JP5486899B2 - Waveguide filter - Google Patents

Description

  The present invention relates to a waveguide filter for suppressing and suppressing transmission of spurious signals (frequency components different from those intended by design, unnecessary waves) in a microwave band radar system and the like.

  A cylindrical waveguide resonator filter (waveguide filter) is known as an antenna filter used in a microwave band radar system or the like. As shown in FIG. 10, the cylindrical waveguide resonator filter is provided with a plurality of resonators 101 having the same shape (same inner diameter and same height) constituted by a cylindrical (cylindrical) space. The resonator 101 is electrically connected via an inter-resonator coupling window 102 located at the center of the resonator 101. In such a cylindrical waveguide resonator filter, low loss and high power durability characteristics are required in order to transmit large power of about several tens to several hundred kW, and from the viewpoint of effective use of frequency and spurious regulation Narrow band and low spurious characteristics are required.

  In response to such a characteristic requirement, in the cylindrical waveguide resonator filter as shown in FIG. 10, the spurious in each resonator 101 is transmitted to the adjacent resonator 101, and the spurious couples to each other, thereby passing the passband. The attenuation characteristic in the vicinity is deteriorated. Furthermore, when a spurious component is generated in the amplifier of the transmitter, it is transmitted as it is from the antenna to the outside, which may adversely affect other wireless devices and radar systems. For this reason, a technique of connecting a low-pass filter or a band-pass filter as an additional circuit in order to suppress spurious is known (see, for example, Patent Document 1).

JP 2004-328458 A

  However, when connecting a low-pass filter or a band-pass filter, it is necessary to design a filter so as to pass a signal in a predetermined frequency band and suppress spurious. For this reason, the filter design becomes complicated and difficult, and a great deal of time and labor is required for development and design, resulting in an increase in development costs. Further, for example, since a wide band pass filter is externally attached to the narrow band filter, the entire filter is increased in size.

  Therefore, an object of the present invention is to provide a waveguide filter capable of suppressing spurious with a simple configuration.

In order to achieve the above object, the invention described in claim 1 is a waveguide filter in which a plurality of waveguide resonators configured by spaces are connected via a coupling window between resonators, The inter-resonator coupling window includes a node of a spurious mode electric field in the waveguide resonator and satisfies the TE mode transmission amount in the passband. Two external coupling windows that are provided between the resonator and connected to the outside to input / output signals to / from the outside are compared with the electric field strength of the TE mode in the passband in the height direction in the waveguide resonator. The spurious mode is provided at a position where the electric field strength is low .

According to the present invention, a signal in a predetermined frequency band is transmitted to an adjacent waveguide resonator via an inter-resonator coupling window, and the inter-resonator coupling window is provided to include a spurious mode electric field node. In addition, since the electric field strength in the inter-resonator coupling window is low , the spurious signal is hardly transmitted to the adjacent waveguide resonator through the inter-resonator coupling window.

Further , a signal in a predetermined frequency band is output to the outside through the external coupling window, and the spurious is difficult to be output to the outside through the external coupling window because the electric field strength in the external coupling window is low.

According to a second aspect of the invention, the waveguide filter of claim 1, have different size of the space between adjacent waveguide resonator, characterized in that.

  According to the present invention, the frequency characteristics and electric field intensity distribution of spurious generated in each adjacent waveguide resonator are different, and spurious transmission can be suppressed by superimposing the spurious in each resonator. .

  According to the first aspect of the present invention, since the inter-resonator coupling window is provided at a position where the electric field strength of the spurious is low, the spurious is transmitted to the adjacent waveguide resonator via the inter-resonator coupling window. It becomes difficult to be done. Moreover, it is only necessary to provide an inter-resonator coupling window at a position where the electric field strength of the spurious is low. In this way, it is possible to suppress spurious transmission between the waveguide resonators with a simple configuration.

In addition , since the external coupling window is provided at a position where the electric field strength of the spurious is low, it is difficult for the spurious to be transmitted to the outside through the external coupling window. Moreover, it is only necessary to provide an external coupling window at a position where the electric field strength of the spurious is low. Thus, it becomes possible to suppress transmission of spurious to the outside with a simple configuration.

According to the second aspect of the present invention, since the space sizes of the adjacent waveguide resonators are different, the frequency characteristics of spurious generated in the adjacent waveguide resonators and the electric field intensity distribution are different. . For this reason, spurious transmission can be suppressed by superimposing the spurious of each waveguide resonator. Moreover, it is only necessary to change the size of the space between adjacent waveguide resonators. In this way, it is possible to suppress spurious transmission between the waveguide resonators with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows the cylindrical waveguide resonator filter which concerns on Embodiment 1 of this invention, (a) is a top view, (b) is a front view. It is a mode chart of a cylindrical waveguide resonator. It is a figure which shows the narrow-band characteristic between the waveguide resonator of the cylindrical waveguide resonator filter of FIG. 1, and the conventional filter. It is a figure which shows the broadband characteristic between the waveguide resonator of the cylindrical waveguide resonator filter of FIG. 1, and the conventional filter. It is a figure which shows the narrow-band characteristic to the exterior of the cylindrical waveguide resonator filter of FIG. 1, and the conventional filter. It is a figure which shows the broadband characteristic to the exterior of the cylindrical waveguide resonator filter of FIG. 1, and the conventional filter. It is a schematic block diagram which shows the cylindrical waveguide resonator filter which concerns on Embodiment 2 of this invention, (a) is a top view, (b) is a front view. It is a figure which shows the narrow-band characteristic between the waveguide resonator of the cylindrical waveguide resonator filter of FIG. 7, and the conventional filter. It is a figure which shows the broadband characteristic between the waveguide resonator of the cylindrical waveguide resonator filter of FIG. 7, and the conventional filter. It is a schematic block diagram which shows the conventional cylindrical waveguide resonator filter, (a) is a top view, (b) is a front view.

  The present invention will be described below based on the illustrated embodiments.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing a cylindrical waveguide resonator filter (waveguide filter) 1 according to Embodiment 1 of the present invention. The cylindrical waveguide resonator filter 1 is a filter that suppresses and suppresses spurious transmission in a microwave band radar system and the like. The cylindrical waveguide resonator filter 1 is made of metal and mainly includes a plurality of (three in this embodiment) conducting. A wave tube resonator 2, an inter-resonator coupling window 3 that connects them, and an external coupling window 4 are provided.

The waveguide resonator 2 is configured by a cylindrical (cylindrical) space, and the inner diameter and height thereof are set based on the frequency of the pass band (use band). That is, a TE mode cylindrical waveguide is generally represented by TE _lmn (l, m, n: 0, 1, 2,...), And an electric field that is l times the half wavelength of the passing frequency in the radial direction of the cylindrical waveguide. It shows that an electric field of m times the half wavelength of the passing frequency is generated in the radial direction of the cylindrical waveguide, and an electric field of n times the half wavelength of the passing frequency is generated in the height direction of the cylindrical waveguide. In this embodiment, the TE mode of the passband is set to TE 0 _mn, and the inner diameter and height of the waveguide resonator 2 are set so as to conform to the TE mode. For example, when the TE mode of the passband is set to TE ₀₁₁ , the waveguide is generated so that an electric field that is one half the wavelength of the pass frequency in the radial direction and an electric field that is one time the half wavelength of the pass frequency are generated in the height direction. The inner diameter and height of the resonator 2 are set. As a result, as shown in FIG. 1A, an electric field E1 is generated in the radial direction of the waveguide resonator 2 that is one half the half wavelength of the pass frequency. That is, an electric field E1 in which the electric field strength depends on the distance from the center is generated in the circumferential direction in the waveguide resonator 2.

Here, TE _0mn is selected as the TE mode of the _passband for the following reason. That is, in TE 0 _mn , the electric field is concentrated near the center of the cylindrical space, and almost no electric field is generated on the wall surface. _Therefore , there is little loss and the electric field is concentrated at a position away from the metal wall surface. Will be better. This is because the TE mode is optimal for radar systems and satellite communication devices that require low loss and high power durability.

The inter-resonator coupling window 3 is a space for electrically connecting adjacent waveguide resonators 2 and is provided in the waveguide resonator 2 at a position where the electric field strength of spurious is low. Here, as shown in FIG. 2, the spurious mode is uniquely determined when the size (inner diameter and height) of the waveguide resonator 2 is determined, that is, when the TE mode of the passband is determined. For example, when the TE mode of the pass band is TE ₀₁₁ , the spurious mode in the vicinity of this pass band is TE ₃₁₁ , and the spurious mode TE ₃₁₁ is coupled to the resonator at a position where the electric field strength is low, that is, the node of the electric field. A window 3 is provided. Specifically, as shown in FIG. 1A, when the electric field of the spurious mode TE ₃₁₁ is generated as indicated by reference numeral E2 and the node of the electric field is at the position of reference numeral E0, the electric field node E0 is included. Thus, the inter-resonator coupling window 3 is provided.

  The size and position of the inter-resonator coupling window 3 are set so as to satisfy the coupling amount / transmission amount of the passband frequency (TE mode). For example, the width (plane direction) is made as narrow as possible with the node E0 of the electric field as the center, and the height direction is secured large so as to satisfy the coupling amount between the resonators. Furthermore, the shape and position are set in consideration of the machinability and productivity for forming the inter-resonator coupling window 3. Two such inter-resonator coupling windows 3 are provided between the waveguide resonator 2 and the waveguide resonator 2.

  The external coupling window 4 is a coupling unit that is connected to the outside and inputs / outputs signals to / from the outside. That is, it is a space that is connected to another circuit via an input / output standard waveguide or the like and inputs / outputs a signal to / from the standard waveguide, and the electric field strength of spurious in the waveguide resonator 2 is increased. It is provided at a low position. Further, the size, shape, and position are set in consideration of the amount of coupling necessary to configure the filter and taking into account machinability and productivity. For example, as shown in FIG. 1B, an electric field E3 that is three times the half wavelength of the pass frequency is generated in the height direction in the TE mode of the pass band, and 1 half of the half wavelength of the pass frequency is formed in the height direction in the spurious mode. When the double electric field E4 is generated, the electric field E3 in the pass band in the height direction of the waveguide resonator 2 has a high strength and the spurious mode electric field E4 has a small strength. A coupling window 4 is provided. That is, the external coupling window 4 is provided on the lower side (illustrated) or the upper side of the waveguide resonator 2 in the height direction.

  Such a waveguide resonator 2 and an inter-resonator coupling window 3 are indicated by only one solid line (no wall thickness) in FIG. It may be formed by machining or the like (a space corresponding to the waveguide resonator 2 and the inter-resonator coupling window 3 is formed), and the waveguide resonator 2 and the inter-resonator coupling window 3 are separately provided. They may be formed as a body and combined. The positions of the inter-resonator coupling window 3 and the external coupling window 4 are set as described above, but the actual detailed position is determined by calculation, simulation, or the like.

  Next, the operation of the cylindrical waveguide resonator filter 1 having such a configuration will be described.

  First, when a signal is input from an external standard waveguide to the first waveguide resonator 2 (for example, the left resonator 2 in FIG. 1) via the external coupling window 4, this waveguide resonance is performed. A signal is transmitted from the resonator 2 to the adjacent waveguide resonator 2 (for example, the resonator 2 in the middle in FIG. 1) via the inter-resonator coupling window 3. At this time, the TE mode in the passband is appropriately and sufficiently transmitted to the adjacent waveguide resonator 2 via the appropriately set inter-resonator coupling window 3. On the other hand, since the electric field strength is zero or weak in the inter-resonator coupling window 3, the spurious mode is difficult to be transmitted to the adjacent waveguide resonator 2 through the inter-resonator coupling window 3. In this way, the frequency signal in the pass band is properly transmitted to the adjacent waveguide resonator 2, and spurious transmission is suppressed.

  In this way, signals are sequentially transmitted between the waveguide resonators 2, and external signals are transmitted from the last waveguide resonator 2 (for example, the right-side resonator 2 in FIG. 1) through the external coupling window 4. A signal is output to the standard waveguide. At this time, since the external coupling window 4 is provided at a position where the electric field strength of the TE mode in the passband is large, the TE mode in the passband is transmitted appropriately and sufficiently to the standard waveguide. On the other hand, since the electric field strength of the spurious mode is weak in the external coupling window 4, it is difficult to output to the standard waveguide through the external coupling window 4. In this way, the passband frequency signal is properly output to the outside, and spurious output is suppressed.

  As described above, according to this cylindrical waveguide resonator filter 1, since the inter-resonator coupling window 3 is provided at a position where the electric field intensity of the spurious mode is zero or low, the spurious inter-resonator coupling window 3 is provided. It becomes difficult to transmit to the adjacent waveguide resonator 2 via the. As a result, it is possible to suppress transmission of spurious between the waveguide resonators 2. For example, as shown in the narrow band characteristic of FIG. 3, the frequency characteristic L2 between the waveguide resonators according to this embodiment is higher than the frequency characteristic L1 between the conventional waveguide resonators. A characteristic value that is more symmetrical about (f / f0 = 1) and a higher pass level can be obtained. Further, as shown in the wideband characteristic of FIG. 4, in the frequency characteristic L1 between the conventional waveguide resonators, a plurality of frequencies having a high pass level appear in addition to the frequency of the passband. In the frequency characteristic L2 between the waveguide resonators, the peak value of the pass level in the frequency band other than the frequency of the pass band is low.

  Further, since the external coupling window 4 is provided at a position where the electric field intensity of the spurious mode is low, it is difficult for the spurious to be output to the outside through the external coupling window 4. As a result, spurious output to the outside can be suppressed, and adverse effects on other radio apparatuses and radar systems can be suppressed. For example, as shown in the narrowband characteristic of FIG. 5, the external frequency characteristic L2 according to this embodiment has a sharper characteristic value centered on the passband frequency as compared with the conventional external frequency characteristic L1. Is obtained. Further, as shown in the wideband characteristic of FIG. 6, in the conventional frequency characteristic L1 to the outside, a peak value having a high pass level appears in a wide frequency band, whereas the frequency characteristic to the outside according to this embodiment is shown. At L2, the pass level peak value of the passband frequency appears more clearly.

  Moreover, according to the cylindrical waveguide resonator filter 1, it is only necessary to provide the inter-resonator coupling window 3 and the external coupling window 4 at a position where the electric field intensity of the spurious mode is low. That is, since it is not necessary to provide a low-pass filter or a band-pass filter, the filter design is not complicated or difficult, and the entire filter is not enlarged. As described above, it is possible to suppress the transmission and output of the spurious to the adjacent waveguide resonator 2 and the outside with a simple configuration.

(Embodiment 2)
FIG. 7 is a schematic configuration diagram showing a cylindrical waveguide resonator filter (waveguide filter) 10 according to Embodiment 2 of the present invention. Here, about the structure equivalent to Embodiment 1, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  This cylindrical waveguide resonator filter 10 is different from the first embodiment in that the space between adjacent waveguide resonators 2 and 21 is different. That is, the central waveguide resonance so that the spurious frequency and electric field generated in the waveguide resonator 21 located at the center are different from the spurious frequency and electric field generated in the waveguide resonator 2 located on the left and right. The inner and outer diameters of the resonator 21 and the left and right waveguide resonators 2 are set. Thus, for example, as shown in the figure, in the left and right waveguide resonators 2, the electric field of the passband frequency appears as E 1 and the electric field of the spurious frequency appears as E 2, whereas the central waveguide resonance. In the device 21, an electric field having a frequency in the pass band appears as E5, and an electric field having a spurious frequency appears as E6. The intensity distribution of the electric field strength of the spurious electric field E2 of the left and right waveguide resonators 2 is different from that of the spurious electric field E6 of the central waveguide resonator 21. For example, in FIG. 2, when the spurious mode of the left and right waveguide resonators 2 is point A, the spurious mode of the central waveguide resonator 21 is point B, and the adjacent waveguide resonators 2 and 21 are adjacent to each other. The spurious mode is different.

  According to the cylindrical waveguide resonator filter 10 as described above, since the electric field distribution of the spurious of the adjacent waveguide resonators 2 and 21 is different, the spurious transmission is performed by superimposing the spurious of each waveguide resonator. Can be suppressed. That is, when the spurious generated in the left waveguide resonator 2 is transmitted into the central waveguide resonator 21, the spurious from the left waveguide resonator 2 and the central waveguide resonator are provided. Since the spurious generated in 21 is superimposed and the distribution of the electric field strength of both spurious is different, both spurious are suppressed (attenuated). In this way, each time the signal is transmitted to the adjacent waveguide resonators 2 and 21, spurious is suppressed.

  For example, as shown in the narrow band characteristic of FIG. 8, the frequency characteristic L2 between the waveguide resonators according to this embodiment has a frequency in the passband as compared with the frequency characteristic L1 between the conventional waveguide resonators. The characteristic value appears more clearly (sharply) around (f / f0 = 1). Further, as shown in the broadband characteristic of FIG. 9, in the frequency characteristic L1 between the conventional waveguide resonators, the peak value of the pass level appears in the frequency band close to the frequency of the pass band. In the frequency characteristic L2 between the waveguide resonators according to the form, a peak value of the pass level appears in a frequency band away from the frequency of the pass band.

  Moreover, it is only necessary to change the inner and outer diameters of the adjacent waveguide resonators 2 and 21. In this way, it is possible to suppress transmission of spurious between the waveguide resonators 2 and 21 with a simple configuration.

Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above-described embodiment, the external coupling window 4 is provided on the lower side in the height direction of the waveguide resonator 2 in the first embodiment. If there is no difference between the electric field distribution and the spurious mode electric field distribution, the external coupling window 4 may be provided at the center of the waveguide resonator 2 in the height direction. In the second embodiment, the inner and outer diameters of the adjacent waveguide resonators 2 and 21 are changed. However, only one of the inner and outer diameters may be changed to change the spurious frequency.
Needless to say, it is necessary to change the length of the tube axis in order to obtain a desired frequency (passband frequency).

1, 10 Cylindrical waveguide resonator filter (waveguide filter)
2, 21 Waveguide resonator 3 Inter-resonator coupling window 4 External coupling window E0 Electric field node E1, E3, E5 Passband electric field E2, E4, E6 Spurious electric field

Claims (2)

A plurality of waveguide resonators configured in space is a waveguide filter connected through a coupling window between resonators,
The inter-resonator coupling window includes a node of a spurious mode electric field in the waveguide resonator and satisfies the TE mode transmission amount in the passband. Two are provided between each resonator.
An external coupling window connected to the outside and for inputting / outputting signals to / from the outside is provided at a position where the electric field strength of the spurious mode is lower than the electric field strength of the TE mode in the pass band in the height direction in the waveguide resonator. and that, the waveguide filter, characterized in that. The waveguide filter according to claim 1 , wherein the space sizes of adjacent waveguide resonators are different.