Ultra-wideband compact circularly polarized antenna based on miniaturized phase shifter

Abstract

The invention discloses an ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, and belongs to the technical field of antenna engineering. According to the antenna, the feed network and the Vivaldi antenna are cascaded, so that the antenna has the characteristic of wide bandwidth; the broadband matching characteristic is realized by designing a metal coupling sheet, a zigzag structure, an inverted L-shaped balun and the like; a novel miniaturized ultra-wideband 90-degree phase shifter is designed by adopting an n network and a negative group delay circuit; and the Vivaldi antenna layer and the feed network layer both adopt a PCB (Printed Circuit Board) technology, so that the processing is easy, and the cost is low. Compared with a traditional phase shifter, the size of the phase shifter is reduced by 75%, and the size of the phase shifter is 67 mm * 44.5 mm (0.071 lambda 1 * 0.047 lambda 1). Meanwhile, a simulation result shows that the provided circularly polarized antenna has a 10dB impedance bandwidth of 0.32 to 1.2 GHz (3.75: 1) and a 3dB axial ratio bandwidth of 0.32 to 1.15 GHz (3.59: 1).

Description

Technical Field

[0001] The invention belongs to the technical field of antenna engineering, and in particular relates to a broadband circularly polarized antenna based on a 90-degree phase shifter, which has the characteristics of ultra-wideband, compact structure, and miniaturized phase shifter structure. Background Art

[0002] In recent years, circularly polarized antennas have been widely studied and applied due to their advantages in multipath anti-interference. At the same time, with the increasing demand for large channel capacity and miniaturization in modern wireless systems, the requirements for circularly polarized antennas in terms of bandwidth, size, and profile have increased dramatically. Therefore, in the face of increasingly complex application scenarios, it is of great significance to design a circularly polarized antenna with wide bandwidth, small size, and low profile. Circularly polarized antennas using a feed network usually have ultra-wideband characteristics. For example, in the paper "Design of wideband circularly polarized Vivaldi antenna with stable radiation pattern", the feed network and the antenna are integrated on a PCB board to achieve a 3.9:1 3dB axial ratio bandwidth. In the paper "Ultrawideband circularly polarized halved-type Vivaldi antenna with symmetrical radiation pattern", a 1-to-4 360-degree phase shifter and a new type of half-type Vivaldi antenna are used to achieve a 3:1 3dB axial ratio bandwidth. Summary of the invention

[0003] Based on the background technology, the present invention proposes an ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, which adopts a Γ balun with a high impedance line, a gradient radiation slot line with a serrated structure, and a metal coupling plate to achieve good impedance matching in a wide bandwidth. In addition, a new type of miniaturized 90-degree phase shifter is proposed, which consists of three parts: an unequal power divider, a Π-type network, and a negative group delay network. Compared with the traditional 90-degree phase shifter, it achieves a 75% size reduction. The single-layer PCB board structure is adopted, which is easy to process and low in cost, and can be better applied in various scenarios.

[0004] The technical solution adopted by the present invention is as follows: an ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, the antenna comprising: an orthogonal Vivaldi antenna, a feeding network, and a bottom plate, the orthogonal Vivaldi antenna comprising two Vivaldi antennas of the same structure, the two Vivaldi antennas being orthogonally arranged, each Vivaldi antenna comprising: a substrate, a metal patch, a Γ-type balun, and a fan-shaped feeding plate, the metal patch being arranged on a layer of the substrate, the Γ-type balun and the fan-shaped feeding plate being arranged on the other side of the substrate, the metal patch comprising a completely symmetrical and isolated left part and right part, each part comprising a main radiation structure and a parasitic radial structure, the main radiation structures of the left part and the right part forming a "γ" shape as a whole, but the left and right sides of the "γ" shape are symmetrical and isolated; the parasitic radiation structure also comprises a left and a right part, which are respectively arranged on both sides of the main radiation structure, each part of the parasitic radiation structure is in a right-angled trapezoid as a whole, and the acute angle of the bottom side of the right-angled trapezoid is connected to the waist of the corresponding part of the main radiation structure;

[0005] The Γ-type balun is arranged at the right part of the main radiating structure, the bottom input end of the Γ-type balun is flush with the bottom of the main radiating structure, the top output end of the Γ-type balun is flush with the side of the right part of the main radiating structure close to the analysis, the top output end of the Γ-type balun is connected to the fan-shaped feed plate, and the fan-shaped feed plate is located at the left part of the main radiating structure; a defective slot is arranged at the corresponding position of the Γ-type balun;

[0006] The orthogonal Vivaldi antennas are arranged on the bottom plate, and each Vivaldi antenna is perpendicular to the bottom plate;

[0007] The bottom plate is the upper layer, the upper layer is the dielectric layer, and the lower layer is the metal layer; the feeding network is arranged on the dielectric layer of the bottom plate, and the feeding network feeds each Vivaldi antenna respectively.

[0008] Furthermore, the projection of the orthogonal Vivaldi antenna on the bottom plate is a "cross" structure, and a metal coupling plate perpendicular to the floor is arranged at each location of the "cross" structure corresponding to the position on the bottom plate, and the metal coupling plate is also perpendicular to the Vivaldi antenna in contact with it.

[0009] Furthermore, the feeding network is an ultra-wideband 90-degree phase shifter.

[0010] Furthermore, a sawtooth structure is arranged on the bottom edge of the parasitic radiation structure.

[0011] Furthermore, sawtooth structures are provided on both sides of the portion below the connection point between the main radiation structure and the parasitic radiation structure.

[0012] Furthermore, a diamond-shaped notch is provided in the lower portion between the left and right portions of the main radiation structure.

[0013] Further, the ultra-wideband 90-degree phase shifter includes: an unequal power divider, a Π-type network, and a negative group delay network. The input end of the unequal power divider is the input end of the ultra-wideband 90-degree phase shifter. The unequal power divider is composed of two serially connected "mouth"-shaped metal patches. The input end is set at the midpoint on the left side of the first "mouth"-shaped metal patch, and the midpoint on the right side of the first "mouth"-shaped metal patch is isolated up and down by a first isolation resistor; the second "mouth"-shaped metal patch is divided into upper and lower parts, the upper part of the metal feeder is narrower than the lower part, and the left sides of the upper and lower parts of the second "mouth"-shaped metal patch are isolated by a first isolation resistor, and the right sides are isolated by a second isolation resistor; the connection point between the upper part on the right side of the second "mouth"-shaped metal patch and the second isolation resistor is used as the upper output end to connect the input end of the Π-type network, and the connection point between the lower part on the right side of the second "mouth"-shaped metal patch and the second isolation resistor is used as the lower output end to connect the input end of the negative group delay network;

[0014] The Π-type network includes a "T"-shaped metal patch, a first inductor, a first capacitor, and a second capacitor. The left port at the top of the "T"-shaped metal patch is the input port, and the right port is connected to one end of an output metal patch through a first capacitor. The other end of the output metal patch is the output port of the Π-type network, which is an output port of the ultra-wideband 90-degree phase shifter. The side of the output metal patch is grounded through a second inductor. The bottom port of the "T"-shaped metal patch is connected to a grounded metal patch through a first inductor, and the other end of the grounded metal patch is connected to the metal layer of the bottom plate through metallization;

[0015] The negative group delay network includes an "L"-shaped metal patch, a "-" shaped metal patch, a second capacitor, a third capacitor, a third inductor, a fourth inductor, a fifth inductor, a first grounding resistor, and a second grounding resistor. The upper top end of the "L"-shaped metal patch is the input of the negative group delay network, and the bottom end is connected to one end of the "-" shaped metal patch through a third inductor. The other end of the "-" shaped metal patch is the output port of the negative group delay network, which is the other output port of the ultra-wideband 90-degree phase shifter; the side at the bottom of the "L"-shaped metal patch is grounded successively through a second capacitor, a fourth inductor, and a first grounding resistor, and the side of the "-" shaped metal patch is grounded through a third capacitor, a fifth inductor, and a second grounding resistor.

[0016] The antenna of the present invention adopts the form of cascading a feeding network and a Vivaldi antenna, and has the characteristic of wide bandwidth; broadband matching characteristics are realized by designing forms such as metal coupling patches, serrated structures, and Γ-type baluns; by adopting a Π network and a negative group delay circuit, a new type of miniaturized ultra-wideband 90-degree phase shifter is designed; both the Vivaldi antenna layer and the feeding network layer adopt PCB board technology, which is easy to process and has low cost. Compared with traditional phase shifters, a 75% size reduction is achieved, and its size is 67mm * 44.5mm (0.071λ l*0.047λ l ). Simultaneously, simulation results show that the proposed circularly polarized antenna has a 10 dB impedance bandwidth of 0.32-1.2 GHz (3.75:1) and a 3 dB axial ratio bandwidth of 0.32-1.15 GHz (3.59:1). BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 3D view of the ultra-wideband compact circularly polarized antenna.

[0018] Figure 2 This is the Vivaldi antenna layer, side view of the antenna.

[0019] Figure 3 It is the feeding network layer.

[0020] Figure 4 This is the reflection coefficient and transmission phase result diagram of the π-type network.

[0021] Figure 5 This is the reflection coefficient, transmission coefficient and transmission phase result diagram of the negative group delay network.

[0022] Figure 6 This is a graph showing the reflection coefficient and gain results for a compact broadband Vivaldi antenna.

[0023] Figure 7 This is a graph showing the reflection coefficient, transmission coefficient, and phase difference between output ports of a miniaturized 90-degree phase shifter.

[0024] Figure 8 This is the reflection coefficient, axial ratio, and gain result diagram after the phase shifter and Vivaldi antenna are cascaded.

[0025] In the figure, 1. dielectric substrate, 2. trapezoidal structure, 3. sawtooth structure, 4. metal coupling plate, 5. defective ground structure, 6. feeding layer, 7. radiation gap, 8. Γ-type balun, 9. sawtooth structure, 10. diamond notch, 11. parasitic radiation structure, 12. fan-shaped feeding plate, 13. feeding port, 14. orthogonal Vivaldi input port one, 15. orthogonal Vivaldi input port two, 16. Π-type network, 17 negative group delay circuit, 18. unequal power divider, 19. metal through hole, 20. first isolation resistor, 21. second isolation resistor. DETAILED DESCRIPTION

[0026] The antenna of this embodiment operates at 0.32-1.15 GHz. The 3D view, side view and bottom view of the antenna structure are shown in FIG. Figures 1 to 3 , antenna size 320mm*340mm*340mm(0.36λ l *0.36λ l *0.34λl , where λ l is the low-frequency wavelength of free space). Two Vivaldi antennas with orthogonal polarizations are placed vertically and crossed and cascaded together through the feeding network layer below to form a broadband circularly polarized antenna.

[0027] From top to bottom, it consists of two parts: a pair of orthogonal compact broadband Vivaldi antennas and a miniaturized broadband 90-degree phase shifter; the pair of compact broadband Vivaldi antennas are respectively printed on a single-layer PCB, and are formed by slotting and crossing from the upper and lower parts; the miniaturized broadband 90-degree phase shifter is printed on a single-layer PCB and is located under the antenna as a floor.

[0028] The compact broadband Vivaldi antenna is composed of a Γ balun with a high impedance line, a serrated edge structure, a gradient radiation slot line and a metal coupling plate. The Γ balun is conducive to achieving broadband impedance matching; the serrated edge structure and the metal coupling plate can effectively extend the resonant current, thereby removing the low-frequency resonance from the operating frequency and improving the low-frequency impedance matching; the gradient slot line effectively radiates energy into free space;

[0029] The miniaturized broadband 90-degree phase shifter is composed of three parts: an unequal power divider, a Π-type network, and a negative group delay network. The group delay between the Π-type network and the negative group delay network is consistent, achieving a broadband stable phase difference while greatly reducing the size of the phase shifter. The unequal power divider is used to balance the additional loss caused by the negative group delay circuit.

[0030] In this embodiment, the orthogonal Vivaldi antenna is printed on the dielectric substrate 1, which is F4BM-300, with a thickness of 0.8mm and a dielectric constant of 3. Structure 2 is a trapezoidal shape with an upper base width of 45mm, a lower base width of 110mm and a height of 85mm, which serves as part of the parasitic radiation structure of the antenna. Structure 3 is a sawtooth structure with a sawtooth shape of 10mm width and 15mm height, which effectively extends the path of the resonant current, moves the resonance outside the low-frequency band, and widens the low-frequency impedance bandwidth. Structure 4 is a metal coupling plate structure with a width of 100mm and a height of 80mm, which also plays a role in extending the resonant current and improving the low-frequency bandwidth. Structure 5 is a defective ground structure as part of the Γ-type balun. Structure 6 is a feed layer, printed on F4BM-220, with a thickness of 1mm and a dielectric constant of 2.2, and also serves as the floor of the antenna.

[0031] The detailed structure of the Vivaldi antenna in this embodiment is as follows: Figure 2As shown. Among them, 7 is an exponentially gradient radiation slot, the slot height is 280mm, the end opening is 100mm, and the slot width is exponentially gradient along the Z-axis direction, which effectively improves the impedance matching of the antenna unit working in a wide band. Structure 8 is a Γ-type balun with a defective ground. The vertical transmission line of the balun is 3mm wide and 84mm high, and the horizontal part is 0.8mm wide and 21mm long. Structure 11 is a side view of structure 2. Structure 10 is a diamond notch with a radius of 42mm and an angle of 90°. It is connected to the gradient slot line to improve the impedance matching. Structure 12 is a fan-shaped feed line with a radius of 12mm and an angle of 90 degrees. The gradient radiation structure is fed by coupling.

[0032] The detailed structure of the feed network layer in this embodiment is as follows Figure 3 As shown. Among them, structures 13, 14, and 15 are the feeding port and the two input ports of the orthogonal Vivaldi, respectively. Structure 16 is a Π-type network, consisting of two parallel grounded inductors and a series capacitor, and their values ​​are 30nH, 9pF, and 56nH from left to right. Structure 17 is a negative group delay circuit, consisting of two series resonant circuits and series inductors, wherein the two series resonant circuits have the same structure, which are 360Ω, 100nH, and 1pF, respectively, and the series inductance is 4.5nH. Structure 18 is an unequal power divider, wherein the line width of the second part is 0.6mm and 2.3mm, respectively. Structure 19 is a metal through hole, which serves as a ground short-circuit post. Structures 20 and 21 are 720Ω and 80Ω, respectively, as isolation resistors.

[0033] The embodiment provides the reflection coefficient and transmission coefficient phase of the Π-type network as it changes with frequency, such as Figure 4 It can be seen that within 0.3-1.1GHz, the reflection coefficient of the structure is less than -15dB, and it has an advanced phase and a large group delay, which is conducive to the miniaturization of the overall structure.

[0034] The embodiment provides the reflection coefficient, transmission coefficient and transmission coefficient phase of the negative group delay network as it changes with frequency, such as Figure 5 It can be seen that within 0.3-1GHz, the reflection coefficient of the structure is less than -10dB, the phase is close to -10 degrees, the group delay is small, which is conducive to achieving broadband stable phase difference, and the loss is less than 1.2dB.

[0035] The simulation results of the Vivaldi antenna are given in the embodiment, such as Figure 6 It can be seen that within the range of 0.32-1.08GHz, the reflection coefficient of the structure is less than -10dB, and the gain changes smoothly within the frequency band.

[0036] The simulation results of a miniaturized broadband 90-degree phase shifter are given in the embodiment. Figure 7In the range of 0.3-1.1GHz, the reflection coefficient is less than -10dB. Due to the loss of the negative group delay circuit, the insertion loss is less than 1dB, the amplitude difference is less than 0.6dB, and the phase difference is less than ±10 degrees.

[0037] The simulation results of the feed network and antenna cascade are given in the embodiment, such as Figure 8 It can be seen that the reflection coefficient is less than -10dB in the range of 0.32-1.2GHz, the axial ratio is less than 3dB in the range of 0.32-1.15GHz, and the gain is greater than 3dBic in the working frequency range, which has great application potential.

Claims

1. An ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, the antenna comprising: An orthogonal Vivaldi antenna, a feeding network, and a bottom plate. The orthogonal Vivaldi antenna comprises two Vivaldi antennas of the same structure. The two Vivaldi antennas are orthogonally arranged. Each Vivaldi antenna comprises: a substrate, a metal patch, a Γ-type balun, and a fan-shaped feeding plate. The metal patch is arranged on a layer of the substrate, and the Γ-type balun and the fan-shaped feeding plate are arranged on the other side of the substrate. The metal patch comprises a completely symmetrical and isolated left and right part. Each part comprises a main radiation structure and a parasitic radiation structure. The main radiation structures of the left and right parts constitute a "γ" shape as a whole, but the left and right sides of the "γ" shape are symmetrical and isolated; the parasitic radiation structure also comprises a left and a right part, which are respectively arranged on both sides of the main radiation structure. Each part of the parasitic radiation structure is in a right-angled trapezoid as a whole. The acute angle of the bottom side of the right-angled trapezoid is connected to the waist of the corresponding part of the main radiation structure. The Γ-type balun is arranged at the right part of the main radiating structure, the bottom input end of the Γ-type balun is flush with the bottom of the main radiating structure, the top output end of the Γ-type balun is flush with the side of the right part of the main radiating structure close to the analysis, the top output end of the Γ-type balun is connected to the fan-shaped feed plate, and the fan-shaped feed plate is located at the left part of the main radiating structure; a defective slot is arranged at the corresponding position of the Γ-type balun; The orthogonal Vivaldi antennas are arranged on the bottom plate, and each Vivaldi antenna is perpendicular to the bottom plate; The bottom plate is the upper layer, the upper layer is the dielectric layer, and the lower layer is the metal layer; the feeding network is arranged on the dielectric layer of the bottom plate, and the feeding network feeds each Vivaldi antenna respectively.

2. The ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter according to claim 1, characterized in that: The projection of the orthogonal Vivaldi antenna on the base plate is a "cross" structure. A metal coupling plate perpendicular to the floor is set at each location of the "cross" structure corresponding to the position on the base plate. The metal coupling plate is also perpendicular to the Vivaldi antenna in contact with it.

3. The ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter according to claim 1, characterized in that: The feeding network is an ultra-wideband 90-degree phase shifter.

4. The ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter according to claim 1, characterized in that: A sawtooth structure is arranged on the bottom edge of the parasitic radiation structure.

5. The ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter according to claim 1, characterized in that: Sawtooth structures are arranged on both sides of the portion below the connection point between the main radiation structure and the parasitic radiation structure.

6. The ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter according to claim 1, characterized in that: A diamond-shaped notch is arranged at the lower part between the left and right parts of the main radiation structure.

7. The ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter as claimed in claim 3, characterized in that: The ultra-wideband 90-degree phase shifter includes: an unequal power divider, a Π-type network, and a negative group delay network. The input end of the unequal power divider is the input end of the ultra-wideband 90-degree phase shifter. The unequal power divider is composed of two serially connected "mouth"-shaped metal patches. The input end is set at the midpoint on the left side of the first "mouth"-shaped metal patch, and the midpoint on the right side of the first "mouth"-shaped metal patch is isolated up and down by a first isolation resistor; the second "mouth"-shaped metal patch is divided into upper and lower parts, the upper part of the metal feeder is narrower than the lower part, and the left sides of the upper and lower parts of the second "mouth"-shaped metal patch are isolated by a first isolation resistor, and the right sides are isolated by a second isolation resistor; the connection point between the upper part on the right side of the second "mouth"-shaped metal patch and the second isolation resistor is used as the upper output end to connect the input end of the Π-type network, and the connection point between the lower part on the right side of the second "mouth"-shaped metal patch and the second isolation resistor is used as the lower output end to connect the input end of the negative group delay network; The Π-type network includes a "T"-shaped metal patch, a first inductor, a first capacitor, and a second capacitor. The left port at the top of the "T"-shaped metal patch is the input port, and the right port is connected to one end of an output metal patch through a first capacitor. The other end of the output metal patch is the output port of the Π-type network, which is an output port of the ultra-wideband 90-degree phase shifter. The side of the output metal patch is grounded through a second inductor. The bottom port of the "T"-shaped metal patch is connected to a grounded metal patch through a first inductor, and the other end of the grounded metal patch is connected to the metal layer of the bottom plate through metallization; The negative group delay network includes an "L"-shaped metal patch, a "-"-shaped metal patch, a second capacitor, a third capacitor, a third inductor, a fourth inductor, a fifth inductor, a first grounding resistor, and a second grounding resistor. The upper top of the "L"-shaped metal patch is used as the input of the negative group delay network, and the bottom end is connected to one end of the "-"-shaped metal patch through a third inductor. The other end of the "-"-shaped metal patch is used as the output port of the negative group delay network, which is the other output port of the ultra-wideband 90-degree phase shifter; the side at the bottom of the "L"-shaped metal patch is grounded successively through a second capacitor, a fourth inductor, and a first grounding resistor, and the side of the "-"-shaped metal patch is grounded through a third capacitor, a fifth inductor, and a second grounding resistor.

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