A low profile horizontal omni directional scanning antenna

Abstract

This invention discloses a low-profile horizontal omnidirectional scanning antenna, comprising a dielectric substrate, a central feed unit disposed on the upper and lower surfaces of the dielectric substrate, a ring-shaped parasitic unit composed of six arc-shaped patches placed around the central feed unit on the lower surface of the dielectric substrate, and six corresponding bias circuits. Each of the six arc-shaped patches of the parasitic unit is equally divided into two sub-arc-shaped patches, which are connected by pin diodes. The bias circuits consist of two inductors and two microstrip lines, used to control the state of the pin diodes. A directional mode is achieved by controlling two reverse-biased and four forward-biased pin diodes; when all diodes are forward-biased, it is in omnidirectional mode. When in directional mode, the antenna operates at 2.478 GHz, can achieve 360° beam switching, has a maximum gain of 7.44 dBi, and a minimum S11 of -27 dB.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology and relates to a low-profile horizontal omnidirectional scanning antenna. Background Technology

[0002] With economic and technological development, people's demand for multimedia communication in daily life is increasing. Improving communication distance, expanding communication coverage, increasing spectrum utilization, and reducing device size have become the main directions of wireless communication research in recent years. Electrically Steerable Parasitic Array Radiator (ESPAR) technology utilizes the mutual coupling between array elements to enable antennas to achieve beam scanning, beam focusing, beamforming, and high gain within a smaller size.

[0003] An ESPAR antenna typically consists of a driving element and multiple parasitic elements. The parasitic elements obtain energy from the driving element through near-field coupling, and an adjustable reactive load creates the necessary phase shift for beam scanning. As a novel antenna structure, the research and application of ESPAR antennas contribute to the advancement of antenna design. By loading components such as adjustable inductors and variable capacitors, ESPAR antennas can control the radiation direction, thereby improving the antenna's gain and scanning range.

[0004] Phased array antennas use phase shifters to appropriately shift or delay the signals of array elements arranged according to a certain pattern, thereby obtaining beam deflection and performing phase compensation simultaneously in different azimuths. Both can achieve electrical beam scanning within the desired observation space without mechanically rotating the array, and achieve pattern reconfigurability. However, the insertion loss of phase shifters is significantly affected at microwave frequencies, and their high cost limits their widespread application. ESPAR antennas not only achieve pattern reconfigurability at microwave frequencies but also significantly reduce costs.

[0005] Modern communication equipment is becoming increasingly integrated, placing stricter demands on antenna size. The Internet of Things (IoT) connects various objects through information sensing devices such as RFID, infrared sensors, GPS, and laser scanners to achieve information exchange and communication. Compact ESPAR antennas are better suited to the needs of modern communication. Antenna size determines both the antenna's operating frequency and its operating mode. ESPAR antennas utilize near-field coupling, with the feed element and parasitic element operating in the same, singular mode, imposing strict requirements on the size of the radiating element and the feed structure. This singular operating mode not only ensures that reactive loads can influence the phase of some currents in the parasitic element but is also necessary to reduce near-field coupling energy loss and improve overall antenna gain. While challenging to design, ESPAR antennas, with their small size, high frequency operation, ability to cover a large area, high stability, and fast transmission rate, are gaining increasing importance.

[0006] ESPAR antennas also have broad application prospects in high-precision direction finding and positioning. For example, in satellite attitude control, wireless positioning and navigation systems, and wireless ad hoc networks, ESPAR antennas can achieve high-precision direction finding of incident signals through their unique signal processing algorithms. This helps improve the positioning accuracy and stability of the system, providing strong support for the development of related fields. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a high-gain, low-profile, electrically tunable parasitic element antenna based on an Alford loop antenna, specifically a low-profile horizontal omnidirectional scanning antenna, comprising a dielectric substrate, a center feed element, and parasitic elements, wherein...

[0008] The central feed unit includes a first disc antenna disposed on the upper surface of the dielectric substrate and a second disc antenna disposed on the lower surface of the dielectric substrate. The first disc antenna includes a first cross patch and four first arc patches. One end of each first arc patch is connected to the outer end of a line segment of the first cross patch, forming a disc-like shape with the first cross patch in the middle and the four first arc patches evenly distributed around its periphery. The second disc antenna includes a second cross patch and four second arc patches. One end of each second arc patch is connected to the outer end of a line segment of the second cross patch, forming a disc-like shape with the second cross patch in the middle and the four second arc patches evenly distributed around its periphery. The first cross patch and the second cross patch have the same position and shape, and the four first arc patches and the four second arc patches form a complementary ring, enabling the central feed unit to generate omnidirectional radiation.

[0009] The parasitic unit is disposed on the outer periphery of the second disc antenna on the lower surface of the dielectric substrate, and includes six evenly distributed arc-shaped patches, forming a ring as a whole. A diode is disposed in the middle of each arc-shaped patch, and the arc-shaped patch is evenly divided into two segments.

[0010] Preferably, the first arc patch has an arc tail, the width of which is greater than the width of the first arc patch.

[0011] Preferably, the second arc patch has an arc tail, the width of which is greater than the width of the second arc patch.

[0012] Preferably, a bias circuit is provided at the diode of the parasitic unit. The bias circuit includes two microstrip lines and two inductors. One microstrip line is connected to one end of an inductor to form a group. The other end of the inductor is connected to one end of the arc patch after it has been divided into equal parts. The other group of microstrip lines is connected to the inductor and the other end of the arc patch after it has been divided into equal parts. The two microstrip lines control the conduction and shutdown of the diode.

[0013] Preferably, the dielectric substrate uses ZYF255DA dielectric material with a relative permittivity of 2.55 and a dielectric loss tangent of 0.0018.

[0014] Preferably, the dielectric substrate has a hole in its center, and a coaxial cable is provided in the hole to supply power to the central power supply unit. The inner conductor of the coaxial cable passes through the hole from the lower surface of the dielectric substrate and is connected to the first cross-shaped patch on the upper surface; the outer conductor of the coaxial cable is connected to the second cross-shaped patch on the lower surface.

[0015] Preferably, the bias circuit provides an impedance of j1507.2Ω at the operating center frequency.

[0016] Preferably, the inductance in the bias circuit is 100nh.

[0017] Preferably, the operating center frequency is 2.478 GHz and the operating bandwidth is 37 MHz.

[0018] Preferably, the distance between the two equally divided segments of the arc-shaped patch of the parasitic unit is 1.5 mm.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The operating center frequency of this invention is 2.478 GHz. By optimizing the impedance configuration of parasitic elements, the sidelobe level can be effectively reduced, making the energy of the main beam more concentrated and further improving the gain. The maximum gain of the radiation pattern at this frequency can reach 7.44 dBi, and the maximum direction is in the horizontal direction of theta = 90°. In contrast, most existing ESPAR antennas have a maximum gain of only about 5 dBi, and the maximum gain of some antennas is in the direction of theta = 50°, requiring additional structures for beam pointing adjustment. Compared with existing ESPAR antennas, this invention has higher gain and better beam pointing.

[0021] This invention achieves 360° omnidirectional beam scanning with a simple design and small size. It achieves this by using near-field coupling between parasitic elements and the feed element, and by employing pin diodes to change the phase difference on the parasitic elements through the forward and reverse biasing of the pin diodes. Compared to existing array antennas that use phase shifters to achieve beam scanning, this design features a simpler feed structure and a smaller size. Compared to non-patch antennas, this design achieves higher gain with fewer elements; compared to patch antennas, this design has a smaller size while achieving high gain, omnidirectional radiation mode, and directional beam scanning capability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the upper surface structure of the dielectric substrate of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention;

[0023] Figure 2 This is a dispersion map of the lower surface structure of the dielectric substrate of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0024] Figure 3 This is a structural diagram of the bias circuit portion of the parasitic element of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0025] Figure 4 A schematic diagram of a complementary circular ring structure formed by the center feed unit of a low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram showing the dimensions of the upper surface of the dielectric substrate of a low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0027] Figure 6 This is a schematic diagram of the lower surface dimensions of the dielectric substrate of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention;

[0028] Figure 7 The figure shows the S11 simulation results of the omnidirectional radiation mode of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0029] Figure 8 The figure shows the H-plane simulation results of the omnidirectional radiation mode of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0030] Figure 9 The figure shows the S11 simulation results of the directional radiation mode of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention.

[0031] Figure 10 The figure shows the H-plane simulation results of the directional radiation mode of the low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0034] See Figure 1 , Figure 2 The image shows a low-profile horizontal omnidirectional scanning antenna according to an embodiment of the present invention, comprising a dielectric substrate 1, a center feed unit, and a parasitic unit. The center feed unit includes a first disc antenna disposed on the upper surface of the dielectric substrate 1 and a second disc antenna disposed on the lower surface of the dielectric substrate 1. The first disc antenna includes a first cross patch 21 and four first arc patches 31. One end of each first arc patch 31 is connected to the outer end of a line segment of the first cross patch 21, forming a first cross patch 21 in the center, with the four first arc patches 31 evenly distributed around it. The outer periphery has a disk-like shape; the second disk-shaped antenna includes a second cross patch 22 and four second arc patches 32, one end of each second arc patch 32 being connected to the outer end of a line segment of the second cross patch 22, forming a disk-like shape with the second cross patch 22 in the middle and the four second arc patches 32 evenly distributed on its outer periphery; wherein, the first cross patch 21 and the second cross patch 22 have the same position and shape, and the positions and shapes of the four first arc patches 31 and the four second arc patches 32 form complementary rings, see [reference]. Figure 4 This generates omnidirectional radiation, resulting in directional beams with the same gain.

[0035] The parasitic unit is disposed on the outer periphery of the second disc-shaped antenna on the lower surface of the dielectric substrate 1, and includes six evenly distributed arc-shaped patches forming a ring. A diode 7 is placed in the middle of each arc-shaped patch. The arc-shaped patch is evenly divided into two segments, sub-arc-shaped patches 51 and 52, see [reference]. Figure 2 The six arc-shaped patches are connected by pin diodes 7 numbered #1 to #6. By controlling the bias of diodes 7 to correspond to different resistances, the phase of the current in the parasitic element is affected, thereby realizing the antenna beam switching.

[0036] In a specific embodiment, see Figure 5 The first arc patch 31 is provided with an arc tail 3, the width of which is greater than the width of the first arc patch 31. Figure 5 The dimensions of the substrate are as follows: the dielectric substrate 1 uses ZYF255DA dielectric material with a relative permittivity of 2.55, a dielectric loss tangent of 0.0018, L of 140mm, and a thickness of 1.52mm. The width W1 of the first cross-shaped patch 21 and the second cross-shaped patch 22 is 10mm, the radius r1 of the arc patch 31 is 19.86mm, the width W2 is 2mm, and the arc tail 3 of the first arc patch 31 has a length r3 of 2.5mm and a width W5 of 1.8mm. The first cross-shaped patch 21 and the second cross-shaped patch 22 on the upper and lower surfaces of the dielectric substrate have the same structure and shape. In particular, the arc length L2 of the second arc patch 32 on the lower surface is 16mm, and the arc length L3 of the first arc patch 31 on the upper surface is 11.16mm. The two complement each other and form a ring.

[0037] In a specific embodiment, see Figure 6 The second arc-shaped patch 32 is provided with an arc-shaped tail 3, the width of which is greater than the width of the second arc-shaped patch 32. The arc-shaped patch of the parasitic unit is evenly divided into sub-arc-shaped patches 51 and 52, with an angle of 22.5°, a radius r2 of 58.56 mm, and a width W3 of 10 mm; the gap distance D between the sub-arc-shaped patches 51 and 52 is 1.5 mm.

[0038] See Figure 3 and Figure 6The antenna includes six bias circuits 6, each consisting of two microstrip lines 9, each 10 mm long (L1) and 0.2 mm wide (W4), and two 100 MHz inductors 8 positioned between the arc-shaped patch and the microstrip lines 9. The external power supply controls the state of the pin diode 7 via the microstrip lines 9. The inductors 8 prevent AC current from the parasitic unit from entering the external DC power supply, protecting the power supply. A bias circuit 6 is located at the diode 7 of the parasitic unit. This bias circuit 6 includes two microstrip lines 9 and two inductors 8. One microstrip line 9 is connected to one end of an inductor 8, forming a pair. The other end of the inductor 8 is connected to one segment of the arc-shaped patch after it has been evenly divided. Another pair of microstrip lines 9 and inductors 8 are connected to the other segment of the arc-shaped patch after it has been evenly divided. The two microstrip lines 9 control the conduction and cutoff of the diode 7. The bias circuit 6 provides an impedance of 7.2 Ω at the operating center frequency.

[0039] A hole is punched in the center of the dielectric substrate 1, and a coaxial cable is installed inside the hole to power the center feed unit. The inner conductor 11 of the coaxial cable passes through the hole from the lower surface of the dielectric substrate 1 and connects to the first cross-shaped patch 21 on the upper surface; the outer conductor 12 of the coaxial cable is connected to the second cross-shaped patch 22 on the lower surface. In particular, when using coaxial cables of different lengths as feed lines, a relative error will occur in the center frequency of the antenna S11. This invention adopts a sleeve balun connected to the outer conductor 12 of the coaxial cable, which effectively reduces the impact of the coaxial cable length on the antenna performance.

[0040] The antenna operates at a center frequency of 2.478 GHz with a bandwidth of approximately 37 MHz. It has excellent S11 parameters, a maximum directional beam gain of 7.44 dBi, and a good 360° beam scanning capability.

[0041] This invention uses an Alford loop antenna structure as the center feed unit, which can generate a horizontally polarized omnidirectional radiation pattern. The desired omnidirectional radiation pattern is achieved using a simple and low-profile structure. A near-circular patch is placed around the center feed on the lower surface as a parasitic element. The pin diode 7 loaded in the middle of each arc-shaped patch exhibits different states under forward and reverse bias voltages. Under forward bias, the pin diode 7 is a short circuit, equivalent to a small resistance of approximately 2.4 ohms; under 0V, the pin diode 7 is an open circuit, equivalent to a 0.12pF capacitor. This state affects the current phase on the parasitic element, causing a phase inconsistency between the current phase on this side and the opposite side, thus deflecting the main lobe direction of the antenna radiation pattern. This, in turn, controls the opening or closing of different pin diodes 7 to achieve 360° beam scanning.

[0042] The antenna in the specific embodiment was simulated using CST2022. The following is a detailed simulation analysis of the antenna's S11, H-plane (XOY plane), and 3-D field pattern. Detailed explanations are provided for each corresponding mode. The pin diodes 7 used are numbered counter-clockwise from #1 to #6. The on and off states are simplified by labeling the on state as "1" and the off state as "0". The omnidirectional radiation mode and directional radiation mode of the antenna are designated as Mode 1 and Mode 2, respectively.

[0043] Mode 1, see Figure 7 All pin diodes 7 are in state "1", and the center frequency of antenna S11 is 2.462GHz, close to -17dB, which has a good impedance matching effect. Figure 8 The image shows the far-field radiation pattern of the antenna in the H-plane at 2.462 GHz. In this state, the gain is approximately 3 dBi, and it is in an omnidirectional radiation mode.

[0044] Mode 2: Four pin diodes are in state "1" and two are in state "0", with six possible combinations: #1#2, #2#3, #3#4, #4#5, #5#6 and #6#1 are in state "0" and the rest are in state "1".

[0045] See Figure 9 The antenna's S11 center frequency is 2.478GHz, and S11 is approximately -27dB, providing excellent impedance matching. Figure 10 The images show the antenna radiation pattern in the H-plane (Theta=90°) at 2.478 GHz under this condition, with a maximum gain of 7.44 dBi. By using six combinations of pin diode 7, a horizontal 360° beam scanning effect was achieved.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-profile horizontal omnidirectional scanning antenna, characterized in that, It includes a dielectric substrate, a central feed unit, and a parasitic unit, wherein, The central feed unit includes a first disc antenna disposed on the upper surface of the dielectric substrate and a second disc antenna disposed on the lower surface of the dielectric substrate. The first disc antenna includes a first cross patch and four first arc patches. One end of each first arc patch is connected to the outer end of a line segment of the first cross patch, forming a disc-like shape with the first cross patch in the middle and the four first arc patches evenly distributed around its periphery. The second disc antenna includes a second cross patch and four second arc patches. One end of each second arc patch is connected to the outer end of a line segment of the second cross patch, forming a disc-like shape with the second cross patch in the middle and the four second arc patches evenly distributed around its periphery. The first cross patch and the second cross patch have the same position and shape, and the four first arc patches and the four second arc patches form a complementary ring, enabling the central feed unit to generate omnidirectional radiation. The parasitic unit is disposed on the outer periphery of the second disc antenna on the lower surface of the dielectric substrate, and includes six evenly distributed arc-shaped patches, forming a ring as a whole. A diode is disposed in the middle of each arc-shaped patch, and the arc-shaped patch is evenly divided into two segments. The first arc patch has an arc tail, the width of which is greater than the width of the first arc patch; The second arc patch has an arc tail, the width of which is greater than the width of the second arc patch; A bias circuit is provided at the diode of the parasitic unit. The bias circuit includes two microstrip lines and two inductors. One microstrip line is connected to one end of an inductor to form a group. The other end of the inductor is connected to one end of the arc patch after it is evenly divided. The other group of microstrip lines is connected to the inductor and the other end of the arc patch after it is evenly divided. The two microstrip lines control the conduction and shutdown of the diode. The dielectric substrate uses ZYF255DA dielectric material, with a relative permittivity of 2.55 and a dielectric loss tangent of 0.0018. The dielectric substrate has a central hole, and a coaxial cable is installed inside the hole to supply power to the central power supply unit. The inner conductor of the coaxial cable passes through the hole from the lower surface of the dielectric substrate and is connected to the first cross-shaped patch on the upper surface; the outer conductor of the coaxial cable is connected to the second cross-shaped patch on the lower surface.

2. The low-profile horizontal omnidirectional scanning antenna according to claim 1, characterized in that, The bias circuit provides an impedance of j1507.2Ω at the operating center frequency.

3. The low-profile horizontal omnidirectional scanning antenna according to claim 1, characterized in that, The inductance in the bias circuit is 100nh.

4. The low-profile horizontal omnidirectional scanning antenna according to claim 1, characterized in that, The operating frequency is 2.478 GHz, and the operating bandwidth is 37 MHz.

5. The low-profile horizontal omnidirectional scanning antenna according to claim 1, characterized in that, The arc-shaped patch of the parasitic unit is divided into two segments with a distance of 1.5 mm between them.

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