TWI495187B - Balanced Ultra Wideband Bandpass Filter with Wide Common Mode Strap - Google Patents

Description

Balanced ultra-wideband pass filter with wide common mode stop band

The present invention relates to a band pass filter, and more particularly to a balanced ultra-wide band pass filter having a wide common mode stop band.

The specifications of communication systems are increasingly being introduced, such as global positioning system (GPS), Bluetooth, and wireless local-area network (WLAN). The frequency bands and specifications used by each product are different. If the designed circuit wants to cover these bands at the same time, the frequency response must have sufficient bandwidth. Therefore, under the demand of high transmission rate and large bandwidth, wideband (WB) and ultra-wideband (UWB) systems have good development potential and practicability. Ultra-wideband has high data transmission rate, low power consumption and strong anti-interference ability, so ultra-wideband filters used in ultra-wideband devices have attracted much attention. In 2002, the Federal Communications Commission (FCC) allocated the 7,500 MHz spectrum from 3.1 GHz to 10.6 GHz to UWB devices. As one of the key components in wireless communication systems, ultra-wideband filters have become a research hotspot. Among the various components of the communication system, the filter is one of the key components, and its function is to filter out other unwanted signals in addition to ensuring the integrity of the received signal. In today's communication systems, various RF and microwave circuits are gradually designed in a balanced architecture. The balanced bandpass filter (BPF) is designed with a good differential mode passband response and wideband. The common mode noise suppression has become the subject of researchers in recent years.

The specification of the Republic of China Patent Publication No. I329987 discloses a four-band pass filter which, although capable of four-frequency operation and has four passbands, still has the following disadvantages:

1. The bandwidth of each of the four passbands is insufficient, so the four passbands cannot be adjacent to each other and cover an ultra-wideband passband, and thus are not suitable for ultra-wideband communications such as 3.1 GHz to 10.6 GHz. .

2. For an unbalanced architecture, if it is necessary to change to a balanced architecture in order to match the surrounding circuits, then in addition to the bandpass filter itself, a balancer (balun) is additionally added before and after the filter, thus increasing Circuit complexity and increased product cost.

The main object of the present invention is to solve the problem of complicated design of the ultra-wideband pass filter of the prior art.

Another object of the present invention is to solve the problem of the prior art having a high cost due to the complicated structure.

To achieve the above object, the present invention provides a balanced ultra-wideband pass filter having a wide common mode stop band, comprising a dielectric plate, a slot line resonator and two microstrip feedthroughs. The dielectric plate includes a first surface and a second surface away from the first surface, the dielectric plate defines a first mirror line parallel to the dielectric board and a second mirror line, the second The mirror line is perpendicular to the first mirror line; the slot line resonator is disposed on the first surface, and includes a linear slot, and two sector slots respectively disposed at opposite ends of the linear slot and communicating with the linear slot, The scallops have a narrow end connected to the linear groove and an arc end away from the narrow end, the straight groove is parallel to the first mirror line; and the microstrip feeding body is disposed on the second surface Symmetrically, the microstrip feeds respectively comprise two microstrip lines and a connecting segment connecting the two microstrip lines, and the two microstrip lines are centered on the first mirror line. And each of the microstrip lines respectively includes a body, a first side, and a distance away from the first side. a second side, the first side is extended by the body An open portion extending two symmetrically disposed, the second side is formed with two symmetrical and extends into the body to form a gap.

As can be seen from the above description, the present invention has the following features:

1. Using the design of the two sector slots, a plurality of continuous length resonant paths can be provided in the vicinity of the resonant mode to increase the overall response bandwidth.

Second, using the design of the open circuit extension and the gap on the microstrip line, the high frequency mixed wave noise outside the band is effectively filtered out, and the overall signal quality is improved.

Third, the design structure is simple, effectively saving circuit size to reduce costs.

10. . . Dielectric plate

11. . . First surface

12. . . Second surface

13. . . First mirror line

14. . . Second mirror line

20. . . Slot line resonator

twenty one. . . Straight groove

twenty two. . . Slotted slot

221. . . Narrow mouth

222. . . Curved end

30. . . Microstrip feedthrough

31. . . microstrip line

311. . . Ontology

312. . . First side

313. . . Second side

314. . . Open circuit extension

314a. . . First stub

314b. . . Second stub

315. . . gap

315a. . . First gap

315b. . . Second gap

316. . . Central extension

32. . . Connection segment

W1. . . Body width

W2. . . Open extension width

W3. . . Central extension width

W4. . . width

G1. . . First gap width

G2. . . Second gap width

L1. . . length

L2. . . Open extension length

L3. . . Connection length

L4. . . Central extension length

L5. . . Microstrip line length

L6. . . Shortest distance between two microstrip feedthroughs

L7. . . Distance between the curved end and the linear groove

L8. . . Straight groove length

S. . . Straight groove width

R. . . Fan slot radius

Θ1. . . First angle

Θ2. . . Fan angle

FIG. 1 is a perspective exploded view of the present invention.

2 is a schematic top view of the present invention.

FIG. 3 is a schematic view showing the enlarged structure of the microstrip feed body of the present invention.

4 is a schematic structural view of a slot line resonator of the present invention.

FIG. 5A is a schematic diagram of the frequency response of the differential mode operation of the present invention.

FIG. 5B is a schematic diagram of the frequency response of the common mode operation of the present invention.

The detailed description and technical content of the present invention will now be described as follows:

Referring to FIG. 1 and FIG. 2, the present invention is a balanced ultra-wideband pass filter having a wide common mode stop band, comprising a dielectric plate 10, a slot line resonator 20 and two The microstrip is fed into the body 30. The dielectric board 10 includes a first surface 11 and a second surface 12 away from the first surface 11. The dielectric board 10 defines a first mirror line 13 parallel to the dielectric board 10 and a first a second mirror line 14 , the second mirror line 14 is perpendicular to the first mirror line 13 ; the slot line resonator 20 is disposed on the first surface 11 and includes a linear slot 21 , and two are respectively disposed in the linear slot 21 The scallops 22 are opposite to each other and communicate with the linear grooves 21, and the two scallops 22 respectively have a narrow end 221 connected to the linear groove 21 and an arc end 222 away from the narrow end 221, the straight line The slot 21 is parallel to the first mirror line 13 , wherein the linear slot 21 and the two sector slots 22 form a symmetrical structure centering on the first mirror line 13 and the second mirror line 14; The injecting body 30 is disposed on the second surface 12 and is symmetrically formed by the second mirror line 14. The two microstrip feeding bodies 30 respectively include two microstrip lines 31 and a connecting portion 32 connecting the two microstrip lines 31. The two microstrip lines 31 are centered on the first mirror line 13 and are respectively clamped to the connecting section 32 by a first angle θ 1 and symmetrically disposed away from the second mirror line 14 , each of the microstrip lines 31 includes a body 311 , a first side 312 , and a second side 313 away from the first side 312 . The first side 312 extends from the body 311 to two symmetrically extending open ends 314. The second side 313 is formed with a gap 315 extending into the body 311 and symmetrically formed.

In this embodiment, the body 311 has a rectangular shape, and the two open portions 314 each include a first stub 314a perpendicularly connected to the first side 312, and a vertical connection to the first stub 314a. a second stub 314b, in other words, the second stub 314b is parallel to the first side 312, and the second stub 314b is connected to the corresponding first stub in a direction away from each other 314a. In addition, the two gaps 315 each include a first gap 315a perpendicular to the second side 313 and a second gap formed in the body 311 and communicating with the first gap 315a. 315b, the second gap 315b is perpendicular to the first gap 315a, that is, the second gap 315b is parallel to the second side 313, wherein the second gap 315b of the gap 315 is connected to each other. And corresponding to the first gap 315a.

In addition, in order to further enhance the effect of filtering, each of the microstrip lines 31 includes a central extension 316 connected to the first side 312, and the central extension 316 is disposed on the two open paths. Between the extensions 314, the central extension 316 is perpendicular to the first side 312, and in the present embodiment, the central extension 316 is disposed intermediate the two open extensions 314.

Please refer to "Figure 2", "Figure 3" and "Figure 4" for details. The dimensions of the present invention are as follows: body width W1 = 0.56, open-end extension width W2 = central extension width W3 = width W4 = Two gap width G2 = 0.15, first gap width G1 = 0.2, length L1 = 1.95, open length L2 = 1.85, joint length L3 = 0.7, central extension length L4 = 0.9, microstrip line length L5 = 7.3 The shortest distance between the two microstrip feedthroughs is L6 = 10.04, the distance between the arcuate end and the linear groove is L7 = 5, the length of the linear groove is L8 = 11.16, the width of the linear groove is S = 0.8, and the radius of the sector groove is R = 6.5. The above length units are all in mm (mm), and the first angle θ1 = 45° and the fan angle θ2 = 30°, wherein the dielectric plate 10 has a thickness of 0.635 mm and a dielectric constant of 10.2.

When the differential mode operation is performed, the position of the first mirror line 13 can be equivalent to an electric wall. For the microstrip feed body 30 of the upper layer, the position of the first mirror line 13 end can be regarded as a short circuit. The current is the largest, and the magnetic field generated around the microstrip line 31 is also strongest, thereby achieving good magnetic coupling with the lower slot line resonator 20; for the lower slot line resonator 20, the first The position of the mirror line 13 can be regarded as an electric wall. The slot line resonator 20 has a similar structure in which the width is halved, so that the characteristics of the general slot line can be preserved, so that it can be transmitted as an ideal differential mode; In the common mode, the position of the first mirror line 13 can be equivalent to a magnetic wall. At this time, the entire microstrip feed body 30 is damaged and becomes incomplete, so that it cannot be used as a resonator in the entire frequency domain. When the signal is transmitted, the common mode signal is suppressed. In the circuit design, the microstrip line 31 with a line width of 50 Ω is matched with the above feeding mode, and fed to the slot line resonator 20, and the line width of the groove line resonator 20 is adjusted to improve the coupling amount of the pass band, and the line width. The wider the magnetic field enclosed in the slot line, the more the coupling of the overall response can be increased.

For the display of the experimental results, please refer to "Figure 5A" and "Figure 5B". Figure 5A shows the differential mode frequency response. In differential mode operation, the measurement center frequency of the broadband is 6.85 GHz. The 3-dB bandwidth is 2.92 to 10.9 GHz. The minimum value of Insertion loss is 1.17 dB. It can be seen that S21 representing the penetration parameter has excellent signal transmission effect in the ultra-wideband 3.1GHz to 10.6GHz; and the common mode frequency shown in "Fig. 5B" In the response diagram, the penetration loss of the penetration parameter S21 at 1-20 GHz is greater than 20 dB, and even in the ultra-wideband, the insertion loss is greater than 40 dB, indicating that the structure of the present invention responds at a common mode frequency. It does have excellent common mode suppression. It should be noted that dd in "Fig. 5A" represents the measurement result in the differential mode state, and cc in "Fig. 5B" represents the measurement result in the common mode state.

In summary, the present invention has the following features:

1. Using the design of the two sector slots, a plurality of continuous length resonant paths can be provided in the vicinity of the resonant mode to increase the overall response bandwidth.

Second, using the design of the open circuit extension and the gap on the microstrip line, the high frequency mixed wave noise outside the band is effectively filtered out, and the overall signal quality is improved.

3. The slot line resonator and the microstrip feed body are respectively symmetrically disposed on the first mirror line and the second mirror line, so that the microstrip feed body spans the slot line resonator. Therefore, when the differential mode is operated, the position of the first mirror line can be regarded as an electric wall, so that the slot line resonator remains as a complete resonant structure, so that the differential mode maintains good transmission characteristics; and in common mode operation, Since the position of the first mirror line is regarded as a magnetic wall and becomes an incomplete resonator structure, the common mode signal can be suppressed.

Fourth, the use of the central extension can be used to further enhance the effect of filtering.

Fifth, the design structure is simple, effectively saving circuit size to reduce costs.

Therefore, the present invention is highly progressive and conforms to the requirements of the invention patent application, and the application is filed according to law, and the praying office grants the patent as soon as possible.

The present invention has been described in detail above, but the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the scope of the invention. That is, the equivalent changes and modifications made by the scope of the present application should remain within the scope of the patent of the present invention.

10. . . Dielectric plate

11. . . First surface

12. . . Second surface

13. . . First mirror line

14. . . Second mirror line

20. . . Slot line resonator

twenty one. . . Straight groove

twenty two. . . Slotted slot

221. . . Narrow mouth

222. . . Curved end

30. . . Microstrip feedthrough

31. . . microstrip line

32. . . Connection segment

Claims (10)

A balanced ultra-wideband pass filter with a wide common mode stop band, comprising:
a dielectric plate includes a first surface and a second surface away from the first surface, the dielectric plate defining a first mirror line parallel to the dielectric board and a second mirror line The second mirror line is perpendicular to the first mirror line;
a slot line resonator disposed on the first surface, comprising a linear groove, and two fan-shaped grooves respectively disposed at opposite ends of the linear groove and communicating with the linear groove, wherein the two sector slots respectively have a line connected to the line a narrow end of the slot and an arcuate end away from the narrow end, the linear slot being parallel to the first mirror line; and two microstrip feeds disposed on the second surface and forming a symmetry with the second mirror line The two microstrip feedthroughs respectively comprise two microstrip lines and a connecting segment connecting the two microstrip lines, the two microstrip lines being centered on the first mirror line and respectively sandwiching the connecting segment The first angle is symmetrically disposed away from the second mirror line, and each of the microstrip lines includes a body, a first side, and a second side away from the first side, the first side Two symmetrically disposed open circuit extensions are extended from the body, and the second side is formed with a gap extending into the body and symmetrically formed. The balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 1, wherein the linear groove and the two sector slots are centered on the first mirror line and the second mirror line. Form a symmetrical structure. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 1, wherein the two open circuit extensions each include a first stub vertically connected to the first side, and A second stub connected perpendicularly to the first stub. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 3, wherein the second stubs of the two open circuit extensions are connected to each other in a direction away from each other The first stub. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 1, wherein the two gaps each include a first gap perpendicular to the second side and a formation a second gap in the body and in communication with the first gap, the second gap being perpendicular to the first gap. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 5, wherein the second gaps of the two gaps are connected to each other corresponding to the first Void. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 1, wherein each of the microstrip lines includes a central extension connected to the first side, the central extension The department is disposed between the two open extensions. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 7 wherein the central extension is perpendicular to the first side. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 8 wherein the width of the body is 0.56 mm, the width of the open extension = the width of the central extension = 0.15 Mm, the length of the open extension = 1.85 mm, the length of the connecting section = 0.7 mm, the length of the central extension = 0.9 mm, the length of the microstrip line = 7.3 mm, between the two microstrip feeds The shortest distance = 10.04mm, the distance between the arc end and the linear groove = 5mm, the length of the linear groove = 11.16mm, the width of the linear groove = 0.8mm, the radius of the sector groove = 6.5mm, the dielectric The thickness of the plate was 0.635 mm and the dielectric constant was 10.2. A balanced ultra-wideband pass filter having a wide common mode stop band as described in claim 1, wherein the sector slots have a sector angle of 30° and the first angle is 45°.