A dual-notch high-isolation ultra-wideband MIMO antenna

Abstract

A dual-notch high-isolation ultra-wideband MIMO antenna comprises a dielectric substrate, a metal layer located on the upper surface of the dielectric substrate, a metal ground plane located on the lower surface of the dielectric substrate, and an F-shaped isolation branch extending from the metal ground plane. The F-shaped isolation branch comprises two axisymmetrically arranged F-shaped units. Each F-shaped unit comprises a rectangular strip and two first-order branches and second-order branches extending from its upper portion, each of which has four equal-width slots etched in the middle of the rectangular strip, one of which is longer than the other three slots of equal length. The metal layer comprises two axisymmetrically arranged non-axisymmetric units. Each unit comprises a radiating unit, a stepped microstrip feeder, an L-shaped slot, and a Z-shaped slot. The F-shaped isolation branch is connected to the metal ground plane and is located between the two radiating units. The ultra-wideband MIMO antenna proposed by the present invention has the advantages of small size, easy processing, dual notch, and high isolation.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-wideband, and in particular relates to a dual-notch high-isolation ultra-wideband MIMO antenna. Background Art

[0002] Antennas are devices that transmit and receive radio waves in radio frequency circuits and are an important component of wireless communication systems.

[0003] Ultra-wideband wireless communication technology has the advantages of high transmission rate, low transmission power, and high multipath resolution, and is currently widely used in

[0004] Indoor positioning systems, radar systems, and imaging systems. The wide bandwidth characteristics of ultra-wideband (UWB) are prone to multipath effects, which can reduce communication quality. MIMO technology, by deploying multiple antennas simultaneously at the signal transmission and reception ends, addresses the practical limitations of UWB technology. By transmitting and receiving signals using multiple antennas, diversity gain is achieved, thereby improving communication quality. While the current UWB frequency band of 3.3 GHz to 10.6 GHz is covered, there are also communication systems operating in many other frequency bands, such as the wireless local area network (WLAN) band (5.15 GHz to 5.825 GHz) and the downlink frequency band of satellite communication systems (7.25 GHz to 7.75 GHz). To avoid interference in these frequency bands, adding filtering circuits would inevitably increase the size and cost of the entire UWB system. Therefore, designing UWB notch MIMO antennas is crucial. Summary of the Invention

[0005] In view of the problems existing in the above background technology, a dual-notch high-isolation ultra-wideband MIMO antenna is proposed, which can solve the frequency band interference problem while controlling the overall volume and cost of the system.

[0006] A dual-notch high-isolation ultra-wideband MIMO antenna comprises a dielectric substrate, a metal layer located on the upper surface of the dielectric substrate, a metal ground plate located on the lower surface of the dielectric substrate, and an F-shaped isolation branch extending from the metal ground plate;

[0007] The F-shaped isolation branch comprises two axially symmetrical F-shaped units; each F-shaped unit comprises a rectangular strip and two first-order branches and second-order branches extending from the upper portion thereof, each having four slits of the same width etched in the middle of the rectangular strip, one of which is longer than the other three slits of the same length;

[0008] The metal layer consists of two units placed axially symmetrically, which are mirror images of each other. Each unit includes a radiating element, a stepped microstrip feeder, an L-shaped slot, and a Z-shaped slot.

[0009] Two ends of the stepped microstrip feeder are connected to the radiation unit and the feeder port respectively;

[0010] The L-shaped slot and the Z-shaped slot are located on the radiating unit, with one end of the slot fitting the edge of the dielectric substrate, and the L-shaped slot located on the side of the Z-shaped slot away from the feeding port;

[0011] The F-shaped isolation branch is connected to the metal ground layer and is located between the two radiating units;

[0012] A stepped groove is etched on the metal ground plane below the stepped microstrip feeder to increase the operating bandwidth.

[0013] Furthermore, the radiation unit is a truncated rectangle with an asymmetric structure, and the curved side of the truncated corner is 1 / 4 of the arc length of the ellipse.

[0014] Furthermore, the stepped microstrip feed line is composed of three integrally formed rectangular parts, and the three rectangles are connected in sequence in width, wherein one end of the rectangle with the smallest width is connected to the radiation unit, and one side of the rectangle with the largest width serves as a feeding port.

[0015] Furthermore, the length of the L-shaped slot is 1 / 4 of the wavelength of the corresponding notch center frequency.

[0016] Furthermore, the length of the Z-shaped slot is 1 / 4 of the wavelength of the corresponding notch center frequency.

[0017] Furthermore, the dielectric substrate adopts FR4 board material with a dielectric constant of 4.4, a loss tangent angle of 0.02, and a size of.

[0018] Furthermore, in the rectangular strip of the F-shaped unit, the length of the second slit starting from one side of the branch is greater than that of the other slits.

[0019] The beneficial effects achieved by the present invention are:

[0020] (1) The antenna exhibits dual notch characteristics by slotting. An L-shaped slot for the notch characteristic of the actual WLAN frequency band is etched on the radiating patch. At the same time, a Z-shaped slot is etched below the L-shaped slot to generate a notch band for the antenna, thereby reducing the complexity of the design. The length of the two slots is approximately 1 / 4 of the wavelength of the corresponding notch center frequency.

[0021] (2) The ultra-wideband antenna has an operating bandwidth of 3.1 GHz to 11 GHz through slotting, generating notched characteristics in the 5.07 GHz to 5.88 GHz and 7.18 GHz to 7.92 GHz frequency bands, effectively suppressing narrowband downlink signals in the WLAN band and X-band.

[0022] (3) This slotting method is smaller in size while ensuring relevant properties, is easy to process, and reduces material and operating costs;

[0023] (4) An F-shaped branch is extended from the metal ground plane to improve the isolation of the antenna.

[0024] In summary, the ultra-wideband MIMO antenna proposed in the present invention has the advantages of small size, easy processing, double notching, and high isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the antenna structure in an embodiment of the present invention.

[0026] Figure 2 1 is a graph of return loss S11 and isolation S21 between two ports in an embodiment of the present invention.

[0027] Figure 3 This is a current distribution diagram of the presence or absence of the F-shaped branch antenna radiation unit and the metal floor surface when Port 1 is excited at 4 GHz, 6 GHz, and 10 GHz in the embodiment of the present invention without adding a notch.

[0028] Figure 4 3 is a current distribution diagram of the antenna radiation unit and the metal floor surface at notch center frequencies of 5.5 GHz and 7.5 GHz when Port 1 is excited in an embodiment of the present invention.

[0029] Figure 5 ] are the normalized radiation patterns of the xoz plane and the yoz plane at 4 GHz, 6 GHz, and 10 GHz in the embodiment of the present invention.

[0030] Figure 6 3 is a gain curve diagram within the working frequency band in an embodiment of the present invention.

[0031] In the figure, 1-dielectric substrate, 2-metal ground plate, 3-radiating element, 4-L-shaped slot, 5-Z-shaped slot, 6-type F-shaped branch, 7-stepped microstrip feeder, 8-stepped slot, 9-first-order branch, 10-second-order branch. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] like Figure 1 As shown, the dual-notch high-isolation ultra-wideband MIMO antenna in this embodiment includes a dielectric substrate 1, a metal ground plate 2, a metal layer, and an F-shaped branch 6; the cross section of the dielectric substrate is rectangular.

[0034] Wherein: the metal layer includes two units arranged axially symmetrically; each unit includes a radiation unit 3, a stepped microstrip feed line 7, an L-shaped slot 4 and a Z-shaped slot 5.

[0035] The radiation unit 3 is a non-axisymmetric rectangular patch with a cut corner, that is, it is cut at a top corner of the lower end of the rectangular patch, and the cut corner curve is a 1 / 4 elliptical arc; the lower end of the radiation unit is connected to a stepped microstrip feed line 7.

[0036] The stepped microstrip feed line 7 is an integrally formed structure, consisting of three rectangular parts, and the wide sides of the three rectangles are connected in order of size; one end of the smallest rectangle in the stepped microstrip feed line is connected to the other side of the corner of the corner-cut rectangular patch, and one side of the largest rectangle serves as a feeding port.

[0037] The metal ground plane 2 is rectangular and is located on the lower surface of the dielectric substrate 1, below the stepped microstrip feed line 7. An F-shaped branch 6 extends from the center of the metal ground plane 2. A stepped groove 8 is etched into the lower metal ground plane corresponding to the back of the radiating element 3. The stepped groove 8 (the first section is 2.0 mm long and 0.5 mm wide, and the second section is 3.0 mm long and 1.0 mm wide) is located below the lowest rectangular portion of the stepped microstrip feed line 7.

[0038] The F-shaped branch includes a first-order branch 9 and a second-order branch 10 extending out of a rectangle, and four rectangular gaps, three of which are of equal length and one is slightly longer.

[0039] Figure 1 In the figure, port1 and port2 represent antenna port 1 and antenna port 2 respectively.

[0040] The dielectric substrate 1 is an FR4 dielectric substrate with a dielectric constant of 4.4, a loss tangent of 0.02, and a size of 26 mm×28 mm×0.8 mm.

[0041] The total length of the L-shaped slot 4 is 8.2 mm, which includes two horizontal and vertical parts. The horizontal part is 4.0 mm long and 0.2 mm wide, and is 1.3 mm away from the upper edge of the radiation unit 3; the vertical part is 4.2 mm long and 0.2 mm wide. The total length of the Z-shaped slot 5 is 6.7 mm, which includes three horizontal, vertical and horizontal parts. The first horizontal part is 1 mm long and 0.2 mm wide, and is 4.0 mm away from the upper edge of the radiation unit; the vertical part is closely connected to the first horizontal part and is connected to the second horizontal part, which is 3.5 mm long and 0.2 mm wide; the second horizontal part is 2.2 mm long and 0.2 mm wide. The total length of the L-shaped slot 4 and the Z-shaped slot 5 corresponds to 1 / 4 of the wavelength of the center frequency of the notch.

[0042] The total length of the stepped microstrip transmission line 7 is 10.4 mm, and it consists of three sections: the first section is 3.0 mm long and 2.0 mm wide; the second section is 4.0 mm long and 1.4 mm wide; and the third section is 3.4 mm long and 1.2 mm wide.

[0043] The F-shaped branch 6 has a total length of 16.0 mm (excluding the left and right extensions). The first extension is 3.0 mm long and 1.0 mm wide. The second extension is 2.0 mm long and 1.0 mm wide. There is a 1.5 mm gap between the two extensions. The four rectangular gaps are 0.5 mm wide, three of which are 12.5 mm long and one is 15.0 mm long.

[0044] In this embodiment, the radiating element 3 uses a rectangular radiating patch cut on only one side according to a quarter-elliptical arc to form the final radiating patch, and the antenna is fed with a stepped microstrip feed line 7, which can increase the current flow path, expand the operating bandwidth, and facilitate impedance matching. The F-shaped branch 6 between the two radiating elements 3 improves the impedance matching of the antenna in the low-frequency band while suppressing the coupling between the two antenna radiating elements 3. The F-shaped branch 6 extending from the middle of the metal ground plate 2 can reflect the directional patterns of the two radiators, and the etched slit (the gap in the F-shaped branch 6) gradually increases the electrical length between the antenna elements, extending the current path between the two ports. The L-shaped slot 4 and Z-shaped slot 5 etched in the radiating patch 3 form dual notches for WLAN (5.15GHz-5.825GHz) and the X-band downlink frequency band (7.25GHz-7.75GHz).

[0045] See also Figure 2 The curves represent the simulated |S11| and |S21| parameters. It can be seen that the antenna of the present invention achieves a -10dB return loss band of 3.1 to 11 GHz. Furthermore, |S11| is greater than -5dB in the 5.07-5.88 GHz and 7.18-7.92 GHz bands, achieving notching in both WLAN and X-band downlink narrowband wireless communication bands. The antenna's isolation is less than -15dB in the 3.1-3.3 GHz operating band and less than -20dB in the 3.3-11 GHz operating band.

[0046] As attached Figure 3 As shown, when Port 1 is excited, the current is mainly distributed on Port 1 and the F-shaped branch 6 on one side thereof, mainly by absorbing the current to achieve low coupling between antennas.

[0047] See also Figure 4 Figure 3 shows the current distribution on the antenna surface under single-port excitation at 5.5 GHz and 7.5 GHz, respectively. The far-field radiation energy at the L-shaped slot 4 and the Z-shaped slot 5 cancel each other out, thus achieving the stopband characteristic.

[0048] Figure 5As can be seen, when port 1 is excited, the antenna has a radiation pattern similar to a dipole in the low and medium frequency bands. At high frequencies, the addition of the F-shaped branch 6 changes the radiation pattern, and the directivity gradually increases with increasing frequency.

[0049] Figure 6 The gain diagram within the antenna operating frequency band is given. It can be seen that the antenna gain tends to be stable. The gain range is 1.8dBi to 5dBi within the UWB range. In the notch band, the gain is less than 0dBi.

[0050] This antenna maintains relevant characteristics while maintaining a smaller size, exhibiting dual-notch characteristics, and achieving high isolation between the two radiating elements. The antenna consists of two radiating elements, fed by a stepped microstrip line. Dual-notch functionality is achieved by slotting the radiating elements. Furthermore, F-shaped branches extend from the metal ground plane, enhancing the antenna's isolation. This invention offers advantages such as small size, ease of fabrication, dual-notch characteristics, and high isolation.

[0051] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. A dual-notch high-isolation ultra-wideband MIMO antenna, characterized by: The antenna includes a dielectric substrate, a metal layer located on the upper surface of the dielectric substrate, a metal ground plate located on the lower surface of the dielectric substrate, and an F-shaped isolation branch extending from the metal ground plate; The F-shaped isolation branch comprises two axially symmetrically arranged F-shaped units; each F-shaped unit comprises a rectangular strip and two first-order branches and second-order branches of different lengths extending from the upper portion thereof; four slits of the same width are etched in the middle of the rectangular strip, one of which is longer than the other three slits of the same length; The metal layer is composed of two units placed axially symmetrically, and the two units are mirror-symmetrical to each other; each unit includes a radiation unit, a stepped microstrip feeder, an L-shaped slot, and a Z-shaped slot; The two ends of the stepped microstrip feeder are connected to the radiation unit and the feeder port respectively; The L-shaped slot and the Z-shaped slot are located on the radiation unit, with one end of the slot being in contact with the edge of the dielectric substrate, and the L-shaped slot being located on the side of the Z-shaped slot away from the feeding port; the length of the L-shaped slot and the Z-shaped slot is 1 / 4 of the wavelength of the corresponding notch center frequency; The F-shaped isolation branch is connected to the metal ground layer and is located between the two radiation units; A stepped groove is etched on the metal ground plane below the stepped microstrip feeder to increase the operating bandwidth.

2. The dual-notch high-isolation ultra-wideband MIMO antenna according to claim 1, characterized in that: The radiation unit is an asymmetrical rectangular cutoff structure, and the curved side of the cutoff corner is 1 / 4 of the arc length of the ellipse.

3. The dual-notch high-isolation ultra-wideband MIMO antenna according to claim 1, characterized in that: The stepped microstrip feed line is composed of three integrally formed rectangular parts, which are connected in sequence in width. One end of the rectangle with the smallest width is connected to the radiation unit, and one side of the rectangle with the largest width serves as a feeding port.

4. The dual-notch high-isolation ultra-wideband MIMO antenna according to claim 1, characterized in that: The total length of the L-shaped groove is 8.2 mm, including two horizontal and vertical parts; the horizontal part is 4.0 mm long and 0.2 mm wide, and is 1.3 mm away from the upper edge of the radiation unit; the vertical part is 4.2 mm long and 0.2 mm wide.

5. The dual-notch high-isolation ultra-wideband MIMO antenna according to claim 1, characterized in that: The total length of the Z-shaped groove is 6.7mm, and it includes three parts: horizontal, vertical and horizontal. The first horizontal part is 1mm long, 0.2mm wide, and 4.0mm away from the upper edge of the radiation unit. The vertical part connects the first and second horizontal parts at the same time, and is 3.5mm long and 0.2mm wide. The second horizontal part is 2.2mm long and 0.2mm wide.

6. The dual-notch high-isolation ultra-wideband MIMO antenna according to claim 1, characterized in that: The dielectric substrate is made of FR4 board with a dielectric constant of 4.4, a loss tangent angle of 0.02, and a size of 26mm×28mm×0.8mm.

7. The dual-notch high-isolation ultra-wideband MIMO antenna according to claim 1, characterized in that: In the rectangular strip of the F-shaped unit, the length of the second slit starting from one side of the branch is greater than that of the other slits.

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