JP2015130586A - Band-rejection filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a band-rejection filter capable of reducing the loss of signals of a frequency band to be passed.SOLUTION: A line 11 having an electrical length of λc/4 is provided on a transmission path, and a line 11a having the same electrical length as the line 11 is provided in the vicinity thereof. Furthermore, the line 11a is connected with a ring-shaped path, a line 13 having an electrical length of λc/4 is provided in the ring-shaped path, and a line 13a having the same electrical length as the line 13 is provided in the vicinity thereof. An open stub 15 having an electrical length of λc/4 is provided at an end of the line 13a. As a result, only the signal of a desired frequency fc can be interrupted selectively from the high frequency signals transmitted on the transmission path 10. Furthermore, since the lines 11 and 11a are interrupted physically, the loss of signals of a frequency band to be passed can be reduced.

Description

  The present invention relates to a band rejection filter that blocks passage of a signal having a desired frequency component, and more particularly to a technique for improving filter characteristics.

  As a conventional band rejection filter, for example, one disclosed in Patent Document 1 is known. In Patent Document 1, an open-type stub having a quarter electrical length of a desired frequency is provided in a ring-shaped filter, thereby removing a signal having a frequency component in a desired band from an input signal.

International Publication No. 2004/105175

  However, in the conventional example disclosed in Patent Document 1 described above, the signal transmission path and the ring filter are physically connected by a conductor. For this reason, particularly when applied to high-frequency signals of millimeter waves or higher, a signal in a desired frequency band can be attenuated by the ring filter, but a part of the frequency band signal to be passed is a ring filter, And it is transmitted to the open stub connected to the ring filter, causing a problem that transmission loss occurs.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a band rejection filter capable of reducing loss of a signal in a frequency band to be passed. There is.

  In order to achieve the above object, the present invention provides a first line provided on a transmission line, the first line having the same electrical length as that of the first line, and arranged in close proximity to the first line. 1 coupling line. Furthermore, a second line provided in the ring-shaped path and a first stub connected directly or indirectly to the second line are provided.

  In the band rejection filter according to the present invention, since the first line and the first coupling line are not in contact with each other, a signal in a frequency band to be passed can be prevented from being transmitted to the ring-shaped path, Loss of the signal in the frequency band to be reduced can be reduced.

It is a block diagram which shows the band-stop filter which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the attenuation | damping characteristic of the band elimination filter which concerns on 1st Embodiment of this invention. It is a block diagram which shows the band-stop filter which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows the attenuation | damping characteristic of the band-stop filter which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the band-stop filter which concerns on 3rd Embodiment of this invention. It is explanatory drawing which shows the attenuation | damping characteristic of the band elimination filter which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the band-stop filter which concerns on 4th Embodiment of this invention. It is a block diagram which shows the band-stop filter which concerns on 5th Embodiment of this invention. It is a block diagram which shows the band-stop filter which concerns on 6th Embodiment of this invention.

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

[Description of First Embodiment]
FIG. 1 is a configuration diagram showing a band rejection filter according to the first embodiment of the present invention. As shown in FIG. 1, this band rejection filter 101 is provided on the path of a transmission line 10 for transmitting a high frequency signal of millimeter wave or more, for example, and has an electrical wavelength of ¼ wavelength with respect to the wavelength λc of the cutoff frequency fc. The line 11 (first line) having a length (λc / 4) is arranged in close contact with the line 11 in a non-contact manner and in parallel, and is ¼ wavelength (the same wavelength as the line 11) with respect to the wavelength λc. ) And a line 11a (first coupled line) having an electrical length (λc / 4). At this time, the distance between the line 11 and the line 11a is preferably set to a distance not more than twice the line width.

  The line 11a includes a line 12 having an electrical length (λc / 2) of ½ wavelength with respect to the wavelength λc, and a line having an electrical length (λc / 4) of ¼ wavelength with respect to the wavelength λc. 13 (second line) and a line 14 having an electrical length (λc / 2) are connected, and these lines 11a, 12, 13, and 14 have a ring shape with a line length of (3/2) * λc. It is a ring-shaped route.

  Further, in the vicinity of the line 13, a line 13 a (second coupled line) having an electrical length (λc / 4) which is close to the line 13 in a non-contact manner and arranged in parallel, and one end of the line 13 a. An open stub 15 (first stub) having an electrical length (λc / 4) connected to the side and an LC stub 16 (second stub) connected to the other end of the line 13a are provided. . At this time, the distance between the line 13 and the line 13a is preferably a distance not more than twice the line width, as in the case of the lines 11 and 11a.

  Here, the lines 11 and 11a have an electrical length (λc / 4) as an example, but {(2p−1) / 4} * λc (where p = 1, 2, 3,...). it can. That is, it can be an odd multiple of a quarter wavelength. (Λc / 4) indicates the case where p = 1. The electrical length of the lines 12 and 14 is, for example, the electrical length (λc / 2), but {(2m−1) / 2} * λc (where m = 1, 2, 3,...). be able to. That is, it can be an odd multiple of ½ wavelength. (Λc / 2) indicates a case where m = 1. In addition, although the electrical length (electrical length of one round) of the entire ring-shaped path including the lines 11a, 12, 13, and 14 is, for example, electrical length (3/2) * λc, {(2m−1) / 2} * λc (where m = 2, 3, 4,...). That is, it can be an odd multiple of ½ wavelength. (3/2) * λc indicates a case where m = 2.

The LC stub 16 has a gap between the line length and the ground so that the inductance L and the capacitance C are ω = 1 / (LC) ^1/2 (where ω is an angular frequency corresponding to the wavelength λc). Is set. Therefore, the signal of the wavelength λc transmitted to the LC stub 16 resonates and attenuates at the LC stub 16.

  Next, the operation of the band rejection filter 101 according to the first embodiment will be described. The high-frequency signal transmitted via the transmission line 10 passes through the line 11, so that the signal with the wavelength λc, which is the wavelength of the cutoff frequency fc, resonates. That is, since the line 11 has an electrical length (λc / 4), signals of the wavelength λc strengthen each other. Further, the signal having the wavelength λc is transmitted to the line 11a disposed in the vicinity of the line 11 by electromagnetic induction.

  Further, the signal of wavelength λc transmitted to the line 11a resonates in a ring-shaped path of (3/2) * λc, and is transmitted to the line 13 of electrical length (λc / 4). Therefore, signals of wavelength λc are strengthened on the line 13 and transmitted to the line 13a disposed in the vicinity of the line 13.

  Thereafter, the signal having the wavelength λc is transmitted to the open stub 15 having the electrical length (λc / 4) and attenuated by the open stub 15. Further, the signal of the wavelength λc is transmitted to the LC stub 16 and resonates and attenuates at the LC stub 16. That is, among the signals passing through the transmission line 10, the signal of the frequency component having the wavelength λc is transmitted from the line 11 to the line 11a, and further transmitted from the line 13 to the line 13a, and the open stub 15 and the LC It is transmitted to the stub 16 and attenuated by the open stub 15 and the LC stub 16.

  Therefore, only the component of the desired cutoff frequency fc (wavelength λc) in the high-frequency signal transmitted through the transmission line 10 can be selectively attenuated. Further, since the line 11 and the line 11a are arranged close to each other and are physically cut off, signals other than the cut-off frequency fc (wavelength λc) among the signals transmitted through the transmission line 10 are set to the line 11a. Almost all the signals are transmitted to the downstream side of the transmission line 10. Therefore, the transmission line 10 can be transmitted without attenuating signals of frequency components other than the cutoff frequency fc.

  FIG. 2 is a diagram showing a cutoff characteristic with respect to the frequency when the desired cutoff frequency fc (wavelength λc) is attenuated by using the band rejection filter 101 shown in FIG. 1, and the desired cutoff frequency as shown in FIG. It is understood that the filter has a steep attenuation characteristic at the frequency fc.

  Thus, in the band rejection filter 101 according to the first embodiment of the present invention, the line 11 (first line) having the electrical length (λc / 4) is provided on the transmission line 10 for signal transmission, Further, in the vicinity of the line 11, a line 11a (first coupled line) is arranged in parallel. Further, a ring-shaped path is constituted by the lines 11a, 12, 13, and 14, and the electrical length of the ring-shaped path is (3/4) * λc, and the line 13a (second line) is near the line 13 (second line). 2 coupled lines) are arranged in parallel. Furthermore, one end of the line 13 is connected to the open stub 15. Therefore, the signal of the cutoff frequency fc transmitted to the ring-shaped path can be attenuated by the open stub 15 and the LC stub 16. As a result, it is possible to selectively remove the component of the cutoff frequency fc from the high-frequency signal transmitted through the transmission line 10.

  Furthermore, since the lines 11 and 11a are physically cut off and the lines 13 and 13a are physically cut off, the fact that a frequency signal other than the cut-off frequency fc is transmitted from the line 11 to the line 11a. Can be prevented, and the Q value of the filter can be increased. As a result, it is possible to reduce the loss of signals in the frequency band to be passed.

  Furthermore, since the LC stub (second stub) is provided at the other end of the line 13, a signal having an electrical length (λc / 4) can be reliably removed.

  Moreover, since the electrical length of the line 11 (first line) is an odd multiple of 1/4 of the cutoff frequency, the cutoff frequency signal can be resonated and transmitted to the ring-shaped path, and the cutoff frequency component Can be reliably removed.

  Similarly, since the electrical length of the line 13 (second line) is an odd multiple of 1/4 of the cut-off frequency, the cut-off frequency signal can be resonated and transmitted to the open stub 15. The frequency component can be reliably removed.

  Furthermore, since the circumference of the ring-shaped path is an odd multiple of half the cutoff frequency (for example, 3/2 * λc), the cutoff frequency component can be resonated in the ring-shaped path, It can be removed reliably.

  Further, since the electrical length of the open stub 15 (first stub) is an odd multiple of 1/4 of the cut-off frequency, the open-type stub 15 reliably removes the signal of the cut-off frequency transmitted to the line 13a. can do.

  In the first embodiment described above, an example in which the lines 13 and 13a are arranged close to each other, that is, an example in which the open stub 15 is indirectly connected to the line 13 has been described. The open stub 15 can be directly connected as in the prior art.

[Description of Second Embodiment]
Next, a second embodiment will be described. FIG. 3 is a block diagram showing a band rejection filter according to the second embodiment of the present invention. As illustrated, in the band rejection filter 102 according to the second embodiment, the electrical length of the open stub 25 is ¼ wavelength “λc2 / 4” with respect to the wavelength λc2 as compared with the first embodiment described above. The difference is that the LC stub 26 is set to resonate at an angular frequency ω corresponding to the wavelength λc2. That is, the electrical lengths of the lines 11 and 11a and the lines 13 and 13a are set to “λc1 / 4”, which is a quarter wavelength of the first wavelength λc1, and the electrical lengths of the lines 12 and 14 are set to the first wavelength λc1. The wavelength of the open stub 25 is “λc2 / 4”, which is a quarter wavelength of the second wavelength λc2.

  Here, the second wavelength λc2 is slightly different from the first wavelength λc1. For example, the second point is such that the point that is 3 dB with respect to the peak value of the transmission characteristic curve of the first wavelength λc1 and the point that is 3 dB with respect to the peak value of the transmission characteristic curve of the second wavelength λc2. Wavelength λc2 can be selected. A specific example will be described with reference to FIG. 2. When a point increased by 3 dB from the peak of the cutoff frequency fc and a point increased by 3 dB from the peak of the cutoff frequency f2 intersect, the wavelength corresponding to the cutoff frequency fc is determined. The first wavelength λc1 may be used, and the wavelength corresponding to the cutoff frequency f2 may be the second wavelength λc2. That is, the open stub 25 (first stub) has an electrical length that is an odd multiple of a quarter wavelength of the second cutoff frequency (λc2) slightly different from the first cutoff frequency (λc1). ing.

  In the band rejection filter 102 according to the second embodiment having such a configuration, the components of the cutoff frequency fc1 (wavelength λc1) can be removed by the lines 11a, 12, 13, and 14 having a link shape, and Since the open-type stub 25 and the LC stub 26 can remove the component of the cutoff frequency fc2 (wavelength λc2), the signal in the frequency band of fc1 to fc2 can be attenuated as a result.

  FIG. 4 is a diagram showing the cutoff characteristics of the band rejection filter 102 according to the second embodiment, and it is understood that signals in the frequency band of λc1 to λc2 can be removed although the cutoff characteristics are not steep as shown in the figure. .

  In this way, in the band rejection filter 102 according to the second embodiment, an open stub 25 that resonates at the first wavelength λc1 and further has the second wavelength λc2 close to the wavelength λc1 as an electrical length, and Since the LC stub 26 having the characteristic of ω corresponding to the second wavelength λc2 is used, signals in the frequency band of λc1 to λc2 can be attenuated. Further, since signals of frequencies other than this band are not transmitted from the line 11 to the line 11a, attenuation is prevented, and loss of signals in the frequency band to be passed can be reduced.

[Description of Third Embodiment]
Next, a third embodiment will be described. FIG. 5 is a block diagram showing a band rejection filter according to the third embodiment of the present invention. As shown in the figure, the band rejection filter 103 according to the third embodiment is different from the first embodiment described above in that two lines 11 provided in the transmission line 10 are provided in parallel. ing. That is, lines 11 and 11-1 having an electrical length λc / 4 are connected to the transmission line 10 in parallel. Further, lines 11a and 11a-1 are provided close to the lines 11, 11-1, and are connected in parallel. That is, a plurality of first lines and first coupling lines are provided and are arranged close to each other.

  At this time, the distance between the line 11 and the line 11a and the distance between the line 11-1 and the line 11a-1 are set equal to each other, the distance between the line 11a-1 and the line 11 and the line 11a-1 and the line 11−. The interval with 1 is set equal. The configuration is the same as that of FIG. 1 described above except that two lines 11, 11-1, and 11a, 11a-1 are provided.

  In the band rejection filter 103 according to the third embodiment, two lines 11 and 11-1 (first lines) are provided in the transmission path 10, and the lines 11a and 11a-1 ( (First coupling line) is provided, and a signal having a cutoff frequency fc (wavelength λc) is transmitted to the ring-shaped path between them, so that the signal having the cutoff frequency fc can be more efficiently removed. It becomes possible. As a result, frequency characteristics can be improved.

  FIG. 6 is a diagram showing a cutoff characteristic with respect to the frequency when the desired cutoff frequency fc (wavelength λc) is attenuated by using the band rejection filter 103 shown in FIG. 5. It is understood that the filter has a steep attenuation characteristic at the frequency fc. Further, it is understood that this frequency characteristic is steeper than the characteristic shown in FIG. 2, and the Q value of the filter is high.

  In this way, in the band rejection filter 103 according to the third embodiment of the present invention, the two lines 11 and 11-1 (the first line) having the electrical length (λc / 4) on the transmission line 10 for signal transmission. 1 line) is provided in parallel, and the lines 11a and 11a-1 (first coupled lines) are arranged in parallel in the vicinity of the lines 11 and 11-1. Further, a ring-shaped path is constituted by the lines 11a, 11a-1, 12, 13, and 14, and the electrical length of the ring-shaped path is (3/2) * λc. Further, a line 13a (second coupled line) is arranged in parallel near the line 13 (second line), one end of the line 13 is connected to the open stub 15 and the other end is connected to the LC stub 16. ing.

  Therefore, the signal having the cutoff frequency fc can be more reliably introduced into the ring-shaped path from the high-frequency signal transmitted through the transmission path 10, and the cutoff frequency component can be removed with higher accuracy.

  Further, since the lines 11 and 11-1 and the lines 11a and 11a-1 are physically cut off similarly to the first and second embodiments described above, the frequency signal other than the band of the cut-off frequency fc is sent to the line 11. Can be prevented from being transmitted to the line 11a, and loss of signals in the frequency band to be passed can be reduced.

  In the third embodiment, the example in which the two lines 11 and 11-1 are provided has been described. However, three or more lines (multiple lines) may be used. Moreover, it is also possible to improve the transmission efficiency of the cut-off frequency signal by using a plurality of systems between the line 13 and the line 13a.

[Description of Fourth Embodiment]
Next, a fourth embodiment will be described. FIG. 7 is a block diagram showing a band rejection filter according to the fourth embodiment of the present invention. As shown in the figure, in the band rejection filter 104 according to the fifth embodiment, the electrical length of the line 22 provided in the ring-shaped path is set to λc / 4, compared with the first embodiment described above. The difference is that the length is 3/4 * λc. That is, the total electrical length of the ring is 3/2 * λ.

  Even if it is set as such a structure, the effect similar to 1st Embodiment mentioned above can be achieved.

[Description of Fifth Embodiment]
Next, a fifth embodiment will be described. FIG. 8 is a block diagram showing a band rejection filter according to the fifth embodiment of the present invention. As shown in the figure, the band rejection filter 105 according to the fifth embodiment differs from the first embodiment described above in that coplanar waveguides 41 and 42 are provided around each line. Yes. That is, a coplanar waveguide 42 is provided inside the ring-shaped path, and a coplanar waveguide 41 is provided on the outer periphery. The coplanar waveguides 41 and 42 are grounded.

  The cut-off frequency fc is set based on the line width W, the line length L, and the gap G with the ground of the LC stub 16. For example, when the line width W = 50 μm, the line length L = 250 μm, and the gap G = 150 μm, the capacitance and inductance of the LC stub 16 are obtained from these data, and the cutoff frequency fc is set from these values.

  In the band rejection filter 105 according to the fifth embodiment, by providing the coplanar waveguides 41 and 42, even when the cutoff frequency is high, the signal of this frequency component does not leak to the outside. A signal having a cutoff frequency can be attenuated efficiently. Therefore, the attenuation characteristic can be improved.

[Explanation of Sixth Embodiment]
Next, a sixth embodiment will be described. FIG. 9 is a block diagram showing a band rejection filter according to the sixth embodiment of the present invention. As illustrated, the band rejection filter 106 according to the sixth embodiment includes a line 31 having an electrical length (λc / 4) of a quarter wavelength with respect to the wavelength λc of the cutoff frequency fc, and the line 31 close to the line 31. And a line 31a that is arranged in parallel and has an electrical length (λc / 4) of a quarter wavelength with respect to the wavelength λc. At this time, the distance between the line 31 and the line 31a is preferably set to a distance equal to or less than twice the line width. Further, the line 31a includes a line 32 having an electrical length (λc / 2) of ½ wavelength with respect to the wavelength λc, and a line having an electrical length (λc / 4) of ¼ wavelength with respect to the wavelength λc. 33 and a line 34 having an electrical length (λc / 2) are connected, and these lines 31a, 32, 33, and 34 are ring-shaped paths having a ring shape with a line length of (3/2) * λc. ing. In this ring-shaped path, the portions of the line 31a and the line 33 are linear, and the other portions are configured in an arc shape. That is, at least a part of the ring-shaped path has an arc shape.

  Inside the ring-shaped path in the vicinity of the line 33, there is provided a line 33a having an electrical length (λc / 4) that is arranged close to and parallel to the line 33. An open stub 35 having an electrical length (λc / 4) connected to one end of the line 33a and an LC stub 36 connected to the other end of the line 33a are provided. At this time, the distance between the line 33 and the line 33a is preferably set to a distance equal to or less than twice the line width as in the case of the lines 31 and 31a.

The LC stub 36 has a gap between the line length and the ground so that the inductance L and the capacitance C are ω = 1 / (LC) ^1/2 (where ω is an angular frequency corresponding to the wavelength λc). Is set.

  In the band rejection filter 106 according to the sixth embodiment configured as described above, the high-frequency signal transmitted via the transmission line 10 passes through the line 31 as in the first embodiment described above. As a result, the signal having the wavelength λc, which is the wavelength of the cutoff frequency fc, resonates. The signal having the wavelength λc is transmitted to the line 31a disposed in the vicinity of the line 31 by electromagnetic induction.

  Further, the signal of wavelength λc transmitted to the line 31a resonates in a ring-shaped path of (3/2) * λc, and is transmitted to the line 33 of electrical length (λc / 4). Accordingly, signals of wavelength λc are strengthened on the line 33 and transmitted to the line 33 a disposed in the vicinity of the line 33.

  Thereafter, the signal having the wavelength λc is transmitted to the open stub 35 having the electrical length (λc / 4) and attenuated by the open stub 35. Further, the 1 / 4λc signal is transmitted to the LC stub 36, and resonates and attenuates at the LC stub 36.

  Therefore, only the component of the desired cutoff frequency fc (wavelength λc) in the high-frequency signal transmitted through the transmission line 10 can be selectively attenuated. Moreover, since the line 31 and the line 31a are disposed close to each other and physically blocked, signals other than the cut-off frequency fc (wavelength λc) among the signals transmitted through the transmission line 10 are determined by the line 31a. Almost all the signals are transmitted to the downstream side of the transmission line 10. Therefore, the transmission line 10 can be transmitted without attenuating signals of frequency components other than the cutoff frequency fc.

  Moreover, since the line 33a, the open stub 35 and the LC stub 36 connected to the line 33a are provided inside the ring-shaped path, the installation space can be reduced and the size can be reduced.

  Furthermore, since the ring-shaped path has an arc shape, the open stub 35 and the LC stub 36 provided in the ring-shaped path and the lines 32 and 34 can be kept away from each other, and electromagnetic waves between the two can be separated. Can be reduced.

  The band rejection filter of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. Can do.

  The present invention can be used to remove a signal in a desired frequency band from a high-frequency signal of millimeter wave or higher.

10 transmission line 11 line (first line)
11a line (first coupled line)
13 track (second track)
13a Line (second coupled line)
15, 25, 35 Open stub 16, 26, 36 LC stub 41, 42 Coplanar waveguide 101, 102, 103, 104, 105, 106 Band stop filter

Claims (12)

A first line provided on the transmission line;
A first coupled line that has the same electrical length as the first line and is disposed in close proximity to the first line; and
A second line provided in a ring-shaped path including the first coupled line;
A first stub directly or indirectly connected to the second line;
A band rejection filter comprising: The second stub has the same electrical length as that of the second line, and further includes a second coupling line disposed in close proximity to the second line, and the first stub is the second coupling line. The bandstop filter according to claim 1, wherein the bandstop filter is connected to one end of the bandstop filter.   The second stub having an inductance that matches a cutoff frequency, a line width that becomes a capacitance, and a line length is connected to the other end of the second coupled line. Band stop filter.   4. The band rejection filter according to claim 2, wherein the second coupled line is provided inside the ring-shaped path. 5.   5. The band rejection filter according to claim 2, wherein a plurality of the first lines and the first coupling lines are provided in parallel and are arranged close to each other. 6.   6. The band rejection filter according to claim 1, wherein the first line has an electrical length that is an odd multiple of a quarter wavelength of a cutoff frequency.   7. The band rejection filter according to claim 1, wherein the second line has an electrical length that is an odd multiple of a quarter wavelength of a cutoff frequency.   8. The band rejection filter according to claim 1, wherein one circumference of the ring-shaped path has an electrical length that is an odd multiple of a half wavelength of a cutoff frequency.   The band elimination filter according to any one of claims 1 to 8, wherein the first stub has an electrical length that is an odd multiple of a quarter wavelength of a cutoff frequency.   The said 1st stub has the electrical length made into the odd multiple of 1/4 wavelength of the 2nd cutoff frequency slightly different from a cutoff frequency, The any one of Claims 1-8 characterized by the above-mentioned. The band rejection filter described in 1.   The band rejection filter according to claim 1, wherein at least a part of the ring-shaped path has an arc shape.   A coplanar waveguide that is not in contact with the first line, the first coupled line, the second line, and the first stub and is connected to the ground inside and around the ring-shaped path. The band rejection filter according to claim 1, wherein the band rejection filter is provided.

Images