JP2010273000A - Electronic tuning bandpass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic tuning bandpass filter which has little insertion loss, a steep out-of-band attenuation characteristic and an optional narrow band to wide band passage characteristic, does not cause distortion due to a nonlinear element, or the like, and controls a resonance frequency having both a characteristic of a resonance (antiresonance) transmission line type bandpass filter, for example, such as an interdigital filter structure and a characteristic of a YIG tuning type filter, etc., that continuously vary an optional frequency. <P>SOLUTION: A piece of crystal for generating a resonance magnetostatic wave mode is installed between the vicinity of the maximum current point of a line of a transmission line resonator and a ground side, and a transmission line type resonance element is included, which controls the resonance frequency of the line by changing an equivalent inductance of the line due to the application of a direct current magnetic field from over the line and due to a change in a permeability that occurs before and after the resonance mode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronically tuned band-pass filter that can electronically vary a high-performance band-pass filter characteristic that can be obtained only by a fixed type.

  In a receiver that covers a wide band in the microwave region, for example, a receiver that extracts a minute signal buried in noise, a band-pass filter that removes an unintended interference input signal and passes only a signal of a target frequency is provided. Necessary for the first stage. Since the insertion loss of this tunable bandpass filter determines characteristics such as noise figure (reception sensitivity) of the entire receiver, a bandpass filter with as low a loss as possible is required.

  In an apparatus that tunes a wide frequency range, in order to prioritize this low insertion loss, a large number of distributed line type mechanical filters are arranged and electrically switched for use.

  On the other hand, in a device that requires continuous variable or high-speed variable, a YIG (yttrium iron garnet) ball filter having an insertion loss of about 5 to 10 decibels is used.

  Furthermore, for example, a radar receiver must be able to withstand not only a minute signal but also a large signal from a reflector at a relatively short distance.

  When a variable capacitance diode or the like is inserted into the open end of the λ / 4 type resonance circuit, a large voltage is applied to the diode and cross modulation due to non-linearity occurs, which is not suitable for a highly reliable device.

The following techniques can be cited as conventional techniques for bandpass filters in the microwave region.
(1) When a narrow band pass characteristic is required, a sufficiently high resonance Q is required, and therefore, for example, an interdigital band by a mechanical structure resonance (anti-resonance) transmission line having a thickness of several millimeters to several centimeters. Configure a pass filter. In order to change the tuning frequency, it is conceivable to insert a varactor diode at the open end of the anti-resonance circuit and change the tuning frequency by changing the capacitance according to the applied bias voltage.

  However, in this method, the open end where the varactor diode is inserted is also the point where the maximum resonance voltage is applied, so there are problems that must be used with attention to various problems such as distortion caused by the nonlinearity of the diode. There is.

(2) In order to variably tune a wide frequency range, a YIG tuning filter having a relatively wide band pass characteristic is used. FIG. 1 is a structural diagram of a conventional YIG tuned filter, in which a YIG single crystal is processed into a sphere of about several hundred microns and a structure in which a high-frequency magnetic field is applied to the YIG sphere by orthogonal loop coils. Furthermore, a DC bias magnetic field orthogonal to the high frequency magnetic field is applied, the YIG magnetostatic mode spin resonance frequency is proportional to the strength of the DC magnetic field, and an arbitrary frequency is passed.

  This is an excellent filter that can be controlled electronically, but it is based on a structure in which two loop coils orthogonal to a small resonance sphere are applied, and several stages are arranged in order to secure attenuation outside the passband. It is necessary to secure out-of-band attenuation. For this reason, there is a disadvantage that the insertion loss increases. Usually, it has an insertion loss of about 5 to 10 dB, and has a larger insertion loss than a high-performance transmission line type mechanical tuning fixed filter or the like. This loss of several decibels is a very big problem for high-performance receivers that have high sensitivity characteristics as the most important issue.

(3) A method is also used in which a band-pass filter of each fixed frequency is obtained by a number of mechanical structure transmission line type filters, these are arranged, this filter is switched by a switch using a PIN diode, and the tuning frequency is varied.
It is used to avoid the disadvantages of the two systems mentioned above, and it has good electrical passage and attenuation characteristics. However, (b) the system becomes very large and expensive, and (b) the switching frequency is discontinuous. There was a drawback of stepping.

  The present invention has been made in view of such points, has a low insertion loss, has a steep out-of-band attenuation characteristic and an arbitrary narrow band to wide band pass characteristic, and does not generate distortion due to a non-linear element, for example. It is an object of the present invention to provide a bandpass filter having both the characteristics of a resonance (antiresonance) transmission line type bandpass filter such as an interdigital filter structure and the characteristics of a YIG tuning type filter that can continuously vary an arbitrary frequency.

In the configuration of the present invention that meets the above-described object, a crystal piece that generates a resonant magnetostatic wave mode is installed between the vicinity of the maximum current point of the line of the distributed transmission line resonator and the ground side, and a DC magnetic field is generated from the line. It includes a transmission line type resonance element that controls the resonance frequency of the line by changing the equivalent inductance of the line by changing the magnetic permeability that occurs before and after the resonance mode when applied (Claim 1). .
The anti-resonance circuit of the transmission line resonator, in which one end is short-circuited and the other end is an open end, is a crystal that generates a resonant magnetostatic wave mode between the short-circuit end side line and the ground side because the short-circuit end is the maximum current point. A transmission line type resonance that controls the resonance frequency of the anti-resonant line by changing the equivalent inductance of the line by changing the permeability that occurs before and after the resonance mode by applying a DC magnetic field from above the short-circuited end side line by installing a piece An element is included (claim 2).

  In addition, the present invention forms a basic band-pass filter structure, for example, an interdigital band-pass filter that combines a number of anti-resonant pieces in order to obtain arbitrary pass characteristics (bandwidth, insertion loss) and attenuation characteristics. A crystal piece that generates a resonant magnetostatic wave mode is installed between each anti-resonant piece short-circuit end side line and the ground side, and a DC magnetic field is applied to the same or separately to change the equivalent electrical length of each anti-resonant piece. Including a transmission line type resonance element that variably controls the center frequency after changing the equivalent inductance of the line due to the change in permeability occurring before and after the resonance mode and obtaining the basic characteristics by the interdigital filter by this means (Claim 3).

  Further, the present invention also has an open-ended transmission line resonator (known as a name such as Coupled Resonator, Hairpin type, Edge Coupled type, etc.), and the vicinity of the line center is the maximum current point. By installing a crystal piece that generates a magnetostatic wave mode between the vicinity of the line center and the ground side, and applying a DC magnetic field from the short-circuited end side line, the equivalent inductance of the line is changed by the change in permeability that occurs before and after the resonance mode. And a transmission line type resonance element that controls the resonance frequency of the resonance line.

  The vicinity of the line center of the short-circuit end side line or the resonator is near the current maximum point, and the DC magnetic field is applied perpendicular to the high-frequency magnetic field applied to the crystal piece that generates the magnetostatic wave mode.

In order to apply a DC magnetic field perpendicular to the high-frequency magnetic field, it is preferable to dispose an electromagnet having an excitation coil wound around a magnetic core between the resonance or anti-resonance line and the crystal piece.
The DC magnetic field is preferably applied at a point where the high frequency magnetic permeability of the magnetic disk can be greatly changed by a slight change in the DC bias magnetic field.

It is preferable to use a YIG disk as the crystal piece for generating the resonant magnetostatic wave mode used in the present invention. Further, as the crystal piece that generates the resonant magnetostatic wave mode, it is preferable to use a single crystal piece instead of a polycrystal in order to minimize the loss term.
The magnetostatic mode crystal piece-loaded transmission line type resonance element according to claim 1 may be a tunable frequency band elimination filter (claim 10), a single electronic variable resonance circuit (claim 11), or a frequency determination element. (Claim 12).

  The magnetostatic mode crystal piece-loaded transmission line type resonance element according to claim 1 can be used as a resonance element of a variable frequency oscillator in combination with an oscillation circuit (claim 13).

  As described above, according to the present invention, while maintaining the characteristics of “low loss”, “narrow band”, “arbitrary design band”, and “out-of-band high attenuation” that can only be obtained with a fixed frequency type, A band-pass filter with a continuously variable tuning frequency function that a variable tuning filter using a variable tuning filter or a varactor diode in combination can be configured, so it is possible to select a received signal with high sensitivity while eliminating interference it can. As a result, it becomes an important element for constructing a highly reliable high sensitivity receiving system. In particular, it is useful for improving the performance of radar receivers in various radio wave monitoring systems, aircraft and airports.

It is structural drawing (sectional drawing) of the YIG tuning filter of a prior art. FIG. 6 is a diagram showing a permeability change near a resonance (magnetostatic wave) mode. It is explanatory drawing which shows the anti-resonance line and variable inductance mechanism of this invention. It is a figure which shows an example of the conventional fixed frequency interdigital type band pass filter. It is a figure which shows the variable inductance location installation type interdigital bandpass filter of this invention. It is a figure which shows the Example of the resonator of open both ends of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings.

  The electrical characteristics and structure of the band-pass filter of the present invention are based on a resonant (or anti-resonant) transmission line type band-pass filter.

  As means for effectively varying the transmission line length, a crystalline magnetic disk that generates a magnetostatic mode is inserted between the conductor near the transmission line current maximum point and the ground plane.

  A high-frequency magnetic field due to a high-frequency current flowing in the line is applied to the disk from the lateral direction. In order to apply a DC magnetic field perpendicular to the high-frequency magnetic field, an electromagnet having an exciting coil wound around a magnetic core such as a permalloy is installed in the vertical direction of the resonance or anti-resonance line and the disk.

  When the DC magnetic field is increased, the electron spin frequency due to the crystal structure in the disk such as a YIG single crystal increases, and reaches the region where the magnetostatic mode is generated. In the system of the present invention, a DC magnetic field (bias) near the magnetostatic mode frequency point is applied at a frequency point slightly lower than the resonance frequency point of the microwave transmission line type resonance circuit. This point is a point where the high frequency magnetic permeability of the magnetic disk can be greatly changed by a slight change in the DC bias magnetic field.

  That is, the behavior is equivalent to inserting an inductance into a transmission line resonance (anti-resonance) circuit when no disk is mounted, and the frequency can be controlled by arbitrarily varying the insertion inductance from a DC bias magnetic field.

  If this structure is arranged in an interdigital type to produce an interdigital variable frequency bandpass filter, a low-loss bandpass filter with an arbitrary pass width possessed by a general interdigital filter can be made to be a variable tuning type.

  FIG. 2 shows a change in permeability according to the resonance (magnetostatic wave) mode. A single crystal piece that generates a magnetostatic mode is inserted between the anti-resonant line (cut to λ / 4) and the ground plane. The single crystal piece may be attached to the anti-resonant line or may be disposed between the anti-resonant line and the ground plane. As shown in FIG. 2, the anti-resonant line has an open end at the right end and a short-circuited end at the left end.

  As shown in FIG. 2, when a direct-current magnetic field is applied in the vertical direction and the strength of the direct-current magnetic field is increased, an inductance variable region (resonance mode) in which the magnetic permeability greatly changes is reached as shown in FIG. A high frequency magnetic field is generated in a lateral direction perpendicular to the direction in which the DC magnetic field is applied.

  The frequency of the anti-resonant line can be controlled by changing the inductance in the inductance variable range.

  FIG. 3 shows an example of a conventional fixed-frequency interdigital bandpass filter, which is a bandpass filter that arranges λ / 4 lines in an interdigital manner and passes a resonance frequency. This is a fixed type in which the frequency cannot be varied as in the present invention.

  FIG. 5 shows an interdigital bandpass filter with a variable inductance location according to the present invention. The open ends and short-circuit ends of a number of anti-resonant pieces are arranged alternately (in reverse), that is, in an interdigital manner. A single crystal piece that generates a magnetostatic mode is inserted at the short-circuited end, and a vertical magnetic field is applied to each anti-resonant piece. Unlike the conventional product of FIG. 4, the inductance can be made variable. .

  FIG. 6 shows an embodiment of an open-ended resonator according to the present invention, which is a 1/2 wavelength transmission line type resonator. An example in which a stripline transmission line is formed by an upper conductor and a ground plane will be described. A single crystal piece such as YIG is inserted at the center current maximum point to change the equivalent inductance.

  In the apparatus of the present invention, the crystal piece that generates the magnetostatic wave mode has a uniform electrical characteristic in its area, so its size (volume) can be freely selected according to the power value handled by the system and the metal electrode Since it can be attached directly, it can be easily dissipated, so it can be applied to high power circuits. In addition, since the tuning characteristic is a substance that performs a linear operation that is directly proportional to the strength of the applied magnetic field, distortion due to non-linearity is extremely small.

(Static magnetoresonance element)
Ferrimagnetic material (ferrite) is a magnetic material used in high frequency and microwave bands. Generally speaking, ferrite is a polycrystalline body, which is used for magnets, circulators, absorbers and the like.

  As the ferrite in the present invention, a single crystal having a uniform crystal lattice is used. As a result, since the internal electron spins rotate together, the loss is extremely reduced, and an electrical constant such as an equivalent dielectric constant and a sharp resonance phenomenon can be obtained.

As shown in FIG. 2, when the external bias magnetic field is increased, a resonance mode is generated. A region in the vicinity of this is a region called a magnetostatic mode, and a region in which the magnetic permeability immediately before the resonance phenomenon changes greatly is used.
The most representative material that generates magnetostatic mode is YIG (yttrium, iron, garnet) single crystal, which has little loss in the microwave band and can exhibit a sharp resonance phenomenon. Material.
In addition to YIG, there are the following substances (ferrites) that exhibit the same phenomenon, and in the present invention, they can be used in the same manner as YIG.
InYIG, GaYIG, BiCaInVIG, NiZn, LiZn, CuZn, MnMgAl

As described above, according to the present invention, while maintaining the characteristics of “low loss”, “narrow band”, “arbitrary design band”, and “out-of-band high attenuation” that can only be obtained with a fixed frequency type, A band-pass filter with a continuously variable tuning frequency function that the variable tuning filter using tunable filters and varactor diodes together has a function of continuously variable tuning frequency can be configured, so that received signals can be selected with high sensitivity while eliminating interfering waves. Therefore, it becomes an important element for constructing a highly reliable high sensitivity receiving system. In particular, it is useful for improving the performance of radar receivers in various radio wave monitoring systems, aircraft, airports, and the like.

Claims (13)

Permeability that occurs before and after the resonance mode by installing a crystal fragment that generates a resonant magnetostatic wave mode between the vicinity of the maximum current point of the transmission line resonator line and the ground side, and applying a DC magnetic field from the line. An electronic tuning bandpass filter comprising a transmission line type resonance element that changes the equivalent inductance of the line by controlling the change of the line and controls the resonance frequency of the line. By installing a crystal piece that generates a resonant magnetostatic wave mode between the short-circuited end-side line and the ground side of the transmission line resonator whose one end is short-circuited, and by applying a DC magnetic field from the short-circuited-end side line, before and after the resonance mode An electronic tuning bandpass filter comprising a transmission line type resonance element that changes the equivalent inductance of a line and controls the resonance frequency of the line by changing the magnetic permeability that occurs. In order to obtain arbitrary pass characteristics (bandwidth, insertion loss) and attenuation characteristics, a basic bandpass filter structure is formed with an interdigital type bandpass filter combined with a number of antiresonant pieces, and each antiresonance is formed. A crystal piece that generates a resonant magnetostatic wave mode is installed between the short-circuited end-side line and the ground side, and a DC magnetic field is applied to the same or individually to vary the equivalent electrical length of each anti-resonant piece before and after the resonance mode. An electronic device characterized by including a transmission line type resonance element that variably controls the center frequency after changing the equivalent inductance of the line due to the change in permeability and obtaining the basic characteristics by the interdigital filter by this means Tuning bandpass filter. Permeability that occurs before and after the resonance mode by installing a crystal fragment that generates a magnetostatic wave mode between the center of the open-ended transmission line resonator and the ground side and applying a DC magnetic field from the short-circuited end-side line. An electronic tuning band-pass filter comprising a transmission line type resonance element that changes the equivalent inductance of the line by controlling the change of the line to control the resonance frequency of the line.   The band-pass filter according to any one of claims 1 to 4, wherein the DC magnetic field is applied perpendicular to a high-frequency magnetic field applied to a crystal piece that generates the magnetostatic wave mode.   6. The bandpass filter according to claim 5, wherein an electromagnet having an excitation coil wound around a magnetic core is disposed between the resonance or antiresonance line and the crystal piece in order to apply a direct current magnetic field to the high frequency magnetic field at a right angle.   The band pass filter according to any one of claims 1 to 6, wherein the DC magnetic field is applied at a point where the high frequency permeability of the magnetic disk can be greatly changed by a slight change in the DC bias magnetic field.   The band-pass filter according to any one of claims 1 to 7, wherein the crystal piece that generates the resonant magnetostatic wave mode is a YIG sphere. The band-pass filter according to claim 1, wherein the crystal piece that generates the resonant magnetostatic wave mode is a single crystal piece. Permeability that occurs before and after the resonance mode by installing a crystal fragment that generates a resonant magnetostatic wave mode between the vicinity of the maximum current point of the transmission line resonator line and the ground side, and applying a DC magnetic field from the line. A variable tuning frequency band eliminate filter comprising a transmission line type resonance element that changes the equivalent inductance of the line by controlling the change of the line and controls the resonance frequency of the line. Permeability that occurs before and after the resonance mode by installing a crystal fragment that generates a resonant magnetostatic wave mode between the vicinity of the maximum current point of the transmission line resonator line and the ground side, and applying a DC magnetic field from the line. An electronic variable resonance circuit comprising a transmission line type resonance element that changes the equivalent inductance of the line by controlling the change of the line and controls the resonance frequency of the line. Permeability that occurs before and after the resonance mode by installing a crystal fragment that generates a resonant magnetostatic wave mode between the vicinity of the maximum current point of the transmission line resonator line and the ground side, and applying a DC magnetic field from the line. A frequency determining element comprising a transmission line type resonance element that changes the equivalent inductance of the line by controlling the change of the line and controls the resonance frequency of the line. Permeability that occurs before and after the resonance mode by installing a crystal piece that generates a resonance magnetostatic wave mode between the vicinity of the maximum current point of the transmission line resonator line and the ground side, and applying a DC magnetic field from the line. A resonance element of a variable frequency oscillator characterized by combining an oscillation circuit with a transmission line type resonance element that changes the equivalent inductance of the line by controlling the change of the line and controls the resonance frequency of the line.

Images