. Composed.

An upper end surface 11a of the pole piece 11 is provided with a permanent magnet 12 which is made of a YIG crystal and has a small temperature characteristic and which applies a bias magnetic field to the resonant elements 3 and 4. . This permanent magnet 1
For 2, a rare earth magnet having a negative temperature characteristic opposite to that of the YIG crystal is used. If the permanent magnet 12 having a negative temperature characteristic with respect to the positive temperature characteristic of the YIG crystal body is provided in a position facing and facing the resonant elements 3 and 4 made of the YIG crystal body, The positive temperature characteristic of the YI is canceled by the negative temperature characteristic of the permanent magnet 12.
The temperature characteristic of the G crystal becomes small.

For the rare earth magnet used for the permanent magnet 12, it is preferable that the frequency drift due to the temperature change is as small as possible, but in that case, if it does not match the temperature characteristic of the YIG crystal body, there is a high possibility of shifting to one side. ,
For example, cerium cobalt, samarium cobalt, and neodymium magnets, which are stable in manufacturing, are preferable.

The permanent magnet 12 is the pole piece 11
However, considering the magnitude of the magnetic field applied to the resonant elements 3 and 4, it is desirable to provide it in a position as close to the resonant elements 3 and 4 as possible.

On the permanent magnet 12, there is provided a magnetic compensating plate 13 for applying a magnetic field generated from the permanent magnet 12 perpendicularly to the resonance elements 3 and 4. Without such a magnetic shunt plate 13, the magnetic flux generated from the permanent magnet 12 is disturbed, and the magnetic field is not applied perpendicularly to the resonant elements 3 and 4. Further, the magnetic shunt plate 13 is provided at a position where a slight gap is opened with respect to the top plate 8 provided on the element yoke 1.

The pole piece 11 is provided inside the exciting yoke 2 and around the outer periphery of the pole piece 11.
A tuning coil 14 is provided so as to surround the. The tuning coil 14 functions as a magnetic field generation unit that applies a magnetic field required to change the resonance frequency within a certain range to the resonance elements 3 and 4. Therefore,
Both terminals of the tuning coil 14 are supplied with a sufficient amount of direct current for varying the resonance frequency within a certain range.

A temperature compensation coil 15 is provided on the tuning coil 14 around the pole piece 11 so as to surround the pole piece 11. The temperature compensating coil 15 is a temperature compensating circuit (not shown) that always controls the temperature characteristics of the resonant elements 3 and 4 to zero.
It is connected to the. In the correction operation, since the temperature characteristics of the resonant elements 3 and 4 are made small by the permanent magnet 12, the correction cycle can be lengthened and the phase drift value can be made small.

The microcomputer data used for the temperature compensation circuit is stored in advance as data for reading the temperature characteristics of the resonant elements 3 and 4 and correcting the drift. If the drift amount in the operation compensation temperature range is small without changing the capacitance of the microcomputer, the drift amount corrected by the microcomputer at one time will be small, and the phase fluctuation will be small.

Element yoke 1 constructed as described above
The excitation yoke 2 and the excitation yoke 2 are coupled to each other to form a closed magnetic circuit, as shown in FIG. In the variable bandpass filter configured as described above, a magnetic field is applied to the resonant elements 3 and 4 by energizing the tuning coil 14 to vary the resonant frequency in the range of 0.4 GHz to 3.6 GHz, for example.

At this time, since the permanent magnet 12 is provided at the tip of the pole piece 11, the permanent magnet 12 is
The lower limit of the variable frequency is 0.4 depending on the bias magnetic field of
It can be GHz. Therefore, 0.4 GHz
A sufficient current (for example, 200 mA) for tuning coil 1
4 does not need to be energized, and the variable frequency lower limit can be reached even when the tuning current is zero. However, in the present embodiment, the tuning coil 14 is energized with about 1/5 of 40 mA. As described above, in the range up to the lower limit of the variable frequency, since the tuning coil 14 does not need to be energized, self-heating does not occur, and the temperature drift at the time of rising due to it does not occur. .

The tuning coil 14 needs to be energized only with the tuning current (160 mA) necessary for the variable frequency of 0.4 GHz to 3.6 GHz, which is a large frequency. Disappears. Therefore, self-heating generated by energizing the tuning coil 14 is naturally suppressed.

Specifically, up to now, 8.36 MHz / ° C.
The temperature characteristics that were less than 1/2 are reduced by the use of the permanent magnet 12.
The frequency could be suppressed to the following 3.7 MHz / ° C. As a result, in the operation compensation temperature range (for example, 0 ° C. to 70 ° C.), the temperature drift amount of the tuning center frequency was about 580 MHz without the permanent magnet shown by the line A in FIG. Approximately 260 when there is a permanent magnet indicated by the middle line B
It has decreased to MHz.

[0035]

As is apparent from the above description, in the variable bandpass filter of the present invention, the variable bandpass filter of the present invention is opposed to the resonant element made of the YIG crystal having a positive temperature characteristic.
Since the rare-earth permanent magnet having a negative temperature characteristic is provided in the magnetic field generating portion, the positive temperature characteristic of the YIG crystal body is canceled by the negative temperature characteristic of the permanent magnet, and the YI crystal has a negative temperature characteristic.
The temperature characteristic in use of the G crystal is suppressed.
As a result, the absolute phase drift value in the operation compensation temperature range can be suppressed, and the phase correction cycle can be increased even when the temperature compensation circuit is used, so that the phase drift amount can be reduced.

Further, in the present invention, since the bias magnetic field of the permanent magnet can be used as a bias applied magnetic field up to a frequency slightly lower than the lower limit of the tuning frequency, the tuning current used in that range is unnecessary. Therefore, it is possible to suppress self-heating, and it is possible to reduce the temperature drift associated therewith, and as a result, it is possible to suppress power consumption to a low level.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a variable bandpass filter.

FIG. 2 is a cross-sectional view showing a state in which a variable bandpass filter is disassembled.

FIG. 3 is a characteristic diagram showing a frequency drift with and without a permanent magnet.

FIG. 4 is a characteristic diagram showing a current value required when varying a resonance frequency within a certain range.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Element yoke 2 ... Excitation yoke 3,4 ... Resonance element 11 ... Pole piece 12 ... Permanent magnet 13 ... Magnet compensator 14 ... Tuning coil 15 ... Temperature Compensation coil

Front page continuation (72) Inventor Junichi Goto 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (5)

[Claims] 1. A variable bandpass filter comprising: a resonance element that magnetically resonates; a magnetic field generation section that applies a magnetic field to the resonance element; and a permanent magnet that is provided in the magnetic field generation section. 2. An element yoke made of a magnetic material, an exciting yoke made of a magnetic material that is in contact with the element yoke and forms a closed magnetic path with the element yoke, and a resonance element provided on the element yoke and magnetically resonating. A magnetic field generating section comprising a tuning coil provided around the pole piece of the exciting yoke so as to surround the pole piece; and the tuning so as to surround the pole piece around the pole piece of the exciting yoke. A temperature compensating coil provided on the coil and connected to a temperature compensating circuit for controlling the temperature characteristic of the resonant element to zero; and a permanent magnet provided on the pole piece of the exciting yoke so as to face the resonant element. A variable bandpass filter equipped with. 3. The variable bandpass filter according to claim 1, wherein the permanent magnet is provided in the vicinity of the resonance element. 4. The variable bandpass filter according to claim 1, wherein the permanent magnet is a rare earth magnet. 5. The variable bandpass filter according to claim 1, wherein the resonant element is a YIG crystal body.