An improved backlobe performance wideband substrate integrated waveguide antenna applied to RFID

Abstract

The application discloses an improved back lobe performance wideband substrate integrated waveguide antenna applied to RFID, which comprises a dielectric plate, the top of the dielectric plate is a metal ground plate, the center of the metal ground plate is etched with a long strip-shaped slot with symmetric branches, the bottom of the dielectric plate is provided with a metal defective ground plate and a microstrip feed line, and the terminal of the microstrip feed line is connected with a 50Ω SMA joint. Wherein, the metal defective ground plate is provided with square metal patches around the microstrip feed line, additional radiation modes are introduced, and the working bandwidth of the antenna is effectively widened. The application improves the gain of the traditional slot antenna, reduces the front-to-back ratio of the antenna, and improves the radiation performance.

Description

Technical Field

[0001] This invention belongs to the field of waveguide antenna technology and relates to a multimode broadband substrate integrated waveguide antenna for RFID applications. Background Technology

[0002] Microstrip slot-coupled antennas have long attracted attention and widespread application from researchers due to their wide operating bandwidth, stable radiation performance, well-established multimode radiation theory, and simple structural design. However, traditional microstrip slot-coupled antennas typically radiate energy through a slot in the upper layer via a feed line located on the lower layer of the dielectric substrate. Therefore, these antennas are usually bidirectional, with significant back radiation and considerable energy loss, which affects their radiation performance. Thus, effectively reducing back radiation and improving antenna gain without adding an additional back cavity remains a persistent challenge.

[0003] Currently, substrate integrated waveguide (SIW) technology is a new technology primarily advocated by Professor Wu Ke's research group at the University of Montreal, Canada, and Professor Hong Wei's research group at the State Key Laboratory of Millimeter Waves, Southeast University. SIW boasts advantages such as light weight, easy integration, low cost, low loss, low profile, and easy conformal integration with circuit boards. It is a novel waveguide structure with low insertion loss and low radiation characteristics that can be integrated into a dielectric substrate. It is achieved by arranging metallized vias on a low-loss dielectric substrate with metal layers on both the top and bottom surfaces, aiming to realize the functions of traditional metal waveguides on a dielectric substrate. SIW combines the excellent performance of similar metal waveguide structures with the many advantages of planar circuits, making it one of the best choices for implementing array antennas. Therefore, how to reliably utilize SIW technology in antennas is a current challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a broadband substrate integrated waveguide antenna with improved back lobe performance for RFID applications, which improves the gain of traditional slot antennas, reduces the antenna front-to-back ratio, and enhances radiation performance.

[0005] The technical solution of the present invention is as follows: it includes a dielectric plate, the top of which is a metal floor, and the center of the metal floor is etched with an elongated slit;

[0006] The bottom of the dielectric substrate consists of a metal defect ground plane and microstrip feed lines. An M×M arrangement of gaps is etched in the center of the metal defect ground plane, forming a square metal patch unit in the middle.

[0007] One end of the metal patch unit has a gap at its center in the x-direction, and the microstrip feed line is located within the gap;

[0008] In the z-direction projection, the gap is located at the center of the metal patch unit in the y-direction, and the center of the microstrip feed line coincides with the center of the gap. The feed line terminal of the microstrip feed line is connected to an SMA connector.

[0009] The dielectric substrate is provided with an SIW resonant cavity, which is located around the metal patch unit. The top and bottom of the metal through-hole of the SIW resonant cavity are connected to a metal ground plane and a metal defect ground plane, respectively.

[0010] Two short branches are symmetrically loaded near the zero point of radiation in the slit.

[0011] The metal patch unit has several square metal patches, and the distance between adjacent metal patches is the same.

[0012] The dielectric substrate is an F4B dielectric substrate with a dielectric constant of 2.65.

[0013] In this invention, an improved defective ground plane design is introduced. Square metal patches are distributed around the microstrip feed line to form a defective ground plane pattern, reducing back radiation and improving the front-to-back ratio and antenna gain. Simultaneously, the use of a SIW resonant cavity design further enhances the antenna's front-to-back ratio. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID according to the present invention;

[0015] Figure 2 This is a comparative diagram showing the evolution of broadband substrate integrated waveguide antennas with improved back lobe performance applied to RFID based on the present invention;

[0016] Figure 3 This is a comparison graph showing the S-parameters of the broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID as a function of frequency.

[0017] Figure 4 This is a comparison graph showing the gain of the broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID as a function of frequency.

[0018] Figure 5 This is a comparison of the gain pattern of the broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID at 5.8GHz as a function of frequency.

[0019] Figure 6 This is a schematic diagram illustrating the S-parameter learning of stub length in a broadband substrate integrated waveguide antenna for improving back lobe performance, which is an application of the present invention to RFID.

[0020] Figure 7This is a schematic diagram illustrating the S-parameter learning of stub spacing in a broadband substrate integrated waveguide antenna for improving back lobe performance, which is an application of the present invention to RFID.

[0021] Figure 8 This invention relates to the simulation and measured S-parameter curves as a function of frequency for a broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID.

[0022] Figure 9 This invention is applied to the simulation and measured gain versus frequency curves of a broadband substrate integrated waveguide antenna with improved back lobe performance for RFID.

[0023] Figure 10 These are schematic diagrams of the front and back sides of the broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID according to the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] This invention is applied to broadband substrate integrated waveguide antennas with improved back lobe performance for RFID, such as... Figure 1 , 10 As shown, the device includes a dielectric substrate with a metal ground plane on top. A long, narrow slit with symmetrical branches is etched at the center of the metal ground plane. Two short branches (i.e., radiation slit branches) are symmetrically loaded near the zero-radiation point of the slit. A microstrip feed line is located at the bottom of the dielectric substrate. L 4 represents the length of the microstrip feeder cable. W 1 represents the width of the microstrip feed line and a metal defect ground plane. The terminals of the microstrip feed line are connected to a 50Ω SMA connector.

[0026] The microstrip feed line is surrounded by M×M arranged (e.g., 12 rows × 12 columns) metal patch units with gaps between them. Each metal patch unit includes several units with a side length of... L Three square metal patches form a defect floor pattern; the M parameter can be selected according to specific working conditions; setting square metal patches is simple in design and the performance parameters are adjustable.

[0027] This invention improves the front-to-back ratio and reduces side lobes by etching gaps of different shapes into a metal defect floor, thereby altering the current distribution.

[0028] SIW resonant cavities are distributed around the metal patch unit (where, L 2 represents the length of the SIW resonant cavity. The metal vias of the SIW resonant cavity connect the metal ground plane and the metal defect ground plane. The dielectric substrate is an F4B dielectric substrate with a dielectric constant of 2.65.

[0029] This invention relates to a broadband substrate integrated waveguide antenna for RFID with improved back lobe performance. The dielectric substrate is an F4B dielectric substrate with a dielectric constant of 2.65 and a thickness of H1. The substrate dimensions are as follows. L 1× L 1.

[0030] The SIW resonant cavity is distributed around the metal patch unit, with a diameter D. siw The distance between them is P siw The metal through-hole connects the metal defect ground plate and the metal ground plate (i.e., the metal through-hole penetrates the metal ground plate, the dielectric plate, and the metal defect ground plate), and the center of the metal ground plate is etched with a long strip of symmetrical branches (i.e., L 5 is the length of the main radiation slot), and a microstrip feed line is set at the bottom of the dielectric plate.

[0031] The broadband substrate integrated waveguide antenna with improved back lobe performance applied to RFID uses side feeding and has one feeding port. The feed line terminal is connected to a 50Ω SMA connector.

[0032] This invention relates to a broadband substrate integrated waveguide antenna for RFID with improved back lobe performance. It introduces multimode resonance theory into the feed section to broaden the antenna bandwidth. Furthermore, square metal patches are distributed around the microstrip feed line to form a defective ground plane mode, further enhancing the overall antenna performance.

[0033] Meanwhile, traditional slot antennas have a large rearward radiation ratio and significant energy loss. The broadband high-gain substrate integrated waveguide resonant cavity antenna of this invention adopts the SIW resonant cavity design, which further improves the antenna's front-to-back ratio.

[0034] Figure 2 For the antenna evolution diagram design, the antenna consists of a single-layer dielectric substrate, fed by a multimode slot antenna, with several sides of length... L A square metal patch (3) is located at the bottom of the dielectric substrate. Based on the antenna, a defective ground plane is introduced around the feed line, along with a SIW resonant cavity, forming antenna 2.

[0035] from Figure 3 and Figure 4 As can be seen, the impedance bandwidth of antenna 2 is slightly reduced (30MHz) in the high-frequency part compared with antenna 1, while the gain is also improved (about 1 dBi). This indicates that the SIW resonant cavity and the defective ground plane do not cause a significant deterioration in the impedance performance of the original antenna, but the gain is improved.

[0036] and Figure 5It can be seen that the SIW resonant cavity and the defective ground plane can effectively reduce back radiation and improve the front-to-back ratio of the antenna. Because the SIW resonant cavity effectively confines the antenna's energy and reduces energy loss, it improves the antenna's gain to a certain extent. At the same time, the design of the defective ground plane reflects the rearward energy, reducing back radiation, thereby improving the overall front-to-back ratio of the antenna.

[0037] Figure 6 and Figure 7 Regarding the length of radial slit branches L 6 and spacing L 7. Perform parameter learning, such as Figure 6 As shown, with L As the frequency increases, the high-frequency resonant point shifts to the low-frequency resonant point, while the low-frequency resonant point remains essentially unchanged. Therefore, when a suitable frequency is selected... L A value of 6 can extend the operating bandwidth of the antenna. For example... Figure 7 As shown, with L 7. As the frequency increases, the high-frequency resonant point shifts to the low-frequency resonant point, while the low-frequency resonant point shifts to the high-frequency resonant point. This is because the stub location is generally selected near the radiation null point. L By observing point 7, the location of the radiation zero point can be found, an additional resonant mode can be introduced, and the operating bandwidth can be increased.

[0038] Figure 8 Simulation and measured graphs of S-parameters varying with frequency are presented. Figure 8 As can be seen, the simulated operating bandwidth of the antenna is 1.45GHz (5.5GHz-6.95GHz), while the measured bandwidth is slightly narrower than the simulation, at 1.4GHz (5.5GHz-6.9GHz). The small difference between the measured and simulated bandwidths may be due to the influence of solder joints and processing errors. Figure 9 Simulation and measured graphs of gain variation with frequency are presented. It can be seen from the graph that the simulated gain is relatively stable within the operating frequency band, with a peak gain of 7.33 dBi at 5.7 GHz. The measured gain is highly similar to the simulated gain.

[0039] This invention uses a multimode slot antenna for feeding, with two short stubs symmetrically added near the radiation null point of the slot, introducing additional radiation modes and effectively widening the antenna's operating bandwidth.

[0040] This invention applies to broadband substrate integrated waveguide antennas with improved back lobe performance for RFID. By introducing an improved design with a defective ground plane, the front-to-back ratio is increased, and the antenna gain is also improved by approximately 1 dBi.

Claims

1. A broadband substrate integrated waveguide antenna with improved back lobe performance for RFID, comprising a dielectric substrate, wherein the top of the dielectric substrate is a metal ground plane, and an elongated slit is etched in the center of the metal ground plane; Its features are, The bottom of the dielectric substrate consists of a metal defect ground plane and microstrip feed lines. An M×M arrangement of gaps is etched in the center of the metal defect ground plane, forming a square metal patch unit in the middle. One end of the metal patch unit has a gap at its center in the x-direction, and the microstrip feed line is located within the gap; On the z-axis projection, the gap is located at the center of the metal patch unit in the y-axis, and the center of the microstrip feed line coincides with the center of the gap. The feed line terminal of the microstrip feed line is connected to the SMA connector. The dielectric substrate is provided with an SIW resonant cavity, which is located around the metal patch unit. The top and bottom of the metal through-hole of the SIW resonant cavity are connected to a metal ground plane and a metal defect ground plane, respectively. Two short branches are symmetrically loaded near the zero point of radiation of the slit; SIW resonant cavity and defective ground plane effectively reduce back radiation and improve the front-to-back ratio of the antenna.

2. The broadband substrate integrated waveguide antenna with improved back lobe performance for RFID as described in claim 1, characterized in that, The metal patch unit has several square metal patches, and the distance between adjacent metal patches is the same.

3. The broadband substrate integrated waveguide antenna with improved back lobe performance for RFID as described in claim 1, characterized in that, The dielectric substrate is an F4B dielectric substrate with a dielectric constant of 2.65.

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