DESC:Form 2
The Patent Act 1970
(39 of 1970)
AND
Patent Rules 2003
Complete Specification
(Sec 10 and Rule 13)

Title A Novel U-slot Aperture Coupled Annular-Ring Microstrip Patch Antenna for Multiband GNSS Applications
Applicant(s) Entuple Technologies Pvt. Ltd.
Nationality India
Address #2730, 80 Feet Road, HAL 3rd Stage Indiranagar, Bangalore - 560038, Karnataka, India.

The following specification particularly describes the invention and the manner in which it is to be performed.

DESCRIPTION
FIELD OF INVENTION
[0001] Embodiments of the present disclosure relate generally to an antenna and more specifically to a novel u-slot aperture coupled annular-ring microstrip patch antenna for multiband GNSS applications.
RELATED ART
[0002] Microstrip patch antennas are being used in a wide variety of applications due to their low cost, light weight, easy fabrication besides ease of installation i.e., direct printing of the patch antenna onto a circuit board. FIG. 1A and 1B are the diagrams illustrating top and side views of a conventional microstrip patch antenna in an example. As shown there, the microstrip patch antenna 101 comprises a microstrip antenna (110), a microstrip transmission line (120), a substrate (130) and a ground plane (140). The microstrip antenna (110), the microstrip transmission line (120) and the ground plane (140) are comprising a high conductivity metal for example, copper.
[0003] The microstrip antenna (110) is placed on top of the substrate (130) for example, a dielectric circuit board. The frequency of operation of the antenna (101) is determined by length (150) of the microstrip antenna (110) while width (160) of the microstrip antenna (110) controls the input impedance as well as the radiation pattern. In an example, increasing the width results in increasing the bandwidth. In another example, the radiating element i.e., the microstrip antenna (110) and the microstrip transmission line (120) are placed by a process of photo etching on the substrate (130). The microstrip antenna (120) may comprise any shape for example, square, circular, rectangular and the like as per the requirement for ease of analysis and fabrication.
[0004] But conventional microstrip patch antennas are inefficient in real time applications such as space craft, air craft and low-profile antenna applications due to poor radiation and narrow frequency bandwidth. Many researchers have provided various configurations of microstrip patch antennas preferred with aperture coupling and a separate feeding mechanism as it offers greater design flexibility. However, all those configurations require a relatively complicated feed arrangement or multilayer construction which results in relatively a small bandwidth.
[0005] Hence, there is a need for a compact, reliable and efficient microstrip patch antenna that covers multiband frequencies.
SUMMARY
[0006] According to an aspect of the present disclosure, a microstrip patch antenna (205) comprising a first layer (202) of substrate equipped with a first annular radiating ring (206) on its upper surface and a second annular radiating ring (204) at its bottom surface, a second layer (210) of substrate equipped with a power divider network (214) at its bottom surface and at least two see-through orthogonal U-slot apertures (216A and 216B) on its upper surface, and a feed port (212) connected to the power divider network (214) to transfer and feed a signal, wherein the two orthogonal U-slot apertures (216A and 216B) excite the two annular radiating rings (204 and 206) in such a way that the antenna (205) covers all three frequency bands IRNSS, GPS and GLONASS for using in multiband GNSS applications.
[0007] Several aspects are described below, with reference to diagrams. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the present disclosure. One who skilled in the relevant art, however, will readily recognize that the present disclosure can be practiced without one or more of the specific details, or with other methods, etc. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the features of the present disclosure.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1A and 1B are the diagrams illustrating top and side views of a conventional microstrip patch antenna in an example.
[0009] FIG. 2A through 2C are the diagrams illustrating a u-slot aperture coupled annular-ring microstrip patch antenna in an embodiment of the present disclosure.
[0010] FIG. 2D is a table illustrating various parameters of the u-slot aperture coupled annular-ring microstrip patch antenna of the present disclosure.
[0011] FIG. 3A through 3C are the diagrams illustrating transmission and radiation characteristics that are simulated as well as measured for the u-slot aperture coupled annular-ring microstrip patch antenna of the present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EXAMPLES
[0012] FIG. 2A through 2C are the diagrams illustrating a u-slot aperture coupled annular-ring microstrip patch antenna (205) in an embodiment of the present disclosure. The microstrip patch antenna (205) of the present disclosure has a stacked structure comprising two layers of substrates (202 and 210) separated by an air gap. As shown in the FIG. 2A and 2B, 201 illustrates a first layer of substrate (202) while 203 illustrates a second layer of substrate. This bi-layered structure of the antenna reduces complexity of conventional stacked structures with more than two layers.
[0013] The first layer of substrate (202) is located on top of the antenna (205) and comprises at least two annular rings which determines the resonant frequencies. In an embodiment, the two annular rings are of different size in that a first ring (206) with smaller radius is on the upper surface of the first layer (202) while the second ring (204) with relatively large radius is located on the bottom surface of the first layer (202). These two rings (204 and 206) are separated by a distance of 2mm in an embodiment.
[0014] The second layer of substrate (210) comprises a power divider feed network (214) and a feed port (212) in the bottom surface while the upper surface of the second layer (210) is a ground plane comprising at least two apertures (216A and 216B) wherein each aperture is an orthogonal U-shaped slot that may be see through from upper surface of the second layer (210). In an embodiment, the power divider network is printed or etched on the bottom surface of the second layer (210) by a process well known in the art. The two apertures (216A and 216B) excite the annular rings (204 and 206) with the transfer of a signal through the feed port (212).
[0015] In an embodiment, the bottom surface of the second layer (210) comprises a Wilkinson power divider feed network and a 50? SMA feed port. In an example, a 1×2 Wilkinson power divider is designed at 1400MHz such that it gives a 90° phase shift between the output arms required for circular polarization. This power divider network is then optimized separately so that all the proposed frequencies are covered. In order to provide isolation between two orthogonal feed lines, a 100? isolation resistor (226) is used in the power divider network (214). In an embodiment, two FR4 substrates of thickness/height Hs=0.8mm, a dielectric constant of ?=4.4 and loss tangent tan d=0.02 are used as the first and second layers of substrates (202 and 210) which are supported by a plurality of Teflon studs and nylon screws (208).
[0016] As shown in the FIG. 2C, the antenna (205) of the present disclosure comprises the first layer/upper substrate (202) and the second/lower substrate (210) wherein the first and second layers are stalked on one another by either sandwiching process or by any conventional mechanical means of sealing them to form an air gap of 10mm between the two layers (202 and 210). The first and second rings (204 and 206) comprises varying inner and outer radii respectively that are separated by a distance of 2mm. In an embodiment, The apertures (216A and 216B) help in radiating the annular rings (204 and 206) in such a way that it covers multiband frequencies with optimized power divider network (214).
[0017] FIG. 2D is a table illustrating various parameters of the u-slot aperture coupled annular-ring microstrip patch antenna of the present disclosure. As shown there, 206a and 206b represents inner and outer radii of the first ring (206) whereas 204a and 204b represents inner and outer radii of the second ring (204) respectively. In an embodiment, the inner and outer radii of the first ring (206) is determined as 23.4mm and 27.6mm respectively whereas the inner and outer radii of the second ring (210) is determined as 29.6mm and 36.1mm respectively. Further, it is determined that the two orthogonal U-slot apertures (216A and 216B) are separated at a distance (218) of 8mm to cover a substantially acceptable multiband frequency. Also, the optimized power divider feeding network (214) comprises a varying length (220a through 220f) of printed/etched circuit such as 37mm, 50mm, 18mm, 5.1mm, 14mm and 5mm respectively in optimum directions as shown in the FIG. 2B and 2D. As shown in the FIG. 2D, 222a and 222b represents the width of the power dividing network at a loop before the location of isolation resistor (226) and after the loop passing through the orthogonal apertures (216A and 216B) which is determined as 1.5mm and 0.85mm respectively. Further, 224a and 224b represents the length of an orthogonal aperture (216B) wherein the power divider network (214) passes beneath the aperture (216B) so that the length of the aperture (216B) is determined as 17.5mm and 20mm just above and below the passing power divider network respectively.
[0018] FIG. 3A through 3C are the diagrams illustrating transmission and radiation characteristics that are simulated as well as measured for the u-slot aperture coupled annular-ring microstrip patch antenna of the present disclosure. In an embodiment, an optimized u-slot aperture coupled annular-ring microstrip patch antenna is fabricated in such a way to that of the antenna as disclosed in the FIG. 2A through 2D. In an example, the design and optimization of the antenna is also done using a conventional tool such as HFSS tool. The transmission and radiation characteristics are then determined for both simulation as well as fabricated antenna. In an embodiment, the measurements of fabricated antenna are taken in an anechoic chamber for accurate results. The simulation and actual measured parameters are compared to analyse the efficiency and bandwidth coverage.
[0019] FIG. 3A is a graph illustrating the simulated and actual measured S11 parameter in an embodiment of the present disclosure. For the frequency range 1076 to 1716 MHz, the actual measured plot is coherent with the simulated plot giving S11 less than -10dB. S-parameters describe the input-output relationship between ports (or terminals) in an electrical/communication system.
[0020] FIG. 3B is a diagram illustrating simulated and measured radiation patterns at 0° and 90° phase angles for varying frequencies of 1227MHz, 1575MHz and 1609MHz respectively. As shown there, 301 and 303 represents the radiation patterns at 0° and 90° phase shift for 1227MHz; 305 and 307 represents the radiation patterns at 0° and 90° phase shift for 1575MHz; and 309 and 311 represents the radiation patterns at 0° and 90° phase shift for 1609MHz respectively. It is determined that the measured patterns exhibit an excellent resemblance with the simulated patterns. The peak gain determined at 1227MHz, 1575MHz and 1609MHz is 5dB, 7.6dB and 7dB respectively. FIG. 3C is a graph illustrating simulated and actual measured axial ratio for the frequencies of 1227MHz, 1575MHz and 1609MHz respectively. It is determined that the axial ratio for the said frequencies are below 2.2dB for circular polarization.
[0021] Thus, the proposed antenna is appropriate and effective for multiband GNSS applications as the three frequency bands IRNSS, GPS and GLONASS are covered by the U-slot aperture coupled annular ring microstrip patch antenna of the present disclosure. Also, it is determined that the axial ratio of less than 2.2dB and S11 less than -10dB has been achieved over the aforementioned bands.
[0022] While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-discussed embodiments but should be defined only in accordance with the following claims and their equivalents.
,CLAIMS:CLAIMS
I/We Claim,
1. A microstrip patch antenna (205) comprising:
a first layer (202) of substrate equipped with a first annular radiating ring (206) on its upper surface and a second annular radiating ring (204) at its bottom surface;
a second layer (210) of substrate equipped with a power divider network (214) at its bottom surface and at least two see-through orthogonal U-slot apertures (216A and 216B) on its upper surface;
and a feed port (212) connected to the power divider network (214) to transfer and feed a signal,
wherein the two orthogonal U-slot apertures (216A and 216B) excite the two annular radiating rings (204 and 206) in such a way that the antenna (205) covers all three frequency bands IRNSS, GPS and GLONASS for using in multiband GNSS applications.
2. The microstrip patch antenna (205) as claimed in claim 1, wherein the first ring (206) is on top of the second ring (204) on same axis such that the first ring is smaller in diameter when compared to the second ring (204).
3. The microstrip patch antenna (205) as claimed in claim 2, wherein the first ring (206) and the second ring (204) are separated by a distance of 2mm.
4. The microstrip patch antenna (205) as claimed in claim 3, wherein the inner and outer radii of the first and second rings (206 and 204) are 23.4mm and 27.6mm, 29.6mm and 36.1mm respectively.
5. The microstrip patch antenna (205) as claimed in claim 4, wherein the two orthogonal U-slot apertures (216A and 216B) are separated at a distance (218) of 8mm to cover a substantially acceptable multiband frequency.
6. The microstrip patch antenna (205) as claimed in claim 5, wherein a 100? isolation resistor (226) is used in the power divider network (214) in order to provide an isolation between two orthogonal feed lines in the power divider network (214).
7. A method, system and apparatus providing one or more features as described in the paragraphs of this specification.

Date: 23-03-2021 Signature………………………
OMPRAKASH S.N
Agent for Applicant IN/PA -1095