Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a non-coplanar asymmetric millimeter wave circularly polarized end fire antenna based on artificial surface plasmon polariton, which comprises: the dielectric substrate comprises an upper metal layer, a dielectric substrate and a lower metal layer; the dielectric substrate is arranged between the upper metal layer and the lower metal layer, the upper metal layer comprises a first microstrip line, a first conical transition structure and a first radiation structure, the first microstrip line, the first conical transition structure and the first radiation structure are sequentially connected, and an artificial surface plasmon polariton radiation structure is etched on the first radiation structure; the lower metal layer comprises a second microstrip line, a second conical transition structure and a second radiation structure, and the second microstrip line, the second transition structure and the second radiation structure are sequentially connected; the artificial surface plasmon polariton radiation structure and the lower radiation structure form a non-coplanar asymmetric structure, and end-fire circularly polarized waves are generated under the combined action.
Preferably, the first microstrip line and the second microstrip line are both rectangular, the lengths of the first microstrip line and the second microstrip line are equal, and the width of the second microstrip line is greater than that of the first microstrip line.
Preferably, the first transition structure is in a right trapezoid shape, and the second transition structure is in a trapezoid shape; the length of the upper bottom of the first transition structure is equal to the width of the first microstrip line, the length of the lower bottom of the second transition structure is equal to the width of the second microstrip line, the heights of the first transition structure and the second transition structure are equal, and the length of the lower bottom of the first transition structure is equal to the length of the upper bottom of the second transition structure.
Preferably, the first radiation structure and the second radiation structure are both right trapezoid, the length of the lower bottom of the first radiation structure is equal to that of the lower bottom of the first transition structure, the length of the lower bottom of the second radiation structure is equal to that of the upper bottom of the second transition structure, and the lengths of the height and the upper bottom of the first radiation structure and the second radiation structure are respectively equal.
Furthermore, the upper bottoms of the first radiation structure and the second radiation structure are positioned on the same straight line to form a horn-shaped opening.
Furthermore, the width of the horn-shaped opening is 0.8 mm-1 mm.
Preferably, the artificial surface plasmon radiation structure is a periodically distributed groove, and the depth of the groove tends to decrease.
Further, the distance between the lower bottom of the first radiation structure and the first groove of the artificial surface plasmon radiation structure is 7 mm-7.5 mm.
The beneficial effects of the invention are as follows: compared with the existing circular polarization antenna based on artificial surface plasmon polaritons with a three-dimensional complex structure, the circular polarization antenna has a simpler structure, is a single-layer dielectric plate structure, realizes end-fire circular polarization with a low profile, and also has simpler processing and lower cost; the invention is a single feed structure, the feed mode is simple, and the SMA connector can be directly connected; according to the invention, the horn-shaped different-surface asymmetric artificial surface plasmon polariton structure is introduced, so that the gain of the antenna is effectively increased.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The invention provides a non-coplanar asymmetric millimeter wave circularly polarized end fire antenna based on artificial surface plasmon polariton, as shown in figure 1, the antenna comprises: an upper metal layer 1, a dielectric substrate 2 and a lower metal layer 3; the dielectric substrate 2 is arranged between the upper metal layer 1 and the lower metal layer 3; the upper metal layer 1 comprises a first microstrip line 11, a first conical transition structure 12 and a first radiation structure 13, the first microstrip line 11, the first conical transition structure 12 and the first radiation structure 13 are sequentially connected, and an artificial surface plasmon radiation structure is etched on the first radiation structure 13; the lower metal layer 3 comprises a second microstrip line 31, a second conical transition structure 32 and a second radiation structure 33, and the second microstrip line 31, the second transition structure 32 and the second radiation structure 33 are connected in sequence; the artificial surface plasmon radiation structure and the lower radiation structure 33 form a non-coplanar asymmetric structure, and the structure can enable vertical polarized waves generated in the upper and lower radiation structures to act together with horizontal polarized waves propagated in the dielectric substrate to generate end-fire circularly polarized waves.
As shown in fig. 2, wherein the dark portions represent the top layer and the light portions represent the bottom layer. The antenna consists of three regions: area i is the microstrip transmission line used as the feed terminal, area II is the transition from the microstrip line to the radiating structure, and area iii is the radiating part of the antenna.
In some embodiments, the dielectric substrate 2 is rectangular, a Rogers RT5880 plate is used, the dielectric substrate has a length L =71mm to 71.5mm, a width W =15mm to 17mm, a thickness t =1.508mm or 1.762mm, a dielectric constant of 2.2, and a dielectric substrate loss angle of 0.0009. The thickness of copper deposited on the upper metal layer and the lower metal layer is 0.018mm or 0.035mm.
The first microstrip line 11 and the second microstrip line 31 are both rectangular, the first microstrip line is a microstrip feed end, and the second microstrip line is of an equivalent structure; the first microstrip line and the second microstrip line have the same length, and the second microstrip line has large widthThe width of the first microstrip line; preferably, the length of the first microstrip line and the length of the second microstrip line are L 1 =4.8 mm-5.2 mm, and the width of the second microstrip line is w g =14.5 mm-15 mm, and the width of the first microstrip line is w 1 =2mm~2.5mm。
The first transition structure 12 is a right trapezoid, the second transition structure 32 is a trapezoid (trapezoid, right trapezoid or isosceles trapezoid), and the length of the upper base of the first transition structure and the width w of the first microstrip line 1 Equal to the length of the lower bottom of the second transition structure and the width w of the second microstrip line g The heights of the first transition structure and the second transition structure are equal, and the length of the lower bottom of the first transition structure is equal to that of the upper bottom of the second transition structure; preferably, the height of the first transition structure and the second transition structure is L 2 =21 mm-21.5 mm, length w of lower bottom of first transition structure s And the length w of the upper bottom of the second transition structure g Are all 3.2mm; the transition structure is equivalent to an impedance transformer, and impedance matching from the rectangular microstrip structure to the radiation structure is realized.
The first radiation structure and the second radiation structure are both right-angled trapezoids, and an equivalent aperture is formed by converting the rectangular structures into the right-angled trapezoids, so that the end-fire gain is further improved; the length of the lower bottom of the first radiation structure is equal to that of the lower bottom of the first transition structure, the length of the lower bottom of the second radiation structure is equal to that of the upper bottom of the second transition structure, and the lengths of the upper bottoms and the height of the first radiation structure and the second radiation structure are respectively equal; preferably, the height of the first radiation structure and the height of the second radiation structure are L r =24mm~25mm。
The upper bottoms of the first radiation structure and the second radiation structure are positioned on the same straight line to form a horn-shaped opening; preferably, the width of the trumpet-shaped opening is w t =0.8 mm-1.2 mm; the gain of the antenna can be further improved by the horn-shaped opening structure.
The artificial surface plasmon radiation structure is grooves which are periodically distributed, the depth of the grooves is in a reduction trend, the groove depth of the head part of the specific artificial surface plasmon radiation structure is the same, and the groove depth of the tail part of the specific artificial surface plasmon radiation structure is gradually reduced; the grooves distributed periodically can generate artificial surface plasmons, effective transmission of electromagnetic waves is achieved through periodic grooving, and the electromagnetic waves are radiated through gradually reducing the depth of the grooves; as shown in fig. 3, the upper left corner of the figure shows details of the structure of the artificial surface plasmon polariton groove unit, preferably, the period p is 1.5mm, the groove width a is p/2, and the groove depth h =1 mm-2 mm on a dielectric substrate with the thickness of Rogers RT5880 1.508 mm; the dispersion characteristic of the artificial surface plasmon can be controlled by adjusting the geometric parameters p, a and h of the groove unit, so that the groove unit can transmit electromagnetic waves in a frequency band. It can be seen from the graph that the artificial surface plasmon has a slow wave characteristic, and the cutoff frequency of the artificial surface plasmon gradually decreases as h increases.
In a preferred embodiment, the second transition structure is an irregular trapezoid, the height of the first transition structure is located on the long perpendicular bisector of the second microstrip line, and the specific dimensions of the structure of the invention are as follows: the length of the dielectric substrate is L =71.2mm, the width is W =16mm, the thickness is t =1.508mm, the thickness of copper deposited on the upper metal layer and the lower metal layer is 0.018mm, and the lengths of the first microstrip line and the second microstrip line are L 1 =5mm, the width of the second microstrip line is w g =15mm, the width of the first microstrip line is w 1 =2.5mm, the height of the first transition structure and the second transition structure is L 2 =21.5mm, lower base length w of first transition structure s Length w of upper base of second transition structure g Are both 3.2mm, and the height of the first radiation structure and the second radiation structure is L r =24mm, width of trumpet-shaped opening is w t =1mm, groove period p is 1.5mm, groove width a is p/2, and groove depth h =1.5mm.
When the present invention is evaluated, as shown in fig. 4, it can be seen from fig. 4 that the range of the S11 parameter (input return loss) of the antenna less than-10 dB is 26.3 to 28.2GHz, so that the antenna designed by the present invention can cover the frequency band of 26.3 to 28.2GHz, indicating that the antenna has stable circular polarization in the operating frequency band.
As shown in fig. 5, it can be seen from fig. 5 that the highest radiation gain in the operating band of the antenna is 10.9dBic, and the radiation efficiency is greater than 97%.
The schematic diagrams of the xy-plane directional diagrams and the xz-plane directional diagrams of the antenna at 27GHz are respectively shown in fig. 6 and fig. 7, and it can be seen from the diagrams that the circular polarization mode of the antenna is left-handed circular polarization and the antenna has good end-fire performance.
The above-mentioned embodiments, which are further detailed for the purpose of illustrating the invention, technical solutions and advantages, should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made to the present invention within the spirit and principle of the present invention should be included in the protection scope of the present invention.