JP2012049941A - Filter, waveguide joint using the same, radar device, and magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron and a radar device of a smaller size which comprises a filter for removing spurious radiation.SOLUTION: A filer comprises: a columnar inner conductor 1 of conductivity; an external conductor 2 of conductivity to cover the whole circumference. The inner conductor 1 has a gap part 3 formed substantially in parallel to the center axis of the column over a prescribed length. The length of the gap part 3 is substantially a quarter of the wavelength corresponding to the frequency of the main vibration mode of the radio wave when used as a passing bandpass filter. When used to remove an unwanted component such as spurious radiation, the length of the gap part 3 is substantially a quarter of the wavelength corresponding to the frequency of the component. The filter is positioned to coincide with the center axis of a cathod of a magnetron, which is made of a cathode on the center axis and an anode in which anode vanes are arranged on the circumference. A radar device has a configuration in which the filter is positioned inside a waveguide to waveguide the radio wave between the magnetron and the antenna.

Description

  The present invention relates to a filter, a waveguide joint using the filter, a radar device, and a magnetron.

  Magnetrons that oscillate microwaves are widely used in home appliances such as radar devices and microwave ovens that are applied to ships and aircraft. In recent years, restrictions on spurious radiation emitted at frequencies other than a predetermined center frequency (wavelength) have been strengthened for devices that emit microwaves, for the purpose of preventing interference and noise generation.

  The magnetron oscillates in a mode called a normal mode as a main oscillation mode. However, the magnetron has a resonance mode that oscillates at a different frequency in addition to this mode.

  For example, in a vane strap type magnetron, the largest spurious component emitted by the magnetron is unnecessary radiation of a component called (? -1) mode. This (? -1) mode unnecessary radiation is caused by the resonance circuit of the magnetron, and has a frequency about 1.1 times the oscillation frequency of the? Mode. For example, in a vane strap type magnetron in which the? Mode oscillates in the 9.4 ??? band, the? -1 mode is in the vicinity of 10.5 ??? and has a higher frequency band than the?

  The ratio of the power level of the (π-1) mode unwanted radiation to the π mode is about −30 dBc to −50 dBc. However, when the microwave is radiated in the radar device, the spurious component becomes an interference or noise source, and thus it is necessary to remove unnecessary radiation. Therefore, in order to suppress spurious radiation, a filter in which the frequency of the π mode is a pass band and the frequency of the π-1 mode is a stop band is used.

  As shown in FIG. 29, the magnetron disclosed in Patent Document 1 includes a filter having a frequency characteristic that allows the main oscillation mode (π mode) of the magnetron to pass and blocks the frequency of the π-1 mode. In particular, the magnetron described in Patent Document 1 has a structure in which a magnetron and the above filter are directly coupled by a transmission line, and the resonance frequency of a circuit system composed of the magnetron, the transmission line, and the filter substantially matches the π-1 mode. Thus, the length of the transmission line is set. In addition, a resonance frequency adjusting mechanism is installed on the transmission line, or an adjusting mechanism for adjusting the transmission output is installed on the transmission line on the load side of the filter.

  For example, a configuration disclosed in Patent Document 2 is known as a small filter for removing a spurious component of a microwave. This is composed of a coaxial line having a center conductor portion in which a large diameter portion and a small diameter portion having a predetermined length are alternately combined as shown in FIG.

JP 2003-331746 A JP-A-7-235803

  However, although the magnetrons disclosed in the above-mentioned patent documents can remove spurious radiation to some extent, it is necessary to dispose a large filter to some extent apart from the magnetron.

  For example, in Patent Document 1, as shown in FIG. 26, a radio wave emitted from a magnetron 1 is once guided through a waveguide 2 serving as a transmission line, and a spurious component frequency band placed in the middle of the transmission line is blocked. The spurious radiation is removed by the filter 3 that performs the above operation. Therefore, the whole magnetron including the filter naturally becomes large. In addition, the power level is lowered due to the fact that the radio wave emitted from the magnetron is guided over a long distance.

  As shown in FIG. 29, the coaxial filter disclosed in Patent Document 2 requires both a large diameter portion and a small diameter portion to be about a quarter of the wavelength λ (lambda) of radio waves. Since it is necessary to arrange several stages in series, there is a problem that the size cannot be reduced.

  The present invention relates to a filter that transmits or blocks radio waves of a specific wavelength, and a waveguide joint, magnetron, and radar device using the filter. In particular, an object of the present invention is to provide a filter that can reduce the size of a device such as a magnetron, and a waveguide joint, a magnetron, and a radar device that can reduce the size and decrease the power level of radio waves. And

  The filter of the present invention includes a columnar inner conductor having conductivity, a conductive outer conductor having a hollow portion in which at least a part of the inner conductor is disposed, and a radio wave input from one end of the inner conductor. And the inner conductor includes an electromagnetic field coupling unit that generates electromagnetic field coupling with the radio wave in the traveling direction of the radio wave.

  The radio wave includes a main oscillation mode, and the electromagnetic field coupling portion has a length in the central axis direction of the inner conductor that is approximately a quarter of the wavelength of the main oscillation mode. Alternatively, in the electromagnetic field coupling portion, the length of the inner conductor in the central axis direction is approximately a quarter of the wavelength other than the wavelength of the main oscillation mode.

  In the filter of the present invention, as the electric field coupling portion, a gap portion is formed in the inner conductor substantially parallel to the central axis.

  In addition, a radio wave input unit for inputting radio waves is provided, and the gap portion has a length of about one quarter of the wavelength corresponding to the frequency of the main oscillation mode of the radio waves in the central axis direction of the inner conductor. . Alternatively, the gap portion is approximately a quarter of the wavelength of the radiated radio wave having a power level that is different from the frequency of the main oscillation mode in the central axis direction and that is smaller than the power level in the main oscillation mode and greater than a predetermined value. The length of 1 is.

  The inner conductor may be a columnar shape or a hollow body having a hollow portion. Further, the gap portion includes a first gap cut in one direction with respect to the inner conductor and a second gap located substantially opposite to the first gap portion with respect to the central axis. You may comprise.

  Further, the filter may include a plurality of gaps formed in series along the central axis. Further, the gap portion may be formed so as not to be substantially parallel but to be inclined outward from the central axis.

  The filter of the present invention includes an inner conductor having conductivity and a conductive outer conductor covering the entire circumference of the inner conductor, and is electrically connected to the inner conductor between the inner conductor and the outer conductor. A resonance part having a parallel part substantially parallel to the inner conductor is provided over the length. The width of the parallel portion increases in a direction perpendicular to the inner conductor from one end electrically connected to the inner conductor toward the tip.

  The waveguide joint of the present invention includes a coaxial line having a conductive columnar inner conductor, and a conductive outer conductor having a hollow portion and at least a part of the inner conductor disposed in the hollow portion, A wave guide having a radio wave incident part on which a radio wave including a main oscillation mode is incident and a waveguide part for guiding the radio wave are provided. The inner conductor has a gap formed in the waveguide substantially parallel to the central axis over a predetermined length.

  The predetermined length is approximately a quarter of the wavelength of the radiation wave having a frequency different from the frequency of the main oscillation mode. This radiated radio wave has a power level that is smaller than the power level in the main oscillation mode and greater than a predetermined value. The waveguide joint is used for the waveguide so that it can cope with the rotation of the antenna when the radio wave (microwave) generated by the radio wave generator in the radar device is guided to the antenna through the waveguide. You may make it provide the rotation mechanism which makes a coaxial track | truck rotatable.

  The radar apparatus of the present invention includes a radio wave generator that generates a radio wave including a main oscillation mode having a predetermined frequency, an antenna that emits the radio wave, and the waveguide joint. In this waveguide joint, the radio wave generated by the radio wave generator is incident from the radio wave incident part, and the radio wave is guided to the antenna through the waveguide part and the coaxial line.

  The radar device of the present invention includes a radio wave generator that generates a radio wave including a main oscillation mode, an antenna that emits the radio wave, a receiving unit that receives an echo signal from the radio wave, the rotary joint, and the radio wave generator. A circulator is provided that guides the generated radio wave to the radio wave incident part and guides the echo signal to the reception part. In this waveguide joint, a radio wave is incident from a radio wave incident part, and the radio wave is guided to an antenna via a waveguide part and a coaxial line.

  The magnetron of the present invention includes an anode having a plurality of anode vanes each having an inner end arranged on the circumference, and a cylindrical cathode whose central axis substantially coincides with the center of the circumference. And a radio wave generator for generating radio waves and the inner conductor central axis so as to coincide with the central axis. Here, the predetermined length is approximately a quarter of the wavelength corresponding to the frequency of the main oscillation mode.

  The radar apparatus of the present invention includes the radio wave generator, an antenna that emits radio waves oscillated by the radio wave generator, and a receiving unit that receives an echo signal from the emitted radio waves.

  By applying the filter of the present invention, it is possible to reduce the size of a device that passes or blocks radio waves having a predetermined frequency. Further, according to the radio wave generator and the radar device of the present invention, spurious radiation can be reduced, and the radio wave generator and the radar device can be downsized.

  A typical example of the radio wave generator is a magnetron, but the filter of the present invention can be applied without being restricted by the principle of radio wave generation.

It is a perspective view which shows the basic structure (1st Embodiment) inside the filter of this invention. It is a longitudinal cross-sectional view of 1st Embodiment. It is a figure which shows the equivalent circuit of 1st Embodiment. It is a figure which shows the relationship (passage / stopping frequency characteristic) of the length of an electromagnetic field coupling | bond part, and passage loss. It is a perspective view which shows the internal structure of 2nd Embodiment of the filter of this invention. It is a longitudinal cross-sectional view of 2nd Embodiment. It is a figure which shows the equivalent circuit of 2nd Embodiment. It is a perspective view which shows the internal structure of 3rd Embodiment of the filter of this invention. It is a longitudinal cross-sectional view of 3rd Embodiment. It is a figure which shows the equivalent circuit of 3rd Embodiment. It is a perspective view which shows the internal structure of 4th Embodiment of the filter of this invention. It is a longitudinal cross-sectional view of 4th Embodiment. It is a figure which shows the equivalent circuit of 4th Embodiment. It is a perspective view which shows the internal structure of 5th Embodiment of the filter of this invention. It is a longitudinal cross-sectional view of 5th Embodiment. It is a perspective view which shows the internal structure of 6th Embodiment of the filter of this invention. It is a longitudinal cross-sectional view of 6th Embodiment. It is a perspective view which shows the internal structure of 7th Embodiment of the filter of this invention. It is a longitudinal cross-sectional view of 7th Embodiment. It is a longitudinal cross-sectional view of 1st Embodiment of the waveguide joint (rotary joint) of this invention. It is a longitudinal cross-sectional view of 2nd Embodiment of the waveguide joint (rotary joint) of this invention. It is a figure which shows the structure of the radar apparatus of this invention. It is a longitudinal cross-sectional view which shows the structure of the magnetron of this invention. It is a figure which shows the frequency characteristic of 1st Embodiment. It is a figure which shows the frequency characteristic of 3rd Embodiment. It is a figure which shows the frequency characteristic of 4th Embodiment. It is a figure which shows the frequency characteristic of 7th Embodiment. It is a characteristic view which respectively shows the frequency characteristic of the microwave input into the waveguide of the waveguide joint (rotary joint) of this invention, and the microwave output from a coaxial line. It is a figure which shows the conventional filter disclosed by patent document 1. FIG. It is a figure which shows the conventional filter disclosed by patent document 2. FIG.

  Hereinafter, embodiments for carrying out the filter of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an internal structure of a filter according to a first embodiment of the present invention, and FIG. 2 is a longitudinal sectional view thereof.

  As shown in FIGS. 1 and 2, the filter of the present invention is constituted by a columnar inner conductor 1 and an outer conductor 2 covering the outer periphery thereof. Both are made of a conductive material. The space between the inner conductor 1 and the outer conductor 2 may be completely hollow, or some insulating material may be interposed in a part and the remaining part may be a gap. Further, an insulating material may be interposed in the entire area including the vicinity of the gap portion serving as a filter.

  Here, the inner conductor 1 is solid and has a gap portion 3 formed in parallel or substantially parallel to the central axis. By forming this gap portion, the inner conductor 1 is formed with the central conductor 4 of the inner conductor 1 and the protruding conductor portion 5 parallel to the central axis of the inner conductor 1.

  Hereinafter, embodiments of the present invention and embodiments will be described using microwaves widely used as examples such as magnetrons used in home appliances such as microwave ovens, radio wave generators used in ships and other radar devices. . In principle, it can be applied to millimeter waves and the like regardless of the frequency of radio waves. Further, in the following description of the embodiment of the present invention, a typical magnetron will be described as an example of a radio wave generator. However, the filter of the present invention can be applied to those that generate radio waves such as microwaves by other principles. can do.

  When a microwave is incident from one end of the filter having the above-described configuration shown in FIG. 1, the microwave travels inside the outer conductor 2. At this time, since the central conductor 4 and the protruding conductor part 5 are arranged substantially parallel to the traveling direction by the notch in the gap part 3, electromagnetic coupling is generated with respect to microwaves of a specific frequency. Works. And it works so as to prevent the subsequent progression to the microwave of the frequency at which this coupling occurs. By utilizing this principle, a microwave having a specific frequency can be selectively blocked.

  It is possible to control the electromagnetic field coupling by adjusting the shapes and relationships of the central conductor 4 and the protruding conductor portion 5 formed by the gap portion 3, and to set the frequency characteristics as desired. The stop band can be set to be wide except for a specific frequency to provide a band pass filter. In principle, if the length of the electromagnetic field coupling, that is, the length of the gap 3 in the central axis direction is about one-fourth of the wavelength of the radio wave in the main oscillation mode, ideally a micro of the frequency Wave progression can be prevented.

  FIG. 3 shows an equivalent circuit of the shape of the first embodiment of the present invention shown in FIG. The open-ended parallel line in the figure corresponds to the protruding conductor portion 5. FIG. 4 shows the frequency characteristics of the microwave due to the electromagnetic field coupling effect of the metal foil formed on two flat plates arranged in parallel to each other. In FIG. 4, the horizontal axis represents the length of the central conductor of the protruding conductor 5 in electrical length, and the vertical axis represents the result of calculating the reflection coefficient. The mode of electromagnetic coupling comprised by the center conductor 4 and the protruding conductor part 5 in FIG. 2 is represented.

  As can be seen from FIG. 4, the reflection coefficient is maximized at a quarter wavelength of electrical length. Therefore, by setting the length of the electromagnetic field coupling part to one quarter of the specific wavelength of the microwave, it is possible to prevent the microwave having the wavelength, that is, the frequency corresponding to the wavelength from passing. For example, among the microwaves generated by the magnetron, the frequency of the main oscillation mode is allowed to pass and spurious components that are unwanted radiation are blocked. For this purpose, the length of the electromagnetic field coupling portion may be set to a length of one quarter of the wavelength corresponding to the frequency. In the configuration shown in FIG. 3, the length of the protruding conductor portion 5 formed by the gap portion 3 may be set to a quarter of the wavelength of the radio wave.

  The gap portion 3 may be provided with a recess in a part of the side surface of the inner conductor 1 in advance, and a portion to be an electromagnetic field coupling portion may be inserted through an insulator (not shown). You may form by the notch | incision as demonstrated in the form of this. This cutting requires a fine processing technique. For example, by using wire cut electric discharge machining or the like, it is possible to accurately form the gap interval, position, and the like.

As described above, taking the first embodiment as an example, the filter according to the present invention includes a columnar inner conductor 1 having conductivity and a conductive outer space that is hollow and has the inner conductor 1 disposed therein. It has a feature in that it has a conductor 2 and is provided with an electromagnetic field coupling portion for generating electromagnetic wave and electromagnetic field coupling in the traveling direction of the radio wave in the inner conductor 1. By arranging the electromagnetic field coupling portion inside the outer conductor 2, the size can be greatly reduced as compared with the conventional case. Further, physical coupling with a magnetron or the like can be easily performed.

  Subsequently, other modified examples (second to seventh embodiments) of the filter of the present invention will be described with reference to the drawings.

First, a second embodiment of the filter of the present invention will be described. FIG. 5 is a diagram showing the internal structure of the second embodiment of the filter of the present invention, and FIG. 6 is a longitudinal sectional view thereof.

  Whereas the inner conductor of the filter of the first embodiment has a columnar shape with no space inside, the filter of the second embodiment has a cylindrical shape in which the inner conductor 1 has a hollow portion 8 inside. (Tubular). The inner conductor 1 has a hollow portion 8, and two projecting conductors 5 facing each other are formed by the gap portions 3 formed on both sides of the side surface of the inner conductor 1. A filter having a wide frequency band characteristic is realized by coupling to.

  In the second embodiment, for example, when a gap is formed by making a cut from the side surface of the inner conductor 1, it is preferable to make the cut so deep that the cut is applied to the hollow portion 8 of the inner conductor 1. This is because electromagnetic field coupling is generated between the protruding conductor formed by cutting and the opposite side surface portion of the tubular inner conductor 1 across the hollow portion 8.

  As shown in FIGS. 5 and 6, the inner conductor 1 may have a cylindrical shape having a hollow portion up to the end surface, or may have a hollow portion only in the region where the gap portion 3 is formed and in the vicinity thereof. The region may be columnar.

  FIG. 7 shows an equivalent circuit of the second embodiment shown in FIGS. FIG. 7 shows an equivalent circuit of two projecting conductors connected in parallel. The parallel lines are electromagnetically coupled, which corresponds to the electromagnetic field coupling amount of the protruding conductors 5 and 6 in FIG. In this case, the change in impedance can be increased as compared with the case where the electromagnetic field coupling is not performed. As a result, the reflection characteristic can be broadened, and a stable characteristic can be obtained against disturbance of the electromagnetic field due to disturbance.

  FIG. 8 is a diagram showing the internal structure of the third embodiment of the filter of the present invention, and FIG. 9 is a longitudinal sectional view thereof.

  Similar to the first embodiment, the third embodiment includes a gap 3 formed in the columnar inner conductor 1 by cutting from the side surface. In the present embodiment, this gap portion 3 (cut) is on both opposing side surfaces, and is provided with protruding conductor portions 5 on both sides with respect to the central axis. The direction of the cut is different from each other.

  FIG. 10 shows an equivalent circuit of the third embodiment. The two open end parallel lines represent the protruding conductors 5 formed by cutting from different directions in the axial direction. The line directly connecting the terminals 1 and 2 corresponds to the central conductor 4 portion. In the equivalent circuit of FIG. 10, a wide band frequency characteristic can be realized by setting the length of the line connecting the terminals 1 and 2 to a quarter wavelength line, and as a result, a stable characteristic can be obtained. In addition, the equivalent circuit has a configuration in which three quarter-wave lines are combined, but by combining the protruding conductors 5, a very small band-stop filter with a total length of approximately one-quarter wavelength is obtained. Can be realized.

  FIG. 11 is a diagram showing the internal structure of the fourth embodiment of the filter of the present invention, and FIG. 12 is a longitudinal sectional view thereof. Similarly to the third embodiment, the fourth embodiment also includes two electromagnetic field coupling portions constituted by the gap portions 3 formed by cutting from both sides. Since the inner conductor 1 is hollow in the present embodiment, unlike the third embodiment, the central conductor 4 of the inner conductor 1 has only a side surface portion, and electromagnetic field coupling occurs between the two protruding conductor portions 5. The two protruding conductor portions 5 are separated from each other and have no central conductor.

  FIG. 13 shows an equivalent circuit in which the two open-ended parallel lines in FIG. 10 are electromagnetically coupled. Thereby, similarly to the relationship in the equivalent circuit shown in FIGS. 3 and 7, the impedance of the parallel stub can be lowered, and further broadening of the band and stabilization of characteristics can be expected.

  FIG. 14 is a diagram showing an internal structure of a fifth embodiment of the filter of the present invention, and FIG. 15 is a longitudinal sectional view thereof. The filter according to the third embodiment has two gaps opposed to the central axis in the central axis direction, whereas the fifth embodiment includes two stages. Therefore, by using the same configuration for the electromagnetic field coupling unit, electromagnetic field coupling can be generated in a superimposed manner to improve the characteristics.

  For example, when the filter of the present invention is used as a blocking filter, the blocking characteristic can be improved by further reducing the power level at a predetermined frequency. Note that the configuration in which the electromagnetic field coupling portions are arranged in series in multiple stages is not limited to the configuration in which the inner conductor 1 is dense as shown in the fifth embodiment, but the second, fourth, and sixth described later. The present invention can also be applied to a configuration in which the conductor 1 is hollow.

  FIG. 16 is a diagram showing an internal structure of a sixth embodiment of the filter of the present invention, and FIG. 17 is a longitudinal sectional view thereof. In the sixth embodiment, the cut is inclined with respect to the central axis of the inner conductor 1. In the example shown in FIG. 16, the cut forming the gap 3 is formed away from the central axis of the inner conductor 1 from the cut opening toward the tip. Thereby, the shape of the protruding conductor portion 5 is formed so as to spread from the base toward the tip (a position opposite to the tip of the cut).

  The width of the protruding conductor portion 5 is electrically related to the impedance. The wider the line width, the lower the impedance, and the narrower the line width, the higher the impedance. In the structure in which the protruding conductors are connected in parallel, the frequency band is widened by lowering the impedance, and conversely, the band is narrowed by raising the impedance.

  For this reason, the impedance of the protruding conductor portion 5 is lowered by widening the protruding conductor portion 5 as it goes to such a tip, and a broadband characteristic can be obtained. Conversely, by making the cut closer to the central axis from the cut opening toward the tip, the shape of the protruding conductor portion 5 can be narrowed from the root toward the tip. In this case, although the characteristics are narrow, it is effective in applications where it is desired to pass nearby frequencies.

  FIG. 18 is a view showing the internal structure of the seventh embodiment of the filter of the present invention, and FIG. 19 is a longitudinal sectional view thereof. While the first to sixth embodiments of the present invention have an electromagnetic field coupling portion formed therein by, for example, making a cut in the inner conductor 1, the inner conductor 1 is formed in the seventh embodiment. An electromagnetic field coupling portion is formed outside the side surface of the. Specifically, a protrusion 11 is provided on the side surface of the inner conductor 1, and the conductive film (for example, a metal) Foil) 12 is formed. The electromagnetic coupling is generated between the conductive thin film 12 formed on the surface of the protrusion 11 and the inner conductor 1. Similar characteristics can be obtained even with such a configuration.

  As described above, according to the filter of the present invention, it is possible to provide an electromagnetic field coupling portion by processing the inner conductor itself and set the pass / stop band of the microwave passing therethrough. By using this as a filter, a small filter can be realized. For example, this filter can be easily integrated as a coaxial filter into a device such as a magnetron or a microwave waveguide. More specifically, an electromagnetic field coupling portion (a portion exhibiting a filter function) provided on the inner conductor may be extended from the outer conductor 2 and disposed inside the waveguide itself. Alternatively, it may be physically integrated with the magnetron cathode.

  Next, a configuration in which the filter of the present invention is applied to a waveguide joint, a magnetron, and a radar device will be described.

  A filter may be placed to selectively pass or block radio waves of a specific frequency through radio wave generators such as magnetrons or rotary joints equipped with a rotation mechanism to guide radio waves to radar antennas. is there. Even in such a case, the filter of the present invention can be rotated between the waveguide and the coaxial line 13 by a rotation mechanism so that the electromagnetic field coupling portion of the inner conductor 1 is disposed inside the waveguide. Thus, the whole can be reduced in size.

  FIG. 20 is a longitudinal sectional view of the first embodiment of the waveguide joint (rotary joint) of the present invention. The waveguide joint shown here can be used, for example, in a radar device, as will be described later. In a radar device, a radio wave generated by a radio wave generator (magnetron: not shown) is guided to an antenna (not shown) via a waveguide, and the radio wave is emitted from the antenna in a predetermined direction. The echo signal is received by the antenna to detect the distance and direction of the target.

  In FIG. 20, a radio wave generated by a magnetron (not shown) enters from a radio wave input part (not shown) of the left waveguide in the same figure, propagates through the waveguide, and is guided to the coaxial line. . The radio wave further propagates through the coaxial line 13 and is guided to the antenna 28 via the waveguide joint (rotary joint) 27.

  Here, in the waveguide joint 27 of the present invention, the coaxial line includes an inner conductor and an outer conductor covering the inner conductor, like the filter of the present invention already described. The inner conductor 14 extends beyond the side wall of the waveguide 16 to the inside. A band rejection filter portion 18 having the same configuration as that of the filter according to the first embodiment of the present invention shown in FIG. 1 is provided at the distal end portion of the inner conductor 14 inside the waveguide 16.

  In order to remove unnecessary radiated radio waves from the radio waves generated by the magnetron, the band rejection filter unit 18 has a length in the central axis direction (length in the vertical direction in the figure) of the gap portion constituting the filter unit. The length is almost the same as the wavelength corresponding to the frequency twice as high as f0.

  FIG. 21 is a longitudinal sectional view of a second embodiment of the waveguide joint (rotary joint) of the present invention. The present embodiment is different from the configuration of the first embodiment in that a band stop filter section 18 employs a filter in which gap portions are arranged in two stages in series along the central axis.

  The length in the central axis direction of each gap portion of the band rejection filter portion 18 is substantially the same as the wavelength corresponding to the frequency twice the oscillation frequency f0, as in the first embodiment. In this embodiment, the reflection characteristics can be improved by the amount of filters arranged in series.

  In both of the embodiments of the waveguide joint of the present invention shown in FIG. 20 and FIG. 21, the electromagnetic field coupling portion is formed by a gap portion formed in a dense inner conductor having no hollow portion. However, it may be a filter made of a hollow inner conductor such as the second embodiment of the filter of the present invention, or may be constituted by a protruding conductor provided on the side surface of the inner conductor. Further, the inner conductor 14 having the filter function may extend the inner conductor 14 of the coaxial line 13 as it is. Further, the filter portion may be configured as a separate part and conductively connected.

  According to the waveguide joint of the present invention, when the radio wave propagated through the waveguide is propagated to the coaxial line 13, the filter unit 18 of the inner conductor 14 selectively allows radio waves having a predetermined frequency to pass / block. Can do. When applied to a radar device or the like, it is required to remove unnecessary radiated radio waves (spurious components) of frequencies other than the frequency of the main oscillation mode as much as possible. Therefore, the length of the gap portion or the parallel portion is set to approximately a quarter of the wavelength of the radio wave constituting the spurious component so that the filter portion functions as a filter that blocks the frequency band of the spurious component. That's fine.

  By the way, in a radar device applied to a ship or the like, target detection is performed in all 360 degrees. In order to cope with this, it is also possible to provide a rotation mechanism 19 at the joint between the waveguide 14 and the coaxial line 13 so that the rotation can be made. Even in this case, the filter portion 18 of the inner conductor 14 can be rotated inside the waveguide 16, and there is no hindrance to downsizing.

  FIG. 22 is a diagram showing the configuration of the radar apparatus of the present invention. A radio wave generator 20, a circulator 21, a rotary joint 22, an antenna 23, and a receiving circuit 24 are provided. The radio wave generator 20 is typically a magnetron, but is not limited thereto.

  The magnetron 20 generates a radio wave including a main oscillation mode having a predetermined frequency. A radio wave generated by the magnetron 20 is incident from a radio wave input section (not shown) of the left waveguide in the figure, propagates through the circulator 21 and is guided to the coaxial line. The radio wave further propagates through the coaxial line and is guided to the antenna 23 via the waveguide joint (rotary joint) 22. The radio wave emitted from the antenna 23 and reflected by the target is received by the antenna 23, and again undergoes signal processing by the receiving circuit 24 through the circulator 21.

  Here, the waveguide joint 22 plays a role in which the radio wave generated by the magnetron 20 is incident from the radio wave incident portion and guided to the antenna 23 through the waveguide and the coaxial line. At this time, in the radar apparatus of the present invention, the radio wave generated by the magnetron 20 is propagated through the waveguide and is guided to the antenna 23 via the coaxial line, and unnecessary radiation is caused by the filter disposed inside the waveguide. Block radio waves. This principle has already been explained in the waveguide joint of the present invention.

  Next, the magnetron of the present invention will be described.

  The magnetron of the present invention has the purpose of reducing radio waves leaking outside from the magnetron itself, and among the radio waves generated by the magnetron, as already explained, only spurious components that become unnecessary radiated radio waves when applied to radar devices etc. It can be applied to both the purpose of selective removal. For the former purpose, a filter that blocks radio waves in the main oscillation mode of radio waves generated by the magnetron may be applied. In the latter case, a filter that blocks unwanted radiated radio waves may be applied.

  FIG. 23 is a longitudinal sectional view showing the structure of the magnetron of the present invention. As shown in the figure, the magnetron of the present invention has an anode 25 having a plurality of anode vanes 26 each having an inner end arranged on the circumference, and a cylindrical shape whose central axis substantially coincides with the center of the circumference. And a cathode 27. By applying a voltage between the anode 25 and the cathode 27, a radio wave including a main oscillation mode having a predetermined frequency is generated.

  The magnetron of the present invention includes a filter disposed so that the inner conductor central axis coincides with the central axis of the cathode 27. A filter may be arranged for the purpose of removing unnecessary radiation by passing radio waves of the main transmission frequency among radio waves generated by the magnetron. The magnetron of the present invention can also be used for the purpose of preventing leakage of the radio wave itself at the main oscillation frequency to the outside. As described above, the former is useful for a radar apparatus that needs to remove unwanted radiation. On the other hand, the latter is useful in a microwave oven or the like.

  In order to achieve the former purpose, the length of the electromagnetic field coupling portion formed by the gap portion or the parallel portion may be set to approximately one-fourth of the wavelength of the radio wave in the main oscillation mode. On the other hand, if the latter purpose is achieved, the length of the electromagnetic field coupling portion may be set to approximately one-fourth of the wavelength of the unnecessary radiation wave.

  Next, examples of the filter of the present invention will be described.

  First, an example of the filter according to the first embodiment of this invention will be described. Note that the structure is the same as that of the drawings referred to in the description of the embodiment, and thus illustration is omitted. The filter has an inner conductor diameter of φ (phi) 2.75 mm and an outer conductor diameter of φ4 mm. A cut is formed in the side surface of the inner conductor along the central axis over a length of 7.4 mm.

  A graph showing the simulation result of the frequency characteristics of this filter is shown in FIG. The horizontal axis indicates the frequency of the input radio wave, and the vertical axis indicates the reflection parameter reflection coefficient S11 and the absolute value of the transmission (transmission) coefficient S21 in decibels. The reflection characteristic (S11) and the transmission characteristic (S21) of the filter. ) Respectively. As can be seen from the figure, the reflectance is high near 9.4 GHz and the pass loss is small, so that the filter functions as a band rejection filter.

  In addition, the stop band can be adjusted by changing the distance between the on-projection conductor portion formed by this cutting and the outer conductor, for example, by bringing them closer. That is, the center band of the filter can be finely adjusted by adjusting the position of the on-projection conductor formed by the cut.

  Next, examples of the filter according to the third and fourth embodiments of the present invention will be described.

  In both examples, the diameter of the inner conductor is φ (phi) 2.75 mm, the diameter of the outer conductor is φ4 mm, and the length of the cut is 7.4 mm as in the first example. In this example, the wire-cut electric discharge machining was used for the cutting, but in the fourth embodiment, the inner conductor is in the form of a pipe (pipe) and the wall thickness is thin, so that etching can also be applied.

  25 and 26 are diagrams illustrating simulation results of the frequency characteristics of the filters of the third embodiment and the fourth embodiment, respectively. In the third embodiment in which the inner conductor is not hollow but dense, the specific bandwidth satisfying the reflection coefficient S11 of 10 dB is about 12%, whereas the inner conductor is formed in a cylindrical shape. In the case of the embodiment, it can be seen that a frequency characteristic having a wider band of about 20% can be obtained. In other words, if the inner conductor is a dense body such as a metal rod that does not have a hollow portion inside, the frequency is lowered, but the bandwidth is narrowed and a sharp blocking characteristic can be obtained.

  Furthermore, an example of the filter according to the seventh embodiment of the present invention will be described. In this embodiment, the inner conductor has a diameter of 1 mm, and the outer conductor has a diameter of 4 mm. A Teflon ring is attached to the outer periphery of the inner conductor. The Teflon ring has an outer diameter of φ2.6 mm and covers the outer periphery of the inner conductor. A metal foil is pasted in the central axis direction over a length of 3.75 mm so as to be a quarter wavelength, and is in contact with the inner conductor inside the Teflon.

  The simulation result of the frequency characteristic of this filter is shown in FIG. In the figure, the frequency range on the horizontal axis is 2 to 16 GHz, and the vertical axis is S11 and S21. It can be seen from the graph that it functions as a band rejection filter in the vicinity of 8.2 GHz.

  Finally, the frequency characteristics of radio waves when the waveguide joint of the present invention is used will be described. FIG. 28 is a graph showing the frequency characteristics of the microwave incident on the waveguide of the waveguide joint of the present invention and the microwave output from the coaxial line 13. Incident radio waves have a large output at a center frequency of 9.4 GHz and its double frequency of 18.8 GHz, but the apparatus is increased in size by designing the filter of the present invention to function only at 18.8 GHz. Therefore, only the double frequency output can be greatly reduced.

  The filter of the present invention can be used widely including devices that oscillate radio waves such as microwaves, such as home appliances such as radar devices and microwave ovens. The magnetron of the present invention can be used for a radar device applied to a ship, an aircraft, and the like.

1: Inner conductor 2: Outer conductor 3: Gap part 4: Center conductor 5: Protruding conductor part 6: Gap by first cut 7: Gap by second cut 8: Hollow part 9: Gap by third cut 10: Gap by the fourth cut 11: Protrusion 12: Conductive thin film 13: Coaxial line 14: Inner conductor 15: Outer conductor 16: Waveguide 17: Radio wave input unit 18: Band stop filter unit 19: Rotating mechanism 20 : Radio wave generator (magnetron)
21: Circulator 22: Waveguide joint (rotary joint)
23: Antenna 24: Reception circuit 25: Anode 26: Anode vane 27: Cathode 28: Band stop filter 29: Band pass filter

Claims (28)

A columnar inner conductor having conductivity;
A conductive outer conductor having a hollow portion and at least a portion of the inner conductor disposed in the hollow portion;
A radio wave input unit for receiving radio waves from one end of the inner conductor;
A filter with
The filter according to claim 1, wherein the inner conductor includes an electromagnetic field coupling unit that generates electromagnetic field coupling with the radio wave in a traveling direction of the radio wave. The radio wave includes a main oscillation mode,
2. The filter according to claim 1, wherein the electromagnetic field coupling portion has a length in a central axis direction of the inner conductor that is approximately a quarter of a wavelength of the main oscillation mode. The radio wave includes a main oscillation mode,
2. The filter according to claim 1, wherein the electromagnetic field coupling portion has a length in a central axis direction of the inner conductor that is approximately a quarter of a wavelength other than the wavelength of the main oscillation mode. A columnar inner conductor having conductivity;
A conductive outer conductor having a hollow portion and at least a portion of the inner conductor disposed in the hollow portion;
A filter with
The inner conductor has a gap formed substantially parallel to the central axis of the inner conductor. The filter according to claim 4,
It has a radio wave input unit that receives radio waves including the main oscillation mode of a predetermined frequency.
The said gap | interval part has the length of about 1/4 of the wavelength of the electromagnetic wave of the said main oscillation mode in the said central axis direction. The filter according to claim 5, wherein
It has a radio wave input unit that receives radio waves including the main oscillation mode of a predetermined frequency.
The said gap | interval part has a length of about 1/4 of the wavelength of the radiation wave which has a frequency different from the said predetermined frequency in the said center axis direction. The inner conductor has an inner conductor hollow part at least in part,
The filter according to any one of claims 4 to 6, wherein the gap portion is formed so as to be connected to the inner conductor hollow portion. The gap is
A first gap cut in one direction with respect to the inner conductor;
8. The device according to claim 4, further comprising: a second gap cut at a position substantially opposite to the first gap portion with respect to the central axis. The filter described. The filter according to any one of claims 4 to 8, wherein the inner conductor includes a plurality of gaps formed in series along the central axis. A filter according to any one of claims 4 to 9, comprising:
The filter is characterized in that, instead of “substantially parallel”, the gap is formed so as to be inclined outward from the central axis. A conductive inner conductor;
A conductive outer conductor having a hollow portion and at least a portion of the inner conductor disposed in the hollow portion;
A filter with
A filter having a parallel portion between the inner conductor and the outer conductor and electrically connected to the inner conductor and substantially parallel to the central axis.   12. The filter according to claim 11, wherein a width of the parallel part in a direction perpendicular to the inner conductor extends from one end electrically connected to the inner conductor to the tip. A filter according to claim 11 or claim 12,
It has a radio wave input unit that receives radio waves including the main oscillation mode of a predetermined frequency.
The filter is characterized in that the gap portion has a length that is approximately one quarter of the wavelength of the radio wave in the main oscillation mode in the central axis direction. A filter according to claim 11 or claim 12,
It has a radio wave input unit that receives radio waves including the main oscillation mode of a predetermined frequency.
The said gap | interval part has the length of about 1/4 of the wavelength of the frequency radiation electromagnetic wave different from the said predetermined frequency in the said center axis direction. A columnar inner conductor having conductivity;
A coaxial line having a hollow portion and a conductive outer conductor in which at least a part of the inner conductor is disposed in the hollow portion;
A rotary joint comprising a radio wave incident portion on which a radio wave including a main oscillation mode of a predetermined frequency is incident, and a waveguide for guiding the radio wave to the coaxial line,
The waveguide joint, wherein the inner conductor has a gap portion formed substantially parallel to the central axis of the inner conductor in the waveguide. The waveguide joint according to claim 15, wherein the gap portion has a length that is substantially a quarter of a wavelength of a radiation wave having a frequency different from the predetermined frequency in the central axis direction. The inner conductor has an inner conductor hollow part at least in part,
The waveguide joint according to claim 15 or 16, wherein the gap portion is formed so as to be connected to the hollow portion of the inner conductor. The gap is
A first gap cut from one direction with respect to the inner conductor;
18. The device according to claim 15, further comprising: a second gap cut at a position substantially opposite to the first gap portion with respect to the central axis. The waveguide joint described. The waveguide according to any one of claims 15 to 18, wherein the inner conductor includes a plurality of the gap portions formed in series along the central axis. Joint. A columnar inner conductor having conductivity;
A coaxial line having a hollow portion and a conductive outer conductor in which at least a part of the inner conductor is disposed in the hollow portion;
A rotary joint comprising a radio wave incident portion on which a radio wave including a main oscillation mode of a predetermined frequency is incident, and a waveguide for guiding the radio wave to the coaxial line,
The inner conductor is between the inner conductor and the outer conductor, and has a parallel portion in the waveguide that is electrically connected to the inner conductor and substantially parallel to the central axis. Characteristic waveguide joint. 21. The waveguide joint according to claim 20, wherein the parallel portion has a length that is approximately one quarter of a wavelength of a radiation wave having a frequency different from the predetermined frequency in the central axis direction. A waveguide joint according to any one of claims 19 to 21, comprising:
A waveguide joint, comprising: a rotation mechanism for rotating the coaxial line relative to the waveguide. A radio wave generator for generating radio waves including a main oscillation mode of a predetermined frequency;
An antenna that emits radio waves,
23. The waveguide joint according to any one of claims 15 to 22, wherein a radio wave generated by the radio wave generator is incident from the radio wave incident portion, and the waveguide portion and the coaxial line And a waveguide joint that guides the antenna through the antenna. A radio wave generator for generating radio waves including a main oscillation mode of a predetermined frequency;
An antenna that emits radio waves,
A receiving unit for receiving an echo signal by radio waves emitted from the antenna;
The waveguide joint according to any one of claims 15 to 23, wherein a radio wave generated by the radio wave generator is incident from the radio wave incident part, and the waveguide part and the coaxial line A waveguide joint that guides the antenna through the antenna, and a circulator that guides the radio wave generated by the radio wave generator to the radio wave incident part, and guides the echo signal to the receiving part,
A radar device comprising: An anode having a plurality of anode vanes each having an inner end disposed on the circumference, and a cylindrical cathode having a central axis substantially coincident with the center of the circumference, and between the anode and the cathode A radio wave generator that generates radio waves including a main oscillation mode of a predetermined frequency;
The filter according to any one of claims 4 to 14, wherein the inner conductor central axis is arranged so as to coincide with the central axis.
A magnetron characterized by comprising: 26. The magnetron according to claim 25, wherein the gap portion has a length of approximately one quarter of a wavelength of the radio wave in the main oscillation mode in the central axis direction. 26. The magnetron according to claim 25, wherein the gap portion has a length of approximately one quarter of a wavelength of a radiation wave having a frequency different from the predetermined frequency in the central axis direction. A magnetron according to claim 24 or claim 26,
An antenna that emits radio waves,
A receiving unit for receiving an echo signal by radio waves emitted from the antenna;
A circulator that guides the radio wave generated by the radio wave generator to the radio wave incident part, and guides the echo signal to the receiving part,
A radar device comprising:

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