A miniaturized coupler based on thin-film medium

Abstract

The present invention discloses a miniaturized coupler based on a thin-film medium, which belongs to the field of microwave communication. The coupler includes a thin-film medium; four-segment stub microstrip lines located on one side of the thin-film medium; and a slotted metal ground located on the other side of the thin-film medium. Among them, the thickness of the thin-film medium is less than 100 um, and the side length dimension of the coupler is less than 0.08 wavelengths. The coupler is formed by alternately connecting miniaturized 90° microstrip lines of two sizes, making full use of the limited space and achieving a high space utilization rate. The present invention has the following three main advantages: ① proposing a high-impedance transmission line design for the thin-film medium to increase the width of the microstrip line of the thin-film medium and reduce the transmission loss; ② proposing a thin-film medium transmission line based on L-C oscillation to realize a miniaturized transmission line based on the thin-film medium; ③ staggered coupling-through stubs to improve the space utilization rate and realize the miniaturized design of the coupler. The present invention uses a thin-film medium in the radio frequency field, providing a new idea for the design of radio frequency systems in the fields of communication and radar.

Description

Technical Field

[0001] The present invention belongs to the field of microwave communication, and particularly relates to a miniaturized coupler based on thin-film dielectric. Background Art

[0002] Radio frequency couplers are indispensable components in radio frequency systems, and are used in various wireless communication fields such as 2 / 3 / 4 / 5G, WiFi / bluetooth, and satellite communication. In addition, they are also widely used in various radar radio frequency systems. The performance of the coupler has a great impact on the performance of the radio frequency links connected before and after the coupler, and plays an important role in the indicators of the entire radio frequency system.

[0003] With the pursuit of miniaturization in many communication products and radar products, each module therein faces the problem of miniaturization, including the widely used coupler. Currently, the couplers used on the market can basically be divided into three types: cavity filters, PCB microstrip filters, and LTCC technology filters. Among them, cavity filters and PCB microstrip filters are large in volume and difficult to meet the requirements of miniaturization for high-frequency use. The filters produced by LTCC technology are relatively complex in design, increasing the manufacturing difficulty and having a relatively high cost.

[0004] In summary, filters should be developed towards lower production costs, smaller sizes, and simpler structures. Summary of the Invention

[0005] The object of the present invention is achieved through the following technical solutions.

[0006] In view of this, the present invention provides a miniaturized coupler based on thin-film dielectric.

[0007] The technical solution of the present invention is as follows:

[0008] First, the present invention proposes a new type of thin-film dielectric transmission line. Its working principle is to set gaps on the metal ground under the microstrip line to increase the inductance of the microstrip transmission line, and then add metal branches on both sides of the microstrip line to increase the capacitance of the transmission line. By adjusting the gaps and branches, L-C resonance at different frequency bands is achieved, thereby shortening the length of the microstrip line and increasing the width of the microstrip line. On the one hand, the size is reduced, and on the other hand, the transmission loss of the microstrip line is reduced. The present invention takes the coupler as an example to illustrate the advantages of this transmission line, and this designed microstrip line is also applicable to other radio frequency components. The following specifically describes the miniaturized coupler based on thin-film dielectric of the present invention.

[0009] A miniaturized coupler based on a thin-film medium, including a thin-film medium, which can be a liquid crystal material or a ferroelectric thin-film material. One side of the thin-film medium is a slotted metal ground, and the other side is a stub microstrip line. In order to achieve better performance, the present invention designs two kinds of miniaturized 90° microstrip lines to be connected in sequence to form the final miniaturized coupler, achieving good matching, low loss, and improving its working efficiency.

[0010] The described stub microstrip line increases the inductance of the transmission line through the floor slotting and increases the capacitance of the transmission line through the open-circuit stub, and finally realizes the LC oscillation under the working frequency band to achieve the purpose of miniaturizing the microstrip line.

[0011] The described thin-film medium is the core technical means used in the present invention. In the embodiment of the present invention, the thickness of this medium is only 5um, which is reduced by 50-200 times compared with the traditional dielectric substrate. Its ultra-thin characteristic is the highlight of the present invention.

[0012] The described slotted metal ground has etched slots designed on the complete metal ground, cooperating with the microstrip line on the other side to form an L-C oscillation.

[0013] All the components described above are designed within a space of 1.7mm * 1.7mm, and the total thickness is only 9um. Therefore, such a coupler is easier to use and is convenient for the design of the RF system.

[0014] The beneficial effects of the present invention are:

[0015] Designed based on a thin-film medium, the thickness of the device is greatly reduced. The microstrip line is improved. The length of the 90° microstrip line is only 0.5mm, which is reduced to less than 1 / 7 of the original compared with the conventional 90° microstrip line of 3.8mm under the same medium. Description of the Drawings

[0016] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference symbols are used to represent the same components.

[0017] In the drawings:

[0018] Figure 1 is the front view of the miniaturized coupler of the present invention;

[0019] Figure 2 is the side view of the miniaturized coupler of the present invention;

[0020] Figure 3 is the structural diagram of the first kind of miniaturized 90° microstrip line of the present invention;

[0021] Figure 4This is the structural diagram of the second miniaturized 90° microstrip line of the present invention;

[0022] Figure 5 This is the schematic diagram of each port of the miniaturized coupler of the present invention;

[0023] Figure 6 This is the S-parameter result of the ports of the miniaturized coupler of the present invention;

[0024] Figure 7 This is the result of the amplitude difference between ports 2 and 3 of the miniaturized coupler of the present invention;

[0025] Figure 8 This is the result of the phase difference between ports 2 and 3 of the miniaturized coupler of the present invention. Detailed implementation manners

[0026] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary 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 by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0027] The coupler involved in the present invention has a center operating frequency of 14 GHz and a bandwidth of more than 500 MHz. Figure 1 This is the front view of the miniaturized coupler, including the following parts: the outer dimension 1 of the coupler, and the actual used area of the coupler is smaller than the outer dimension; the surface circuit part 2 of the miniaturized coupler, which includes four 90° stub microstrip lines and four feed port microstrip lines; the metal ground etched slit 3, which is a rectangular slit etched on the metal ground and interacts with the stub microstrip lines to form an LC oscillation and shorten the length of the microstrip line.

[0028] Figure 2 This is the side view of the miniaturized coupler of the present invention. From top to bottom, they are the coupler metal layer 11 (i.e., Figure 1 the surface circuit part 2 in

[0029] The principle of the coupler of the present invention is the same as that of the traditional directional coupler. It is formed by connecting four 90° microstrip lines. The technical means for reducing the size of the present invention is to transform the 90° microstrip line. Figure 3 and Figure 4 These are two 90° microstrip lines of the present invention, and the specific description is as follows.

[0030] Figure 3It is the structural diagram of the first type of miniaturized 90° microstrip line, which is a microstrip line structure with double stubs and triple slots. The widths of the microstrip lines at both ends are wl1_1 = 0.29 mm. The lengths and widths of the stubs are respectively: ll1 = 0.21 mm, wl1_2 = 0.7 mm. The distance between the two microstrip stubs is dis1 = 0.035 mm. The three slots have the same size, and their lengths and widths are respectively: sl1 = 0.558 mm, sw1 = 0.02 mm.

[0031] Figure 4 It is the structural diagram of the second type of miniaturized 90° microstrip line, which is also a microstrip line structure with double stubs and triple slots. The widths of the microstrip lines at both ends are wl2_1 = 0.18 mm. The lengths and widths of the stubs are respectively: ll2 = 0.18 mm, wl2_2 = 0.6 mm. The distance between the two microstrip stubs is dis2 = 0.035 mm. The three slots have the same size, and their lengths and widths are respectively: sl2 = 0.692 mm, sw2 = 0.02 mm.

[0032] Connect the above two types of miniaturized 90° microstrip lines in sequence by rotation to form the surface circuit 2 of the miniaturized coupler, maximizing the space utilization rate and making full use of the square-size site. Figure 5 Four RF ports are marked, namely the input port <1>, the through port <2>, the coupled port <3> and the isolated port <4>. All subsequent results are referenced by these ports.

[0033] Figure 6 Regarding the results of this coupler, S11 represents the matching condition of port 1, and it is below -18 dB within the frequency band, indicating good matching. S21 and S31 are respectively the transmission coefficients of the through port <2> and the coupled port <3>, and they are basically the same, both around -4 dB. S41 is the port isolation degree, and it is below -20 dB within the frequency band, indicating good isolation.

[0034] Figure 7 It is the amplitude difference between the through port <2> and the coupled port <3> of the miniaturized coupler with the thin-film medium of the present invention, and it remains within 0.05 dB within the frequency band, indicating good consistency.

[0035] Figure 8 It is the phase difference between the through port <2> and the coupled port <3> of the miniaturized coupler with the thin-film medium of the present invention, and it varies within the range of 90° ± 1°.

[0036] The greatest advantage of the thin-film medium used in the present invention is its thinness. Its thickness is 50 to 200 times smaller than that of traditional media, which has obvious advantages for the miniaturization and lightweight of devices. Moreover, for high-frequency signals, it can suppress the generation of spurious signals and make the useful signals purer. However, its physical strength is relatively weak, and the risk of using it alone is relatively high. It should be attached to materials with high physical strength. With the continuous increase of the frequency bands used in the communication field and the increasingly strict requirements for size, this thin-film medium will be more and more necessary to use.

[0037] As described above, it is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the said claims.

Claims

1. A miniaturized coupler based on a thin-film medium, characterized in that, Comprising: A thin-film medium; Four-section stub microstrip lines located on one side of the thin-film medium; And A slotted metal ground located on the other side of the thin-film medium; The slotted metal ground is formed by etching slits on a complete metal ground, and cooperates with the microstrip lines on the other side to form an L-C oscillation; By setting slits on the metal ground under the microstrip lines, the inductance of the microstrip transmission line is increased, and then metal stubs are added on both sides of the microstrip lines to increase the capacitance of the transmission line. The L-C resonance at different frequency bands is achieved by adjusting the slits and stubs; The stub microstrip lines are 90° stub microstrip lines; The four-section stub microstrip lines include two first stub microstrip lines and two second stub microstrip lines; The first stub microstrip line is a double-stub, triple-slit microstrip line structure. The width of the microstrip lines at both ends is wl1_1 = 0.29 mm, and the length and width of the stubs are respectively: ll1 = 0.21 mm, wl1_2 = 0.7 mm. The distance between the two microstrip stubs is dis1 = 0.035 mm, and the three slits have the same size, with the length and width being respectively: sl1 = 0.558 mm, sw1 = 0.02 mm; The second stub microstrip line is a double-stub, triple-slit microstrip line structure. The width of the microstrip lines at both ends is wl2_1 = 0.18 mm, and the length and width of the stubs are respectively: ll2 = 0.18 mm, wl2_2 = 0.6 mm. The distance between the two microstrip stubs is dis2 = 0.035 mm, and the three slits have the same size, with the length and width being respectively: sl2 = 0.692 mm, sw2 = 0.02 mm.

2. A miniaturized coupler based on a thin-film medium according to claim 1, characterized in that The thin-film medium is a liquid crystal material or a ferroelectric thin-film material, and the thickness is less than 100 um.

3. The miniaturized coupler based on a thin-film medium according to claim 1, characterized in that, The stubs of the four-section stub microstrip lines are rectangular or fan-shaped.

4. A miniaturized coupler based on a thin-film medium according to claim 1, characterized in that The first stub microstrip line and the second stub microstrip line are sequentially rotationally connected to form the surface circuit of the miniaturized coupler.

5. A miniaturized coupler based on a thin-film medium according to claim 4, characterized in that The surface circuit is rectangular. The two first stub microstrip lines are located at the obliquely crossed positions of the rectangle, and the two second stub microstrip lines are also located at the obliquely crossed positions of the rectangle.

6. A miniaturized coupler based on a thin-film medium according to claim 4 or 5, characterized in that The surface circuit has four RF ports, namely an input end, a through end, a coupling end, and an isolation end.

Images