Ferrite film parameter characterization clamp and characterization method thereof

Abstract

The invention discloses a ferrite film parameter characterization clamp and characterization method, the characterization clamp comprises a transduction structure, a 50-ohm feeder line and a terminal matching, the transduction structure is composed of two parallel microstrip transmission lines, one end of each parallel microstrip transmission line is connected to a clamp test interface through the feeder line, and the other end of each parallel microstrip transmission line is connected to the clamp test interface. The other end of the transduction structure is connected with a terminal to be matched or connected to the clamp test interface through a feeder line; and the ferrite film to be tested covers the transduction structure. A vector network analyzer is used for testing to obtain an S parameter of a ferrite film load characterization clamp, and a de-embedding technology is combined to analyze transmission frequency band boundary frequency, phase delay and insertion loss of a two-port coupling structure of the ferrite film load, so as to characterize saturation susceptibility, film thickness and ferromagnetic resonance line width of the ferrite film. According to the method, the characterization clamp is used for characterizing three different key parameters of the ferrite film, so that the parameter characterization cost is remarkably reduced, and the characterization efficiency is greatly improved.

Description

Technical Field

[0001] This invention relates to the fields of microwave testing technology and magnetic technology, specifically to a ferrite thin film parameter characterization fixture and its characterization method. Background Technology

[0002] Ferrite thin film materials have been widely used in the research of microwave ferrite devices in recent years due to their excellent magnetic tunability and low loss characteristics. The dimensional and material parameters of ferrite thin films play a crucial role in the accuracy of simulation models and the performance of microwave ferrite devices, especially film thickness, saturation magnetic susceptibility, and ferromagnetic resonance linewidth. However, due to fluctuations in the fabrication process and the influence of the fabrication environment, the actual parameters of the prepared ferrite thin films often deviate from the preset values, thus requiring further parameter characterization. Traditional characterization methods suffer from problems such as limited characterization dimensions, complex processes, and expensive equipment, making it difficult to meet the demand for rapid and efficient parameter characterization. Therefore, there is an urgent need to develop low-cost, high-efficiency characterization methods to improve the design efficiency of microwave ferrite devices, further optimize device performance, and promote their large-scale application in next-generation wireless communication scenarios. Summary of the Invention

[0003] The purpose of this invention is to address the technical problems mentioned in the background section by providing a ferrite thin film parameter characterization fixture and its characterization method. This invention utilizes a magnetostatic wave transmission line characterization fixture to characterize ferrite thin films, specifically their saturation magnetic susceptibility, film thickness, and ferromagnetic resonance linewidth. This significantly reduces the cost of parameter characterization and improves characterization efficiency.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0005] A ferrite thin film parameter characterization fixture includes a transducer structure and an interface transmission circuit. The transducer structure consists of two parallel microstrip transmission lines. One end of the parallel microstrip transmission line is connected to the fixture test interface through the interface transmission circuit, and the other end is connected to a terminal match or connected to the fixture test interface through the interface transmission circuit. The ferrite thin film to be tested is covered on the transducer structure.

[0006] To optimize the technical solution, the following further improvements were made:

[0007] The interface transmission circuit is a feeder or matching network. The feeder is a 50-ohm feeder, and the terminal matching is an open-circuit stub.

[0008] A method for characterizing ferrite thin film parameters, which extracts ferrite thin film parameters using the aforementioned ferrite thin film parameter characterization fixture, specifically includes the following steps:

[0009] Step 1: Testing and de-embedding of ferrite thin film loaded transducer structure: A ferrite thin film is covered on the transducer structure to form a ferrite thin film loaded transducer structure. The S-parameters of the ferrite thin film loaded characterization fixture are measured by a vector network analyzer. The measured S-parameters of the ferrite thin film loaded characterization fixture are imported into the simulation platform to perform de-embedding processing, thus forming a ferrite thin film loaded transducer structure model.

[0010] Step 2: Modeling of the ferrite thin film load two-port coupling structure: Import the ferrite thin film load transducer structure model obtained by de-intercalation processing into the simulation platform to form the ferrite thin film load two-port coupling structure.

[0011] Step 3: By analyzing the upper and lower frequency limits of the transmission band of the ferrite thin film-loaded two-port coupled structure, the saturation magnetization of the ferrite thin film is characterized.

[0012] Step 4: Based on the saturation magnetic susceptibility of the ferrite thin film obtained in Step 3, analyze the phase delay of the ferrite thin film loaded two-port coupling structure and characterize the thickness of the ferrite thin film.

[0013] Step 5: Combining the saturation magnetic susceptibility of the ferrite film obtained in Step 3 and the film thickness obtained in Step 4, analyze the insertion loss of the ferrite film loaded two-port coupling structure and characterize the ferromagnetic resonance linewidth of the ferrite film.

[0014] In step one, the S-parameters of the fixture are characterized by measured parameters using a vector network analyzer, and the test S-parameters are de-embedded using the deembedsparams function in the Matlab platform to obtain the S-parameters of the ferrite thin film load transducer structure. The S-parameters are then imported into the Advanced Design System 2024 simulation platform to form a two-port coupling structure for the ferrite thin film load.

[0015] In step three, the upper and lower frequency limits of the transmission band of the ferrite thin film loaded two-port coupling structure under different bias magnetic fields are extracted in the Matlab platform. The saturation magnetic susceptibility of each set of upper and lower frequency limits is calculated using the Kittel formula, and the least squares method is used for fitting to characterize the saturation magnetic susceptibility of the ferrite thin film.

[0016] Kittel's formula is as follows:

[0017] (1)

[0018] (2)

[0019] in, and These are the upper and lower limits of the frequency, respectively. For bias magnetic field, It is the gyromagnetic ratio. denoted as saturation magnetic susceptibility of the ferrite thin film.

[0020] In step four, the phase delay of the ferrite thin film loaded with the two-port coupling structure is extracted on the Matlab platform. The phase delay is expanded and the initial phase is calibrated to 0 rad. The wave number of the magnetostatic surface wave is obtained by combining the spacing of the parallel microstrip transmission lines in the transducer structure. The obtained wave number and saturation magnetic susceptibility are substituted into the dispersion equation of the magnetostatic surface wave to solve for the thickness of the ferrite thin film.

[0021] The dispersion equation for a magnetostatic surface wave is as follows:

[0022] (3)

[0023] in, The wave number of a static magnetic surface wave. Where t is the thickness of the dielectric substrate, and t is the thickness of the ferrite thin film. and Let be the permeability of the thin film, where

[0024] (4)

[0025] in , , , For signal frequency, For bias magnetic field, It is the gyromagnetic ratio. denoted as saturation magnetic susceptibility of the ferrite thin film.

[0026] In step five, the bidirectional loss during excitation and the propagation delay during transmission of the ferrite film are calculated by combining the saturation magnetic susceptibility and the thickness of the ferrite film. The insertion loss of the ferrite film-loaded two-port coupled structure and the matching loss of its input port are extracted on the Matlab platform. The propagation loss of the ferrite film-loaded two-port coupled structure is obtained by calculating the above three losses. The ferromagnetic resonance linewidth of the ferrite film is then calculated by combining the propagation delay and the scaling factor.

[0027] The specific formula for calculating the ferromagnetic resonance linewidth of the ferrite thin film is as follows:

[0028] (5)

[0029] in, The ferromagnetic resonance linewidth of the ferrite thin film. This refers to the bidirectional loss during the excitation of a statically magnetized surface wave in a ferrite thin film-loaded two-port coupled structure. For transmission delay, The insertion loss of a ferrite thin film-loaded two-port coupled structure. 76.4 represents the matching loss at the input port and the proportional gain value.

[0030] Compared with the prior art, the present invention has the following significant advantages:

[0031] 1. This invention significantly improves the characterization efficiency of ferrite thin film saturation magnetic susceptibility, film thickness and ferromagnetic resonance linewidth by analyzing the transmission band boundary frequency, phase delay and insertion loss of the ferrite thin film loaded two-port coupling structure.

[0032] 2. Compared with traditional characterization methods that require specific fixtures to test specific parameters, this invention uses only one four-port parameter to characterize the fixture. Through S-parameter testing, three parameters can be characterized: saturation magnetic susceptibility of ferrite thin film, film thickness, and ferromagnetic resonance linewidth.

[0033] 3. In the characterization of ferromagnetic resonance linewidth, traditional methods require the use of high-power (> -10 dBm) radio frequency signals for parameter testing. The characterization method adopted in this invention only requires low-power (-30 dBm) radio frequency signals to achieve parameter characterization.

[0034] Characterization results show that the saturation magnetic susceptibility of the ferrite film is 1850 G, and the ferromagnetic resonance linewidth is between 0.8 Oe and 1.2 Oe in the 3-5 GHz range.

[0035] The thickness and saturation magnetic susceptibility of ferrite thin films do not change due to variations in operating conditions after film fabrication. Regarding the ferromagnetic resonance linewidth, it remains almost constant at lower operating frequencies (< 2.5 GHz), while at higher operating frequencies (> 2.5 GHz), it is proportional to the operating frequency. Attached Figure Description

[0036] Figure 1 Design of a jig for characterizing a magnetostatic wave transmission line for ferrite thin films, wherein (a) is a four-port form and (b) is a two-port form;

[0037] Figure 2 The insertion loss of a ferrite thin film-loaded two-port coupled structure under different bias magnetic fields;

[0038] Figure 3 The phase delay of the ferrite thin film-loaded two-port coupled structure under the above bias magnetic field;

[0039] Figure 4 The results represent the characterization of the ferrite film thickness.

[0040] Figure 5The characterization results are for the ferromagnetic resonance linewidth of ferrite thin films;

[0041] The attached diagrams are labeled as follows: 1. Transducer structure; 2. Feeder; 3. Ferrite thin film; 4. Terminal matching. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0043] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0044] like Figure 1 As shown, a parameter characterization fixture for ferrite thin films according to the present invention includes a transducer structure 1, a 50-ohm feed line 2, and a termination match 4. The transducer structure 1 is composed of two parallel microstrip transmission lines. One end of the parallel microstrip transmission line is connected to the fixture test interface through the feed line 2, and the other end is connected to the termination match 4 or connected to the fixture test interface through the feed line 2. The ferrite thin film 3 to be tested covers the transducer structure 1.

[0045] Feeder 2 can also be replaced with a matching network to perform impedance matching on the transducer structure.

[0046] The electromagnetic wave on the transducer structure 1 is converted into a static magnetic surface wave by the ferrite thin film 3 and transmitted from one microstrip transmission line to another.

[0047] The 50-ohm feeder 2 is a 90-degree bent microstrip line with a characteristic impedance of 50 ohms, used to connect the port of the transducer structure 1 and the fixture test interface.

[0048] Terminal matching 4 is an open-circuit stub used for impedance matching of the transducer structure in a two-port characterization fixture.

[0049] The present invention also provides a method for parameter characterization of ferrite thin films, comprising the following steps:

[0050] The parameter characterization process is as follows:

[0051] Testing and deintercalation of ferrite thin film loaded transducer structures: Testing: A 5-thickness transducer... A ferrite thin film with an area of ​​10 mm × 10 mm is applied to the transducer structure to form a ferrite thin film loaded transducer structure. The S-parameters of the ferrite thin film loaded characterization fixture are measured using a vector network analyzer. De-embedding: The deembedsparams function is used in the Matlab simulation platform to de-embedding the measured S-parameters of the ferrite thin film loaded characterization fixture, thus constructing a ferrite thin film loaded transducer structure model.

[0052] Modeling of ferrite thin film load two-port coupling structure: The ferrite thin film load transducer structure model obtained by de-intercalation is imported into the Advanced Design System (ADS) 2024 simulation platform to form a ferrite thin film load two-port coupling structure.

[0053] Saturation susceptibility characterization: Extraction of ferrite thin film loaded two-port coupled structure under different bias magnetic fields on the Matlab platform ( The upper and lower frequency limits of the transmission band were used to calculate the saturation magnetic susceptibility of each set of frequency limits using the Kittel formula, and the least squares method was used for fitting to characterize the saturation magnetic susceptibility of the ferrite thin film. The Kittel formula is as follows, where... It is the gyromagnetic ratio.

[0054] (1) (2)

[0055] Thin film thickness characterization: The phase delay of the ferrite thin film loaded two-port coupling structure was extracted on the Matlab platform. The phase delay was expanded and the initial phase was calibrated to 0 rad. The wave number of the magnetostatic surface wave was obtained by combining the spacing of the parallel microstrip transmission lines in the transducer structure. The obtained wavenumber and the characterized saturation magnetic susceptibility were substituted into the dispersion equation of the magnetostatic surface wave to solve for the thickness (t) of the ferrite film. The dispersion equation of the magnetostatic surface wave is as follows, where... and The magnetic permeability of the thin film is defined by the Polder tensor. The thickness of the dielectric substrate.

[0056] (3)

[0057] Ferromagnetic linewidth characterization: Combining the saturation magnetic susceptibility and film thickness obtained from the characterization, the bidirectional loss during excitation of static magnetic surface waves in a ferrite film-loaded two-port coupled structure is obtained by calculating the radiation impedance of the static magnetic surface waves. Meanwhile, by solving the dispersion equation (3), the propagation delay of the magnetostatic surface wave is obtained. The insertion loss of the ferrite thin film-loaded two-port coupled structure was extracted using the Matlab platform. Matching loss between its input port and its input port ( The propagation loss of the static magnetic surface wave in the two-port coupled structure with the ferrite thin film load is calculated using the above three loss methods. Combined with the propagation delay and the scaling factor (76.4), the ferromagnetic resonance linewidth of the ferrite thin film is calculated. The specific calculation formula is as follows: (4)

[0058] Figure 1 (a) in the figure represents the four-port formal parameter characterization of fixture design. Figure 1 (b) shows the design of a two-port form parameter characterization fixture. Both fixture types can be used for parameter characterization of ferrite thin films. Under a certain bias magnetic field, electromagnetic waves are input to the ferrite thin film load transducer structure via a 50-ohm feed line. The ferrite thin film converts the electromagnetic waves on the covered microstrip transmission line into magnetostatic surface waves (MSWs). The MSWs are then transmitted via the ferrite surface to another microstrip transmission line and converted back into electromagnetic waves. The MSWs cause changes in insertion loss and phase delay during excitation and transmission, which can be used for parameter characterization of ferrite thin films. Since the 50-ohm feed line introduces additional losses and phase delays, de-intercalation techniques are needed to improve the accuracy of characterization.

[0059] Figure 2 The values ​​represent the insertion loss of a ferrite thin film-loaded two-port coupled structure when the input signal power is -30 dBm and the bias magnetic field is 200 Oe, 400 Oe, and 600 Oe. Figure 3 This is the phase delay of the ferrite thin film-loaded two-port coupled structure under the above test conditions. From Figure 2 As can be seen, the frequency response of the ferrite thin film-loaded two-port coupled structure under a bias magnetic field exhibits a transmission band, which corresponds to the operating band of the magnetostatic surface wave. As the bias magnetic field increases, the transmission band and its upper and lower limits also increase. Using multiple sets of upper and lower limits of the transmission band varying with the bias magnetic field strength, the saturation magnetization of the ferrite thin film can be fitted to be 1850 G. Figure 3 As can be seen, the phase delay of the ferrite thin film-loaded two-port coupling structure corresponds to the phase delay of the static magnetic surface wave, which is much greater than the phase delay of the electromagnetic wave at the same frequency.

[0060] Figure 4This is the characterization result of the ferrite film thickness. With an input signal power of -30 dBm and a bias magnetic field of 600 Oe, the phase delay of the ferrite film-loaded two-port coupled structure (e.g., ...) is extracted. Figure 3 As shown), the wavenumber of the magnetostatic surface wave under the current test environment was obtained by combining the spacing (4 mm) of the parallel microstrip transmission lines in the transducer structure. The obtained wavenumber and the characterized saturation magnetic susceptibility were substituted into the dispersion equation of the magnetostatic surface wave to solve for the thickness of the ferrite film, which is 5 mm. m matches the actual size parameters of the thin film.

[0061] Figure 5 These are the characterization results of the ferromagnetic resonance linewidth of the ferrite thin film. With an input signal power of -30 dBm, the bias magnetic field was adjusted from 100 Oe to 1100 Oe, and the ferromagnetic resonance linewidth was characterized every 100 Oe interval. The ferromagnetic resonance frequency of the ferrite thin film is proportional to the strength of the bias magnetic field. Observations of the characterization results show that when the ferromagnetic resonance frequency is low (<2.5 GHz), the ferromagnetic resonance linewidth remains almost unchanged; when the ferromagnetic resonance frequency is high (>2.5 GHz), the ferromagnetic resonance linewidth is proportional to the frequency. This result is consistent with the ferromagnetic resonance linewidth measured using conventional methods.

[0062] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A ferrite thin film parameter characterization fixture, characterized in that, It includes a transducer structure (1) and an interface transmission circuit. The transducer structure (1) consists of two parallel microstrip transmission lines. One end of the parallel microstrip transmission line is connected to the fixture test interface through the interface transmission circuit, and the other end is connected to the terminal matching (4) or connected to the fixture test interface through the interface transmission circuit. The ferrite film (3) to be tested is covered on the transducer structure (1).

2. The ferrite thin film parameter characterization fixture according to claim 1, characterized in that, The interface transmission circuit is a feeder (2) or a matching network. The feeder (2) is a 50-ohm feeder, and the terminal matching (4) is an open-circuit stub.

3. A method for characterizing parameters of ferrite thin films, characterized by: The extraction of ferrite film parameters using the ferrite film parameter characterization fixture as described in claim 1 or 2 specifically includes the following steps: Step 1: Testing and de-embedding of ferrite thin film loaded transducer structure: The ferrite thin film (3) is covered on the transducer structure (1) to form a ferrite thin film loaded transducer structure. The S-parameters of the ferrite thin film load characterization fixture are measured by a vector network analyzer and imported into the simulation platform to perform de-embedding processing on the measured S-parameters of the ferrite thin film load characterization fixture to form a ferrite thin film loaded transducer structure model. Step 2: Modeling of the ferrite thin film load two-port coupling structure: Import the ferrite thin film load transducer structure model obtained by de-intercalation processing into the simulation platform to form the ferrite thin film load two-port coupling structure. Step 3: By analyzing the upper and lower frequency limits of the transmission band of the ferrite thin film-loaded two-port coupled structure, the saturation magnetization of the ferrite thin film is characterized. Step 4: Based on the saturation magnetic susceptibility of the ferrite thin film obtained in Step 3, analyze the phase delay of the ferrite thin film loaded two-port coupling structure and characterize the thickness of the ferrite thin film. Step 5: Combining the saturation magnetic susceptibility of the ferrite film obtained in Step 3 and the film thickness obtained in Step 4, analyze the insertion loss of the ferrite film loaded two-port coupling structure and characterize the ferromagnetic resonance linewidth of the ferrite film.

4. The method for characterizing ferrite thin film parameters according to claim 3, characterized in that: In step one, the S-parameters of the fixture are characterized by measured parameters using a vector network analyzer, and the test S-parameters are de-embedded using the deembedsparams function in the Matlab platform to obtain the S-parameters of the ferrite thin film load transducer structure. The parameters are then imported into the Advanced DesignSystem 2024 simulation platform to form a two-port coupling structure for the ferrite thin film load.

5. The method for characterizing ferrite thin film parameters according to claim 3, characterized in that: In step three, the upper and lower frequency limits of the transmission band of the ferrite thin film loaded two-port coupling structure under different bias magnetic fields are extracted in the Matlab platform. The saturation magnetic susceptibility of each set of upper and lower frequency limits is calculated using the Kittel formula, and the least squares method is used for fitting to characterize the saturation magnetic susceptibility of the ferrite thin film.

6. The method for characterizing ferrite thin film parameters according to claim 4, characterized in that: Kittel's formula is as follows: (1) (2) in, and These are the upper and lower limits of the frequency, respectively. For bias magnetic field, It is the gyromagnetic ratio. denoted as saturation magnetic susceptibility of the ferrite thin film.

7. The method for characterizing ferrite thin film parameters according to claim 4, characterized in that: In step four, the phase delay of the ferrite thin film loaded with the two-port coupling structure is extracted on the Matlab platform. The phase delay is expanded and the initial phase is calibrated to 0 rad. The wave number of the magnetostatic surface wave is obtained by combining the spacing of the parallel microstrip transmission lines in the transducer structure. The obtained wave number and saturation magnetic susceptibility are substituted into the dispersion equation of the magnetostatic surface wave to solve for the thickness of the ferrite thin film.

8. The method for characterizing ferrite thin film parameters according to claim 7, characterized in that: The dispersion equation for a magnetostatic surface wave is as follows: (3) in, The wave number of a static magnetic surface wave. Where t is the thickness of the dielectric substrate, and t is the thickness of the ferrite thin film. and Let be the permeability of the thin film, where (4) in , , , For signal frequency, For bias magnetic field, It is the gyromagnetic ratio. denoted as saturation magnetic susceptibility of the ferrite thin film.

9. The method for characterizing ferrite thin film parameters according to claim 4, characterized in that: In step five, the bidirectional loss during excitation and the propagation delay during transmission of the ferrite film are calculated by combining the saturation magnetic susceptibility and the thickness of the ferrite film. The insertion loss of the ferrite film-loaded two-port coupled structure and the matching loss of its input port are extracted on the Matlab platform. The propagation loss of the ferrite film-loaded two-port coupled structure is obtained by calculating the above three losses. The ferromagnetic resonance linewidth of the ferrite film is then calculated by combining the propagation delay and the scaling factor.

10. The method for characterizing ferrite thin film parameters according to claim 9, characterized in that: The specific formula for calculating the ferromagnetic resonance linewidth of the ferrite thin film is as follows: (5) in, The ferromagnetic resonance linewidth of the ferrite thin film. This refers to the bidirectional loss during the excitation of a statically magnetized surface wave in a ferrite thin film-loaded two-port coupled structure. For transmission delay, The insertion loss of a ferrite thin film-loaded two-port coupled structure. 76.4 represents the matching loss at the input port and the proportional gain value.

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