Patent Grant
11777211
This patent application claims the benefit and priority of Chinese Patent Application No. 202011261301.1 filed on Nov. 12, 2020, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.
The present disclosure relates to a technical field of antennas, and specifically, to an impedance matching method for a low-profile ultra-wideband array antenna.
In recent years, with developments of ultra-wideband phased array radars and wireless communications systems, phased array antennas with a broadband, a wide-angle scan, a low profile, a low cross-polarization, and a high gain have becoming a research hot spot. A traditional design method for an ultra-wideband array antenna is to design antenna elements with wideband characteristics, and then combine them to an array. However, due to a mutual coupling effect between array elements, the wideband characteristics deteriorate much. To solve a problem existing in the ultra-wideband array antenna design, a brand new ultra-wideband antenna design concept, called a tightly coupled array, is proposed. The tightly coupled array may offset an influence from an inductance between the antenna and a floor with the mutual coupling between the array elements, instead of adjusting or suppressing reflections between ground planes. This design method marks a revolutionary breakthrough in the wideband array antennas design. However, there are some key challenges need to be addressed to implement the tightly coupled array antenna with many ideal characteristics, for example, a matching network with a same bandwidth is required to effectively realize the bandwidth of the array, so as to achieve an impedance transformation and a conversion process from a balance to nonbalance.
To promote the development of the tightly coupled ultra-wideband array antennas, various feed methods have been proposed, such as commercial passive baluns. However, the commercial passive baluns generally have a narrow bandwidth, and are relatively heavy and expensive. In contrast, active baluns have a narrow application range because the active baluns are usually only suitable for receiving systems. To maximize the bandwidth, some matching circuits use a heavy external balun and a 180-degree mixer under the ground plane, which increases an overall size and costs of the array antenna. A tightly coupled dipole array with an integrated Marchand balun (TCDA-IB) achieves a large bandwidth without using the heavy external balun, but the matching circuit uses a complex multilayer structure in which different line layers are connected via multiple via holes, making the processing more complex.
Considering the broadband a large impedance span, and a high frequency of the ultra-wideband array antenna, and matching methods of a narrowband and lumped circuit is not suitable for the impedance matching of broadband antennas, researchers have successively proposed some methods for the impedance matching of the ultra-wideband antennas to adapt to the development of the broadband antennas. However, limited by a process difficulty, such as a multi-layer structure design, or a necessity of adding an extra heavy 180° mixer, these methods cannot be widely used. To achieve the impedance matching of the low-profile ultra-wideband array antennas and realize a rapid development of the ultra-wideband array antennas, a new impedance matching method for the low-profile ultra-wideband array antenna is required.
To solve the above problems, the present disclosure connects a hyperbolic microstrip balun in series with an open circuit line, directly couples the open circuit line to a radiator layer of an antenna for matching, and uses an arm of an array element as a ground for both the radiator layer and the open circuit line. In this way, the open circuit line is integrated into a matching circuit without adding any other dielectric layer, thereby keeping the array antenna elements compact, small, and cost-effective. In addition, due to its special structure, the hyperbolic microstrip balun can achieve a balance-nonbalance conversion while achieving an impedance transformation. Theoretically, the hyperbolic microstrip balun may realize the impedance transformation between any two impedances, and may be used for the impedance matching in a broadband.
The present disclosure provides an impedance matching method for a low-profile ultra-wideband array antenna, including a hyperbolic microstrip balun, a radiator layer, an open circuit impedance, and a coaxial line. The method includes: connecting an arm of a balanced end of the hyperbolic microstrip balun in series with the open circuit line, directly coupling the open circuit line to the radiator layer, connecting another arm of the balanced end of the hyperbolic microstrip balun to the radiator layer via a metallized via hole, and welding an unbalanced end of the hyperbolic microstrip balun to the coaxial line, so that the coaxial line feeds a power to the antenna via the hyperbolic microstrip balun.
In an embodiment, the arm of the balanced end of the hyperbolic microstrip balun is connected in series with the open circuit line, and the open circuit line is directly coupled to the radiator layer, to form an impedance matching circuit.
In an embodiment, the open circuit line and the radiator layer share a same dielectric layer.
In an embodiment, the open circuit line and the radiator layer are electromagnetically coupled.
In an embodiment, the hyperbolic microstrip balun has a curvilinear structure.
The present disclosure has at least the following beneficial effects.
In the figures, there are: an input impedance;
To make the objectives, technical solutions, and advantages of the present disclosure clearer, the present disclosure is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended to illustrate the present disclosure and are not intended to limit the present disclosure.
Instead, any substitution, modification, equivalent methods and solutions defined by the claims within the spirit and scope of the present disclosure may be covered by the present disclosure. Further, for better understanding of the present disclosure, some specific details of the present disclosure are described in detail below. Those skilled in the art may fully understand the present disclosure without these specific details.
Theoretical analysis: In embodiments of the present disclosure, λ is a propagation distance of a vibration signal in a medium in a cycle. Generally, λ is related to a frequency and a material of the medium. Generally, a wave speed in the medium meets the following relationship:
Then from Z(−l)=−jZ0 cot βl, an input impedance formula of the open circuit line 3, it can be known that when a length of the open circuit line 3 is set to λ/4 corresponding to the resonant frequency point, the input impedance is 0, a capacitance characteristic is presented in a low band of the resonant frequency, and an inductance characteristic is presented in a high band of the resonant frequency, which is just the opposite of a reactance characteristic of the antenna, and may be used to reduce the reactance value. Herein, l is a distance between an input end of the open circuit line 3 and an open circuit point, Zo is a characteristic impedance of the open circuit line 3, β is a phase constant, j is a symbol of a complex number, j2=−1, and β=2π/λ.
Referring to
As can be known from the matching circuit diagram, the impedance of the antenna is taken as the fixed load of the matching circuit, and the reactance part in the antenna impedance is taken as stage 1 of the matching circuit. The reactance is reduced by using the characteristic that the reactance near the resonant frequency point is opposite to the reactance of the antenna when the open circuit line 3 is connected in series. And then the impedance transformation is achieved by the hyperbolic microstrip balun 5. In the antenna element, the open circuit line 3 is integrated to the matching circuit without adding the dielectric layer 1, which simplifies the processing and reduces material costs. The hyperbolic microstrip balun 5, consisting of two gradient microstrip lines, may be divided into the balanced end 52 and the unbalanced end 53. The hyperbolic microstrip balun 5 transforms an unbalanced circuit at a feed port of the coaxial line 6 into a balanced circuit at a feed port of the antenna, without adding an external balun to the circuit for the balance-nonbalance conversion. In addition, due to its gradually changing impedance, the hyperbolic microstrip balun 5 may achieve the transformation between any two impedances in the broadband, thereby achieving the impedance matching in the broadband.
The above are merely preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modification, equivalent substitution and improvement without departing from the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011261301.1 | Nov 2020 | CN | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 10320088 | Johnson | Jun 2019 | B1 |
| 20090015502 | Haapala | Jan 2009 | A1 |
| 20100225554 | Huang | Sep 2010 | A1 |
| 20110043432 | Ineichen | Feb 2011 | A1 |
| Entry |
|---|
| R. He et al., “A 1×8 Linear Ultra-Wideband Phased Array With Connected Dipoles and Hyperbolic Microstrip Baluns,” in IEEE Access, vol. 6, pp. 52953-52968, 2018 (Year: 2018). |
| Number | Date | Country | |
|---|---|---|---|
| 20220149524 A1 | May 2022 | US |
