Broadband omnidirectional filter antenna applied in ISM frequency band

Abstract

The application relates to a broadband omnidirectional filter antenna applied in an ISM frequency band, which comprises a substrate and three kinds of half-wavelength dipole metal patches above the substrate and a metal resonance ring below the substrate; the half-wavelength dipole metal patches are composed of three half-wavelength metal patches, which are a linear half-wavelength dipole patch, a linear half-wavelength dipole patch with a groove and a U-shaped half-wavelength dipole patch. The electromagnetic coupling relationship of the three half-wavelength metal patches is utilized to widen the bandwidth and realize the filter function, and the resonance ring below the substrate is used for further strengthening the filter function. The broadband omnidirectional filter antenna working in the ISM frequency band has good radiation performance and filter performance, has low transmission insertion loss in a passband, high radiation efficiency, stable gain, keeps good radiation patterns, has strong radiation suppression performance outside the passband, and has important application prospects in a microwave wireless communication system.

Description

Technical Field

[0001] This invention relates to the field of passive device broadband antenna technology, and more particularly to a broadband omnidirectional filtering antenna used in the ISM band. Background Technology

[0002] The ISM band is the most widely used radio frequency in industrial, scientific, and medical fields. Due to its openness and uniformity, many radio systems, such as Wi-Fi, Bluetooth, Zigbee, and RFID, also choose to operate within the ISM band. The main problem facing the ISM band is interference. Because these bands can be used by any device, multiple devices may transmit simultaneously in the same band, causing mutual interference. Therefore, many wireless communication systems need to employ techniques to handle this interference, such as adding filters at the antenna front end to filter the signal before transmission, which can effectively reduce interference between communication systems.

[0003] However, besides interference issues, current antenna technology also faces challenges in meeting the demands of high-performance and multi-band applications. Existing antennas typically perform well within specific frequency bands, but often exhibit poor performance in multi-band applications. Existing antenna systems usually require multiple antennas to meet the needs of different frequency bands, increasing the complexity of system design and implementation, as well as costs. Secondly, because antennas exhibit different radiation characteristics at different frequency bands, signal attenuation or changes in radiation direction may occur during band switching. Furthermore, communication systems are often affected by interference signals from other frequency bands, which can lead to a deterioration in communication quality.

[0004] An omnidirectional antenna is a widely used antenna type in wireless communication, capable of receiving and transmitting wireless signals from multiple directions. Compared to directional antennas, the main advantage of omnidirectional antennas lies in their wide coverage, making them ideal for many applications, such as home wireless networks, mobile communication base stations, and wireless sensor networks. With the continuous development and innovation of wireless communication technologies, omnidirectional antennas will continue to play a crucial role in achieving higher performance and more diverse application scenarios.

[0005] Therefore, the demand for omnidirectional broadband filtering antennas is increasing in the existing technology. Such antennas can exhibit excellent omnidirectional radiation characteristics and high out-of-band radiation suppression in multi-band applications. However, a solution that simplifies system design and implementation complexity to achieve broadband filtering functionality and improve bandwidth coverage and anti-interference performance is currently lacking. Therefore, it is necessary to design a new omnidirectional broadband filtering antenna to meet the needs of multi-band applications and address the problems and shortcomings of existing technologies.

[0006] Traditional filtering antennas typically use the antenna as the final stage of a filter, radiating the signal that has passed through the filter. This is equivalent to cascading the filter and the antenna, often resulting in excessively large antennas. Recently, much work has utilized parasitic elements incorporated into antenna designs to introduce radiated nulls for filtering. Compared to cascading the filter and antenna, this approach significantly reduces antenna size. Furthermore, filtering can still be achieved using non-radiating components in the antenna's feed network. However, both of these methods of adding extra elements still increase antenna size. Therefore, it is necessary to provide new solutions that allow antennas to achieve the widest possible bandwidth and most stable radiation performance without increasing antenna size. Summary of the Invention

[0007] The purpose of this invention is to solve the aforementioned problems in the prior art and provide a compact omnidirectional broadband antenna that operates in the ISM band, possessing a wide passband, high out-of-band suppression, and stable radiation performance. The bandwidth is broadened and filtering functionality is achieved by utilizing the electromagnetic coupling relationship of three half-wavelength dipole patches, with a resonant ring beneath the substrate further enhancing the filtering effect. This broadband omnidirectional filtering antenna operating in the ISM band exhibits excellent radiation and filtering performance, low insertion loss, high radiation efficiency, stable gain, and good radiation pattern maintenance within the passband, and strong out-of-band radiation suppression performance, making it a promising candidate for applications in microwave wireless communication systems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A broadband omnidirectional filtering antenna for use in the ISM band includes a substrate and metal layers. The metal layers are located on the upper and lower sides of the substrate, respectively. The upper metal layer is provided with three types of half-wavelength dipole patches, and the lower metal layer is provided with a resonant ring.

[0010] The three types of half-wavelength dipole patches include a U-shaped half-wavelength dipole patch, a linear half-wavelength dipole patch, and a grooved linear half-wavelength dipole patch arranged sequentially, with the linear half-wavelength dipole patch placed inside the U-shaped half-wavelength dipole patch; the grooved linear half-wavelength dipole patch has a rectangular gap in the middle for power feeding; grooves are provided on both sides of the rectangular gap for adjusting antenna impedance matching, and the openings of the grooves face the linear half-wavelength dipole patch; the position of the resonant ring is opposite to the position of the grooved linear half-wavelength dipole patch.

[0011] The U-shaped half-wavelength dipole patch includes a main body, main arms, and secondary arms; the main arms are perpendicular to the main body, and the two main arms are connected to both ends of the main body; the secondary arms are in the same direction as the main body, and the two secondary arms are respectively connected to the two main arms.

[0012] The three types of half-wavelength dipole patches, substrates, and C-shaped resonant rings extend in the same direction to reduce device length and broaden bandwidth and filtering characteristics.

[0013] The resonant ring is a C-shaped resonant ring, and the opening direction of the C-shape is consistent with the opening direction of the groove of the grooved linear half-wavelength dipole patch.

[0014] The spacing between adjacent half-wavelength dipole patches of the three types is 0.4~0.9mm.

[0015] The length of the three types of half-wavelength dipole patches is half the wavelength of the operating frequency. The length of the grooved linear half-wavelength dipole patch is 62~62.5mm, the length of the linear half-wavelength dipole patch is 44~46mm, and the length of the U-shaped half-wavelength dipole patch is the sum of its main body length, the lengths of the two main arms and the lengths of the two auxiliary arms, which is 88~88.5mm.

[0016] The grooved linear half-wavelength dipole patch has a linewidth of 3.2 mm, the linear half-wavelength dipole patch has a linewidth of 7.9 mm, and the U-shaped half-wavelength dipole patch has a linewidth of 1 mm.

[0017] The grooved linear half-wavelength dipole patch has a rectangular gap in the middle, with a length F of 4mm and a width W2 of 3.2mm. This gap is used for power feeding, and the feed line is soldered to the half-wavelength linear dipole patches at both ends of the gap. Rectangular grooves are provided on both sides of the rectangular gap, with a depth G2 of 3.1mm and a width G1 of 1.5mm, for adjusting antenna impedance matching.

[0018] The U-shaped half-wavelength dipole patch and the grooved linear half-wavelength dipole patch surround the linear half-wavelength dipole patch. This structure can effectively reduce the device width and adjust the relative positional relationship of the three types of half-wavelength dipole patches.

[0019] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0020] (1) The broadband omnidirectional filtering antenna proposed in this invention for use in the ISM band has a wide frequency range.

[0021] (2) The broadband omnidirectional filtering antenna proposed in this invention for use in the ISM band uses a flexible substrate, which can be used for conformal transmission of microwave electromagnetic waves through bending deformation.

[0022] (3) The three slender dipole patches of different shapes used in the broadband omnidirectional filtering antenna proposed in this invention for use in the ISM band achieve the function of a broadband antenna without increasing the length of the device by utilizing the electromagnetic coupling principle. At the same time, the filtering characteristics are improved and the signal outside the passband is well suppressed.

[0023] (4) The broadband omnidirectional filtering antenna proposed in this invention has excellent performance in the ISM band. Within the operating frequency band, S11 is less than -10dB, and outside the operating frequency band, S11 is greater than -0.5dB. The gain can reach 2.35dBi~4.55dBi within the band, which meets the performance requirements of modern wireless communication systems.

[0024] (5) The radiation characteristics of the broadband omnidirectional filter antenna proposed in this invention for use in the ISM band mainly depend on the length of the half-wavelength dipole patch, the spacing between adjacent half-wavelength dipole patches, and the corresponding sensitive parameters of the resonant ring. It is convenient and flexible to design manually. By changing the scale, the sensitive parameters can be adjusted to change the radiation performance and the operating frequency band.

[0025] (6) The broadband omnidirectional filtering antenna proposed in this invention for use in the ISM band has a flat structure and can be used with various microwave power dividers, filters and other passive and active circuits, devices or even components or systems. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the broadband omnidirectional filtering antenna applied in the ISM band in Example 1;

[0027] Figure 2 The low-frequency null tuning curve of the broadband omnidirectional filter antenna applied in the ISM band in Example 1 is shown.

[0028] Figure 3 The high-frequency null tuning curve of the broadband omnidirectional filter antenna applied in the ISM band in Example 1 is shown.

[0029] Figure 4 The S-parameter curves of the broadband omnidirectional filter antenna used in the ISM band in Example 1 are shown.

[0030] Figure 5 The graph shows the achievable gain curve of the broadband omnidirectional filtering antenna applied in the ISM band in Example 1.

[0031] Figure 6 The efficiency curve of the broadband omnidirectional filtering antenna applied in the ISM band in Example 1 is shown.

[0032] Figure 7 The radiation pattern of the broadband omnidirectional filter antenna used in Example 1 in the ISM band is shown.

[0033] Reference numerals: 1. Substrate; 2. U-shaped half-wavelength dipole patch; 3. Linear half-wavelength dipole patch; 4. Linear half-wavelength dipole patch with groove; 5. Resonant ring. Detailed Implementation

[0034] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Example 1

[0036] Figure 1 (a) is a top view of the structure of the present invention, and (b) is a bottom view. The broadband omnidirectional filtering antenna for the ISM band proposed in Embodiment 1 includes a flexible substrate 1 and a U-shaped half-wavelength dipole patch 2, a linear half-wavelength dipole patch 3, and a grooved linear half-wavelength dipole patch 4 on top of it. The substrate 1 is made of Rogers RT5880 material with a dielectric constant of 2.2, a thickness of 0.508 mm, and a transmission loss angle of 0.0009. A resonant ring 5 is located on the other side of the substrate 1, opposite to the grooved linear half-wavelength dipole patch 4. The grooved linear half-wavelength dipole patch 4 is symmetrical about its center, with a rectangular opening in the middle for feeding power. Grooves are provided on both sides of the rectangular opening for adjusting antenna matching. The overall structure of this embodiment is axially symmetrical.

[0037] The U-shaped half-wavelength dipole patch 2 consists of a main body of length L1, a main arm of length L6, and a secondary arm of length L3, with a width of W1. The relevant parameters of the U-shaped half-wavelength dipole patch 2 are L1=62.4mm, L3=3.1mm, L6=9.9mm, and W1=1mm.

[0038] The linear half-wavelength dipole patch 3 is composed of a rectangular patch with a length of L2 and a width of W4, with relevant parameters of L2=45mm and W4=7.9mm.

[0039] The grooved linear half-wavelength dipole patch 4 consists of a rectangular patch with a length of L1 and a width of W2, with grooves cut out at the center and on both sides. The rectangular gap at the center has a length of F and a width of W2 and is used for power feeding. The grooves on both sides have a width of G2 and a length of G1. The distances between the grooves on both sides and the central groove are the same. The relevant parameters are F=4mm, W2=3.2mm, G1=1.5mm, and G2=3.1mm.

[0040] The resonant ring 5 consists of a main body of length L5, a main arm of length L7, and a secondary arm of length L4. The width is W3, and the relevant parameters are L4=5mm, L5=25.5mm, L7=2.4mm, and W3=0.3mm.

[0041] The distance between the U-shaped half-wavelength dipole patch 2 and the linear half-wavelength dipole patch 3 is S2, and the distance between the grooved linear half-wavelength dipole patch 4 and the linear half-wavelength dipole patch 3 is S1. The relevant parameters are S1=0.9mm and S2=0.6mm.

[0042] All three types of half-wavelength dipole patches and resonant rings mentioned above are metals, specifically copper.

[0043] The simulation results of Example 1 are as follows: Figure 2 and Figure 3 As shown, by changing the spacing S2 between the U-shaped half-wavelength dipole patch 2 and the linear half-wavelength dipole patch 3, the electromagnetic coupling relationship between the half-wavelength dipole patches is altered. Electrical coupling easily occurs at the two ends of the half-wavelength dipole, while magnetic coupling easily occurs in the center. Cross-coupling theory states that electrical coupling typically introduces transmission zeros at low frequencies in the passband, while magnetic coupling typically introduces transmission zeros at high frequencies in the passband. From... Figure 2 As can be seen, in this embodiment 1, the position of the zero point at low frequency can be controlled by adjusting S2, and the length of L7 can be adjusted to control the length of the resonant ring, thereby changing the transmission zero point at high frequency. The zero point in this embodiment has a tunable function.

[0044] Depend on Figure 4 Simulation results show that the broadband omnidirectional filter antenna applied in the ISM band in this embodiment has a passband range of 1.61 GHz to 2.64 GHz, a bandwidth of 1.03 GHz, a relative bandwidth of 48.47%, and a reflection coefficient below -13 dB within the passband. Figure 5 Simulation results show that Example 1 achieves a gain from 2.35 dBi to 4.55 dBi within the passband, with a low-frequency null at 1.46 GHz and a high-frequency null at 2.74 GHz. Out-of-band gains are all less than -13 dBi. Antenna efficiency is as follows... Figure 6 As shown, the antenna efficiency within the passband is higher than 90%, and the antenna efficiency outside the passband is less than 10%, demonstrating good filtering characteristics. Figure 7 The radiation patterns of Example 1 at three operating points in the ISM band show that Example 1 has good omnidirectional radiation pattern stability in the ISM band.

[0045] The broadband omnidirectional filtering antenna proposed in this invention for the ISM band introduces low-frequency radiation points by utilizing the electromagnetic coupling relationship between three half-wavelength dipole patches, and uses a resonant ring to introduce high-frequency nulls to achieve filtering. By adjusting the length of the resonant ring and the size and distance between different half-wavelength dipole patches, the operating frequency band and the position of the radiation null can be changed, enabling signal transmission in microwave and millimeter-wave bands.

Claims

1. A broadband omnidirectional filter antenna for use in the ISM band, characterized in that: It includes a substrate and a metal layer, the metal layer being located on the upper and lower sides of the substrate respectively. The upper metal layer is provided with three types of half-wavelength dipole patches, and the lower metal layer is provided with a resonant ring. The three types of half-wavelength dipole patches include a U-shaped half-wavelength dipole patch, a linear half-wavelength dipole patch, and a grooved linear half-wavelength dipole patch arranged sequentially, with the linear half-wavelength dipole patch placed inside the U-shaped half-wavelength dipole patch; the grooved linear half-wavelength dipole patch has a rectangular gap in the middle for power feeding; grooves are provided on both sides of the rectangular gap for adjusting antenna impedance matching, and the openings of the grooves face the linear half-wavelength dipole patch; the position of the resonant ring is opposite to the position of the grooved linear half-wavelength dipole patch.

2. The wideband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The U-shaped half-wavelength dipole patch includes a main body, main arms, and secondary arms; the main arms are perpendicular to the main body, and the two main arms are connected to both ends of the main body; the secondary arms are in the same direction as the main body, and the two secondary arms are respectively connected to the two main arms.

3. The broadband omnidirectional filter antenna for ISM bands as claimed in claim 1, wherein: The three types of half-wavelength dipole patches, substrates, and C-shaped resonant rings all extend in the same direction.

4. The broadband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The resonant ring is a C-shaped resonant ring, and the opening direction of the C-shape is consistent with the opening direction of the groove of the grooved linear half-wavelength dipole patch.

5. The wideband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The spacing between adjacent half-wavelength dipole patches of the three types is 0.4–0.9 mm.

6. The broadband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The length of the three types of half-wavelength dipole patches is half the wavelength of the operating frequency. The length of the grooved linear half-wavelength dipole patch is 62-62.5 mm, the length of the linear half-wavelength dipole patch is 44-46 mm, and the length of the U-shaped half-wavelength dipole patch is the sum of its main body length, the lengths of its two main arms and the lengths of its two auxiliary arms, which is 88-88.5 mm.

7. The broadband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The grooved linear half-wavelength dipole patch has a linewidth of 3.2 mm, the linear half-wavelength dipole patch has a linewidth of 7.9 mm, and the U-shaped half-wavelength dipole patch has a linewidth of 1 mm.

8. The broadband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The rectangular gap is 4mm long and 3.2mm wide.

9. The broadband omnidirectional filtered antenna for ISM bands as claimed in claim 1, wherein: The groove has a width of 1.5 mm and a depth of 3.1 mm.

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