Disclosure of Invention
The invention provides a wide-bandwidth wide-angle scanning planar reflection array antenna, which solves the problems of narrow bandwidth and low phase compensation precision of the traditional planar reflection array antenna unit by utilizing a tight coupling structure and a multi-bit digital coding phase shifter, and realizes the design of the planar reflection array antenna with the characteristics of wide bandwidth, wide-angle scanning, low profile, light weight, low cost and the like.
The technical scheme for realizing the invention is as follows: the wide-bandwidth wide-angle scanning plane reflection array antenna comprises a reflection array surface, a feed source antenna and a multi-bit digital coding phase shifter, wherein the reflection array surface consists of a close-coupled antenna array and a metal floor, N first dielectric substrates are printed with M close-coupled antenna units, the N first dielectric substrates are vertically inserted into the metal floor etched with N gaps one by one, and M multiplied by N close-coupled antenna units form the close-coupled antenna array.
The tightly coupled antenna unit is formed by improving a Vivaldi structure, balanced current reaches two arms of a dipole through an arc-shaped opening, a first arm of the dipole is directly connected with the arc-shaped opening, a second arm of the dipole is connected at the tail end of the arc-shaped opening through a metal via hole, the first arm and the second arm of the dipole are printed on two sides of a dielectric substrate, and an overlapping structure is adopted.
The logarithmic period antenna is used as a feed source antenna and is placed in the phase center right above the tightly coupled antenna array of the reflecting array surface, electromagnetic waves radiated by the logarithmic period antenna are received by the tightly coupled antenna array of the reflecting array surface, the phases of the electromagnetic waves are compensated by the multi-bit digital coding phase shifter, and finally, the reflected electromagnetic waves radiate linear polarized waves through the tightly coupled antenna array.
The two layers of double-sided frequency selective surface matching layers are positioned above the dipole arms, the wide-angle scanning capability of the reflecting array is enhanced, each layer of frequency selective surface matching layer consists of double-sided and four metal patches, and the weight of the antenna array can be remarkably reduced by adopting a frequency selective surface matching layer structure.
Compared with the prior art, the invention has the remarkable advantages that: compared with the traditional planar reflective array, the invention is greatly improved, and the phase is compensated by utilizing the tight coupling unit with a sub-wavelength structure and the multi-bit digital coding phase shifter, so that the continuous distribution of electromagnetic wave phases of the reflective array surface is realized, and the working bandwidth (6-18 GHz) and the beam airspace coverage (E surface is more than or equal to 60 degrees and H surface is more than or equal to 45 degrees) of the planar reflective array antenna are widened. The planar reflective array has the characteristics of wide working frequency band, high gain (high radiation efficiency), low profile (the profile height is smaller than 0.2 low-frequency working wavelength), light weight (a frequency selective surface matching layer is adopted, a medium block matching layer with large weight is avoided), low cost and the like, and has wide application prospects in the fields of reconnaissance, detection and the like.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by one of ordinary skill in the art without creative efforts, are within the scope of the present invention based on the embodiments of the present invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; the "connection" may be mechanical or electrical. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to base that the technical solutions can be implemented by those skilled in the art, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered to be absent, and not included in the scope of protection claimed in the present invention.
The following describes the specific embodiments, technical difficulties and inventions of the present invention in further detail in connection with the present design examples.
Referring to fig. 1-4, the wideband wide-angle scanning plane reflection array antenna of the invention comprises a reflection array surface, a feed source antenna and a multi-bit digital coding phase shifter, wherein the reflection array surface is composed of a tightly coupled antenna array and a metal floor 1, N pieces of first dielectric substrates 3 with the model of F4B have relative dielectric constants of 4 and dielectric loss of 0.003, M tightly coupled antenna units are printed on each piece of first dielectric substrates, N pieces of first dielectric substrates 3 are vertically inserted into the metal floor 1 with N slots etched one by one, and M multiplied by N tightly coupled antenna units form the tightly coupled antenna array.
The tightly coupled antenna unit is formed by improving a Vivaldi antenna structure, a plurality of sections of microstrip lines 2 to a fan-shaped open-circuit branch 5 are printed on the front surface of a first dielectric substrate 3, an impedance transformation function is achieved, a circular short-circuit cavity 11 and a pair of arc-shaped openings 9 are printed on the back surface of the first dielectric substrate 3, a broadband balun structure from the microstrip lines to the slot lines is formed, a dipole comprises a first arm 4 and a second arm 12, the first arm 4 of the dipole is connected to the tail ends of the pair of arc-shaped openings 9, the second arm 12 of the dipole is printed on the back surface of the first dielectric substrate 3, and a part of the second arm 12 of the dipole is overlapped with the first arm 4 through a metal post 6 penetrating through the first dielectric substrate 3 and the tail ends of the arc-shaped openings 9 to provide a coupling capacitance to offset inductance from a floor, and the working bandwidth of the tightly coupled antenna unit is widened.
The periodic structure frequency selection surface has wide application in wave absorption, polarization conversion, filtering and other aspects, and the periodic structure frequency selection surface is applied to the design of a phased array antenna, so that the impedance matching of the line width and angle scanning of the phased array antenna can be improved, the beam airspace scanning range of the phased array antenna is widened, and compared with a traditional medium block matching layer, the weight of the antenna array surface can be obviously reduced by the periodic structure frequency selection surface. In phased array antenna design, a single-layer periodic structure frequency selective surface is generally adopted, but the wide-angle scanning impedance matching effect is generally adopted, in the invention, two layers of periodic structure frequency selective surfaces are adopted, a first layer 7 and a second layer 8 are positioned above a dipole, the height and the width of periodic patches in the first layer 7 and the distance between the patches are larger than the size of corresponding structures in the second layer 8, and the contribution of the first layer 7 to the improvement of the wide-angle scanning impedance matching is larger. The two layers of periodic structure frequency selective surfaces are printed on the front and back sides of the first dielectric substrate 3, the positions and structures of the first layer 7 and the second layer 8 on the front and back sides are identical, and the wide-angle scanning impedance matching is improved, so that the radiation efficiency of the planar reflection array antenna is improved.
The feed antenna adopts a log periodic antenna, and the log periodic antenna has non-frequency-variant characteristics and has extremely wide working bandwidth. The log periodic antenna used in the present invention comprises 25 pairs of dipoles, the first and second arms of the dipoles are respectively printed on two sides of the second dielectric substrate 13, the model of the second dielectric substrate 13 is Rogers5880, the relative dielectric constant is 2.2, and the dielectric loss is 0.0009. As can be seen from FIG. 5, at 6-18GHz, feed antenna S11 <17dB, exhibiting good radiation performance.
The multi-bit digital coding phase shifters are connected to M x N tightly coupled antenna elements via coaxial lines 10, respectively, for directing a target beam according to a reflective arrayCalculating the required reflection phase phi (xi ,yi )，Wherein k is0 x free space wavenumber, (x)i ,yi ) R is the position of the ith row and jth column close-coupled antenna elementi For the distance theta between the ith row and jth column close-coupled antenna unit and the feed source phase centerb Is the included angle between the main beam and the normal direction of the reflective array surface, < >>Is azimuth angle, according to the calculated reflection phase phi (xi ,yi ) The phase of the multi-bit digital coding phase shifter is adjusted so that the phases of the reflective array surface tightly coupled antenna units are continuously distributed. When the main beam points to different angles, the phase distribution of the reflective array surface close-coupled antenna units is shown in fig. 4.
It can be seen from fig. 6 and fig. 7 that the antenna array has the characteristics of wide band, wide angle scanning and high gain when scanning different frequency points.
The main innovation point of the invention is that:
the tight coupling antenna technology is adopted, so that the coupling among the reflecting array antenna units is enhanced, and the working bandwidth of the reflecting array is increased; the sub-wavelength structure of the tightly coupled antenna unit is beneficial to adjusting the phase of the tightly coupled unit of the reflecting array surface.
The two periodic structure frequency selective surface matching layers are adopted, so that the antenna width angle scanning impedance matching of the planar reflection array can be better improved, and the radiation efficiency is improved.
Compared with the traditional true time delay line, the multi-bit digital coding phase shifter improves the accuracy of phase adjustment of the reflecting array surface tightly coupled antenna unit.
The foregoing is only a specific embodiment of the invention. It should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.