Passive self-regulated rectenna liquid crystal antenna system

Abstract

The application discloses a kind of passive self-regulation rectification liquid crystal antenna systems, belong to wireless communication and microwave technical field.The system includes: liquid crystal antenna, rectifier circuit and MOS tube;Liquid crystal antenna receives microwave signal, the rectifier circuit is converted and outputs direct current voltage received microwave signal, the direct current voltage acts on the gate and drain of the MOS tube, the source of the MOS tube is connected to the surface of the liquid crystal antenna.The application is combined with the design of liquid crystal antenna and rectifier, forms feedback structure, without external supply direct current, through the output direct current voltage of rectifier to realize resonant frequency continuous reconfiguration, simple structure, easy to manufacture, effectively control the size of liquid crystal antenna, expand application scenario.

Description

Technical Field

[0001] This invention relates to a self-controlled rectifier liquid crystal antenna system, belonging to the field of wireless communication and microwave technology. Background Technology

[0002] Antennas are essential wireless devices for transmitting and receiving electromagnetic waves, and are indispensable components in radar, communication, and other systems. Liquid crystal antennas, as a passive microwave tunable technology, leverage the anisotropy of liquid crystal molecules. By controlling the alignment of these molecules with electrical signals, the dielectric parameters of the microwave medium are altered, allowing for continuous reconfiguration of the antenna's resonant frequency. Compared to other tuning techniques, liquid crystal antennas offer advantages such as lower bias voltage and a wider tuning range. They have broad application prospects in satellite receiving antennas, vehicle-mounted radar, and base station antennas. Meanwhile, rectifier antennas are a key technology for microwave wireless power transmission and environmental energy harvesting, converting received external microwave signals into DC while maintaining high energy conversion efficiency.

[0003] However, due to the inherent properties of liquid crystals, they require external electrical signals to achieve continuous reconfiguration of their resonant frequency. This necessitates the use of an external adjustable DC power supply, increasing the size of the liquid crystal antenna and limiting its applicable scenarios. Meanwhile, rectifier antennas mostly operate at a single frequency, resulting in a small frequency range for energy harvesting. Furthermore, some liquid crystal antennas and rectifier antennas have complex structures, low production yields, and are difficult to mass-produce. Summary of the Invention

[0004] To address the above problems, the present invention provides a self-controlled rectifier liquid crystal antenna system, comprising: a liquid crystal antenna, a rectifier circuit, and a MOSFET;

[0005] The liquid crystal antenna receives microwave signals, the rectifier circuit converts the received microwave signals into DC voltage, the DC voltage is applied to the gate and drain of the MOS transistor, and the source of the MOS transistor is connected to the surface of the liquid crystal antenna.

[0006] Optionally, the rectifier circuit includes: a DC block, a matching circuit, a GaN diode, a post-filter, a filter capacitor, and a load resistor;

[0007] The DC block, matching circuit, and post-filter are connected in sequence. The post-filter is connected to the filter capacitor and the load resistor, respectively. The matching circuit is also connected to the GaN diode.

[0008] Optionally, the MOS transistor is an N-channel depletion-type transistor.

[0009] Optionally, the liquid crystal antenna includes: liquid crystal, quartz glass, and a radiating plate, wherein the liquid crystal and the radiating plate are encapsulated in the quartz glass.

[0010] Optionally, the dielectric constant of the liquid crystal is in the range of [2.47, 3.25].

[0011] Optionally, the dielectric constant of the quartz glass is 3.78.

[0012] Optionally, the upper and lower surfaces of the liquid crystal are further provided with alignment films to constrain the orientation of the long axis of the molecules.

[0013] Optionally, the upper and lower surfaces of the liquid crystal are further provided with conductive glass for connecting bias voltage lines.

[0014] Optionally, the orientation film is a polyimide coating.

[0015] Optionally, the frequency band received by the liquid crystal antenna is 5.5G-6.1G.

[0016] The beneficial effects of this invention are:

[0017] The present invention provides a self-controlled rectifier liquid crystal antenna. By combining the liquid crystal antenna with the rectifier to form a feedback structure, it eliminates the need for an external DC power supply. The resonant frequency is continuously reconfigurable through the output DC voltage of the rectifier. This solves the problem of excessive size caused by the need for an external electrical signal for the liquid crystal antenna, effectively controls the size of the liquid crystal antenna, expands the application scenarios, and is simple in structure and easy to manufacture.

[0018] Based on the characteristics of GaN diodes, this invention designs a rectifier circuit in the system that achieves 80% rectification efficiency when receiving signals in the 5.5G-6.1G frequency band. This solves the problem of low rectification efficiency in most existing rectifier circuits, enabling the output voltage of the rectifier circuit to meet the tunability requirements of the liquid crystal antenna and expanding the frequency range of the rectifier antenna that can collect energy.

[0019] This invention adopts a design concept that combines a liquid crystal antenna, a rectifier circuit, and a MOSFET, which solves the problem that most rectifier antennas operate at a single frequency and have a small frequency range for energy collection. It achieves control over the dielectric constant of the liquid crystal from 2.47 to 3.25, and further enables the system to operate in a wider frequency range of 5.5G-6.1G with good antenna gain. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a diagram of a self-controlled rectifier liquid crystal antenna system according to Embodiment 1 of the present invention.

[0022] Figure 2 This is a top view of the box body according to Embodiment 1 of the present invention.

[0023] Figure 3 This is a side view of the box body according to Embodiment 1 of the present invention.

[0024] Explanation of reference numerals in the attached diagram: 1. Coaxial feed hole; 2. Radiation patch; 3. Liquid crystal medium; 4. Quartz glass protective layer; 5. Lower substrate layer; 6. Upper substrate layer.

[0025] Figure 4 This is a radiation patch diagram of Embodiment 1 of the present invention.

[0026] Figure 5 This is a diagram of the rectifier circuit designed in this invention.

[0027] Figure 6 This is a diagram of the DC voltage output of the rectifier circuit in Embodiment 1 of the present invention.

[0028] Figure 7 This is Figure S11 of the liquid crystal antenna under different dielectric constants according to Embodiment 1 of the present invention.

[0029] Figure 8A The dielectric constant ε of the liquid crystal r The rectification efficiency diagram for a signal with frequency fre = 5.5 GHz at a value of 3.25.

[0030] Figure 8B The dielectric constant ε of the liquid crystal r The rectification efficiency diagram for a signal with frequency fre = 5.7 GHz at a time of 3.00.

[0031] Figure 8C The dielectric constant ε of the liquid crystal r The rectification efficiency diagram for a signal with frequency fre = 5.8 GHz at a frequency of 2.86.

[0032] Figure 8D The dielectric constant ε of the liquid crystal r The rectification efficiency diagram for a signal with frequency fre = 6.1G at a frequency of 2.47 is shown.

[0033] Figure 9A The dielectric constant ε of the liquid crystalr Antenna gain diagram for a signal with frequency fre = 5.5 GHz at 3.25 GHz.

[0034] Figure 9B The dielectric constant ε of the liquid crystal r Antenna gain diagram for a signal with frequency fre = 5.7 GHz at 3.00 GHz.

[0035] Figure 9C The dielectric constant ε of the liquid crystal r Antenna gain diagram for a signal with frequency fre = 5.8 GHz at fre = 2.86.

[0036] Figure 9D The dielectric constant ε of the liquid crystal r Antenna gain diagram for a signal with frequency fre = 6.1G at 2.47. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0038] Example 1:

[0039] In this embodiment, the liquid crystal antenna, rectifier, and MOSFET are connected to form a feedback structure. This enables the liquid crystal antenna to receive microwave signals, and the rectifier to output the received microwave signals as DC voltage. At the same time, the DC voltage is applied to the gate and drain of the MOSFET, controlling the voltage output to the source, which is then applied to the liquid crystal surface. This changes the dielectric constant of the liquid crystal and further changes the operating frequency of the liquid crystal antenna, allowing it to receive signals of different frequencies, specifically in the 5.5G-6.1G frequency band.

[0040] like Figure 1 As shown, the self-controlled rectifier liquid crystal antenna system of this embodiment consists of a liquid crystal antenna, a rectifier circuit, and an N-channel depletion-type transistor. The liquid crystal antenna receives external energy input and then transfers the energy to the rectifier circuit, which converts the AC signal into a DC voltage. The N-channel depletion-type transistor, with its gate and drain shorted, is already turned on at 0V. The DC voltage output by the rectifier circuit is applied to the upper and lower surfaces of the liquid crystal antenna through the N-channel depletion-type transistor, thereby changing the dielectric constant of the liquid crystal.

[0041] This embodiment uses GT3-23001 liquid crystal with voltage-controlled dielectric constant as the dielectric substrate. Data on the types of liquid crystals used and their corresponding characteristics are available from various manufacturers, so the liquid crystal material is a readily available material. Its electrical parameters at room temperature are as follows:

[0042] Table 1: Electrical Parameters of LCD GT3-23001

[0043]

[0044] Due to the fluid properties of liquid crystals at room temperature, they cannot be manufactured into fixed shapes and sizes to directly serve as dielectric layers for separating patches and metal grounds, unlike other materials. Instead, they require the support of a housing. This embodiment designs as follows... Figure 2 , Figure 3 The housing structure is simple and easy to manufacture, simulating the actual packaging of liquid crystals. The liquid crystal is placed within quartz glass, where the upper and lower substrate layers and the protective layer around the liquid crystal are made of quartz glass (ε). r =3.78), the liquid crystal medium is liquid crystal GT3-23001 (ε r =2.47-3.25), and the radiation patch is also encapsulated in quartz glass.

[0045] Furthermore, the orientation of liquid crystal molecules at room temperature is random, and the long axis orientation of the molecules must be constrained by adding alignment films (usually polyimide coatings) to the upper and lower surfaces. Finally, to achieve the electrotunable characteristics of the liquid crystal layer, bias voltage lines need to be added to the upper and lower surfaces. This can be achieved by simply extending conductive glass from the upper and lower surfaces of the liquid crystal; the voltage can be directly applied to the conductive glass of the protruding parts of the cell, i.e., the lower surface of the upper quartz glass plate and the upper surface of the lower quartz glass plate, thus controlling the dielectric constant of the liquid crystal through voltage. The alignment film polyimide coating needs to be applied between the conductive glass and the liquid crystal. When the dielectric constant of the liquid crystal GT3-23001 changes from 0V to 20V, the equivalent dielectric constant of the liquid crystal dielectric layer changes from 2.14 to 3.25.

[0046] The rectifier circuit designed independently in this embodiment is as follows: Figure 5 As shown, the rectifier circuit consists of a DC block, a matching circuit, a GaN diode, a post-filter, a filter capacitor, and a load resistor. The DC block prevents DC current from entering the signal source. The matching circuit adjusts the impedance of the GaN diode and the filter, reducing the circuit's reflection coefficient. The post-filter is used to recover the fundamental, second, and third harmonics, reducing microwave energy on the load resistor while increasing rectification efficiency. The charging and discharging effect of the filter capacitor eliminates high-frequency noise and voltage fluctuations at the rectifier output, making the output signal more stable and smooth.

[0047] This embodiment designs a high-efficiency rectifier circuit based on GaN diodes, capable of outputting a DC voltage of 0-22V. The output DC voltage of this rectifier circuit is as follows: Figure 6 As shown. Therefore, this rectifier circuit can control the dielectric constant of the liquid crystal from 2.47 to 3.25.

[0048] For liquid crystal antennas, the dielectric constant of the liquid crystal varies from 2.47 to 3.25, the resonant frequency of the antenna varies from 5.5 GHz to 6.1 GHz, and the bandwidth is relatively wide (S11 < -10 dB). Figure 7 As shown. When the output voltage of the rectifier is different, the resonant frequency of the antenna can also be continuously varied in the frequency band of 5.51 GHz-6.12 GHz, realizing the absorption of microwave energy in this frequency band, improving the overall efficiency of the system, and thus further transmitting it to the rectifier circuit. Compared with ordinary rectifier antennas operating at a single frequency or multiple frequency points, the resonant frequency of the liquid crystal rectifier antenna in this embodiment is continuously adjustable, varying from 5.5 GHz to 6.1 GHz, with a wide frequency band continuously adjustable range of 0.6 GHz. This also helps the subsequent rectifier circuit to absorb energy from signals of different frequencies, improving rectification efficiency and controlling the subsequent output DC voltage.

[0049] For signals of different frequencies, the simulated maximum rectification efficiency of the rectifier circuit is greater than 80%, reaching as high as 84.5%. Figures 8A-8D As shown. Compared to the 60%-70% rectification efficiency of most existing rectifier circuits, this invention has high rectification efficiency, which helps to control the DC output of the liquid crystal antenna and meets the voltage requirements of the GT3-23001 liquid crystal with varying dielectric constant.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-controlled rectifier liquid crystal antenna system, characterized in that, The system includes: a liquid crystal antenna, a rectifier circuit, and a MOSFET; The liquid crystal antenna receives microwave signals, the rectifier circuit converts the received microwave signals into DC voltage, the DC voltage is applied to the gate and drain of the MOS transistor, and the source of the MOS transistor is connected to the surface of the liquid crystal antenna. The rectifier circuit includes: a DC block, a matching circuit, a GaN diode, a post-filter, a filter capacitor, and a load resistor; The DC Block, matching circuit, and post-filter are connected in sequence. The post-filter is connected to the filter capacitor and the load resistor respectively. The matching circuit is also connected to the GaN diode. The MOS transistor is an N-channel depletion-type transistor; The liquid crystal antenna includes: liquid crystal, quartz glass, and a radiating plate, wherein the liquid crystal and the radiating plate are encapsulated in the quartz glass; The upper and lower surfaces of the liquid crystal are also provided with alignment films to constrain the orientation of the long axis of the molecules. The upper and lower surfaces of the liquid crystal are also provided with conductive glass for connecting bias voltage lines.

2. The self-controlled rectifier liquid crystal antenna system according to claim 1, characterized in that, The dielectric constant of the liquid crystal is in the range of [2.47, 3.25].

3. The self-controlled rectifier liquid crystal antenna system according to claim 1, characterized in that, The dielectric constant of the quartz glass is 3.

78.

4. The self-controlled rectifier liquid crystal antenna system according to claim 1, characterized in that, The orientation film is a polyimide coating.

5. The self-controlled rectifier liquid crystal antenna system according to claim 1, characterized in that, The frequency band received by the liquid crystal antenna is 5.5G-6.1G.

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