DESC:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of wideband low-profile planar substrate integrated waveguide (SIW) cavity-backed antennas, and in specific relates to design a wideband SIW cavity-backed antenna that provides wide bandwidth, high gain, and a unidirectional radiation pattern over the operating bandwidth.
Background of the invention:
[0002] Traditional waveguide back cavity antenna has characteristics of large power capacity, small loss, easiness in realizing narrow beams and the like, but is high in section, heavy in structure, high in machining precision requirement and not easy to integrate. The substrate integrated waveguide back cavity antenna has the characteristics of low insertion loss, low profile, light weight and the like, is limited by cavity resonance, and has the inherent problems of narrow bandwidth and the like in the traditional substrate integrated waveguide back cavity antenna.
[0003] One of the earlier works on substrate integrated waveguide cavity-backed antenna is done by Wu et al., where two types of substrate integrated waveguide (SIW) cavity-backed slot (CBS) antennas are proposed for bandwidth enhancement. First, a quad-resonance SIW CBS antenna is proposed using a cross-shaped slot and loading unbalanced shorting vias. Next, a penta-resonance SIW CBS antenna with a cross-shaped slot is proposed, in which two pairs of shorting vias are loaded. However, a cross shaped slot is utilized in this antenna and uses unbalanced vias to achieve high fractional bandwidth.
[0004] The existing antenna design requires the removal of the substrate behind the conductor portion of the cavity. This can be challenging to achieve using traditional fabrication techniques, such as printed circuit board (PCB) etching or laser cutting. Another difficulty in the existing antenna design is the construction of antenna arrays. Antenna arrays are typically made up of multiple individual antennas that are arranged in a specific way to achieve a desired radiation pattern. Constructing antenna arrays can be challenging, especially when the individual antennas are complex in design.
[0005] Further, some antenna designs require the use of stacked cavities in different layers. This can be challenging to fabricate, as it requires careful alignment of the different layers. Many antenna designs need to be integrated with planar circuits, such as microwave filters and amplifiers. This can be challenging, as the antenna and the planar circuit must be carefully matched to each other in order to achieve optimal performance. Another difficulty is achieving a wideband antenna with high gain. Wideband antennas are typically more difficult to design and fabricate than narrowband antennas.
[0006] In addition to the difficulties mentioned above, there are a number of other challenges that can arise in antenna fabrication, depending on the specific design of the antenna. For example, it can be challenging to fabricate antennas with very fine features or with very tight tolerances.
[0007] Therefore, there is a need to design a wideband substrate integrated waveguide (SIW) cavity-backed antenna that is low-profile, cost-effective, and low cross-polarization, and that has wide bandwidth, high gain, and a unidirectional radiation pattern. There is also a need for a wideband SIW cavity-backed antenna that have a simple construction with a single cavity to overcome the fabrication difficulties and integration problems.
Objectives of the invention:
[0008] The primary objective of the invention is to design a wideband substrate integrated waveguide (SIW) cavity-backed antenna that provides wide bandwidth, high gain, and a unidirectional radiation pattern over the operating bandwidth.
[0009] The other objective of the invention is to provide a wideband SIW cavity-backed antenna with L-shaped slot for X-band applications.
[0010] Another objective of the invention is to provide a wideband SIW cavity-backed antenna that is low-profile, cost-effective, and that archives low cross-polarization.
[0011] The other objective of the invention is to provide a wideband SIW cavity-backed antenna that can generate and merge two narrow bands into a wide bandwidth.
[0012] Yet another objective of the invention is to design a simple wideband SIW cavity-backed antenna with a single cavity to overcome fabrication difficulties.
[0013] Further objective of the invention is to design a simple wideband SIW cavity-backed antenna that overcome integration problems with planar circuits.
Summary of the invention:
[0014] The present disclosure proposes a wideband SIW cavity-backed antenna with L-shaped slot for X-band applications. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
[0015] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a wideband cavity-backed antenna to enhance the bandwidth of the antenna with an L-shaped slot utilizing a substrate integrated waveguide (SIW) cavity.
[0016] According to an aspect, the invention provides a wideband substrate integrated waveguide (SIW) cavity-backed antenna with L-shaped slot. Introduction of the L-shaped slot perturbs the current distribution of the TE120 mode, resulting in the generation of two narrow bands such as 600 MHz (9.6 GHz to 10.2 GHZ) and 300 MHz (10.5 GHz to 10.8 GHz). With the placement of a metallic via the two bands may be merged and resulting in a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz.
[0017] Due to its wide bandwidth, high gain, and compact form, the suggested antenna demonstrates suitability for a range of practical applications, including satellite communication, radar systems, and various wireless applications operating in the X-band frequencies. The proposed wideband operation utilizes a dielectric substrate known as Rogers RT/Duroid 5880, which has a height of 1.57 mm and a dielectric constant of 2.2 and peak gain 6.3 dBi.
[0018] According to another aspect, the invention provides the SIW cavity may be created by positioning metallic cylinders or vias along the edges of the substrate, effectively shorting the top and bottom conductors. The pitch is the distance between two adjacent vias, may be carefully selected to minimize energy leakage from the sidewalls of the SIW cavity. The L-shaped slot acts as a radiator and may be etched on the bottom metal plate of the substrate to minimize the spurious radiation effects from the micro-strip feeding line.
[0019] The L-shaped slot may be positioned at some distance from the top wall, which may be formed by the vias in x-direction. In the proposed structure of the SIW cavity, a grounded coplanar waveguide (GCPW) feeding method may be employed at the bottom sidewall of the SIW cavity. For ease of measurement, one end of the 50Omicro-strip line may be attached to the center conductor of the GCPW, which has the same width as the micro-strip line. This arrangement also facilitates planar integration of the components.
[0020] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0021] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.
[0022] FIG. 1 illustrates a schematic diagram of a wideband substrate integrated waveguide (SIW) cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0023] FIG. 2A illustrates a reflection coefficient plot of a SIW cavity-backed antenna comprises the SIW Cavity with L-shaped slot, in accordance to an exemplary embodiment of the invention.
[0024] FIG. 2B illustrates a reflection coefficient plot of the proposed wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0025] FIG. 3A illustrates electric field intensities of the proposed wideband SIW cavity-backed antenna at a resonant frequency of 10 GHz, in accordance to an exemplary embodiment of the invention.
[0026] FIG. 3B illustrates electric field intensities of the proposed wideband SIW cavity-backed antenna at a resonant frequency of 10.73 GHz, in accordance to an exemplary embodiment of the invention.
[0027] FIGs. 4A to 4D illustrate radiation patterns of H-Plane at two resonant frequencies, in accordance to an exemplary embodiment of the invention.
[0028] FIGs. 5A to 5D illustrate radiation patterns of E-Plane at two resonant frequencies, in accordance to an exemplary embodiment of the invention.
[0029] FIG. 6 illustrates an input impedance plot for a stage I antenna, a stage II antenna, and the wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0030] FIG. 7 illustrates a reflection coefficient plot for the stage II antenna, and the wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0031] FIG. 8 illustrates a reflection coefficient plot for simulated versus experimental values of the wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0032] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.
[0033] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a wideband cavity-backed antenna to enhance the bandwidth of the antenna with an L-shaped slot utilizing a substrate integrated waveguide (SIW) cavity.
[0034] According to an exemplary embodiment of the invention, FIG. 1 refers to a schematic diagram of a wideband substrate integrated waveguide (SIW) cavity-backed antenna 100. In some embodiments, the present invention discloses about the wideband SIW cavity-backed antenna 100 with an L-shaped slot 104 and a metallic via 106. In specific, this design to enhance the bandwidth of the wideband SIW cavity-backed antenna 100 with the L-shaped slot 104 may be proposed, utilizing a substrate integrated waveguide (SIW) cavity.
[0035] The introduction of the L-shaped slot 104 perturbs the current distribution of the TE120 mode, resulting in the generation of two narrow bands such as 600 MHz (9.6 GHz to 10.2 GHZ) and 300 MHz (10.5 GHz to 10.8 GHz). With the placement of a metallic via 106 the two bands may be merged and resulting in a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz. Due to its wide bandwidth, high gain, and compact form, the proposed wideband SIW cavity-backed antenna 100 demonstrates suitability for a range of practical applications.
[0036] The wideband SIW cavity-backed antenna 100 may be utilises a dielectric substrate 102 known as either Rogers RT/Duroid 5880 or any similar substrate, which has a height of 1.57 mm and a dielectric constant of 2.2 and peak gain 6.3 dBi. The wideband SIW cavity-backed antenna 100 has a bandwidth of 1270 MHz. Further, the wideband SIW cavity-backed antenna 100 may be created by positioning plurality of metallic cylinders 108 (or vias) along the edges of the dielectric substrate 102, effectively shorting the top and bottom conductors, as depicted in FIG. 1.
[0037] The diameter of the vias, denoted as 'd', and the pitch, denoted as 'p' (the distance between two adjacent vias), may be carefully selected to minimize energy leakage from the sidewalls of the wideband SIW cavity-backed antenna 100. The L-shaped slot 104 acts as a radiator and may be etched on the bottom metal plate of the dielectric substrate 102 to minimize the spurious radiation effects from a micro-strip feeding line 110. It may be positioned at a distance of 'dsu' from the top wall, which may be formed by the vias in the x-direction, as illustrated in FIG. 1.
[0038] In one embodiment herein, in the proposed structure of the wideband SIW cavity-backed antenna 100, a grounded coplanar waveguide (GCPW) feeding method may be employed at the bottom sidewall of the SIW cavity. For ease of measurement, one end of the 50 O micro-strip line 110 may be attached to the center conductor of the GCPW, which. The same width as the micro-strip line 110. This arrangement may also facilitate planar integration of the components.
[0039] Referring to FIG. 1, LSub and WSub are the length and width of the dielectric substrate 102, where length and width of the dielectric substrate 102 are 28.5 mm and 24.5 mm, respectively. The height of the dielectric substrate 102 is of at least 1.57 mm, which is denoted as h. LCav and WCav are the length and width of the SIW cavity, where the length and width of the SIW cavity are 22.5 mm and 22.5 mm, respectively. LS1 and LS2 are the lengths of the two segments of the L-shaped slot 104, where lengths of the two segments of the L-shaped slot 104 are 20.5 mm and 8.4 mm, respectively. Lms and Wms are the length and width of the micro-strip feed line 110, where the length and width of the micro-strip feed line 110 are 4 mm and 3.8 mm, respectively.
[0040] The distance between the L-shaped slot 104 and the top wall of the SIW cavity is of at least 5.5 mm, which is denoted as dsu. The length of the metal via 108 that connects the micro-strip feed line 110 to the SIW cavity is of at least 6 mm, which is denoted as Lm. The gap between the micro-strip feed line 110 and the metal via 108 is of at least 0.6 mm, which is denoted as gm of 0.6. The pitch of the metal vias 108 that form the sidewalls of the SIW cavity is of at least 1.5 mm, which is denoted as p. The diameter of the metal vias 108 that form the sidewalls of the SIW cavity is at least 1 mm, which is denoted as d.
[0041] In some embodiment herein, the designed proposed wideband SIW cavity-backed antenna 100 is evolved in three stages. In first stage, the SIW cavity-backed antenna comprises only the SIW Cavity (stage I antenna). In second stage, the SIW cavity-backed antenna comprises the SIW Cavity with L-shaped slot (stage II antenna). In third stage, the wideband SIW cavity-backed antenna 100 comprises the SIW Cavity with the L-shaped slot 104 and one metallic via 106, as shown in FIG. 1.
[0042] Initially, the resonant frequency of the SIW cavity (stage I) is found out from the formula:

[0043] The wideband SIW cavity-backed antenna 100 with the L-shaped slot 104 with the metallic via 106, providing a bandwidth of 1.27GHz (12.13%) and a gain of 6.35 dBi, featuring a unidirectional radiation pattern. The combination of the L-shaped slot 104 and the metallic via 106 assists the SIW cavity to merge at least two hybrid modes, resulting in a broad bandwidth response. The wideband SIW cavity-backed antenna 100 is excited using a simple GCPW feeding technique, simplifying the design while maintaining consistent gain in the desired bandwidth within its planar structure.
[0044] According to another exemplary embodiment of the invention, FIG. 2A refers to a reflection coefficient plot 200 of the stage II antenna (the SIW cavity-backed antenna comprises the SIW Cavity with L-shaped slot). The L-shaped slot is etched on the ground plane of the cavity. This L-shaped slot acts as a radiating element for the cavity and generates two narrow bands: Band 1 from 9.6 GHz to 10.2 GHz (600 MHz wide) and Band 2 from 10.5 GHz to 10.8 GHz (300 MHz wide), as shown in FIG. 2A.
[0045] According to another exemplary embodiment of the invention, FIG. 2B refers to a reflection coefficient plot of 202 for the wideband SIW cavity-backed antenna 100. The metallic via 106 is placed in the SIW cavity, as shown in FIG. 1. The metallic via 106 acts as an inductive load, which merges the two narrow bands into a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz, as shown in FIG. 2B. This approach is configured for generating wide bandwidth in SIW slot antennas.
[0046] The SIW cavity is built using a grid of metallic pins on a circuit board. These pins trap electromagnetic waves like a tiny cage, enabling the design of compact, high-performance antennas. The size and spacing of the pins are crucial for minimizing energy leakage, as depicted in FIG. 1. The via dimensions (diameter, d, and pitch, p) are meticulously chosen, with p = 2d and d = 0.1?0, to minimize energy leakage from the SIW cavity's sidewalls (?0 being the free-space wavelength)
[0047] The stage II antenna features an L-shaped slot etched on the bottom substrate plate, positioned dsu mm away from the via-formed top wall in the x-direction. The wideband SIW cavity-backed antenna 100 employs a GCPW feed on the SIW cavity sidewall. The 50O microstrip line conveniently connects to the GCPW center conductor (sharing the same width) for easy measurement and facilitates planar integration. The metallic via 106 sits 5.4mm from the L-slot 104, minimizing spurious radiation from the microstrip feeding line due to the slots ground plane placement.
[0048] According to another exemplary embodiment of the invention, FIG. 3A refers to electric field intensities 300 of the proposed wideband SIW cavity-backed antenna 100 at a resonant frequency of 10 GHz. FIG. 3B refers to electric field intensities 302 of the proposed wideband SIW cavity-backed antenna 100 at a resonant frequency of 10.73 GHz.
[0049] At the lower resonant frequency, 10 GHz, the electric field distribution is more predominant below the L-shaped slot 104. This means that the electric field is stronger in the region below the slot than in the region above the L-shaped slot 104, as shown in FIG. 3A. At the upper resonant frequency, 10.73 GHz, the electric field distribution is more predominant above the L-shaped slot 104, as shown in FIG. 3B.
[0050] This non-uniform electric field distribution is beneficial for wideband SIW cavity-backed antenna’s radiation. When the electric field is not uniform, the wideband SIW cavity-backed antenna 100 creates a current distribution that is also not uniform. This non-uniform current distribution is what generates the wideband SIW cavity-backed antenna’s radiation pattern.
[0051] The radiation patterns of the wideband SIW cavity-backed antenna 100 in the H-plane at the two resonant frequencies are shown in FIG. 3A and FIG. 3B. The non-uniform electric field distribution is particularly beneficial for generating wideband radiation. This is because the non-uniform electric field distribution can be controlled to produce different current distributions at different frequencies. This allows the antenna to radiate effectively over a wide range of frequencies.
[0052] In conclusion, the non-uniform electric field distribution in the proposed wideband SIW cavity-backed antenna 100 assists to radiate effectively by generating a non-uniform current distribution, which in turn generates a magnetic field and an electric field that is radiated by the wideband SIW cavity-backed antenna 100.
[0053] According to another exemplary embodiment of the invention, FIGs. 4A to 4D refers to radiation patterns 400 to 406 of H-Plane at two resonant frequencies. FIG. 4A shows the H-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 4B shows the H-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°). FIG. 4C shows the H-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 4D shows the H-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°).
[0054] The peak values of the co-polarization and cross-polarization components are 5.7 dBi and -47 dBi, respectively. The co-polarization component is the desired signal that is radiated by the wideband SIW cavity-backed antenna 100. The cross-polarization component is an undesired signal that is radiated by the antenna in a direction perpendicular to the desired signal. The high peak value of the co-polarization component and the low peak value of the cross-polarization component indicate that the wideband SIW cavity-backed antenna 100 is radiating effectively.
[0055] According to another exemplary embodiment of the invention, FIGs. 5A to 5D refers to radiation patterns 500 to 506 of E-Plane at two resonant frequencies. FIG. 5A shows the E-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 5B shows the E-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°). FIG. 5C shows the E-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 5D shows the E-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°).
[0056] The peak values of the co-polarization and cross-polarization components are 6.3 dBi and -47 dBi, respectively. The co-polarization component is the desired signal that is radiated by the wideband SIW cavity-backed antenna 100.
[0057] According to another exemplary embodiment of the invention, FIG. 6 refers to an input impedance plot 600 for the stage I antenna, the stage II antenna, and the wideband SIW cavity-backed antenna 100. The stage I antenna of the design, a simple SIW cavity without slots, exhibits three prominent cavity modes: TE110 at 6.7 GHz, TE120 at 10.3 GHz, and TE130 at 13.5 GHz. These modes are readily identified by peaks in the real part of the input impedance plot, as shown in FIG. 6. Introducing an L-shaped slot (the stage II antenna) significantly disrupts these modes, leading to the emergence of two hybrid modes: odd TE120 and even TE120 at 9.7 GHz and 10.7 GHz, respectively. This translates to two narrow bands in the impedance response: Band 1 (600 MHz, 9.6-10.2 GHz) and Band 2 (300 MHz, 10.5-10.8 GHz), as shown in FIG. 6.
[0058] According to another exemplary embodiment of the invention, FIG. 7 refers to a reflection coefficient plot 700 for the stage II antenna, and the wideband SIW cavity-backed antenna 100. The metallic via 106 disrupts the electric field distribution around the L-shaped slot 104, particularly at the two resonant frequencies of the narrow bands. This disruption alters the current distribution within the SIW cavity, leading to improved impedance matching at the frequencies between the two original resonances. This, in turn, merges the two bands into a wider one (1.1 GHz) with a more consistent impedance response across the range.
[0059] The introduction of the metallic via 106 significantly improves impedance matching by acting as a coupling element between two distinct resonant modes identified in the stage II antenna (without the via): odd TE120 at 9.7 GHz and even TE120 at 10.7 GHz. This coupling effectively merges the two narrow bands, resulting in a significantly wider bandwidth of 1.1 GHz (9.78 GHz to 10.88 GHz), as evidenced in FIG. 7.
[0060] Analyzing the electric field distribution in FIG. 7 further elucidates the mechanism behind the enhanced bandwidth. We observe significant field concentration around the metallic via 106, particularly at the resonant frequencies of the individual modes. This suggests that the metallic via 106 acts as a local perturbation, modifying the current distribution within the cavity and enhancing the interaction between the two mode fields. This interaction results in the merging of the resonant frequencies and broadening of the bandwidth.
[0061] While the overall resonant frequencies remain relatively unperturbed by the metallic via 106. The concentrated field intensity around the metallic via 106 indicates localized modifications to the field pattern, potentially affecting higher-order cavity modes beyond the fundamental TE120.
[0062] According to another exemplary embodiment of the invention, FIG. 8 refers to a reflection coefficient plot 800 for simulated versus experimental values of the wideband SIW cavity-backed antenna 100. The fabricated wideband SIW cavity-backed antenna 100 achieves an impressive 1.27 GHz bandwidth (12.13%) spanning from 9.84 GHz to 11.11 GHz. The strategic integration of the L-shaped slot 104 and the metallic via 106 facilitates this superior bandwidth performance while simultaneously delivering a notable peak gain of 6.35 dBi. Additionally, the wideband SIW cavity-backed antenna 100 exhibits a well-defined unidirectional radiation pattern, making it suitable for applications requiring focused signal transmission.
[0063] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, a wideband SIW cavity-backed antenna 100 to enhance the bandwidth of the antenna with an L-shaped slot utilizing a substrate integrated waveguide (SIW) cavity.
[0064] The proposed wideband SIW cavity-backed antenna 100 is a low profile, cost effective, and low cross polarization antenna. The proposed wideband SIW cavity-backed antenna 100 achieves wide bandwidth, high gain and a unidirectional radiation pattern over the operating bandwidth. The wideband SIW cavity-backed antenna 100 has the L-shaped slot 104 engraved on the ground plane of the cavity, which acts as a radiating slot for the cavity. This design assists in generation of two narrow bands such as 600 MHz (9.6GHz to 10.2 GHZ) and 300 MHz (10.5GHz to 10.8GHz).
[0065] The wideband SIW cavity-backed antenna 100 has the metallic via 106 at its center, which results in a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz. This is due to the inductive loading of the metallic via 106, which aid in generating wide bandwidth in the wideband SIW cavity-backed antenna 100. The wideband SIW cavity-backed antenna 100 comprises a simple construction with usage of a single cavity, thereby overcome the fabrication difficulties. The wideband SIW cavity-backed antenna 100 utilises the micro-strip line 110 as the feeding technique, thereby overcome integration problems with planar circuits.
[0066] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
,CLAIMS:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of wideband low-profile planar substrate integrated waveguide (SIW) cavity-backed antennas, and in specific relates to design a wideband SIW cavity-backed antenna that provides wide bandwidth, high gain, and a unidirectional radiation pattern over the operating bandwidth.
Background of the invention:
[0002] Traditional waveguide back cavity antenna has characteristics of large power capacity, small loss, easiness in realizing narrow beams and the like, but is high in section, heavy in structure, high in machining precision requirement and not easy to integrate. The substrate integrated waveguide back cavity antenna has the characteristics of low insertion loss, low profile, light weight and the like, is limited by cavity resonance, and has the inherent problems of narrow bandwidth and the like in the traditional substrate integrated waveguide back cavity antenna.
[0003] One of the earlier works on substrate integrated waveguide cavity-backed antenna is done by Wu et al., where two types of substrate integrated waveguide (SIW) cavity-backed slot (CBS) antennas are proposed for bandwidth enhancement. First, a quad-resonance SIW CBS antenna is proposed using a cross-shaped slot and loading unbalanced shorting vias. Next, a penta-resonance SIW CBS antenna with a cross-shaped slot is proposed, in which two pairs of shorting vias are loaded. However, a cross shaped slot is utilized in this antenna and uses unbalanced vias to achieve high fractional bandwidth.
[0004] The existing antenna design requires the removal of the substrate behind the conductor portion of the cavity. This can be challenging to achieve using traditional fabrication techniques, such as printed circuit board (PCB) etching or laser cutting. Another difficulty in the existing antenna design is the construction of antenna arrays. Antenna arrays are typically made up of multiple individual antennas that are arranged in a specific way to achieve a desired radiation pattern. Constructing antenna arrays can be challenging, especially when the individual antennas are complex in design.
[0005] Further, some antenna designs require the use of stacked cavities in different layers. This can be challenging to fabricate, as it requires careful alignment of the different layers. Many antenna designs need to be integrated with planar circuits, such as microwave filters and amplifiers. This can be challenging, as the antenna and the planar circuit must be carefully matched to each other in order to achieve optimal performance. Another difficulty is achieving a wideband antenna with high gain. Wideband antennas are typically more difficult to design and fabricate than narrowband antennas.
[0006] In addition to the difficulties mentioned above, there are a number of other challenges that can arise in antenna fabrication, depending on the specific design of the antenna. For example, it can be challenging to fabricate antennas with very fine features or with very tight tolerances.
[0007] Therefore, there is a need to design a wideband substrate integrated waveguide (SIW) cavity-backed antenna that is low-profile, cost-effective, and low cross-polarization, and that has wide bandwidth, high gain, and a unidirectional radiation pattern. There is also a need for a wideband SIW cavity-backed antenna that have a simple construction with a single cavity to overcome the fabrication difficulties and integration problems.
Objectives of the invention:
[0008] The primary objective of the invention is to design a wideband substrate integrated waveguide (SIW) cavity-backed antenna that provides wide bandwidth, high gain, and a unidirectional radiation pattern over the operating bandwidth.
[0009] The other objective of the invention is to provide a wideband SIW cavity-backed antenna with L-shaped slot for X-band applications.
[0010] Another objective of the invention is to provide a wideband SIW cavity-backed antenna that is low-profile, cost-effective, and that archives low cross-polarization.
[0011] The other objective of the invention is to provide a wideband SIW cavity-backed antenna that can generate and merge two narrow bands into a wide bandwidth.
[0012] Yet another objective of the invention is to design a simple wideband SIW cavity-backed antenna with a single cavity to overcome fabrication difficulties.
[0013] Further objective of the invention is to design a simple wideband SIW cavity-backed antenna that overcome integration problems with planar circuits.
Summary of the invention:
[0014] The present disclosure proposes a wideband SIW cavity-backed antenna with L-shaped slot for X-band applications. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.
[0015] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a wideband cavity-backed antenna to enhance the bandwidth of the antenna with an L-shaped slot utilizing a substrate integrated waveguide (SIW) cavity.
[0016] According to an aspect, the invention provides a wideband substrate integrated waveguide (SIW) cavity-backed antenna with L-shaped slot. Introduction of the L-shaped slot perturbs the current distribution of the TE120 mode, resulting in the generation of two narrow bands such as 600 MHz (9.6 GHz to 10.2 GHZ) and 300 MHz (10.5 GHz to 10.8 GHz). With the placement of a metallic via the two bands may be merged and resulting in a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz.
[0017] Due to its wide bandwidth, high gain, and compact form, the suggested antenna demonstrates suitability for a range of practical applications, including satellite communication, radar systems, and various wireless applications operating in the X-band frequencies. The proposed wideband operation utilizes a dielectric substrate known as Rogers RT/Duroid 5880, which has a height of 1.57 mm and a dielectric constant of 2.2 and peak gain 6.3 dBi.
[0018] According to another aspect, the invention provides the SIW cavity may be created by positioning metallic cylinders or vias along the edges of the substrate, effectively shorting the top and bottom conductors. The pitch is the distance between two adjacent vias, may be carefully selected to minimize energy leakage from the sidewalls of the SIW cavity. The L-shaped slot acts as a radiator and may be etched on the bottom metal plate of the substrate to minimize the spurious radiation effects from the micro-strip feeding line.
[0019] The L-shaped slot may be positioned at some distance from the top wall, which may be formed by the vias in x-direction. In the proposed structure of the SIW cavity, a grounded coplanar waveguide (GCPW) feeding method may be employed at the bottom sidewall of the SIW cavity. For ease of measurement, one end of the 50Omicro-strip line may be attached to the center conductor of the GCPW, which has the same width as the micro-strip line. This arrangement also facilitates planar integration of the components.
[0020] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0021] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.
[0022] FIG. 1 illustrates a schematic diagram of a wideband substrate integrated waveguide (SIW) cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0023] FIG. 2A illustrates a reflection coefficient plot of a SIW cavity-backed antenna comprises the SIW Cavity with L-shaped slot, in accordance to an exemplary embodiment of the invention.
[0024] FIG. 2B illustrates a reflection coefficient plot of the proposed wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0025] FIG. 3A illustrates electric field intensities of the proposed wideband SIW cavity-backed antenna at a resonant frequency of 10 GHz, in accordance to an exemplary embodiment of the invention.
[0026] FIG. 3B illustrates electric field intensities of the proposed wideband SIW cavity-backed antenna at a resonant frequency of 10.73 GHz, in accordance to an exemplary embodiment of the invention.
[0027] FIGs. 4A to 4D illustrate radiation patterns of H-Plane at two resonant frequencies, in accordance to an exemplary embodiment of the invention.
[0028] FIGs. 5A to 5D illustrate radiation patterns of E-Plane at two resonant frequencies, in accordance to an exemplary embodiment of the invention.
[0029] FIG. 6 illustrates an input impedance plot for a stage I antenna, a stage II antenna, and the wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0030] FIG. 7 illustrates a reflection coefficient plot for the stage II antenna, and the wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
[0031] FIG. 8 illustrates a reflection coefficient plot for simulated versus experimental values of the wideband SIW cavity-backed antenna, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0032] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.
[0033] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a wideband cavity-backed antenna to enhance the bandwidth of the antenna with an L-shaped slot utilizing a substrate integrated waveguide (SIW) cavity.
[0034] According to an exemplary embodiment of the invention, FIG. 1 refers to a schematic diagram of a wideband substrate integrated waveguide (SIW) cavity-backed antenna 100. In some embodiments, the present invention discloses about the wideband SIW cavity-backed antenna 100 with an L-shaped slot 104 and a metallic via 106. In specific, this design to enhance the bandwidth of the wideband SIW cavity-backed antenna 100 with the L-shaped slot 104 may be proposed, utilizing a substrate integrated waveguide (SIW) cavity.
[0035] The introduction of the L-shaped slot 104 perturbs the current distribution of the TE120 mode, resulting in the generation of two narrow bands such as 600 MHz (9.6 GHz to 10.2 GHZ) and 300 MHz (10.5 GHz to 10.8 GHz). With the placement of a metallic via 106 the two bands may be merged and resulting in a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz. Due to its wide bandwidth, high gain, and compact form, the proposed wideband SIW cavity-backed antenna 100 demonstrates suitability for a range of practical applications.
[0036] The wideband SIW cavity-backed antenna 100 may be utilises a dielectric substrate 102 known as either Rogers RT/Duroid 5880 or any similar substrate, which has a height of 1.57 mm and a dielectric constant of 2.2 and peak gain 6.3 dBi. The wideband SIW cavity-backed antenna 100 has a bandwidth of 1270 MHz. Further, the wideband SIW cavity-backed antenna 100 may be created by positioning plurality of metallic cylinders 108 (or vias) along the edges of the dielectric substrate 102, effectively shorting the top and bottom conductors, as depicted in FIG. 1.
[0037] The diameter of the vias, denoted as 'd', and the pitch, denoted as 'p' (the distance between two adjacent vias), may be carefully selected to minimize energy leakage from the sidewalls of the wideband SIW cavity-backed antenna 100. The L-shaped slot 104 acts as a radiator and may be etched on the bottom metal plate of the dielectric substrate 102 to minimize the spurious radiation effects from a micro-strip feeding line 110. It may be positioned at a distance of 'dsu' from the top wall, which may be formed by the vias in the x-direction, as illustrated in FIG. 1.
[0038] In one embodiment herein, in the proposed structure of the wideband SIW cavity-backed antenna 100, a grounded coplanar waveguide (GCPW) feeding method may be employed at the bottom sidewall of the SIW cavity. For ease of measurement, one end of the 50 O micro-strip line 110 may be attached to the center conductor of the GCPW, which. The same width as the micro-strip line 110. This arrangement may also facilitate planar integration of the components.
[0039] Referring to FIG. 1, LSub and WSub are the length and width of the dielectric substrate 102, where length and width of the dielectric substrate 102 are 28.5 mm and 24.5 mm, respectively. The height of the dielectric substrate 102 is of at least 1.57 mm, which is denoted as h. LCav and WCav are the length and width of the SIW cavity, where the length and width of the SIW cavity are 22.5 mm and 22.5 mm, respectively. LS1 and LS2 are the lengths of the two segments of the L-shaped slot 104, where lengths of the two segments of the L-shaped slot 104 are 20.5 mm and 8.4 mm, respectively. Lms and Wms are the length and width of the micro-strip feed line 110, where the length and width of the micro-strip feed line 110 are 4 mm and 3.8 mm, respectively.
[0040] The distance between the L-shaped slot 104 and the top wall of the SIW cavity is of at least 5.5 mm, which is denoted as dsu. The length of the metal via 108 that connects the micro-strip feed line 110 to the SIW cavity is of at least 6 mm, which is denoted as Lm. The gap between the micro-strip feed line 110 and the metal via 108 is of at least 0.6 mm, which is denoted as gm of 0.6. The pitch of the metal vias 108 that form the sidewalls of the SIW cavity is of at least 1.5 mm, which is denoted as p. The diameter of the metal vias 108 that form the sidewalls of the SIW cavity is at least 1 mm, which is denoted as d.
[0041] In some embodiment herein, the designed proposed wideband SIW cavity-backed antenna 100 is evolved in three stages. In first stage, the SIW cavity-backed antenna comprises only the SIW Cavity (stage I antenna). In second stage, the SIW cavity-backed antenna comprises the SIW Cavity with L-shaped slot (stage II antenna). In third stage, the wideband SIW cavity-backed antenna 100 comprises the SIW Cavity with the L-shaped slot 104 and one metallic via 106, as shown in FIG. 1.
[0042] Initially, the resonant frequency of the SIW cavity (stage I) is found out from the formula:

[0043] The wideband SIW cavity-backed antenna 100 with the L-shaped slot 104 with the metallic via 106, providing a bandwidth of 1.27GHz (12.13%) and a gain of 6.35 dBi, featuring a unidirectional radiation pattern. The combination of the L-shaped slot 104 and the metallic via 106 assists the SIW cavity to merge at least two hybrid modes, resulting in a broad bandwidth response. The wideband SIW cavity-backed antenna 100 is excited using a simple GCPW feeding technique, simplifying the design while maintaining consistent gain in the desired bandwidth within its planar structure.
[0044] According to another exemplary embodiment of the invention, FIG. 2A refers to a reflection coefficient plot 200 of the stage II antenna (the SIW cavity-backed antenna comprises the SIW Cavity with L-shaped slot). The L-shaped slot is etched on the ground plane of the cavity. This L-shaped slot acts as a radiating element for the cavity and generates two narrow bands: Band 1 from 9.6 GHz to 10.2 GHz (600 MHz wide) and Band 2 from 10.5 GHz to 10.8 GHz (300 MHz wide), as shown in FIG. 2A.
[0045] According to another exemplary embodiment of the invention, FIG. 2B refers to a reflection coefficient plot of 202 for the wideband SIW cavity-backed antenna 100. The metallic via 106 is placed in the SIW cavity, as shown in FIG. 1. The metallic via 106 acts as an inductive load, which merges the two narrow bands into a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz, as shown in FIG. 2B. This approach is configured for generating wide bandwidth in SIW slot antennas.
[0046] The SIW cavity is built using a grid of metallic pins on a circuit board. These pins trap electromagnetic waves like a tiny cage, enabling the design of compact, high-performance antennas. The size and spacing of the pins are crucial for minimizing energy leakage, as depicted in FIG. 1. The via dimensions (diameter, d, and pitch, p) are meticulously chosen, with p = 2d and d = 0.1?0, to minimize energy leakage from the SIW cavity's sidewalls (?0 being the free-space wavelength)
[0047] The stage II antenna features an L-shaped slot etched on the bottom substrate plate, positioned dsu mm away from the via-formed top wall in the x-direction. The wideband SIW cavity-backed antenna 100 employs a GCPW feed on the SIW cavity sidewall. The 50O microstrip line conveniently connects to the GCPW center conductor (sharing the same width) for easy measurement and facilitates planar integration. The metallic via 106 sits 5.4mm from the L-slot 104, minimizing spurious radiation from the microstrip feeding line due to the slots ground plane placement.
[0048] According to another exemplary embodiment of the invention, FIG. 3A refers to electric field intensities 300 of the proposed wideband SIW cavity-backed antenna 100 at a resonant frequency of 10 GHz. FIG. 3B refers to electric field intensities 302 of the proposed wideband SIW cavity-backed antenna 100 at a resonant frequency of 10.73 GHz.
[0049] At the lower resonant frequency, 10 GHz, the electric field distribution is more predominant below the L-shaped slot 104. This means that the electric field is stronger in the region below the slot than in the region above the L-shaped slot 104, as shown in FIG. 3A. At the upper resonant frequency, 10.73 GHz, the electric field distribution is more predominant above the L-shaped slot 104, as shown in FIG. 3B.
[0050] This non-uniform electric field distribution is beneficial for wideband SIW cavity-backed antenna’s radiation. When the electric field is not uniform, the wideband SIW cavity-backed antenna 100 creates a current distribution that is also not uniform. This non-uniform current distribution is what generates the wideband SIW cavity-backed antenna’s radiation pattern.
[0051] The radiation patterns of the wideband SIW cavity-backed antenna 100 in the H-plane at the two resonant frequencies are shown in FIG. 3A and FIG. 3B. The non-uniform electric field distribution is particularly beneficial for generating wideband radiation. This is because the non-uniform electric field distribution can be controlled to produce different current distributions at different frequencies. This allows the antenna to radiate effectively over a wide range of frequencies.
[0052] In conclusion, the non-uniform electric field distribution in the proposed wideband SIW cavity-backed antenna 100 assists to radiate effectively by generating a non-uniform current distribution, which in turn generates a magnetic field and an electric field that is radiated by the wideband SIW cavity-backed antenna 100.
[0053] According to another exemplary embodiment of the invention, FIGs. 4A to 4D refers to radiation patterns 400 to 406 of H-Plane at two resonant frequencies. FIG. 4A shows the H-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 4B shows the H-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°). FIG. 4C shows the H-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 4D shows the H-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°).
[0054] The peak values of the co-polarization and cross-polarization components are 5.7 dBi and -47 dBi, respectively. The co-polarization component is the desired signal that is radiated by the wideband SIW cavity-backed antenna 100. The cross-polarization component is an undesired signal that is radiated by the antenna in a direction perpendicular to the desired signal. The high peak value of the co-polarization component and the low peak value of the cross-polarization component indicate that the wideband SIW cavity-backed antenna 100 is radiating effectively.
[0055] According to another exemplary embodiment of the invention, FIGs. 5A to 5D refers to radiation patterns 500 to 506 of E-Plane at two resonant frequencies. FIG. 5A shows the E-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 5B shows the E-plane co-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°). FIG. 5C shows the E-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10 GHz in the XZ plane (F=0). FIG. 5D shows the E-plane cross-polarization radiation pattern of the proposed wideband SIW cavity-backed antenna 100 at 10.73 GHz in the YZ plane (F=90°).
[0056] The peak values of the co-polarization and cross-polarization components are 6.3 dBi and -47 dBi, respectively. The co-polarization component is the desired signal that is radiated by the wideband SIW cavity-backed antenna 100.
[0057] According to another exemplary embodiment of the invention, FIG. 6 refers to an input impedance plot 600 for the stage I antenna, the stage II antenna, and the wideband SIW cavity-backed antenna 100. The stage I antenna of the design, a simple SIW cavity without slots, exhibits three prominent cavity modes: TE110 at 6.7 GHz, TE120 at 10.3 GHz, and TE130 at 13.5 GHz. These modes are readily identified by peaks in the real part of the input impedance plot, as shown in FIG. 6. Introducing an L-shaped slot (the stage II antenna) significantly disrupts these modes, leading to the emergence of two hybrid modes: odd TE120 and even TE120 at 9.7 GHz and 10.7 GHz, respectively. This translates to two narrow bands in the impedance response: Band 1 (600 MHz, 9.6-10.2 GHz) and Band 2 (300 MHz, 10.5-10.8 GHz), as shown in FIG. 6.
[0058] According to another exemplary embodiment of the invention, FIG. 7 refers to a reflection coefficient plot 700 for the stage II antenna, and the wideband SIW cavity-backed antenna 100. The metallic via 106 disrupts the electric field distribution around the L-shaped slot 104, particularly at the two resonant frequencies of the narrow bands. This disruption alters the current distribution within the SIW cavity, leading to improved impedance matching at the frequencies between the two original resonances. This, in turn, merges the two bands into a wider one (1.1 GHz) with a more consistent impedance response across the range.
[0059] The introduction of the metallic via 106 significantly improves impedance matching by acting as a coupling element between two distinct resonant modes identified in the stage II antenna (without the via): odd TE120 at 9.7 GHz and even TE120 at 10.7 GHz. This coupling effectively merges the two narrow bands, resulting in a significantly wider bandwidth of 1.1 GHz (9.78 GHz to 10.88 GHz), as evidenced in FIG. 7.
[0060] Analyzing the electric field distribution in FIG. 7 further elucidates the mechanism behind the enhanced bandwidth. We observe significant field concentration around the metallic via 106, particularly at the resonant frequencies of the individual modes. This suggests that the metallic via 106 acts as a local perturbation, modifying the current distribution within the cavity and enhancing the interaction between the two mode fields. This interaction results in the merging of the resonant frequencies and broadening of the bandwidth.
[0061] While the overall resonant frequencies remain relatively unperturbed by the metallic via 106. The concentrated field intensity around the metallic via 106 indicates localized modifications to the field pattern, potentially affecting higher-order cavity modes beyond the fundamental TE120.
[0062] According to another exemplary embodiment of the invention, FIG. 8 refers to a reflection coefficient plot 800 for simulated versus experimental values of the wideband SIW cavity-backed antenna 100. The fabricated wideband SIW cavity-backed antenna 100 achieves an impressive 1.27 GHz bandwidth (12.13%) spanning from 9.84 GHz to 11.11 GHz. The strategic integration of the L-shaped slot 104 and the metallic via 106 facilitates this superior bandwidth performance while simultaneously delivering a notable peak gain of 6.35 dBi. Additionally, the wideband SIW cavity-backed antenna 100 exhibits a well-defined unidirectional radiation pattern, making it suitable for applications requiring focused signal transmission.
[0063] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, a wideband SIW cavity-backed antenna 100 to enhance the bandwidth of the antenna with an L-shaped slot utilizing a substrate integrated waveguide (SIW) cavity.
[0064] The proposed wideband SIW cavity-backed antenna 100 is a low profile, cost effective, and low cross polarization antenna. The proposed wideband SIW cavity-backed antenna 100 achieves wide bandwidth, high gain and a unidirectional radiation pattern over the operating bandwidth. The wideband SIW cavity-backed antenna 100 has the L-shaped slot 104 engraved on the ground plane of the cavity, which acts as a radiating slot for the cavity. This design assists in generation of two narrow bands such as 600 MHz (9.6GHz to 10.2 GHZ) and 300 MHz (10.5GHz to 10.8GHz).
[0065] The wideband SIW cavity-backed antenna 100 has the metallic via 106 at its center, which results in a wide bandwidth of 1.1 GHz from 9.78 GHz to 10.88 GHz. This is due to the inductive loading of the metallic via 106, which aid in generating wide bandwidth in the wideband SIW cavity-backed antenna 100. The wideband SIW cavity-backed antenna 100 comprises a simple construction with usage of a single cavity, thereby overcome the fabrication difficulties. The wideband SIW cavity-backed antenna 100 utilises the micro-strip line 110 as the feeding technique, thereby overcome integration problems with planar circuits.
[0066] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.