Non-common-ground bandpass filter circuit with electrostatic discharge protection

A non-common-ground bandpass filter circuit with electrostatic discharge (ESD) protection is disclosed. The non-common-ground bandpass filter circuit with ESD protection includes a non-common-ground plane, a dielectric substrate and a conductor. The conductor is disposed above the non-common-ground plane. The dielectric substrate is disposed between the conductor and the non-common-ground plane. The non-common-ground plane at least has a first ground region and a second ground region separated and insulated from each other. The first ground region corresponds to a first terminal of the conductor and the second ground region corresponds to a second terminal of the conductor. When an ESD event occurs on one of the first ground region and the second ground region, the other of the first ground region and the second ground region will not be damaged by the ESD event. The non-common-ground bandpass filter circuit also provides surge protection.

FIELD OF THE INVENTION

The invention relates to a bandpass filter circuit, and specifically to a non-common-ground bandpass filter circuit with electrostatic discharge (ESD) protection.

BACKGROUND OF THE INVENTION

Microstrip is a type of electrical transmission line which can be fabricated using printed circuit board technology, and is used to convey microwave-frequency signals. It consists of a conducting strip separated from a ground plane by a dielectric layer known as the substrate. Microwave components such as antennas, couplers, filters, power dividers etc. can be formed from microstrip, with the entire device existing as the pattern of metallization on the substrate. Microstrip is thus much less expensive than traditional waveguide technology, as well as being far lighter and more compact. The disadvantages of microstrip compared with waveguide are the generally lower power handling capacity and higher losses. Also, unlike waveguide, microstrip is not enclosed, and is therefore susceptible to cross-talk and unintentional radiation.

Please refer toFIG. 1AandFIG. 1B.FIG. 1Aillustrates a schematic view of a conventional bandpass filter circuit andFIG. 1Billustrates simulation results of the conventional bandpass filter circuit shown inFIG. 1A.

As shown inFIG. 1A, in the conventional bandpass filter circuit1, a conductor is disposed above a common-ground plane10to form a microstrip structure12and a dielectric substrate (e.g., a FR-4 substrate) is disposed between the microstrip structure12and the common-ground plane10.

Please refer toFIG. 2.FIG. 2illustrates a simulation circuit diagram of the conventional bandpass filter circuit1shown inFIG. 1A. As shown inFIG. 2, the microstrip cross junction MCROSO is coupled to the resistor Term through the microstrip line MLIN and coupled to the microstrip short-circuited stub MLSC; two microstrip cross junctions MCROSO are coupled through the microstrip line MLIN.

Please refer toFIG. 3.FIG. 3illustrates a schematic view of the simulated S-parameters of the conventional bandpass filter circuit1shown inFIG. 1A. As shown inFIG. 3, m1 represents dB(S(4,3))=−0.308 at the frequency of 2.4 GHz; m2 represents dB(S(4,3))=−0.316 at the frequency of 2.5 GHz; m3 represents dB(S(4,3))=−0.650 at the frequency of 5.2 GHz; m4 represents dB(S(4,3))=−0.772 at the frequency of 5.801 GHz.

However, since the entire common-ground plane10in the conventional bandpass filter circuit1is electrically connected, as shown in the simulation results ofFIG. 1B, when an electrostatic discharge (ESD) event occurs, the conventional bandpass filter circuit1fails to provide any ESD protection, so that the circuits coupled to the conventional bandpass filter circuit1will be damaged by the ESD event.

SUMMARY OF THE INVENTION

In light of the above, one of the objectives of the invention is to provide a non-common-ground bandpass filter circuit with electrostatic discharge (ESD) protection.

An embodiment of the invention is a non-common-ground bandpass filter circuit with ESD protection. In this embodiment, the non-common-ground bandpass filter circuit with ESD protection includes a non-common-ground plane, a dielectric substrate and a conductor. The conductor is disposed above the non-common-ground plane. The dielectric substrate is disposed between the conductor and the non-common-ground plane. The non-common-ground plane at least has a first ground region and a second ground region. The first ground region and the second ground region are separated and insulated from each other. The first ground region and the second ground region correspond to a first terminal and a second terminal of the conductor respectively.

In an embodiment of the invention, when an ESD event occurs on one of the first ground region and the second ground region, the other of the first ground region and the second ground region is not damaged by the ESD event, and the non-common-ground bandpass filter circuit also provides surge protection.

In an embodiment of the invention, shapes of the first ground region and the second ground region are complementary to each other.

In an embodiment of the invention, the non-common-ground plane has a defected ground structure (DGS) to form the first ground region and the second ground region separated and insulated from each other.

In an embodiment of the invention, the DGS includes a slot disposed on the non-common-ground plane.

In an embodiment of the invention, the slot has a linear shape or a polyline shape.

In an embodiment of the invention, the slot is disposed along a length direction of the non-common-ground plane.

In an embodiment of the invention, the slot is disposed along a width direction of the non-common-ground plane.

In an embodiment of the invention, some parts of the slot are disposed along a length direction of the non-common-ground plane and the other parts of the slot are disposed along a width direction of the non-common-ground plane.

In an embodiment of the invention, the DGS further includes at least one space disposed between the first ground region and the second ground region and connected to the slot.

In an embodiment of the invention, a width of the space is larger than a width of the slot.

In an embodiment of the invention, the non-common-ground plane has arbitrary geometry.

In an embodiment of the invention, a microstrip structure is formed by the conductor.

In an embodiment of the invention, the microstrip structure includes a microstrip transmission line, a first terminal and a second terminal of the microstrip transmission line are disposed above the first ground region and the second ground region respectively.

In an embodiment of the invention, the microstrip structure further includes at least one microstrip antenna electrically connected to the microstrip transmission line.

In an embodiment of the invention, the microstrip antenna has a first portion and a second portion electrically connected to each other.

In an embodiment of the invention, the first portion of the microstrip antenna is electrically connected to the microstrip transmission line and vertical to a length direction of the microstrip transmission line.

In an embodiment of the invention, the second portion of the microstrip antenna is electrically connected to the first portion and parallel to the length direction of the microstrip transmission line.

In an embodiment of the invention, a size of the non-common-ground plane is changed by adjusting a length of the first ground region or the second ground region.

In an embodiment of the invention, a size of the non-common-ground plane is changed by adjusting a width of the first ground region or the second ground region.

Compared to the prior art, the non-common-ground bandpass filter circuit with ESD protection of the invention has a non-common-ground plane including at least two ground regions separated and insulated from each other by a defect ground structure such as a slot or a space, so that when an ESD event occurs on one ground region, the other ground region(s) will not be damaged by the ESD event. Therefore, the non-common-ground bandpass filter circuit with ESD protection of the invention can provide better ESD protection function than the common-ground bandpass filter circuit of the prior art. In addition, the non-common-ground bandpass filter circuit of the invention can also provide good surge protection function.

To further learn the features and technical content of the invention, please refer to the following detailed descriptions and drawings related to the invention. However, the provided drawings are used only for providing reference and descriptions, and are not intended to limit the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention is a non-common-ground bandpass filter circuit with ESD protection. In this embodiment, the non-common-ground bandpass filter circuit with ESD protection can include a non-common-ground plane, a dielectric substrate and a conductor. The conductor is disposed above the non-common-ground plane to form a microstrip structure. The dielectric substrate is disposed between the conductor and the non-common-ground plane.

The non-common-ground plane at least has a first ground region and a second ground region separated and insulated from each other. The first ground region and the second ground region correspond to a first terminal and a second terminal of the conductor respectively. The shapes of the first ground region and the second ground region are complementary to each other. When an ESD event occurs on one of the first ground region and the second ground region, the other of the first ground region and the second ground region is not damaged by the ESD event.

Please refer toFIG. 4AandFIG. 4B.FIG. 4Aillustrates a schematic view of a non-common-ground bandpass filter circuit with ESD protection in an embodiment of the invention;FIG. 4Billustrates simulation results of the non-common-ground bandpass filter circuit with ESD protection shown inFIG. 4A.

As shown inFIG. 4A, in a non-common-ground bandpass filter circuit with ESD protection2, a microstrip structure22including a microstrip transmission line22A and microstrip antennas22B is formed by a conductor disposed above the non-common-ground plane20. The dielectric substrate (not shown) is disposed between the microstrip structure22and the non-common-ground plane20. The microstrip antennas22B can be coupled to the ground through the via, but not limited to this. In this embodiment, the length of the non-common-ground plane20is 28.6 mm and the width of the non-common-ground plane20is 20 mm, the size of the non-common-ground plane20is 28.6 mm*20 mm and the width of the microstrip antennas22B is 0.3 mm, but not limited to this.

It should be noticed that the non-common-ground plane20has a first ground region20A and a second ground region20B. The first ground region20A and the second ground region20B are separated from each other by a narrow slot24. And, the first ground region20A and the second ground region20B are insulated from each other.

It can be found that the shapes of the first ground region20A and the second ground region20B are complementary to each other. The first ground region20A is disposed near the upper side of the non-common-ground plane20and the second ground region20B is disposed near the lower side of the non-common-ground plane20. The area of the first ground region20A is smaller than the area of the second ground region20B.

Since a first terminal T1of the microstrip transmission line22A is disposed above the upper side of the non-common-ground plane20and a second terminal T2of the microstrip transmission line22A is disposed above the lower side of the non-common-ground plane20, it is believed that the first ground region20A corresponds to the first terminal T1of the microstrip transmission line22A disposed above the upper side of the non-common-ground plane20and the second ground region20B corresponds to the second terminal T2of the microstrip transmission line22A disposed above the lower side of the non-common-ground plane20.

Since the first ground region20A and the second ground region20B of the non-common-ground plane20are separated and insulated from each other, when an ESD event occurs on one of the first ground region20A and the second ground region20B of the non-common-ground plane20, the other of the first ground region20A and the second ground region20B of the non-common-ground plane20will not be damaged by the ESD event.

After comparing the curve inFIG. 4Bwith the curve inFIG. 1B, it can be found that when the frequency is 2-3 GHz, the curve inFIG. 4Bis not dropped so deep as the curve inFIG. 1B; that is to say, the drop of the curve caused by the ESD event in the conventional bandpass filter circuit1can be obviously improved by the non-common-ground bandpass filter circuit with ESD protection2shown inFIG. 4A.

Therefore, according to the simulation results ofFIG. 4B, it can be said that the non-common-ground bandpass filter circuit with ESD protection2in this embodiment can provide well ESD protection for the circuits electrically connected to it, so that the non-common-ground bandpass filter circuit with ESD protection2of the invention can obviously improve the poor ESD protection of the conventional bandpass filter circuit1in the prior art.

Then, please refer toFIG. 5AtoFIG. 5F. As shown inFIG. 5AtoFIG. 5F, the non-common-ground plane can have arbitrary geometry without specific limitations; the shapes of the separated first ground region and second ground region of the non-common-ground plane are complementary to each other.

As shown inFIG. 6A, an interdigital slot SL is disposed on a 100 mm*100 mm non-common-ground plane GP and the height of the interdigital slot SL is 10 mm; a transmission line TL is disposed above the non-common-ground plane GP. And,FIG. 6Billustrates simulation results ofFIG. 6A.

As shown inFIG. 7A, a narrow slot SL is disposed on a 100 mm*100 mm non-common-ground plane GP and the width of the narrow slot SL is 0.2 mm; a transmission line TL is disposed above the non-common-ground plane GP. And,FIG. 7Billustrates simulation results ofFIG. 7A.

As shown inFIG. 8A, a wide slot SL is disposed on a 100 mm*100 mm non-common-ground plane GP and the width of the narrow slot SL is 9.8 mm; a transmission line TL is disposed above the non-common-ground plane GP. And,FIG. 8Billustrates simulation results ofFIG. 8A.

As shown inFIG. 9A, an interdigital slot SL is disposed on a 50 mm*50 mm non-common-ground plane GP and the height of the interdigital slot SL is 10 mm, that is to say, the height of the interdigital slot SL ofFIG. 9Ais the same with the height of the interdigital slot SL ofFIG. 6A, but the size of the non-common-ground plane GP ofFIG. 9Ais smaller than the size of the non-common-ground plane GP ofFIG. 6A; a transmission line TL is disposed above the non-common-ground plane GP. And,FIG. 9Billustrates simulation results ofFIG. 9A.

As shown inFIG. 10A, an interdigital slot SL is disposed on a 50 mm*50 mm non-common-ground plane GP and the height of the interdigital slot SL is 4 mm, that is to say, the size of the non-common-ground plane GP ofFIG. 10Ais the same with the size of the non-common-ground plane GP ofFIG. 9A, but the height of the interdigital slot SL ofFIG. 10Ais smaller than the height of the interdigital slot SL ofFIG. 9A. And,FIG. 10Billustrates simulation results ofFIG. 10A.

As shown inFIG. 11A, an interdigital slot SL is disposed on a 50 mm*50 mm non-common-ground plane GP and the height of the interdigital slot SL is 2 mm, that is to say, the size of the non-common-ground plane GP ofFIG. 11Ais the same with the size of the non-common-ground plane GP ofFIG. 10A, but the height of the interdigital slot SL ofFIG. 11Ais smaller than the height of the interdigital slot SL ofFIG. 10A. And,FIG. 11Billustrates simulation results ofFIG. 11A.

As shown inFIG. 12A, an interdigital slot SL is disposed on a 50 mm*50 mm non-common-ground plane GP and the height of the interdigital slot SL is 1 mm, that is to say, the size of the non-common-ground plane GP ofFIG. 12Ais the same with the size of the non-common-ground plane GP ofFIG. 11A, but the height of the interdigital slot SL ofFIG. 12Ais smaller than the height of the interdigital slot SL ofFIG. 11A. And,FIG. 12Billustrates simulation results ofFIG. 12A.

As shown inFIG. 13A, a narrow slot SL is disposed on a 50 mm*50 mm non-common-ground plane GP and the width of the narrow slot SL is 0.2 mm; a transmission line TL is disposed above the non-common-ground plane GP. And,FIG. 13Billustrates simulation results ofFIG. 13A.

As shown inFIG. 14A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 1) GP having a narrow slot SL (width=0.2 mm); the transmission line TL and the antenna AN are disposed above the non-common-ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 14Billustrates simulation results ofFIG. 14A.

As shown inFIG. 15A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 2) GP having a wide space SP (width=5 mm) and a narrow slot SL (width=0.2 mm) which are connected; the transmission line TL and the antenna AN are disposed above the non-common-ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 15Billustrates simulation results ofFIG. 15A.

As shown inFIG. 16A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 3) GP having a narrow slot SL (width=0.4 mm) and two round spaces (diameter=7 mm) which are connected through the narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 16Billustrates simulation results ofFIG. 16A.

As shown inFIG. 17A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 4) GP having a narrow slot SL (width=0.2 mm) and two rectangle spaces (size=10 mm*5 mm) which are connected through the narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 17Billustrates simulation results ofFIG. 17A.

As shown inFIG. 18A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 4) GP having a narrow slot SL (width=0.2 mm) and two rectangle spaces (size=15 mm*5 mm) which are connected through the narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 18Billustrates simulation results ofFIG. 18A.

As shown inFIG. 19A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 4) GP having a narrow slot SL (width=0.2 mm) and two rectangle spaces (size=10 mm*5 mm) which are connected through the narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 19Billustrates simulation results ofFIG. 19A.

As shown inFIG. 20A, the non-common-ground bandpass filter circuit has a 46 mm*50 mm defected ground plane (Type 4) GP having a narrow slot SL (width=0.2 mm) and two rectangle spaces (size=5 mm*5 mm) which are connected through the narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 20Billustrates simulation results ofFIG. 20A.

As shown inFIG. 21A, the non-common-ground bandpass filter circuit has a 40 mm*20 mm defected ground plane (Type 1) GP having a narrow slot SL (width=0.2 mm) and one rectangle space (size=5 mm*10 mm) which are connected. The antenna AN can be coupled to the ground through the via SHVIA, but not limited to this. And,FIG. 21Billustrates simulation results ofFIG. 21A.

As shown inFIG. 22A, the non-common-ground bandpass filter circuit has a 40 mm*20 mm defected ground plane (Type 2) GP having a narrow slot SL (width=0.2 mm), one rectangle space (size=2.5 mm*5 mm) and one square space (size=5 mm*5 mm), wherein the rectangle space (2.5 mm*5 mm) and the square space (5 mm*5 mm) are connected through the narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 22Billustrates simulation results ofFIG. 22A.

As shown inFIG. 23A, the non-common-ground bandpass filter circuit has a 40 mm*20 mm defected ground plane (Type 3) GP having a narrow slot (width=0.2 mm) SL, one rectangle space (size=5 mm*10 mm) and one square space (size=5 mm*5 mm), wherein the narrow slot SL and the rectangle space (size=5 mm*10 mm) are connected through the square space (size=5 mm*5 mm). The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 23Billustrates simulation results ofFIG. 23A.

As shown inFIG. 24A, only one narrow slot SL (width=0.2 mm) is disposed on the center of a 40 mm*20 mm defected ground plane (Type 4) GP along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And, FIG.24B illustrates simulation results ofFIG. 24A.

As shown inFIG. 25A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 40 mm*20 mm defected ground plane (Type 5) GP along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 25Billustrates simulation results ofFIG. 25A.

As shown inFIG. 26A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 40 mm*20 mm defected ground plane (Type 6) GP along the length direction of the defected ground plane GP, wherein a right-angle slot is connected with one terminal of each narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 26Billustrates simulation results ofFIG. 26A.

As shown inFIG. 27A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 40 mm*20 mm defected ground plane (Type 7) GP along the length direction of the defected ground plane, wherein a right-angle slot is connected with one terminal of each narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 27Billustrates simulation results ofFIG. 27A.

As shown inFIG. 28A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 40 mm*20 mm defected ground plane (Type 8) GP along the length direction of the defected ground plane GP, wherein a linear slot is connected with one terminal of each narrow slot SL. The antenna AN can be coupled to the ground through the via, but not limited to this. And, FIG.28B illustrates simulation results ofFIG. 28A.

As shown inFIG. 29A, a narrow slot SL (width=0.2 mm) is disposed on one side of a 40 mm*20 mm defected ground plane (Type 9) GP along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 29Billustrates simulation results ofFIG. 29A.

As shown inFIG. 30A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 25.6 mm*20 mm defected ground plane (Type 1) GP along the width direction of the defected ground plane GP, wherein a distance between the upper side/the lower side of the defected ground plane GP and the narrow slot SL is 7 mm. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 30Billustrates simulation results ofFIG. 30A.

As shown inFIG. 31A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 25.6 mm*20 mm defected ground plane (Type 1) GP along the width direction of the defected ground plane GP, wherein a distance between the upper side/the lower side of the defected ground plane GP and the narrow slot SL is 5 mm. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 31Billustrates simulation results ofFIG. 31A.

As shown inFIG. 32A, two narrow slots SL (width=0.2 mm) are disposed on two sides of a 25.6 mm*20 mm defected ground plane (Type 1) GP along the width direction of the defected ground plane GP, wherein a distance between the upper side/the lower side of the defected ground plane GP and the narrow slot SL is 3.5 mm. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 32Billustrates simulation results ofFIG. 32A.

As shown inFIG. 33A, two narrow polyline slots SL (width=0.2 mm) are disposed on two sides of a 25.6 mm*20 mm defected ground plane (Type 2) GP, wherein some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 33Billustrates simulation results ofFIG. 33A.

As shown inFIG. 34A, one narrow slot SL (width=0.2 mm) is disposed on one side near the upper side of a 25.6 mm*20 mm defected ground plane (Type 3) GP along the width direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 34Billustrates simulation results ofFIG. 34A.

As shown inFIG. 35A, one polyline narrow slot SL (width=0.2 mm) is disposed on one side near the upper side of a 28.6 mm*20 mm defected ground plane (Type 4) GP, wherein some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 35Billustrates simulation results ofFIG. 35A.

As shown inFIG. 36A, one polyline narrow slot SL (width=0.2 mm) is disposed on a (28.6 mm+20 mm)*20 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 36Billustrates simulation results ofFIG. 36A.

As shown inFIG. 37A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*30 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 37Billustrates simulation results ofFIG. 37A.

As shown inFIG. 38A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*40 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 38Billustrates simulation results ofFIG. 38A.

As shown inFIG. 39A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*50 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 39Billustrates simulation results ofFIG. 39A.

As shown inFIG. 40A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*100 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 40Billustrates simulation results ofFIG. 40A.

As shown inFIG. 41A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 38.6 mm*20 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 41Billustrates simulation results ofFIG. 41A.

As shown inFIG. 42A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 48.6 mm*20 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 42Billustrates simulation results ofFIG. 42A.

As shown inFIG. 43A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 78.6 mm*20 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 43Billustrates simulation results ofFIG. 43A.

As shown inFIG. 44A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 128.6 mm*20 mm defected ground plane (Type 5) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 44Billustrates simulation results ofFIG. 44A.

As shown inFIG. 45A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*20 mm defected ground plane (Type 6) GP, wherein some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 45Billustrates simulation results ofFIG. 45A.

As shown inFIG. 46A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*40 mm defected ground plane (Type 6) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 46Billustrates simulation results ofFIG. 46A.

As shown inFIG. 46C, one polyline narrow slot SL (width=0.2 mm) is disposed on a 28.6 mm*70 mm defected ground plane (Type 6) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 46Dillustrates simulation results ofFIG. 46C.

As shown inFIG. 47A, one polyline narrow slot SL (width=0.2 mm) is disposed on a 48.6 mm*20 mm defected ground plane (Type 6) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot PL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 47Billustrates simulation results ofFIG. 47A.

As shown in47C, one polyline narrow slot SL (width=0.2 mm) is disposed on a 78.6 mm*20 mm defected ground plane (Type 6) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 47Dillustrates simulation results ofFIG. 47C.

As shown inFIG. 48A, one linear narrow slot SL (width=0.2 mm) is disposed near the upper side of a 72.5 mm*40 mm defected ground plane (Type 1) GP along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 48Billustrates simulation results ofFIG. 48A.

As shown inFIG. 49A, one polyline narrow slot SL (width=0.2 mm) is disposed near the upper side of a 72.5 mm*40 mm defected ground plane (Type 2) GP, wherein the size of the ground plane is changed, and some parts of the narrow polyline slot SL are disposed along the width direction of the defected ground plane GP and the other parts of the narrow polyline slot SL are disposed along the length direction of the defected ground plane GP. The antenna AN can be coupled to the ground through the via, but not limited to this. And,FIG. 49Billustrates simulation results ofFIG. 49A.

Compared to the prior art, the non-common-ground bandpass filter circuit with ESD protection of the invention has a non-common-ground plane including at least two ground regions separated and insulated from each other by a defect ground structure such as a slot or a space, so that when an ESD event occurs on one ground region, the other ground region(s) will not be damaged by the ESD event. Therefore, the non-common-ground bandpass filter circuit with ESD protection of the invention can provide better ESD protection function than the common-ground bandpass filter circuit of the prior art. In addition, the non-common-ground bandpass filter circuit of the invention can also provide good surge protection function.

The present invention has been described with reference to the above embodiments, but the above embodiments are merely examples for implementing the present invention. It should be noted that the disclosed embodiments are not intended to limit the scope of the present invention. On the contrary, any modification and equivalent configuration within the spirit and scope of the appended claims shall fall within the scope of the present invention.