A Ultra-wideband Compact Circularly Polarized Antenna Based on a Miniaturized Phase Shifter

Abstract

The present invention discloses a ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, belonging to the technical field of antenna engineering. 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; the broadband matching characteristic is realized by designing forms such as a metal coupling sheet, a serrated structure, and a Γ-shaped balun; a novel miniaturized ultra-wideband 90-degree phase shifter is designed by adopting a Π network and a negative group delay circuit; both the Vivaldi antenna layer and the feeding network layer adopt the PCB process, which is easy to process and has low cost. Compared with the traditional phase shifter, a 75% size reduction is achieved, and its size is 67mm * 44.5mm (0.071λ l * 0.047λ l ). At the same time, the 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).

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna engineering, and particularly relates to a broadband circularly polarized antenna based on a 90-degree phase shifter, which has the characteristics of ultra-wideband, compact structure, and miniaturization of the 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 sharply. 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 feeding network usually have ultra-wideband characteristics. For example, in the paper "Design of wideband circularly polarized Vivaldi antenna with stable radiation pattern", the feeding network and the antenna are integrated on a single PCB board, achieving a 3dB axial ratio bandwidth of 3.9:1. 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 halved Vivaldi antenna are used to achieve a 3dB axial ratio bandwidth of 3:1. Summary of the Invention

[0003] Based on the background art, the present invention proposes an ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, which uses a Γ balun with a high-impedance line, a tapered radiation slot line with a serrated structure, and a metal coupling sheet to achieve good impedance matching within a large bandwidth range. In addition, a new type of miniaturized 90-degree phase shifter is proposed, which is composed of an unequal power divider, a Π-type network, and a negative group delay network, achieving a 75% size reduction compared to traditional 90-degree phase shifters. The structure of a single-layer PCB board is used, which is convenient for processing and has a low cost, and can be better applied in various scenarios.

[0004] The technical solution adopted by the present invention is as follows: A ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter, the antenna comprising: orthogonal Vivaldi antennas, a feeding network, and a bottom plate. The orthogonal Vivaldi antennas include two Vivaldi antennas with the same structure, and the two Vivaldi antennas are orthogonally arranged. Each Vivaldi antenna includes: a substrate, a metal patch, a Γ-shaped balun, and a fan-shaped feeding patch. The metal patch is disposed on one layer of the substrate, and the Γ-shaped balun and the fan-shaped feeding patch are disposed on the other side of the substrate. The metal patch includes a left part and a right part that are completely symmetric and isolated. Each part includes a main radiation structure and a parasitic radiation structure. The main radiation structures of the left part and the right part together form a "γ" shape, but the left and right sides of this "γ" shape are symmetric and isolated; the parasitic radiation structure also includes left and right parts, which are respectively disposed on both sides of the main radiation structure. Each part of the parasitic radiation structure is in the shape of a right-angled trapezoid, and the acute angle at the bottom of this right-angled trapezoid is connected to the waist of the corresponding part of the main radiation structure.

[0005] The Γ-shaped balun is disposed on the right part of the main radiation structure. The bottom input end of the Γ-shaped balun is flush with the bottom of the main radiation structure, and the top output end of the Γ-shaped balun is flush with the side of the right part of the main radiation structure close to the gap. The top output end of the Γ-shaped balun is connected to the fan-shaped feeding patch, and the fan-shaped feeding patch is located on the left part of the main radiation structure; a defect slot is provided at the corresponding position of the Γ-shaped balun.

[0006] The orthogonal Vivaldi antennas are disposed 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 a dielectric layer, and the lower layer is a metal layer; the feeding network is disposed on the dielectric layer of the bottom plate, and the feeding network feeds each Vivaldi antenna respectively.

[0008] Further, the projection of the orthogonal Vivaldi antennas on the bottom plate is a "cross" structure, and a metal coupling patch perpendicular to the floor is provided at the position corresponding to each location of this "cross" structure on the bottom plate. This metal coupling patch is also perpendicular to the Vivaldi antenna it contacts.

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

[0010] Further, a serrated structure is provided on the bottom edge of the parasitic radiation structure.

[0011] Further, serrated structures are provided on both sides of the part below the connection point between the main radiation structure and the parasitic radiation structure.

[0012] Further, a diamond-shaped notch is provided in the lower part between the left and right parts of the main radiation structure.

[0013] Furthermore, 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 "mouth"-shaped metal patches connected in series. 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 vertically and horizontally 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. 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. 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. 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 sequentially 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; the broadband matching characteristic is realized by designing forms such as metal coupling patches, serrated structures, and Γ-type baluns; a new type of miniaturized ultra-wideband 90-degree phase shifter is designed by adopting a Π network and a negative group delay circuit; 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 the traditional phase shifter, a 75% size reduction is achieved, and its size is 67mm * 44.5mm (0.071λ l*0.047λ l )。 Meanwhile, the 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 is the 3D view of the ultra-wideband compact circularly polarized antenna.

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

[0019] Figure 3 is the feed network layer.

[0020] Figure 4 is the graph of the reflection coefficient and transmission phase of the Π-type network.

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

[0022] Figure 6 is the graph of the reflection coefficient and gain of the compact broadband Vivaldi antenna.

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

[0024] Figure 8 is the graph of the reflection coefficient, axial ratio and gain after cascading the phase shifter and the Vivaldi antenna.

[0025] In the figure, 1. dielectric substrate, 2. trapezoidal structure, 3. serrated structure, 4. metal coupling sheet, 5. defected ground structure, 6. feed layer, 7. radiation slot, 8. Γ-type balun, 9. serrated structure, 10. diamond-shaped notch, 11. parasitic radiation structure, 12. fan-shaped feed piece, 13. feed 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 via hole, 20. first isolation resistor, 21. second isolation resistor. DETAILED DESCRIPTION OF THE EMBODIMENTS

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

[0027] It consists of two parts from top to bottom: 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 cross from the upper part to the lower part with slots; the miniaturized broadband 90-degree phase shifter is printed on a single-layer PCB and also serves as the ground plane under the antenna.

[0028] The compact broadband Vivaldi antenna consists of a Γ balun with a high-impedance line, a serrated edge structure, a tapered radiation slot line, and a metal coupling patch. Among them, the Γ balun is beneficial to achieve broadband impedance matching; the serrated edge structure and the metal coupling patch can effectively extend the resonant current, so as to remove the low-frequency resonance outside the operating frequency and improve the low-frequency impedance matching; the tapered slot line effectively radiates energy into free space;

[0029] The miniaturized broadband 90-degree phase shifter consists of an unequal power divider, a Π-type network, and a negative group delay network. Among them, the group delays between the Π-type network and the negative group delay network are consistent, achieving a broadband and stable phase difference, while greatly reducing the size of the phase shifter; the unequal power divider is to balance the additional loss brought by the negative group delay circuit.

[0030] In this embodiment, the orthogonal Vivaldi antennas are printed on the dielectric substrate 1, which is F4BM-300, with a thickness of 0.8 mm and a dielectric constant of 3. Structure 2 is trapezoidal, with an upper base width of 45 mm, a lower base width of 110 mm, and a height of 85 mm, serving as part of the parasitic radiation structure of the antenna. Structure 3 is a serrated structure, with a serrated width of 10 mm and a height of 15 mm, effectively extending the path of the resonant current, shifting the resonance outside the low-frequency band, and broadening the low-frequency impedance bandwidth. Structure 4 is a metal coupling patch structure, with a width of 100 mm and a height of 80 mm, also playing the role of extending the resonant current and improving the low-frequency bandwidth. Structure 5 is a defected ground structure, serving as part of the Γ balun. Structure 6 is the feeding layer, printed on F4BM-220, with a thickness of 1 mm and a dielectric constant of 2.2, and also serving as the ground plane of the antenna.

[0031] The detailed structure of the Vivaldi antenna in this embodiment is as Figure 2As shown in the figure. Among them, 7 is a radiation slot with exponential gradient, the slot height is 280 mm, the end opening is 100 mm, and the slot width varies exponentially along the Z-axis direction, effectively improving the impedance matching of the antenna element in the wide frequency band. Structure 8 is a Γ-shaped balun with a defected ground plane. The vertical transmission line of the balun has a width of 3 mm and a height of 84 mm, and the horizontal part has a width of 0.8 mm and a length of 21 mm. Structure 11 is the side view of Structure 2 respectively. Structure 10 is a diamond-shaped notch with a radius of 42 mm and an angle of 90°, which is connected to the tapered slot line, and plays the role of improving impedance matching. Structure 12 is a fan-shaped feeder with a radius of 12 mm and an angle of 90°, and feeds the tapered radiation structure through coupling.

[0032] In this embodiment, the detailed structure of the feeding network layer is as Figure 3 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, which consists of two shunt grounded inductors and a series capacitor, and their values are 30 nH, 9 pF, and 56 nH from left to right in sequence. Structure 17 is a negative group delay circuit, which consists of two series resonant circuits and a series inductor. The two series resonant circuits have the same structure, which are 360 Ω, 100 nH, and 1 pF respectively, and the series inductor is 4.5 nH. Structure 18 is an unequal power divider, and the line widths of the second part are 0.6 mm and 2.3 mm respectively. Structure 19 is a metal through-hole, which serves as a grounding shorting post. Structures 20 and 21 serve as isolation resistors with values of 720 Ω and 80 Ω respectively.

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

[0034] In the embodiment, the reflection coefficient, the transmission coefficient, and the phase of the transmission coefficient of the negative group delay network varying with frequency are given, as Figure 5 shown. It can be seen that within 0.3 - 1 GHz, the reflection coefficient of this structure is less than -10 dB, the phase is close to -10 degrees, the group delay is small, which is beneficial to achieving a broadband stable phase difference, and at the same time the loss is less than 1.2 dB.

[0035] In the embodiment, the simulation results of the Vivaldi antenna are given, as Figure 6 shown. It can be seen that within 0.32 - 1.08 GHz, the reflection coefficient of this structure is less than -10 dB, and at the same time the gain variation in the frequency band is stable.

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

[0037] The simulation results after cascading the feeding network and the antenna are given in the embodiments, as Figure 8 shown. It can be seen that the reflection coefficient is less than -10 dB in the range of 0.32 - 1.2 GHz, the axial ratio is less than 3 dB in the range of 0.32 - 1.15 GHz, and the gain is greater than 3 dBic in the operating frequency range, having great application potential.

Claims

1. A compact ultra-wideband circularly polarized antenna based on a miniaturized phase shifter, the antenna comprising: Orthogonal Vivaldi antennas, a feeding network, and a bottom plate. The orthogonal Vivaldi antennas include two Vivaldi antennas with the same structure, which are orthogonally arranged. Each Vivaldi antenna includes a substrate, a metal patch, a Γ-shaped balun, and a fan-shaped feeding piece. The metal patch is arranged on one layer of the substrate, and the Γ-shaped balun and the fan-shaped feeding piece are arranged on the other side of the substrate. The metal patch includes a left part and a right part that are completely symmetric and isolated. Each part includes a main radiation structure and a parasitic radiation structure. The main radiation structures of the left part and the right part together form a "γ" shape, but the left and right sides of this "γ" shape are symmetric and isolated. The parasitic radiation structure also includes left and right parts, which are respectively arranged on both sides of the main radiation structure. Each part of the parasitic radiation structure is in the shape of a right-angled trapezoid, and the acute angle at the bottom of this right-angled trapezoid is connected to the waist of the corresponding part of the main radiation structure. The Γ-shaped balun is arranged on the right part of the main radiation structure. The bottom input end of the Γ-shaped balun is flush with the bottom of the main radiation structure, and the top output end of the Γ-shaped balun is flush with the side of the right part of the main radiation structure close to the gap. The top output end of the Γ-shaped balun is connected to the fan-shaped feeding piece, and the fan-shaped feeding piece is located on the left part of the main radiation structure. A defect slot is arranged at the corresponding position of the Γ-shaped 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 a dielectric layer, and the lower layer is a 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 antennas on the bottom plate is a "cross" structure. A metal coupling piece perpendicular to the floor is arranged at each position corresponding to the "cross" structure on the bottom plate, and this metal coupling piece is also perpendicular to the Vivaldi antenna it contacts.

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 serrated 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, Serrated structures are arranged on both sides of the part 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 according to 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. 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. 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. 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. 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 also 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. 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 end of the "L"-shaped metal patch is the input of the negative group delay network. 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 also 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 sequentially through a second capacitor, a fourth inductor, and a first grounding resistor. 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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