Patent Application
20240039162
The present invention relates generally to an antenna, and more particularly to a microstrip antenna.
With the development of technology, the uses of wireless signals, such as data transmission, radar, etc., increase gradually. A bandwidth of the wireless signal depends on a structure of an antenna no matter what the use of the wireless signal is. Therefore, increasing the bandwidth of the antenna is one of the directions of research and innovation.
For example, in the use of radar, a conventional embedded microstrip antenna 100 is shown in
The substrate 10 is made of RO4350. The feedline 12 and the patch radiator 14 construct a metal layer 16 and are disposed on a top surface of the substrate 10, and another metal layer 18 is disposed on a bottom surface of the substrate 10. A side of the patch radiator 14 closer to the feedline 12 has a recess 142, and the feedline 12 feeds into the recess 142 and is connected to the patch radiator 14. Both a thickness the metal layer 16 in the third axial direction Z and a thickness of the metal layer 18 in the third axial direction Z are 0.05 mm. Referring to
In the use of radar, a resolution of the antenna is directly proportional to the bandwidth of the antenna. The larger the bandwidth of the antenna is, the larger the resolution of the antenna is, and the more updated information detected by the radar. However, as an impedance of the feedline 12 of the conventional embedded microstrip antenna 100 is 50 ohms and an area of the patch radiator 14 is relatively larger than an area of the feedline 12, an impedance of the patch radiator 14 is much smaller than the impedance of the feedline 12. As the feedline 12 directly feeds into the patch radiator 14 with the smaller impedance, the impedance from the feedline 12 to the patch radiator 14 greatly decreases, causing a large energy loss caused by a rapid impedance change, thereby affecting the bandwidth of the antenna.
Therefore, the conventional embedded microstrip antenna 100 still has room for improvement.
In view of the above, the primary objective of the present invention is to provide a microstrip antenna which could increase a bandwidth of an antenna.
The present invention provides a microstrip antenna including a substrate, a feedline, an impedance matching structure, and a patch radiator, wherein the substrate has a surface. The feedline is disposed on the surface and extends along a first axial direction. The impedance matching structure is disposed on the surface and has a first end and a second end in the first axial direction, wherein the first end is connected to the feedline. The impedance matching structure has a first section, a second section, and a third section in the first axial direction, wherein the first section has the first end, the third section has the second end, and the second section is located between the first section and the third section. The first section has a first width in a second axial direction perpendicular to the first axial direction, the second section has a second width in the second axial direction, and the third section has a third width in the second axial direction, wherein the second width is smaller than the first width and the third width. The patch radiator is disposed on the surface. The patch radiator and the second end of the impedance matching structure are adjacent and spaced by a distance in the first axial direction, and the second end of the impedance matching structure is coupled with the patch radiator through the distance.
With the aforementioned design, as an energy is fed into the patch radiator in a coupling way through the stepped impedance change and the distance, an energy loss caused by the impedance change could be reduced and the bandwidth of the antenna could be increased, thereby providing a greater resolution.
The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which
A microstrip antenna 1 according to a first embodiment of the present invention is illustrated in
The substrate 20 has two opposite surfaces (i.e., a top surface 202 and a bottom surface 204 in the third axial direction Z), wherein the top surface 202 and the bottom surface 204 respectively are perpendicular to the first axial direction X and second axial direction Y. The top surface 202 is for disposing the feedline 22, the impedance matching structure 24, and the patch radiator 26. A metal layer 28 is disposed on the bottom surface 204, wherein a thickness of the metal layer 28 in the third axial direction Z is, but not limited to, about 0.05 mm. In the current embodiment, the substrate 20 is made of RO4350 as an example, which could also be made of RO4835, RO3003, or a ceramic substrate. A thickness of the substrate 20 in the third axial direction Z ranges between 0.127 mm and 0.2 mm, wherein the thickness of the substrate 20 in the third axial direction Z in the current embodiment is 0.17 mm as an example.
The feedline 22, the impedance matching structure 24, and the patch radiator 26 construct a metal layer 30 and are laid out in order along the first axial direction X on the top surface 202 of the substrate 20. A thickness of the metal layer 30 in the third axial direction Z is 0.05 mm as an example.
The feedline 22 is a rectangular line, wherein a longitudinal direction of the feedline 22 extends along the first axial direction X. The feedline 22 has a constant width W in the second axial direction Y. In the current embodiment, the width W of the feedline 22 in the second axial direction Y is 0.24 mm as an example, and a length L of the feedline 22 in the first axial direction X is, but not limited to, 1.25 mm. An impedance of the feedline 22 is 50 ohms. An end of the feedline 22 extends to a side edge of the substrate 20, and is adapted to be a feeding end of a signal.
The impedance matching structure 24 is adapted to adjust an impedance and has a first end 24a and a second end 24b opposite to the first end 24a in the first axial direction X, wherein the first end 24a is connected to the feedline 22, and the second end 24b is adjacent to the patch radiator 26 without direct contact. In the current embodiment, the impedance matching structure 24 includes a first section 242, a second section 244, and a third section 246 in the first axial direction X, wherein the first section 242 has the first end 24a, the second section 244 is connected between the first section 242 and the third section 246, and the third section 246 has the second end 24b.
The first section 242 has a first width W1 in the second axial direction Y, the second section 244 has a second width W2 in the second axial direction Y, and the third section 246 has a third width W3 in the second axial direction Y. In the current embodiment, the first width W1 of the first section 242 is a constant, the second width W2 of the second section 244 is a constant, and the third width W3 of the third section 246 is a constant. The second width W2 is smaller than the first width W1 and the third width W3, and the third width W3 is smaller than or equal to the first width W1. In the current embodiment, the first width W1 is 0.83 mm as an example, the second width W2 is 0.5252 mm as an example, and the third width W3 is 0.7452 mm as an example. The first width W1 is about 1.580 times the second width W2, and the third width W3 is about 1.419 times the second width W2.
The first section 242 has a first length L1 in the first axial direction X, the second section 244 has a second length L2 in the first axial direction X, and the third section 246 has a third length L3 in the first axial direction X. The second length L2 is at least 3 times the third length L3, and the first length L1 is at least 7 times the third length L3. In the current embodiment, the first length L1 is 0.715 mm as an example, the second length L2 is 0.372 mm as an example, the third length L3 is 0.1 mm as an example, and a sum of the first length L1, the second length L2, and the third length L3 (i.e., a length from the first end 24a to the second end 24b) is, but not limited to, about 1.187 mm. The first length L1 is 7.15 times the third length L3, and the second length L2 is 3.72 times the third length L3.
The patch radiator 26 and the second end 24b of the impedance matching structure 24 are adjacent and spaced by a distance D in the first axial direction X, wherein the second end 24b of the impedance matching structure 24 is coupled with the patch radiator 26 through the distance D. In the current embodiment, the distance D ranges between 0.1 mm and 0.2 mm. The patch radiator 26 is a rectangular shape and has a fourth length L4 in the first axial direction X and a fourth width W4 in second axial direction Y. In the current embodiment, the fourth width W4 is larger than the third width W3 and the first width W1. The fourth length L4 could be similar to or equal to the sum of the first length L1, the second length L2, and the third length L3. In the current embodiment, the fourth length L4 is, but not limited to, slightly smaller than the sum of the first length L1 to the third length L3. The fourth length L4 could be equal to or slightly larger than the sum of the first length L1 to the third length L3. Preferably, an absolute value of a difference between the fourth length L4 and the sum of the first length L1 to the third length L3 is less than or equal to 0.05 mm. In the current embodiment, the distance D is, but not limited to, 0.1 mm, the fourth length L4 is 1.143 mm as an example, and the fourth width W4 is 1.168 mm as an example.
An equivalent circuit of the microstrip antenna 1 is shown in
The first section 242, the second section 244, and the third section 246 of the impedance matching structure 24 form a stepped impedance change, wherein an energy loss caused by a rapid impedance change could be reduced through the stepped impedance change, and a bandwidth could be increased due to the parasitic capacitance C3 formed in the distance D that feeds an energy to the patch radiator 26 in a coupling way. A capacitance value of the parasitic capacitance C3 could be correspondingly adjusted by adjusting the third width W3 of the third section 246, thereby obtaining the needed bandwidth.
A microstrip antenna 2 according to a second embodiment of the present invention is shown in
It must be pointed out that the embodiments described above are only some preferred embodiments of the present invention. All equivalent structures which employ the concepts disclosed in this specification and the appended claims should fall within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111128447 | Jul 2022 | TW | national |
