Patent Description:
The variable capacitor is a capacitor of which its capacitance can be adjusted within a certain range. It is widely used in the time-frequency response, frequency selection, phase shift control, transmission matching and other technology fields, especially the realization method based on the variable capacitor structure of phase shifter became the technical hot spot.

The phase shifters are widely used in many RF devices such as the phased array antennas, phase modulators and harmonic distortion cancelers. In order to obtain better application effect, the higher requirements such as the miniaturization, light weight, miniaturized, light weight, low insertion loss, and good flatness within the entire operating bandwidth, large phase shift range, wide operating bandwidth, good input and output port matching, low power consumption, and lower costs for the performance of phase shifters were also presented.

There are many realization methods of the existing phase shifters, but they all have certain application limitations. Among them, the active phase shifter consumes large power and has limited application scenarios. In the passive phase shifters, the switch-type phase shifters based on PIN diodes, CMOS, MEMS, etc. can't achieve the continuous phase adjustment, which are limited in the application scenarios that require the miniaturization and high phase shift accuracy; the reflective or variable capacitor phase shifters based on the variable capacitance diodes will reduce the figure of merit (FOM) due to the increased insertion loss in the high-frequency applications and affect performance indicators. In recent years, the variable capacitor phase shifters based on the ferroelectric thin film BST, liquid crystal and other metamaterials have received more and more attention because of their large adjustable range of dielectric constant or high FOM and the huge application prospect in the design research with the development of materials science. There were also many related patent applications, such as electronically steerable plane phased array antenna (<CIT>), liquid crystal phase shifter and antenna (<CIT>), a liquid crystal phase shifter and electronic equipment (<CIT>) and MULTI-LAYERED SOFTWARE DEFINED ANTENNA AND METHOD OF MANUFACTURE (<CIT>), but the existing designs require the longer transmission line to achieve <NUM>° phase shift, thereby resulting in larger size, decreased FOM, etc., which are not conducive to the miniaturization and integration of RF microwave devices and antennas, but also reduce the design freedom of antennas. They are not conducive to the multi-polarization ability of antennas, and increase the design and processing difficulty of the feeding network; In addition, there is no better solution to minimize the influence of the bias circuit for adjusting the dielectric constant of metamaterial dielectric layer on the RF signal. <CIT> relates to a phase shifter based on liquid crystal materials. <CIT> relates to an electronically steerable planar phase array antenna. And <CIT> relates to a liquid crystal phase shifter and a liquid crystal antenna.

In order to overcome the existing technical deficiencies, the present invention discloses a metamaterial-based variable capacitor structure, the structure effectively reduces the size of the variable capacitance structure and the shunt attenuation of the radio frequency signal by the bias circuit, thereby improving the figure of merit (FOM) of the structure, largely solving the miniaturization, batching, integration and cost reduction problems of radio frequency microwave devices and antenna, and also adding more freedom to the antenna design.

Technical solution used in the present invention for solving the above-mentioned problems is provided by the claims.

Compared with the existing technologies, the present invention has the following beneficial effects:.

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the detailed description of the preferred embodiments below. The drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the invention. Moreover, the same reference numerals are used throughout the drawings to indicate the same parts. In the drawings:.

Hereinafter, the illustrative embodiments of the present disclosure will be described in more detail with reference to the attached drawings. Although the illustrative embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. On the contrary, these embodiments are provided to get a thorough understanding of the present disclosure, and to fully convey the scope of the present disclosure to the technicians in the art.

As shown in <FIG>, the embodiment of the present invention provides a metamaterial-based variable capacitor structure <NUM>, comprising: the first substrate <NUM> and the second substrate <NUM> set oppositely, and the metamaterial dielectric layer <NUM> located between the first substrate <NUM> and the second substrate <NUM>, the metal floor layer <NUM> located between the first substrate <NUM> and the metamaterial dielectric layer <NUM>, at least two periodically arranged gaps <NUM> and isolation holes <NUM> on the metal floor layer <NUM>, the microstrip line <NUM>, bias line <NUM> and choke branch <NUM> located between the second substrate <NUM> and the metamaterial dielectric layer <NUM>, and two feeding terminals <NUM> and <NUM> on both ends of microstrip line <NUM>.

<FIG> and <FIG> are respectively the top views of the first substrate <NUM> lower surface, the second substrate <NUM> upper surface, and overall body of the metamaterial-based variable capacitor structure according to a specific embodiment <NUM> of the present invention. In this structure, the periodically arranged gaps <NUM> are slotted on floor layer <NUM> directly facing the microstrip line <NUM> to form the slow-wave transmission structure, so that the transmission route required for phase shift <NUM>° in the metamaterial dielectric layer is shortened, thereby effectively reducing the overall structure size and obtaining better FOM.

The metamaterial-based variable capacitor structure is composed of the metal floor layer <NUM>, the periodically arranged gaps <NUM>, the metamaterial dielectric layer <NUM>, and the microstrip line <NUM>. Among them, the metamaterial dielectric layer <NUM> is composed of one or multiple layers of variable dielectric constant material, and the material can be the liquid crystal, ferroelectric thin film BST, etc. The dielectric constant of the metamaterial dielectric layer can be adjusted to change the capacitance value of the metamaterial-based variable capacitor, thereby changing the phase shift amount of the metamaterial-based phase shifter. The bias line <NUM> for changing the dielectric constant of the metamaterial dielectric layer <NUM> is loaded on the microstrip line <NUM>. In order to reduce the impact of the bias line <NUM> on the radio frequency signal, the isolation hole <NUM> is punched on the corresponding bias line <NUM> at the floor layer <NUM> where the isolation hole is close to the microstrip line <NUM>. The principle of radio frequency transmission line mismatch caused by the impedance mutation can effectively suppress the phenomenon of radio frequency signal loss caused by the transmission along the bias line. Meanwhile, combined with the choke branch <NUM> loaded on the bias line <NUM> having a certain distance from the microstrip line <NUM>, the structure can greatly reduce the shunt attenuation of RF signals by the bias line compared with the conventional bias line.

According to the liquid crystal metamaterial-based variable capacitor described in Embodiment <NUM> and the test results of physical prototype working at <NUM>-<NUM> showing that FOM is <NUM>° / dB and the area required for phase shift <NUM>° is only <NUM> * <NUM> in the design with a liquid crystal layer thickness of only <NUM>, the index is better than the existing similar phase shifters.

As shown in <FIG>, the embodiment of the present invention provides a metamaterial-based variable capacitor structure <NUM>, comprising: the first substrate <NUM> and the second substrate <NUM> set oppositely, and the metamaterial dielectric layer <NUM> located between the first substrate <NUM> and the second substrate <NUM>, the metal floor layer <NUM> located between the first substrate <NUM> and the metamaterial dielectric layer <NUM>, at least two periodically arranged gaps <NUM> and isolation holes <NUM> on the metal floor layer <NUM>, the microstrip line <NUM> between the second substrate <NUM> and the metamaterial dielectric layer <NUM>, the branches <NUM>, the bias line <NUM> and choke branch <NUM> periodically loaded on the microstrip line <NUM>, and two feeding terminals <NUM> and <NUM> on both ends of microstrip line <NUM>.

<FIG>, <FIG> are respectively the top views of the first substrate <NUM> lower surface, the second substrate <NUM> upper surface, and overall body of the metamaterial-based variable capacitor structure according to a specific embodiment <NUM> of the present invention. In this structure, the periodically arranged gaps <NUM> on the floor layer <NUM> directly facing the microstrip line <NUM> and the branches <NUM> periodically loaded on the microstrip line <NUM> together form the slow-wave transmission structure, so that the transmission route required for phase shift <NUM>° in the metamaterial dielectric layer is shortened, thereby effectively reducing the size of phase shifter and obtaining better FOM.

The metamaterial-based variable capacitor structure is composed of the metal floor layer <NUM>, the periodically arranged gaps <NUM>, the metamaterial dielectric layer <NUM>, and the microstrip line <NUM>. Among them, the metamaterial dielectric layer <NUM> is composed of one or multiple layers of variable dielectric constant material, and the material can be the liquid crystal, ferroelectric thin film BST, etc..

<FIG> is the equivalent circuit model according to a specific embodiment <NUM> of the present invention; <NUM> is the equivalent inductance formed by the gaps <NUM> and the metal floor layer <NUM>, <NUM> is the equivalent capacitance formed by the microstrip line <NUM> and the metal floor layer <NUM>, and <NUM> is the equivalent variable capacitance formed by the microstrip line <NUM> and the loaded branches <NUM> together with the metal floor layer <NUM>.

The <NUM> capacitance value can be changed by adjusting the dielectric constant of the metamaterial dielectric layer, thereby changing the phase shift amount of the metamaterial-based phase shifter. The bias line <NUM> for changing the dielectric constant of the metamaterial dielectric layer <NUM> is loaded on the microstrip line <NUM> or branch <NUM>. In order to reduce the impact of the bias line <NUM> on the radio frequency signal, the isolation hole <NUM> is punched on the corresponding bias line <NUM> at the floor layer <NUM> where the isolation hole is close to the microstrip line <NUM>. The principle of radio frequency transmission line mismatch caused by the impedance mutation can effectively suppress the phenomenon of radio frequency signal loss caused by the transmission along the bias line. Meanwhile, combined with the choke branch <NUM> loaded on the bias line <NUM> having a certain distance from the microstrip line <NUM>, the structure can greatly reduce the shunt attenuation of RF signals by the bias line compared with the conventional bias line.

As shown in <FIG>, the embodiment of the present invention provides a metamaterial-based variable capacitor <NUM>. The structure is a curved connection structure extended from the metamaterial-based variable capacitor <NUM> described in Embodiment <NUM>. This structure makes the routing of phase shifter more flexible, and can better adapt to the routing of phase shifter under different space conditions.

As shown in <FIG>, the bias line for the metamaterial-based variable capacitors <NUM>, <NUM> and <NUM> said in the embodiments of the present invention can be replaced by the bias line <NUM> made from ITO (indium tin oxide), NiCr (nickel chromium), or some other material with a resistivity greater than <NUM>×<NUM><NUM>Ω·m. When the bias line <NUM> is made from ITO (indium tin oxide), NiCr (nickel chromium), or some other material with a resistivity greater than <NUM>×<NUM><NUM>Ω·m, the bias line structure can be loaded with the isolation hole <NUM> and choke branch <NUM> according to Embodiments <NUM>, <NUM> or <NUM> or directly loaded without the isolation hole <NUM> and choke branch <NUM> on the microstrip line <NUM>. In such case, the thickness of the bias line <NUM> can be from <NUM>~<NUM>, and the choke attenuation can be also decreased by properly controlling the thickness and square resistance of the coating on the bias line <NUM>.

As shown in <FIG>, the isolation hole <NUM> on the floor layer <NUM> can be either rectangular or circular, or but not be limited to triangular, rhombic, or polygonal hole.

As shown in <FIG>, the choke branch <NUM> can be either the loaded fan-shaped or the loaded triangular, or but not be limited to the loaded rectangular structure, etc..

Claim 1:
A metamaterial-based variable capacitor structure, comprising:
a first substrate (<NUM>) and a second substrate (<NUM>) set oppositely, and a metamaterial dielectric layer (<NUM>) located between the first substrate (<NUM>) and the second substrate (<NUM>);
a metal floor layer (<NUM>) between the first substrate (<NUM>) and the metamaterial dielectric layer (<NUM>); at least <NUM> gaps periodically arranged on the said metal floor layer (<NUM>);
a microstrip line (<NUM>) between the second substrate (<NUM>) and the metamaterial dielectric layer (<NUM>), and a bias line (<NUM>) loaded on the microstrip line (<NUM>);
characterized in that the said metal floor layer (<NUM>) also has an isolation hole (<NUM>), punched on the bias line, and the said bias line (<NUM>) is further loaded with a choke branch (<NUM>).