Thin film matching load circuit

Abstract

The invention provides a thin-film matched load circuit, which comprises one or more matching sections, the matching sections are connected in series, each matching section comprises a microstrip line and a thin-film resistor, the output end of the microstrip line in each matching section is connected with the input end of the thin-film resistor, and the output end of the thin-film resistor is connected with the output end of the microstrip line; the output end of the film resistor of each matching section is connected with the input end of the microstrip line of the next matching section, and the matching sections are used for impedance matching between the load and the transmission line; the input end of the fan-shaped microstrip line is connected with the output end of the last matching section, and the fan-shaped microstrip line serves as a terminal open-circuit line; the matching section and the fan-shaped microstrip line are located on the upper surface of the substrate, and the fan-shaped microstrip line and the substrate are equivalent to a capacitor grounding process. According to the invention, the broadband is provided, the more the matching sections are, the wider the bandwidth is, the film circuit is high in precision and good in stability, the fan-shaped microstrip line is equivalent to a capacitor grounding process, physical connection grounding is not needed, and the processing difficulty and cost are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of matching loads, and in particular to a thin film matching load circuit. Background Art

[0002] Impedance matching load is a terminal device that can absorb all incident power and is widely used in power transmission, wireless communication and radio frequency systems. The matching load is a terminator that absorbs all incident wave power, so it is equivalent to the characteristic impedance line connected to the terminal.

[0003] For TEM (Transverse Electric and Magnetic) modes such as microstrip or coaxial, the load can be achieved directly using thin film resistors or resistors; for waveguide types, the matching load is achieved using lossy materials. Figure 1 The matching load in (a) is generally composed of three parts: substrate, microstrip line and thin film resistor. The matching load substrate is generally made of ceramic materials with good thermal conductivity and high dielectric constant such as BeO or AlN. The electrodes are mostly made of silver or gold with good electrical conductivity. The resistor film is made of corrosion-resistant and stable TaN material. One end of the metal microstrip line is grounded, and the other end is the signal input end and performs impedance matching between the input signal and the TaN resistor. Figure 1 The matching load in (b) mainly uses a resistor to match the load. The other end of the resistor is connected to the ground plane of the substrate through a metallized through-hole. Figure 1 The matching load in (c) is achieved by embedding a wedge or plate made of lossy material into the waveguide.

[0004] These three types of matching load circuits are mainly used in situations where a load is required in microwave passive devices, such as waveguide magic T, coupler, and coaxial matching load, so that all the power transmitted along the passive device is absorbed without reflection. In addition, matching loads are often used as false antennas to eliminate spatial radiation without interfering with other electronic equipment.

[0005] In the existing technology, the microstrip line structure is highly dependent on the PCB (Printed Circuit Board) ground, and the resistance grounding process needs to be achieved by drilling ground holes or microstrip grounding. In addition, the microstrip grounding needs to be connected to the bottom metal surface by side plating, which undoubtedly increases the processing difficulty and cost. For the waveguide type, the precision of the lossy material may not be high, which is not the matching load value required by the waveguide, resulting in the mismatch of the waveguide. Summary of the invention

[0006] The present invention provides a thin film matching load circuit, which is used to solve the defects in the prior art that the matching load of a microstrip line needs to be grounded by drilling a ground hole or a microstrip grounding method to achieve resistance grounding, and the lossy material precision of the waveguide type matching load is not high, and realizes a matching load circuit with broadband, high precision and good stability, and does not require physical connection to ground.

[0007] The present invention provides a thin film matching load circuit, comprising:

[0008] One or more matching sections, the multiple matching sections are connected in series, each matching section includes a microstrip line and a thin film resistor, the output end of the microstrip line in each matching section is connected to the input end of the thin film resistor, the output end of the thin film resistor of each matching section is connected to the input end of the microstrip line of the next matching section, and the matching section is used for impedance matching between a load and a transmission line;

[0009] A fan-out microstrip line, wherein the input end of the fan-out microstrip line is connected to the output end of the last matching section, and the fan-out microstrip line serves as an open-ended terminal line;

[0010] The matching section and the fan-shaped microstrip line are located on the upper surface of the substrate, and the fan-shaped microstrip line and the substrate are equivalent to a capacitor grounding process.

[0011] According to a thin film matching load circuit provided by the present invention, the number of the matching sections is determined according to the relative bandwidth of the thin film matching load circuit design;

[0012] In the case where the relative bandwidth is less than a first preset threshold, the matching section is a single section;

[0013] When the relative bandwidth is greater than or equal to the first preset threshold, the matching section is multiple sections.

[0014] According to a thin film matching load circuit provided by the present invention, the calculation formula of the relative bandwidth is as follows:

[0015]

[0016] Among them, Δf is the signal bandwidth of the design operating frequency, which is obtained by the difference between the highest end and the lowest end of the design operating frequency, f0 is the center frequency of the design operating frequency, and f m is the lowest operating frequency, Γ m is the reflection coefficient, Z0 is the impedance of the transmission line, Z L is the impedance of the load.

[0017] According to a thin film matching load circuit provided by the present invention, when there are multiple matching sections, the widths of the microstrip lines of the multiple matching sections satisfy the first gradient law and / or the lengths satisfy the second gradient law, and the widths of the thin film resistors of the multiple matching sections satisfy the third gradient law and / or the lengths satisfy the fourth gradient law, so that the total reflection coefficient of the matching section is minimized.

[0018] According to a thin film matching load circuit provided by the present invention, the first gradient law is binomial, Chebyshev or exponential, the second gradient law is binomial, Chebyshev or exponential, the third gradient law is binomial, Chebyshev or exponential, and the fourth gradient law is binomial, Chebyshev or exponential.

[0019] According to a thin film matching load circuit provided by the present invention, the width of the microstrip line in the matching section is calculated by the following formula:

[0020]

[0021] Where Z0 is the impedance of the transmission line, ε re is the dielectric constant of the substrate, h is the thickness of the substrate, and W is the width of the microstrip line.

[0022] According to a thin film matching load circuit provided by the present invention, the width of the thin film resistor in the matching section is calculated by the following formula:

[0023] R=(L*ρ) / W1

[0024] Wherein, R is the resistance value of the thin film resistor, L is the length of the thin film resistor, ρ is the unit resistivity, and W1 is the width of the thin film resistor.

[0025] According to a thin film matching load circuit provided by the present invention, when the thin film matching load circuit is applied to a radio frequency system, when the radio frequency frequency of the radio frequency system is less than a second preset threshold, the size of the fan-shaped microstrip line is adjusted to achieve the impedance matching.

[0026] According to a thin film matching load circuit provided by the present invention, the impedance value required by the load is met by adjusting the sizes of the microstrip line and the thin film resistor in the matching section and the size of the fan-shaped microstrip line.

[0027] According to a thin film matching load circuit provided by the present invention, the substrate is ceramic aluminum oxide, and the bottom surface of the substrate is a copper clad layer.

[0028] The thin film matching load circuit provided by the present invention uses one or more matching sections including microstrip lines and thin film resistors for impedance matching between a load and a transmission line, and uses a fan-shaped microstrip line at the end of the matching section to be equivalent to a capacitor grounding process, which does not require physical connection grounding, thereby reducing the difficulty and cost of processing; it has a broadband, and as the number of matching sections increases, the bandwidth included in the thin film matching load becomes wider; the impedance value required by the terminal load can be met by changing the values ​​of the microstrip line and the thin film resistor, and the required matching impedance value can be well controlled, with strong adaptability and good stability; and the thin film circuit has high processing precision, and can be used in a waveguide as a matching load by means of a probe to achieve impedance matching at the waveguide load end, thereby improving the accuracy of impedance matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a schematic diagram of the structure of three common types of matching load circuits provided by the prior art;

[0031] Figure 2 It is a structural schematic diagram of a single-section matching section matching load in a thin film matching load circuit provided by the present invention;

[0032] Figure 3 It is a structural schematic diagram of a plurality of matching sections and matching loads in a thin film matching load circuit provided by the present invention;

[0033] Figure 4 It is a structural schematic diagram of a single-section impedance matching transformer in a thin film matching load circuit provided by the present invention;

[0034] Figure 5 It is a schematic diagram of the structure of a multi-section impedance matching transformer in a thin film matching load circuit provided by the present invention;

[0035] Figure 6 It is a schematic diagram of an equivalent circuit structure of a single-section matching section and a multi-section matching section in a thin film matching load circuit provided by the present invention;

[0036] Figure 7 It is a schematic diagram of simulation results of a single-section thin film matching load and a multi-section thin film matching load in the thin film matching load circuit provided by the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0039] Combine the following Figure 2 and Figure 3 A thin film matching load circuit of the present invention is described, comprising:

[0040] One or more matching sections, the multiple matching sections are connected in series, each matching section includes a microstrip line and a thin film resistor, the output end of the microstrip line in each matching section is connected to the input end of the thin film resistor, the output end of the thin film resistor of each matching section is connected to the input end of the microstrip line of the next matching section, and the matching section is used for impedance matching between a load and a transmission line;

[0041] A fan-out microstrip line, wherein the input end of the fan-out microstrip line is connected to the output end of the last matching section, and the fan-out microstrip line serves as an open-ended terminal line;

[0042] The matching section and the fan-shaped microstrip line are located on the upper surface of the substrate, and the fan-shaped microstrip line and the substrate are equivalent to a capacitor grounding process.

[0043] When a transmission line with impedance Z0 and length L is connected to a L When the load is 100%, the two form a network. At this time, the input impedance looking at this network will no longer be Z0 but Z in The load impedance is Z L , the impedance of the transmission line is Z0, and a suitable thin film matching load circuit is selected as an impedance transformer (impedance is Z1) to match the impedance between the load and the transmission line, thereby achieving signal transmission without reflection.

[0044] The matching section in the thin film matching load circuit includes a microstrip line and a thin film resistor to achieve the impedance matching value required by the load. The thin film resistor can use corrosion-resistant and stable materials such as tantalum nitride TaN. The matching section can be a single section or multiple sections, and the number of matching sections can be determined according to the relative bandwidth of the thin film matching load circuit design.

[0045] For an open-ended microstrip line, if the given frequency is f0, when the length of the open transmission line is less than a quarter wavelength, it exhibits capacitance and can be used as a capacitor. Its equivalent circuit impedance is Where ω is the angular frequency, L is the inductance of the inductor, and C is the inductance of the capacitor.

[0046] The last section of the fan-shaped microstrip line in the thin film matching load circuit can also serve as a terminal open line. The entire fan-shaped microstrip line and the substrate are equivalent to a capacitor grounding process. The larger the fan-shaped capacitor angle, the wider the bandwidth of the fan-shaped capacitor impedance Xc.

[0047] This embodiment uses one or more matching sections including microstrip lines and thin film resistors for impedance matching between loads and transmission lines. A fan-shaped microstrip line is used at the end of the matching section to be equivalent to a capacitor grounding process. Physical connection to grounding is not required, thereby reducing processing difficulty and cost. The embodiment has a wide bandwidth, and as the number of matching sections increases, the bandwidth included in the thin film matching load becomes wider. The impedance value required by the terminal load can be met by changing the values ​​of the microstrip line and the thin film resistor, and the required matching impedance value can be well controlled, with strong adaptability and good stability. In addition, the thin film circuit has high processing precision and can be used in a waveguide as a matching load through a probe to achieve impedance matching at the waveguide load end, thereby improving the accuracy of impedance matching.

[0048] Based on the above embodiment, the number of matching sections in this embodiment is determined according to the relative bandwidth of the thin film matching load circuit design;

[0049] In the case where the relative bandwidth is less than a first preset threshold, the matching section is a single section;

[0050] When the relative bandwidth is greater than or equal to the first preset threshold, the matching section is multiple sections.

[0051] Figure 2 and Figure 3 They are schematic diagrams of the structures of a single-section matching load and a plurality of matching-section matching loads in the thin-film matching load circuit provided by the present invention. Figure 2 and Figure 3 As shown, the matching section can be a single section or multiple sections.

[0052] When the relative bandwidth is less than the first preset threshold, it means that the relative bandwidth requirement of the design is not high, and a single matching section can be used to meet the impedance matching. When the relative bandwidth is greater than or equal to the first preset threshold, it means that the relative bandwidth of the design is relatively large, and multiple matching sections are required to meet the requirements. The first preset threshold is set based on experience. The specific number of matching sections can be further determined based on the relative bandwidth. The larger the relative bandwidth, the more matching sections there are, and the smaller the relative bandwidth, the fewer matching sections there are.

[0053] Figure 4 The schematic diagram of the structure of a single-section impedance matching transformer in a thin film matching load circuit provided by the present invention. For single-section impedance matching, the impedance matching achieved by the transformer is narrowband, and complete matching is achieved only at a single frequency point.

[0054] Figure 5 This is a schematic diagram of the structure of a multi-section impedance matching transformer in a thin film matching load circuit provided by the present invention. For a network with a relatively large impedance difference, that is, a broadband circuit, it is necessary to use Figure 5 The multiple impedance matching sections shown in the figure are used to achieve the transition from high impedance to low impedance, thereby achieving a broadband matching process.

[0055] This embodiment determines whether the matching section is a single section or multiple sections according to the relative bandwidth. In the case of multiple matching sections, the specific number of matching sections can be further determined according to the relative bandwidth. The larger the relative bandwidth, the greater the number of matching sections, so that the thin film matching load circuit has a bandwidth that can meet the needs.

[0056] Based on the above embodiment, the calculation formula of the relative bandwidth in this embodiment is as follows:

[0057]

[0058] Among them, Δf is the signal bandwidth of the design operating frequency, which is obtained by the difference between the highest end and the lowest end of the design operating frequency, f0 is the center frequency of the design operating frequency, and f m is the lowest operating frequency, Γ m is the reflection coefficient, Z0 is the impedance of the transmission line, Z L is the impedance of the load.

[0059] For single-section impedance matching, the reflection coefficient is calculated as:

[0060]

[0061] in, Z inis the input impedance seen from the matched transmission line, Z1 is the characteristic impedance of the film matched load circuit, Z0 is the impedance of the transmission line, that is, the real impedance value that the load is expected to match, and Z L is the impedance of the load and θ is the electrical length.

[0062] To achieve no reflection, the signal needs Γ = 0 (i.e. Z in =Z0). When the load impedance Z L When Z is not equal to Z0, signal reflection will occur. If a single or multiple matching sections are inserted between the load and the transmission line, the transformation between different impedances can be completed to obtain a good match. L is a real number), as long as the input impedance is matched, the device that realizes impedance transformation is called an impedance transformer.

[0063] For single-section impedance matching, if the impedances Z0 and Z1 and Z1 and Z L The discontinuity between is very small, then the above reflection coefficient calculation formula is transformed into:

[0064] Γ=Γ1+Γ2e -2jθ

[0065] The total reflection mainly comes from the initial discontinuity reflection Γ1 between Z0 and Z1 and the reflection between Z1 and Z L The first reflection of the discontinuity between Γ2e- 2jθ to decide.

[0066] According to the calculation formula of relative bandwidth, the relative bandwidth is related to the two impedances to be matched, and the impedance ratio Z L The larger / Z0 is, the smaller the relative bandwidth is. L The smaller / Z0 is, the larger the relative bandwidth is. For a network with a large impedance difference, that is, a broadband circuit, multiple matching sections are required to achieve it. The reflections of each matching section will experience multiple reflections and then be superimposed at Z0. The final total reflection coefficient can be approximated as:

[0067] Γ(θ)=Γ0+Γ1e -2jθ +Γ2e -4jθ +…+Γ N e -4jNθ

[0068] When Γ in Γ(θ) N When there are enough matching sections N, the formula can be approximated to any smooth function. Compared with single-section matching sections, multi-section matching sections are easier to achieve broadband. Matching sections are composed of microstrip lines and thin-film resistors, so the total number of matching sections N is the total number of microstrip lines and thin-film resistors added together.

[0069] This embodiment determines whether the matching section is a single section or multiple sections according to the relative bandwidth. In the case of multiple matching sections, the specific number of matching sections can be further determined according to the relative bandwidth. The larger the relative bandwidth, the greater the number of matching sections, so that the thin film matching load circuit has a bandwidth that can meet the needs.

[0070] On the basis of the above embodiments, in this embodiment, when there are multiple matching sections, the widths of the microstrip lines of the multiple matching sections satisfy the first gradient law and / or the lengths satisfy the second gradient law, and the widths of the thin film resistors of the multiple matching sections satisfy the third gradient law and / or the lengths satisfy the fourth gradient law, so that the total reflection coefficient of the matching section is minimized.

[0071] The optimal matching can be achieved by minimizing the total reflection coefficient Γ(θ) by making the width and / or length of the microstrip line in each matching section satisfy a certain gradient rule, and the width and / or length of the thin film resistor in each matching section satisfy a certain gradient rule.

[0072] In this embodiment, when there are multiple matching sections, the width and / or length of the microstrip line and the thin film resistor in each matching section are adjusted to meet a certain gradual change rule so that the total reflection coefficient Γ(θ) is minimized, thereby achieving optimal load matching.

[0073] Based on the above embodiments, in this embodiment, the first gradual change law is binomial, Chebyshev or exponential, the second gradual change law is binomial, Chebyshev or exponential, the third gradual change law is binomial, Chebyshev or exponential, and the fourth gradual change law is binomial, Chebyshev or exponential.

[0074] A binomial is a polynomial that contains only first-order power terms and constant terms, and is in the form of ax + b. A Chebyshev polynomial is a polynomial that contains a constant term and first-order power terms or more, and is in the form of a0 + a1x + a2x 2 +...+a n x n The exponential form is the power operation a n (a≠0), where a is the base and n is the exponent. The exponent is located in the upper right corner of the base. The power operation represents the multiplication of the exponential base.

[0075] The width and length of the matching section may satisfy the same or different gradual change rules, which is not specifically limited in this embodiment.

[0076] In this embodiment, when there are multiple matching sections, the width and / or length of the microstrip line and the thin film resistor in each matching section are adjusted to meet a certain gradual change rule so that the total reflection coefficient Γ(θ) is minimized, thereby achieving optimal load matching.

[0077] Based on the above embodiment, the width of the microstrip line in the matching section in this embodiment is calculated by the following formula:

[0078]

[0079] Where Z0 is the impedance of the transmission line, ε re is the dielectric constant of the substrate, h is the thickness of the substrate, and W is the width of the microstrip line.

[0080] The required impedance value can be roughly known according to the needs, and then the width of the microstrip line can be adjusted according to different impedance values. Regardless of the microstrip line with any impedance value, the width can be calculated by this formula.

[0081] Generally, the substrate thickness h is selected by processing, and there are a series of substrate thicknesses such as 0.128, 0.254, 0.508, etc. Secondly, the substrate material is selected according to the needs. Once the substrate material is determined, the dielectric constant ε re It will also be determined. At this time, when the characteristic impedance of the microstrip line is known, the width of the microstrip line can be inferred through the formula. Different characteristic impedances present different widths, and microstrip lines of different widths are connected to present a gradient.

[0082] Based on the above embodiment, the width of the thin film resistor in the matching section in this embodiment is calculated by the following formula:

[0083] R=(L*ρ) / W1

[0084] Wherein, R is the resistance value of the thin film resistor, L is the length of the thin film resistor, ρ is the unit resistivity, and W1 is the width of the thin film resistor.

[0085] This formula is a formula for calculating the size of a thin film resistor. ρ is the unit resistivity, which is generally selected as 50 ohms / square. L is the required length of the thin film resistor, which can be selected by yourself. Generally, a processing accuracy greater than 0.1mm is required. When the resistance value of the thin film resistor is determined, the width of the thin film resistor can be obtained through this formula. Thin film resistors of different widths are connected to present a gradient.

[0086] Based on the above embodiments, in this embodiment, when the thin film matching load circuit is applied to a radio frequency system, when the radio frequency frequency of the radio frequency system is less than a second preset threshold, the size of the fan-shaped microstrip line is adjusted to achieve the impedance matching.

[0087] The fan-shaped microstrip line is equivalent to a capacitor, and its impedance is When the RF frequency of the RF system is less than the second preset threshold, it means that the RF frequency is low, the capacitor will participate in matching, and the size of the fan-shaped microstrip line can be appropriately adjusted to achieve impedance matching to offset the parasitic inductance in the circuit. The second preset threshold is set based on experience.

[0088] Impedance matching can be achieved by changing the angle and length of the fan-shaped microstrip line. The angle of the fan-shaped microstrip line can initially be set to a 90-degree arc, and the length can be set to a quarter wavelength of the signal. The length and angle of the fan-shaped microstrip line can then be adjusted based on the impedance matching in the S parameter or Smith original diagram.

[0089] When the RF frequency of the RF system is greater than or equal to the second preset threshold, it means that the RF frequency is high (microwave / millimeter wave), the value of the angular frequency ω is large, and the impedance value of the capacitor will be small, so the entire fan-shaped microstrip line can be simply regarded as a process directly to the ground. Regardless of whether the RF frequency is high or low, the matching process is mainly participated by the microstrip line and the thin film resistor.

[0090] On the one hand, the fan-shaped microstrip line acts as an open-ended line, which is equivalent to a capacitor grounding process with the substrate. On the other hand, the bandwidth can be controlled by controlling the opening angle of the fan-shaped microstrip line. The fan-shaped microstrip line is equivalent to a capacitor. The larger the opening angle of the fan-shaped capacitor, the wider the bandwidth of the fan-shaped capacitor impedance.

[0091] In this embodiment, when the RF frequency is low, the fan-shaped capacitor will participate in the matching. By properly adjusting the dimensions of the fan-shaped microstrip line, such as length and angle, impedance matching can be achieved to offset the parasitic inductance in the circuit, thereby achieving precise impedance matching.

[0092] On the basis of the above embodiments, the impedance value required by the load in this embodiment is met by adjusting the size of the microstrip line and the thin film resistor in the matching section and the size of the fan-shaped microstrip line.

[0093] For example, the first section of the microstrip line is a standard 50 ohm microstrip line, and the impedance of each section of the microstrip line is Zx (x = 1, 3 ... N), which can be measured by the width W of each section of the microstrip line. i and length L i If the film resistance R i (i=2,4…M) is Z i , then from the input end, it can be simply viewed as the process of a single-section impedance matcher and a multi-section impedance matcher.

[0094] Figure 6 FIG. 1 is a schematic diagram of an equivalent circuit structure of a single-section matching section and a multi-section matching section in a thin film matching load circuit provided by the present invention. Figure 6As shown, when the matching section is a single section, the impedance of the microstrip line in the matching section is Z1, the impedance of the thin film resistor is Z2, and the fan-shaped microstrip line is equivalent to a capacitor C1.

[0095] In the case of multiple matching sections, Figure 6 There are three matching sections in the circuit. From the input end, the impedance of the microstrip line in the first matching section is Z1, and the impedance of the thin film resistor is Z2; the impedance of the microstrip line in the second matching section is Z3, and the impedance of the thin film resistor is Z4; the impedance of the microstrip line in the third matching section is Z3, and the impedance of the thin film resistor is Z4. The impedance value required by the load is met by adjusting the size (including length and width) of the microstrip line and the thin film resistor in each matching section and the size (angle and length) of the fan-shaped microstrip line.

[0096] The entire branch of the thin film matching load circuit is equivalent to a resistor grounding form. The purpose of making it into a matching load is to in The circuit impedance seen is equal to the expected matching real impedance value, achieving the role of matching load. There are other RF or microwave circuits in front of the thin film matching load circuit, which will have a real impedance value that needs to be matched, and the thin film matching load circuit is used to achieve the load impedance value expected by this RF or microwave circuit.

[0097] When the impedance difference between the transmission line and the load changes, the load matching can be achieved by changing the size of the microstrip line and the thin film resistor in the matching section and the size of the fan-shaped microstrip line. The electrical length θ is changed by changing the length of the microstrip line and the thin film resistor, and the impedance Z is changed by changing the width of the microstrip line and the thin film resistor.

[0098] The signal is output from the 50 ohm microstrip line, passes through multiple matching sections consisting of matching microstrip lines and thin film resistors, and finally passes through the fan-shaped microstrip line to achieve impedance matching. The required load impedance value is met by changing the size of the matching microstrip line, thin film resistor, and fan-shaped microstrip line. This technology is suitable for situations where load matching is required in passive devices of RF microwaves and is easy to integrate. And by changing the number of matching sections, the bandwidth can be easily expanded to cover a wider frequency band.

[0099] This embodiment can meet the impedance value required by the terminal load by changing the length and / or width of the microstrip line in the matching section, the length and / or width of the thin film resistor, and the length and angle of the fan-shaped microstrip line, so that the thin film matching load circuit can be flexibly adjusted according to the required matching impedance value to achieve load matching, and the number of matching sections can be adjusted according to the relative bandwidth, which can meet various matching impedance and bandwidth requirements, and has a wide range of applications, strong adaptability, and good stability.

[0100] On the basis of the above embodiments, the substrate in this embodiment is ceramic aluminum oxide (Al2O3), and the bottom surface of the substrate is a copper clad layer.

[0101] Alumina ceramic substrate is widely used in the RF microwave electronics industry as a substrate material. It has a high dielectric constant, which can make the circuit miniaturized. It has good thermal stability, small temperature drift, high substrate strength and chemical stability, and better performance than most other oxide materials. It can be used in various thick film circuits, thin film circuits, hybrid circuits and microwave component modules.

[0102] Alumina ceramic substrates can be used for circuit processing based on thin film photolithography technology, and its accuracy can reach the micron level. Many passive devices can be designed based on alumina ceramic substrates. Since its dielectric constant is higher than that of general PCB substrates, the designed device size is small, which has a very significant advantage in the development trend of miniaturization of various component modules. Alumina ceramic substrates play an important role in the development of microwave radio frequency.

[0103] Therefore, in this embodiment, ceramic aluminum oxide is selected as the substrate, and the grounding surface of the substrate is a copper clad layer.

[0104] Figure 7 It is a schematic diagram of simulation results of a single-section thin film matching load and a multi-section thin film matching load in the thin film matching load circuit provided by the present invention. Figure 7 (a) and Figure 7 (b) HFSS (High Frequency Structure Simulator) simulation results of single-section film matching load and multi-section matching load at 35 to 45 GHz. From the simulation results, it can be seen that when the input impedance is 50 ohms, the two matching loads achieve a good match, and the return loss of the multi-section matching load is better than that of the single-section matching load, proving that the multi-section impedance transformer mentioned above is easier to achieve broadband effect.

[0105] This embodiment uses one or more matching sections including microstrip lines and thin film resistors for impedance matching between loads and transmission lines. A fan-shaped microstrip line is used at the end of the matching section to be equivalent to a capacitor grounding process. Physical connection to grounding is not required, thereby reducing processing difficulty and cost. The embodiment has a wide bandwidth, and as the number of matching sections increases, the bandwidth included in the thin film matching load becomes wider. The impedance value required by the terminal load can be met by changing the values ​​of the microstrip line and the thin film resistor, and the required matching impedance value can be well controlled, with strong adaptability and good stability. In addition, the thin film circuit has high processing precision and can be used in a waveguide as a matching load through a probe to achieve impedance matching at the waveguide load end, thereby improving the accuracy of impedance matching.

[0106] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A thin film matching load circuit, characterized in that: include: One or more matching sections, the multiple matching sections are connected in series, each matching section includes a microstrip line and a thin film resistor, the output end of the microstrip line in each matching section is connected to the input end of the thin film resistor, the output end of the thin film resistor of each matching section is connected to the input end of the microstrip line of the next matching section, and the matching section is used for impedance matching between a load and a transmission line; A fan-out microstrip line, wherein the input end of the fan-out microstrip line is connected to the output end of the last matching section, and the fan-out microstrip line serves as an open-ended terminal line; The matching section and the fan-shaped microstrip line are located on the upper surface of the substrate, and the fan-shaped microstrip line and the substrate are equivalent to a capacitor grounding process.

2. The thin film matching load circuit according to claim 1, characterized in that: The number of matching sections is determined according to the relative bandwidth of the thin film matching load circuit design; In the case where the relative bandwidth is less than a first preset threshold, the matching section is a single section; When the relative bandwidth is greater than or equal to the first preset threshold, the matching section is multiple sections.

3. The thin film matching load circuit according to claim 2, characterized in that: The calculation formula of the relative bandwidth is as follows: Among them, Δf is the signal bandwidth of the design operating frequency, which is obtained by the difference between the highest end and the lowest end of the design operating frequency, f0 is the center frequency of the design operating frequency, and f m is the lowest operating frequency, Γ m is the reflection coefficient, Z0 is the impedance of the transmission line, Z L is the impedance of the load.

4. The thin film matching load circuit according to claim 1, characterized in that: In the case where there are multiple matching sections, the widths of the microstrip lines of the multiple matching sections satisfy the first gradient law and / or the lengths satisfy the second gradient law, and the widths of the thin film resistors of the multiple matching sections satisfy the third gradient law and / or the lengths satisfy the fourth gradient law, so that the total reflection coefficient of the matching section is minimized.

5. The thin film matching load circuit according to claim 4, characterized in that: The first gradual change law is binomial, Chebyshev or exponential, the second gradual change law is binomial, Chebyshev or exponential, the third gradual change law is binomial, Chebyshev or exponential, and the fourth gradual change law is binomial, Chebyshev or exponential.

6. The thin film matching load circuit according to claim 1, characterized in that: The width of the microstrip line in the matching section is calculated by the following formula: Where Z0 is the impedance of the transmission line, ε re is the dielectric constant of the substrate, h is the thickness of the substrate, and W is the width of the microstrip line.

7. The thin film matching load circuit according to claim 1, characterized in that: The width of the thin film resistor in the matching section is calculated by the following formula: R=(L*ρ) / W1 Wherein, R is the resistance value of the thin film resistor, L is the length of the thin film resistor, ρ is the unit resistivity, and W1 is the width of the thin film resistor.

8. The thin film matching load circuit according to claim 1, characterized in that: In the case where the thin film matching load circuit is applied to a radio frequency system, when the radio frequency frequency of the radio frequency system is less than a second preset threshold, the size of the fan-shaped microstrip line is adjusted to achieve the impedance matching.

9. The thin film matching load circuit according to any one of claims 1 to 8, characterized in that: The impedance value required by the load is met by adjusting the sizes of the microstrip line and the thin film resistor in the matching section and the size of the fan-shaped microstrip line.

10. The thin film matching load circuit according to any one of claims 1 to 8, characterized in that: The substrate is ceramic aluminum oxide, and the bottom surface of the substrate is a copper-clad layer.

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