CN112688057B - Broadband circularly polarized microstrip antenna based on crossed dipole - Google Patents
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Abstract
The invention discloses a broadband circularly polarized microstrip antenna based on a crossed dipole, which comprises two layers of dielectric plates, four radiation units, a broadband equipower distribution 90-degree phase shift network (5) and a metal column balanced feed structure, wherein the two layers of dielectric plates are arranged on the two sides of the broadband circular polarized microstrip antenna; the two-layer dielectric plate has a certain distance and is arranged in parallel from top to bottom, a first radiation unit (1) and a second radiation unit (2) are printed on the upper surface of an upper-layer dielectric plate (10) respectively, a third radiation unit (3) and a fourth radiation unit (4) are printed on the lower surface of the upper-layer dielectric plate (10) respectively, the first radiation unit (1) and the third radiation unit (3) are arranged oppositely, the second radiation unit (2) and the fourth radiation unit (4) are arranged oppositely, the four radiation units sequentially differ by 90 degrees in feeding to realize a circular polarization working mode, and a broadband equal-power-division 90-degree phase-shift network (5) is printed on the lower surface of a lower-layer dielectric plate (11).
Description
Technical Field
The invention relates to the technical field of microstrip antennas, in particular to a broadband circularly polarized microstrip antenna based on a crossed dipole.
Background
Due to its unique characteristics, the circularly polarized antenna is widely used in wireless communication systems such as Global Navigation Satellite System (GNSS), mobile satellite communication, radio Frequency Identification (RFID), wireless Local Area Network (WLAN), direct television broadcast service (DBS), and Worldwide Interoperability for Microwave Access (WIMAX).
A circularly polarized antenna is an antenna that radiates or receives electromagnetic waves in a circularly polarized form. The practical significance of circularly polarized antennas lies mainly in: 1) Any polarized wave can be decomposed into two circularly polarized waves with opposite rotation directions. Therefore, the circularly polarized antenna can receive incoming waves in any direction, and the electromagnetic waves radiated by the circularly polarized antenna can be received by the antenna with any polarization, so that the circularly polarized antenna is widely used in electronic detection and interference; 2) The rotation direction orthogonality of the circularly polarized antenna is widely utilized in the applications of polarization diversity work, electronic countermeasure and the like of communication radar; 3) The circular polarization wave is incident to a symmetrical target, and the back rotation direction of the circular polarization wave is inverted, so that the circular polarization antenna is applied to mobile communication, GPS and the like, and can inhibit rain and fog interference and resist multipath reflection.
With the development of Remote Sensing technology, SAR has been extended from single polarization to dual polarization and even full polarization, but because the disadvantage of full polarization SAR data is that swath width is too small, reference [1] ("Rizki Akbar, p., s.s.j.tetuko, and h.kuze." a novel polarized synthetic aperture radar (CP-SAR) "system on board a space board plan. CP SAR transmits circular polarization and receives two orthogonal linear polarizations. Microstrip array antennas are a good choice for SAR antennas due to their high compatibility, easy fabrication, light weight, and the like.
The existing implementation methods of the circularly polarized microstrip array antenna mainly include two forms: 1) Circularly Polarized radiating elements and broadband feed networks, reference [2] (Gan, zheng, et al, "Compact wireless broadband Polarized micro Antenna Array for 45GHz Application." IEEE Transactions on Antennas and Propagation 66.11 (2018): 6388-6392.) proposed this method, which requires the circular Polarized elements and feed networks to be designed separately, the element structure and feed network being relatively complex but the bandwidth ratio being relatively wide; 2) The linear polarization array unit and a specific feed network are used for realizing the conversion from linear polarization to circular polarization. Reference [3] (Zou, yanlin, et al, "A high-gain polarized micro antenna array antenna with a linearly fed network." International Journal of RF and Microwave Computer-air Engineering 8 (2019) ") suggests that these implementations are complicated in feed network, high in antenna profile, and narrow in implemented axial ratio bandwidth.
The method mainly comprises a single-feed method, a multi-feed method and a multivariate method, wherein the single-feed method selects a proper position single-point feed to excite an orthogonal mode, and introduces perturbation through slotting on a radiation patch and other modes to realize degenerate separation to form a pair of orthogonal modes with equal amplitude and phase difference of 90 degrees to realize circular polarization; the multi-feed method adopts probe multi-point feed with 90-degree phase difference, so that a plurality of pairs of degenerate modes of orthogonal polarization are simultaneously excited to realize circular polarization, two-point feed and four-point feed are common, four-point feed has many advantages in the aspects of bandwidth expansion and cross polarization inhibition, but the feed network is more complex; the multi-element method adopts four linearly polarized antennas which are sequentially rotated by 90 degrees to form a four-element array, and the method needs to reasonably arrange the position of each unit antenna to inhibit cross polarization and realize circular polarization, and simultaneously increases the size of the antenna. The single-feed cross dipole uses the inner core and outer skin feed of the coaxial line, and adds a 90 ° phase shift line to realize sequential 90 ° rotation feed, which is equivalent to the performance of four-point feed realized by using single-point feed, but in the single-point feed scheme, because the 90 ° phase shift line corresponds to a quarter of the central frequency wavelength, further broadening of the bandwidth is limited.
At present, a method for designing an array element of a broadband circularly polarized microstrip array antenna by adopting a multi-feed point method is less, and the technical advantages of multi-feed excitation need to be further fully utilized so as to solve the problem of narrow axial ratio bandwidth in the design of a high-frequency band broadband circularly polarized microstrip array antenna.
Disclosure of Invention
The invention aims to overcome the defect of narrow bandwidth of the conventional circularly polarized microstrip array antenna and provides a broadband circularly polarized microstrip antenna based on a crossed dipole.
In order to achieve the purpose, the invention provides a broadband circularly polarized microstrip antenna based on a crossed dipole, which is characterized by comprising two layers of dielectric plates, four radiation units, a broadband equipower 90-degree phase shift network and a metal column balanced feed structure; wherein the content of the first and second substances,
the two dielectric plates are arranged in parallel from top to bottom at a certain distance, a first radiation unit and a second radiation unit are respectively printed on the upper surface of the upper dielectric plate, a third radiation unit and a fourth radiation unit are respectively printed on the lower surface of the upper dielectric plate, wherein the first radiation unit and the third radiation unit are oppositely arranged, the second radiation unit and the fourth radiation unit are oppositely arranged, the four radiation units are sequentially fed by 90 degrees in difference, so that a circular polarization working mode is realized, and a broadband equipower 90-degree phase shift network is printed on the lower surface of the lower dielectric plate;
the metal column balanced feed structure is arranged between an upper dielectric slab and a lower dielectric slab and comprises a first coaxial line, a second coaxial line, a first metal column and a second metal column which are symmetrically arranged, the first coaxial line is used for feeding a first radiating element and a third radiating element, the second coaxial line is used for feeding a second radiating element and a fourth radiating element, the first metal column is used for matching the first coaxial line to realize balanced feed, the second metal column is used for matching the second coaxial line to realize balanced feed, the first coaxial line and the second coaxial line have the same amplitude, and the phase difference is 90 degrees.
As an improvement of the above antenna, the distance between the two dielectric plates is a quarter wavelength of the center frequency of the broadband circularly polarized microstrip antenna.
As an improvement of the above antenna, the first radiating element, the second radiating element, the third radiating element and the fourth radiating element have the same shape, the shape is a sector, the arc part of the sector is formed by connecting two arcs with equal length, and the distance from the connecting point of the two arcs to the bottom edge of the sector is a quarter wavelength of the center frequency.
As an improvement of the antenna, the broadband equal power division 90-degree phase shift network (5) comprises a Wilkinson power divider and a Schonfmann broadband 90-degree phase shifter, and two output ends of the Wilkinson power divider are respectively connected with two input ends of the Schonfmann broadband 90-degree phase shifter to form cascade connection.
As an improvement of the antenna, the inner core at the upper end of the first coaxial line penetrates through the upper-layer dielectric plate to be connected with the first radiating element, the outer conductor at the upper end of the first coaxial line is connected with the third radiating element, and the inner core at the lower end of the first coaxial line penetrates through the lower-layer dielectric plate to be connected with one input end of the snowman broadband 90-degree phase shifter;
an inner core at the upper end of the second coaxial line penetrates through the upper-layer dielectric plate to be connected with the second radiation unit, an outer conductor at the upper end of the second coaxial line is connected with the fourth radiation unit, and an inner core at the lower end of the second coaxial line penetrates through the lower-layer dielectric plate to be connected with the other input end of the Schumann broadband 90-degree phase shifter.
Compared with the prior art, the invention has the advantages that:
1. the broadband circularly polarized microstrip antenna based on the cross dipole combines the advantages of a multi-feed-point feed technology and a sequential rotation feed technology, not only realizes the purpose of widening the axial ratio bandwidth, but also simplifies the design of a feed network and reduces the volume of the antenna;
2. the broadband circularly polarized microstrip antenna based on the crossed dipole is simple in structure and easy to implement, and has certain significance for research on a method for widening a circularly polarized microstrip array antenna.
Drawings
FIG. 1 is a top view of a cross-dipole based broadband circularly polarized microstrip antenna of the present invention;
FIG. 2 is a perspective view of a cross-dipole based broadband circularly polarized microstrip antenna of the present invention;
FIG. 3 is a front view of a cross-dipole based broadband circularly polarized microstrip antenna of the present invention;
FIG. 4 is a schematic diagram of a metal post balanced feed structure of the present invention;
FIG. 5 is an equivalent circuit diagram of the Wilkinson power divider of the present invention;
FIG. 6 is an equivalent circuit diagram of a Schonfman 90 ° wide band phase shifter of the present invention;
FIG. 7 is a schematic diagram of a 90 ° broadband phase shifter configuration;
FIG. 8 is a graph of the return loss versus frequency characteristic of an antenna of the present invention;
FIG. 9 is a graph of the antenna axial ratio versus frequency characteristic of the present invention;
fig. 10 is an overall pattern of the inventive antenna at a center frequency;
FIG. 11 is a schematic diagram of a quaternary array antenna feed network structure;
FIG. 12 is a graph of return loss versus frequency for a quad-array antenna;
FIG. 13 is a graph of the axial ratio versus frequency characteristics of a quaternary array antenna;
fig. 14 is an overall pattern of a quaternary array antenna at a center frequency.
Reference numerals
1. First radiation unit 2 and second radiation unit
3. Third radiation unit 4 and fourth radiation unit
5. Broadband equipower 90-degree phase shift network 6 and first coaxial line
7. Second coaxial line 8, first metal column
9. Second metal pillar 10, upper dielectric plate
11. Lower dielectric plate I1, coaxial line inner conductor current
I2, symmetrical antenna right arm current I3 and metal column internal current
I4, coaxial line outer conductor inner surface current I5, symmetrical antenna left arm current
I6, outer surface current of coaxial line outer conductor
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1 and fig. 2, the present invention provides a broadband circularly polarized microstrip antenna based on crossed dipoles. Fig. 1 is a top view of the antenna, and fig. 2 is a perspective view of the antenna.
On the basis of a cross dipole antenna, a broadband circularly polarized microstrip array antenna unit is provided. The broadband circularly polarized microstrip array antenna unit adopts a method that the difference of two coaxial lines is 90 degrees and the constant-amplitude feed is adopted to realize the broadening of the axial ratio bandwidth; four radiation units are respectively printed on the front and the back of an upper-layer dielectric slab, as shown in fig. 1, a third radiation unit 3 and a fourth radiation unit 4 are printed on the back, a first radiation unit 1 and a second radiation unit 2 are printed on the front, a sheath and an inner core of a first coaxial line 6 respectively feed the first radiation unit 1 and the third radiation unit 3, a sheath and an inner core of a second coaxial line 7 respectively feed the second radiation unit 2 and the fourth radiation unit 4, in order to avoid the crossing of the front feeders, a feeder is bent, the upper layer and the lower layer are connected through a metal through hole, the phase difference between the coaxial lines is 90 degrees, and the inner core and the sheath of the coaxial lines have a phase difference of 180 degrees, so that the four radiation units sequentially feed with a phase difference of 90 degrees to realize a circular polarization working mode.
The design of the scheme comprises three parts: 1) The design of a broadband circular polarization crossed dipole antenna comprises four radiation units which are respectively printed on the front and the back of a dielectric plate and are respectively fed by a double-coaxial-line inner core and an outer skin which have 90-degree difference and have the same amplitude; 2) The design of the balanced feed structure, the coaxial line is the unbalanced feed structure, therefore will cause the inner core of the coaxial line and scarfskin to the radiation paster to feed the amplitude the same, therefore load the metal column structure in the symmetrical position of the coaxial line feed, connect the front radiation paster and metal layer of the lower floor, regulate the axial ratio performance of the antenna by regulating the size of the metal column; 3) The design of the broadband 90-degree phase shift equal power division feed network is characterized in that the feed network is positioned below a grounding plate, and the broadband characteristic of the feed network is realized by adopting a Wilkinson power divider cascaded with a Scheffman broadband 90-degree phase shifter.
The broadband circularly polarized microstrip antenna comprises two layers of dielectric plates, four radiation units, a broadband equipower 90-degree phase shift network 5 and a metal column balance feed structure; wherein, the first and the second end of the pipe are connected with each other,
the two dielectric slabs are arranged in parallel up and down at a certain distance, a first radiation unit 1 and a second radiation unit 2 are respectively printed on the upper surface of the upper dielectric slab 10, a third radiation unit 3 and a fourth radiation unit 4 are respectively printed on the lower surface of the upper dielectric slab 10, wherein the first radiation unit 1 is opposite to the third radiation unit 3, the second radiation unit 2 is opposite to the fourth radiation unit 4, the four radiation units sequentially differ by 90 degrees in feeding to realize a circular polarization working mode, and a broadband equal-power-division 90-degree phase-shift network 5 is printed on the lower surface of the lower dielectric slab 11;
the metal column balanced feed structure is arranged between an upper dielectric slab and a lower dielectric slab and comprises a first coaxial line 6, a second coaxial line 7, a first metal column 8 and a second metal column 9 which are symmetrically arranged, wherein the first coaxial line 6 is used for feeding the first radiating element 1 and the third radiating element 3, the second coaxial line 7 is used for feeding the second radiating element 2 and the fourth radiating element 4, the first metal column 8 is used for matching the first coaxial line 6 to realize balanced feeding, the second metal column 9 is used for matching the second coaxial line 7 to realize balanced feeding, the first coaxial line 6 and the second coaxial line 7 have the same amplitude, and the phase difference is 90 degrees.
The radiation cell geometry is shown in figure 1. The radiation unit can be seen as a closed figure formed by a trapezoid and two arc sections, wherein the arc sections are formed by a closed area formed by an end point A and a middle point B at the lower bottom of the trapezoid and a point C which is one fourth of the lower bottom of the trapezoid and is away from the bottom side by a distance P, namely three points ABC in figure 1. Four radiating elements, namely radiating patches, form a shape of 'clover', and the length L of the radiating patches is about a quarter wavelength. The arc structure at the end is used for reducing the size of the reflected current so as to reduce the influence of the reflected current on the input impedance of the antenna. The distance between the radiating elements is d, and the size of the distance J between the radiating elements influences the coupling effect between the antennas, so that the axial ratio performance of the antennas in a high frequency band is influenced.
The array element antenna adopts double coaxial line feed, the position of the coaxial line feed is f away from the edge of the radiation patch, the phase difference between the two coaxial lines is 90 degrees, the amplitude is the same, the sheath of the coaxial line feeds the back radiation unit, the inner core is connected with the front radiation unit, the first coaxial line 6 feeds the first radiation unit 1 and the third radiation unit 3, the second coaxial line 7 feeds the second radiation unit 2 and the fourth radiation unit 4, in order to avoid the crossing of the feed, the bending treatment is carried out on one of the feed lines, the upper feed line and the lower feed line are connected through a metal through hole, as shown in figure 1, the width of the feed line is 0.2 mm, and the diameter of the metal through hole is 0.2 mm. The coaxial line is an unbalanced feed structure, and the current flows as shown in fig. 4. The antenna comprises a coaxial line inner conductor current I1, a symmetrical antenna right arm current I2, a metal column inner current I3, a coaxial line outer conductor inner surface current I4, a symmetrical antenna left arm current I5 and a coaxial line outer conductor outer surface current I6. If there is no balanced feed structure, the inner core of the coaxial line is connected with the right arm, so the current I1 on the inner core of the coaxial line is equal to the current I2 on the right arm of the symmetric antenna. Because I2 is greater than I5, this can cause the current amplitude on two arms of symmetrical antenna to be different, for solving this problem, load the metal column in the position of feed point symmetry, the diameter of metal column is D, connects the ground plate of front radiation paster and lower floor, therefore, coaxial line inner conductor's electric current I1 has divided into two parts: one part is the current I2 flowing to the radiation arm, the other part is the current I3 flowing to the metal post, and the size of the metal post is reasonably selected, so that the coaxial line can ensure the balanced feeding of the dipole antenna.
The broadband 90-degree phase shift equal power division feed network is positioned below the grounding plate, and the broadband characteristic of the feed network is realized by adopting a mode that a Wilkinson power divider is cascaded with a Scheffman broadband 90-degree phase shifter. An equivalent schematic diagram of the wilkinson power divider is shown in fig. 5, the power divider can be regarded as a three-port network, each port is matched, a signal enters from the port 1 and is output from the ports 2 and 3, and an isolation resistor is loaded between the ports 2 and 3. The load impedance of all ports is Z0 when
At this time, the power input from port 1 is output from ports 2, 3, etc.
The equivalent circuit diagram of the snowman wideband phase shifter is shown in fig. 6, the phase shifter is provided with two branches, the upper branch consists of two pairs of microstrip branch lines with the electrical length of lambda/8 and microstrip transmission main lines with the electrical length of lambda/2, which are respectively short-circuited and open-circuited, and the lower branch consists of a microstrip transmission line with the electrical length of 3 lambda/4. Four input/output ports all have impedance Z 0 . Resistance Z m And Z s And Z 0 Satisfies the following relationship:
Z m ＝1.24Z 0
Z s ＝2.51Z 0
two input ends of the Schumann phase shifter are connected with two output ends of the Wilkinson power divider, and therefore the broadband 90-degree equal-power-division phase-shifting network is formed. Thus, the design of the array element of the broadband circularly polarized microstrip array antenna is completed.
The microstrip circular polarization array antenna unit can still maintain the performance of a broadband after array formation, in order to reduce the design of a post-array feed network, an antenna array can adopt a T-shaped power division network cascade mode to carry out constant-amplitude in-phase feed on array elements, the T-shaped power division network is simple in structural design, and in the array antenna, whether two output ports of the T-shaped power divider strictly have constant-amplitude in-phase influence on the axial ratio of the antenna is not large, so that the T-shaped power divider can meet the requirement.
In order to better understand the technical solution of the present invention, the following further describes the present invention with reference to the attached drawings.
The broadband circularly polarized microstrip array antenna unit provided by the invention can be used for various common microwave frequency bands without loss of generality, and only takes a Ku wave band as an example, the antenna consists of three layers, two dielectric plates and an intermediate air layer, wherein the layers are in parallel relation, as shown in figure 3. The upper dielectric material of the antenna adopts an RO4003 laminated board with the thickness of 0.203 mm and the relative dielectric constant of 3.55, the lower dielectric layer adopts an RO5880 laminated board with the thickness of 0.254 mm and the relative dielectric constant of 2.22, and the height of the middle air layer is 5.7 mm and is about a quarter wavelength of the central frequency. The radiation unit can be regarded as a closed figure formed by enclosing of a trapezoid and two arc sections, and the size of the trapezoid is optimized and selected through HFSS as follows: the upper bottom is 0.69 mm, the lower bottom is 4.7 mm, the height is 3 mm, the circular arc section is composed of an end point and a middle point of the trapezoid lower bottom and a closed area composed of a point which is one fourth of the trapezoid lower bottom and is away from the bottom edge by P, as shown in figure 1, the P is 0.7 mm after the structure diagram of the radiation patch is optimized, and the smoothness degree of the tail part of the radiation patch can be changed by adjusting the size of P, so that the input impedance of the antenna is improved, and the edge reflection current is reduced. The radiation patches are respectively printed on the front side and the back side of the upper dielectric slab, the front side and the back side are respectively provided with two radiation patches, the radiation patches are sequentially rotated by 90 degrees by taking a Z axis as an axis to form clover-shaped arrangement, and the distance J between the radiation patches is 1.02 mm.
The feed structure of the antenna is shown in fig. 1, and the coaxial line used has a characteristic impedance of 50 ohms, an inner conductor diameter of 0.1 mm, an outer conductor diameter of 0.51 mm, a dielectric layer made of PTFE material and having a diameter of 0.38 mm. The coaxial line is located at the position of 0.4 mm of the edge of the radiating patch for feeding, the coaxial line is symmetrical left and right, the impedance matching of the antenna can be adjusted by adjusting the feeding position of the coaxial line, the two coaxial line skins are respectively connected with the two adjacent radiating patches at the lower layer for feeding, the inner core penetrates through the dielectric layer to be connected with the two adjacent radiating patches at the upper layer for feeding, the coaxial line 1 feeds the radiating patches 1 and 3, the coaxial line 2 feeds the radiating patches 2 and 4, in order to avoid the crossing between the feeder lines at the upper layer, one feeder line is bent, the upper feeder line and the lower feeder line are connected through the metal through hole, the diameter of the through hole is 0.2 mm, the metal column is loaded at the symmetrical position of the coaxial line feeding, the diameter of the metal column is 0.4 mm, the radiating patches at the symmetrical position at the upper layer and the ground plate at the lower layer are connected, and the metal column can be used for adjusting the current amplitude on the radiating arm and can also play a role of supporting the dielectric layer at the upper layer.
The metal reflecting plate is placed at the position which is about one-fourth of the wavelength of the central frequency and is below the upper dielectric layer, so that the antenna radiates in a single direction, meanwhile, the reflected wave can be superposed at the radiation patch to play a role of increasing the gain due to the distance of the quarter wavelength, and the height h of the middle air layer is 5.7 mm through optimization in the HFSS.
The broadband 90-degree moving network is positioned below the lower metal plate and printed on the lower surface of the lower dielectric layer, and the upper surface is a metal plate serving as a grounding plate. The lower metal plate adopts RO5880 with the thickness of 0.254 mm and the relative dielectric constant of 2.22, the feed network adopts a mode that a Wilkinson power divider is cascaded with a Scheffman broadband 90-degree phase shifter to realize broadband characteristics, and equivalent circuit diagrams of the Wilkinson power divider and the Scheffman phase shift network are shown in figures 5 and 6. The phase shift network is shown in fig. 7 in an HFSS modeling structure, a feed network P1 is an input end, P6 and P7 are output ends, the phase of a P7 port lags behind the phase of a P6 port by 90 °, and impedances of the three ports are all 50 ohms, and because of the limitation of space size, part of microstrip lines in a schematic diagram are bent. And finishing the design of the antenna array element.
FIG. 8 is a graph showing the return loss versus frequency characteristic of the circularly polarized antenna of the present invention, showing that it has good S parameter and standing wave ratio at 10-22.77GHz, and FIG. 9 is a graph showing the axial ratio versus frequency characteristic of the circularly polarized antenna of the present invention, wherein the frequency band with the axial ratio less than 3dB is 10-21.69GHz. As shown in fig. 10, the overall pattern of the broadband circularly polarized microstrip antenna at the center frequency was calculated using HFSS full-wave analysis software. The circular polarization bandwidth of the antenna is comprehensively considered by the impedance bandwidth and the axial ratio bandwidth of the antenna, so that the antenna realizes 63% of relative circular polarization bandwidth. The maximum gain of the antenna in the frequency band is 13.66dB.
In order to illustrate the broadband effect of the array unit array, a 4-element array is designed below. The 4-element array is arranged at equal intervals of 2 x 2, namely, the distances between adjacent antenna units are the same. The size of the spacing can affect the overall gain of the array, the height of the directional diagram side lobe and other parameters, and when the spacing is optimized by HFSS to be 15 mm, the optimal solution is obtained. In order to reduce the design of an array feedback network, an antenna array usually adopts a two-stage T-shaped power division network cascade connection mode to carry out constant-amplitude in-phase feeding on four array elements, the T-shaped power division network is simple in structural design, and in the antenna, whether two output ports of a T-shaped power divider are strictly constant-amplitude in phase or not does not have large influence on the axial ratio of the antenna, so that the T-shaped power divider can meet the requirement. Due to the limitation of the space structure, bending processing is performed on part of the microstrip line, and the feed network of the antenna is shown in fig. 11.
FIG. 12 is a graph showing the return loss versus frequency characteristic of the circularly polarized array antenna of the present invention, which shows that it has good S parameter and standing wave ratio at 11.29-22GHz, and FIG. 13 is a graph showing the axial ratio versus frequency characteristic of the circularly polarized array antenna of the present invention, wherein the frequency band with the axial ratio less than 3dB is 10-21.69GHz. The circularly polarized bandwidth of the antenna is to be considered in combination with the impedance bandwidth and the axial ratio bandwidth of the antenna, because the antenna realizes a relative circularly polarized bandwidth of 63%. The maximum gain of the antenna in the frequency band is 13.66dB.
As shown in fig. 14, the overall pattern of the broadband circularly polarized microstrip array antenna at the center frequency was calculated using HFSS full-wave analysis software.
Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (3)
1. A broadband circularly polarized microstrip antenna based on a crossed dipole is characterized by comprising two layers of dielectric plates, four radiation units, a broadband equipower 90-degree phase shift network (5) and a metal column balanced feed structure; wherein the content of the first and second substances,
the two layers of dielectric plates are arranged in parallel at a certain distance from top to bottom, a first radiation unit (1) and a second radiation unit (2) are respectively printed on the upper surface of an upper layer of dielectric plate (10), a third radiation unit (3) and a fourth radiation unit (4) are respectively printed on the lower surface of the upper layer of dielectric plate (10), wherein the first radiation unit (1) and the third radiation unit (3) are oppositely arranged, the second radiation unit (2) and the fourth radiation unit (4) are oppositely arranged, the four radiation units sequentially feed by 90 degrees to realize a circular polarization working mode, and a broadband equal-power-division 90-degree phase-shift network (5) is printed on the lower surface of a lower layer of dielectric plate (11);
the metal column balanced feed structure is arranged between an upper dielectric slab and a lower dielectric slab and comprises a first coaxial line (6), a second coaxial line (7), a first metal column (8) and a second metal column (9), wherein the first coaxial line (6) is symmetrically arranged and used for feeding a first radiating element (1) and a third radiating element (3), the second coaxial line (7) is used for feeding a second radiating element (2) and a fourth radiating element (4), the first metal column (8) is used for matching with the first coaxial line (6) to realize balanced feed, the second metal column (9) is used for matching with the second coaxial line (7) to realize balanced feed, the first coaxial line (6) and the second coaxial line (7) have the same amplitude, and the phase difference is 90 degrees;
the distance between the two dielectric plates is one quarter wavelength of the central frequency of the broadband circularly polarized microstrip antenna;
the first radiation unit (1), the second radiation unit (2), the third radiation unit (3) and the fourth radiation unit (4) are identical in shape and are a sector, the arc part of the sector is formed by connecting two arcs with equal length, and the distance from the connecting point of the two arcs to the bottom edge of the sector is one quarter wavelength of the central frequency.
2. The cross-dipole based broadband circularly polarized microstrip antenna according to claim 1, wherein the broadband equipower 90 ° phase shift network (5) comprises a wilkinson power divider and a snowman broadband 90 ° phase shifter, and two output ends of the wilkinson power divider are respectively connected with two input ends of the snowman broadband 90 ° phase shifter to form a cascade.
3. The cross-dipole based broadband circularly polarized microstrip antenna according to claim 1, wherein the inner core at the upper end of the first coaxial line (6) passes through the upper dielectric plate to connect the first radiating element (1), the outer conductor at the upper end connects the third radiating element (3), and the inner core at the lower end passes through the lower dielectric plate to connect to one output end of the snowman broadband 90 ° phase shifter;
the inner core at the upper end of the second coaxial line (7) penetrates through the upper-layer dielectric slab to be connected with the second radiating unit (2), the outer conductor at the upper end of the second coaxial line is connected with the fourth radiating unit (4), and the inner core at the lower end of the second coaxial line penetrates through the lower-layer dielectric slab to be connected with the other output end of the Schumann broadband 90-degree phase shifter.
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| CN113745834A (en) * | 2021-09-07 | 2021-12-03 | 重庆大学 | Parasitic resonance decoupling structure of broadband circularly polarized compact antenna array |
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| CN112688057A (en) | 2021-04-20 |
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