CN115207647A - Estimation method of equivalent lumped parameter of antenna - Google Patents
Estimation method of equivalent lumped parameter of antenna Download PDFInfo
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- CN115207647A CN115207647A CN202110377736.0A CN202110377736A CN115207647A CN 115207647 A CN115207647 A CN 115207647A CN 202110377736 A CN202110377736 A CN 202110377736A CN 115207647 A CN115207647 A CN 115207647A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q23/00—Antennas with active circuits or circuit elements integrated within them or attached to them
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Abstract
The application discloses an estimation method of equivalent lumped parameters of an antenna, wherein the antenna works at a working angular frequency omega, the antenna comprises a positive input end and a negative input end, and an equivalent model of the antenna comprises: a capacitor is equivalently coupled between the positive input terminal of the antenna and the negative input terminal of the antenna; and a resistor and an inductor are equivalently connected in series between the positive input end of the antenna and the negative input end of the antenna, wherein the equivalent lumped parameters of the antenna comprise a capacitance value of the capacitor, a resistance value of the resistor and an inductance value of the inductor, and the method comprises: obtaining an impedance value of the antenna looking into the antenna from the positive input end and the negative input end of the antenna under the working angular frequency; and obtaining the resistance value according to the impedance value.
Description
Technical Field
The application belongs to the field of near field communication, and particularly relates to an antenna equivalent lumped parameter estimation method.
Background
When designing an antenna, such as a near field communication antenna, the problem of impedance matching between a chip and the antenna needs to be considered, and when the impedance is more matched, the lower the reflected signal generated when a signal enters the antenna from the chip, the higher the power output from the chip to the antenna, and the higher the efficiency. In order to achieve impedance matching, a matching network needs to be provided between the antenna and the chip, and values of devices in the matching network need to be tuned. The antenna together with the matching network may be referred to as an antenna network. According to the circuit principle, the network impedance of the antenna network changes along with the change of the signal source frequency, the network impedance of the antenna network is pure resistance at certain specific frequency points, the output power to the antenna network is the highest, and the radiation magnetic field of the antenna is the strongest. Tuning is to make the network impedance of the antenna network a pure resistance at the operating frequency.
In a general tuning method, values of each tuned device need to be calculated by using antenna equivalent lumped parameters, and therefore, the antenna equivalent lumped parameters need to be estimated before tuning. In addition, when calculating the antenna quality factor (Q value), the antenna equivalent lumped parameters also need to be used. Therefore, accurate antenna equivalent lumped parameters are a crucial premise for antenna design, when the antenna equivalent lumped parameters and actual values are input and output, the impedance matching effect of the designed antenna network is not as expected, and meanwhile, the difference between the actual Q value and the target Q value of the finally designed antenna is caused due to the estimation misalignment of the Q value of the antenna.
Therefore, how to accurately estimate the equivalent lumped parameters of the antenna has become one of the problems to be solved in the art.
Disclosure of Invention
One objective of the present application is to disclose a method for estimating equivalent lumped parameters of an antenna, so as to solve the above problems.
An embodiment of the present application discloses an estimation method of equivalent lumped parameters of an antenna, wherein the antenna operates at an operating angular frequency ω, the antenna includes a positive input end and a negative input end, and an equivalent model of the antenna includes: a capacitor is equivalently coupled between the positive input terminal of the antenna and the negative input terminal of the antenna; and a resistor and an inductor which are equivalently connected in series between the positive input end of the antenna and the negative input end of the antenna, wherein the equivalent lumped parameter of the antenna comprises a capacitance value C of the capacitor a Resistance value R of the resistor a And an inductance value L of the inductor a The method comprises the following steps: obtaining an impedance value Z of the antenna looking into the antenna from the positive input end and the negative input end of the antenna under a working angular frequency omega a (ii) a And according to the impedance value Z a To obtain a resistance value R a 。
By the antenna equivalent lumped parameter estimation method, more accurate antenna equivalent lumped parameters can be obtained, and further the accuracy of other estimation based on the antenna equivalent lumped parameters is improved, such as estimation of an antenna Q value and antenna tuning.
Drawings
Fig. 1 is a schematic diagram of an antenna.
Fig. 2 is a schematic diagram of an equivalent model of the antenna of fig. 1 represented by equivalent set total parameters.
Detailed Description
The following disclosure provides various embodiments or illustrations that can be used to implement various features of the disclosure. The embodiments of components and arrangements described below serve to simplify the present disclosure. It is to be understood that such descriptions are merely illustrative and are not intended to limit the present disclosure. For example, in the description that follows, forming a first feature on or over a second feature may include certain embodiments in which the first and second features are in direct contact with each other; and may also include embodiments in which additional elements are formed between the first and second features described above, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or characters in the various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Although numerical ranges and parameters setting forth the broad scope of the application are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain standard deviations found in their respective testing measurements. As used herein, "about" generally refers to actual values within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range. Alternatively, the term "about" indicates that the actual value falls within the acceptable standard error of the mean, subject to consideration by those of ordinary skill in the art to which this application pertains. It is understood that all ranges, amounts, values and percentages used herein (e.g., to describe amounts of materials, length of time, temperature, operating conditions, quantitative ratios, and the like) are modified by the term "about" in addition to the experimental examples or unless otherwise expressly stated. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, these numerical parameters are to be understood as meaning the number of significant digits and the number resulting from applying ordinary rounding techniques. Herein, numerical ranges are expressed from one end to the other or between the two ends; unless otherwise indicated, all numerical ranges set forth herein are inclusive of the endpoints.
Fig. 1 is a schematic diagram of an antenna 100. The antenna 100 may be coupled to a chip through a positive input terminal Ip and a negative input terminal In to achieve various applications, such as a Near Field Communication (NFC) chip (not shown), to implement an electronic device capable of supporting NFC, and implement applications such as NFC card consumption and NFC tag identification.
Taking the NFC application as an example, since the operating frequency of NFC is 13.56MHz, which corresponds to a wavelength of about 22m in vacuum, and for a common NFC antenna, the size of the antenna is much smaller than the wavelength, the NFC antenna can be equivalent to a lumped parameter to obtain an equivalent model, so as to facilitate analysis.
Fig. 2 is a schematic diagram of an equivalent model of the antenna 100 of fig. 1, which includes a capacitor 102, a resistor 104, and an inductor 106, represented by equivalent ensemble parameters. Wherein the capacitor 102 is equivalently coupled between the positive input terminal Ip of the antenna 100 and the negative input terminal In of the antenna 100; the resistor 104 and the inductor 106 are equivalently connected In series between the positive input end Ip of the antenna 100 and the negative input end In of the antenna 100, in other words, the resistor 104 and the inductor 106 are connected In parallel with the capacitor 102; wherein the capacitor 102 has a capacitance value C a The resistor 104 has a resistance value R a The inductor 106 has an inductance L a . The operating angular frequency ω is the angular frequency of the antenna 100 during operation, and its value depends on the application, for example, when applied to NFC, the operating angular frequency ω is 2 π 13.56 10 6 Radian/second.
Obtaining lumped parameters (capacitance C) of antenna 100 a Resistance value R a And inductance L a ) The premise is that a curve of the impedance of the antenna 100 changing with the frequency is obtained by an actual measurement or simulation method, and then the self-resonant angular frequency omega is obtained r And impedances at certain predetermined frequency points, and calculates lumped parameters of the antenna 100 based on the impedances at the certain predetermined frequency points. The impedance of the antenna 100 is specifically an impedance value looking into the antenna 100 from the positive input terminal Ip and the negative input terminal In of the antenna 100. In the actual measurement or simulation method, the actual measurement method may be, for example, directly inputting signals (including some of the preset frequency points) with different frequencies from a low frequency to a high frequency from a positive input end Ip of the actual antenna 100 and a negative input end In of the antenna 100 by using a vector network analyzer, and measuring a corresponding impedance value of the antenna, where when a pure resistance is measured for the first time, a corresponding angular frequency is a self-resonant frequency, taking the application to NFC as an example, and the self-resonant frequency is about 20MHz to 100MHz; the simulation method may be, for example, using a computing unit (e.g., a computer with simulation software) to input signals with different frequencies from low frequency to high frequency based on the structure, including shape, material, size, etc., of the antenna 100 shown in fig. 1, and simulate the impedance value of the antenna 100 to obtain the impedance at some predetermined frequency points of the self-resonant frequency.
The present application will describe three ways of estimating lumped parameters of the antenna 100 and comparing the accuracy thereof, wherein the most significant difference of the three ways is calculated by using different preset frequency points, and the details thereof are described below.
< method one >
In the first method, the preset frequency point is a low-frequency angular frequency omega 1 And self-resonant angular frequency ω r . At an angular frequency of 0 rad/sec, a low frequency angular frequency omega 1 And self-resonant angular frequency ω r In a relative relationship of (c), a low frequency angular frequency ω 1 Closer to 0 rad/sec, less close to the self-resonant angular frequency ω r . In the present embodiment, the low frequency angular frequency ω 1 Is 2 pi.10 6 Radian/second.
First, the self-resonant angular frequency ω r is obtained, and then the angular frequency ω r at the low frequency is obtained 1 And self-resonant angular frequency ω r The impedance of the antenna 100 at the bottom of the slot,having an impedance value of Z 1 And Z r . Then, the operation angular frequency omega and the low-frequency angular frequency omega can be only used 1 Self-resonant angular frequency omega r And an impedance value Z 1 And Z r Obtaining inductance L a Value of capacitance C a And a resistance value R a 。
Specifically, the impedance value Z may be first determined only by the impedance value Z 1 And low frequency angular frequency omega 1 Obtaining inductance value
Then only according to the inductance L a And self-resonant angular frequency ω 1 Obtaining the capacitance value
Then only according to the impedance value Z 1 Operating angular frequency omega, inductance value L a Impedance value Z r And self-resonant angular frequency omega 1 Obtaining the resistance value
Where im () and re () are the imaginary and real parts taken, respectively, on the complex numbers.
< method II >
In the second method, the preset frequency point is a low-frequency angular frequency ω 1 And an operating angular frequency ω. At an angular frequency of 0 rad/sec, a low frequency angular frequency omega 1 Low frequency angular frequency omega in relation to the operating angular frequency omega 1 Closer to 0 rad/sec, less close to the operating angular frequency ω. In the present embodiment, the low frequency angular frequency ω 1 Is 2 pi.10 6 Radian/second.
The second method firstly obtains the self-resonance angular frequency omega r And obtaining the angular frequency omega at low frequencies 1 And the impedance of the antenna 100 at the operating angular frequency omega, with respective values of Z 1 And Z a . Then, the operation angular frequency omega and the low frequency angular frequency omega can be only used 1 Self-resonant angular frequency omega r And an impedance value Z a Obtaining inductance L a Value of capacitance C a And a resistance value R a 。
Specifically, the impedance value Z may be first determined only by the impedance value Z 1 And low frequency angular frequency omega 1 Obtaining the inductance value
Then only according to the inductance L a And self-resonant angular frequency ω r Obtaining the capacitance value
Then only according to the impedance value Z a And a capacitance value C a Obtaining the resistance value
< method III >
In the third method, the preset frequency point only contains the working angular frequency ω.
Method three-step obtaining self-resonance angular frequency omega r And obtaining an impedance of the antenna 100 at the operating angular frequency ω, the impedance value of which is Z a . Then, the working angular frequency omega and the self-resonant angular frequency omega can be only used r And an impedance value Z a Obtaining the inductance L a Value of capacitance C a And a resistance value R a 。
Specifically, the resistance value R is derived based on circuit principles a ＝X(a 2 +b 2 ) In which
Wherein X = re (Z) a )，Y＝im(Z a ) (ii) a Inductance value
And the capacitance value
TABLE 1
Table 1 shows that for an NFC antenna, impedance values of the NFC antenna near working frequency points (13.56 MHz, 12.56MHz, and 14.56 MHz) are estimated by using the antenna equivalent models of the first method, the second method, and the third method, and the simulation result is provided in table 1 as a reference, and can be regarded as an ideal value.
Because the second method and the third method are used for calculating the resistance value R a The impedance value Z of the antenna under the working angular frequency omega is utilized a While the first method only utilizes the antenna at the low frequency angular frequency omega 1 And self-resonant angular frequency ω r Lower impedance value Z 1 And Z r In table 1, the impedance values near the working frequency points estimated by the antenna equivalent models of the second method and the third method are closer to ideal values. And the impedance value near the working frequency point estimated by using the antenna equivalent model of the first method has a larger difference with an ideal value.
And the second method is to calculate the inductance L a While still using the low angular frequency ω 1 Lower impedance value Z 1 However, according to the characteristics of the NFC antenna, the value of the inductance value at low frequency is larger than the value at the working frequency point, so that the imaginary part of the impedance value estimated by the antenna equivalent model using the second method is larger than the ideal value near the working frequency point, as shown in table 1.
The preset frequency point adopted by the third method only contains the working angular frequency omega, namely the low-frequency angular frequency omega is not used at all 1 Lower impedance value Z 1 Or self-resonant angular frequency omega r Lower impedance value Z r And estimating the equivalent lumped parameters of the antenna, so that the impedance value estimated by using the antenna equivalent model of the third method is very close to an ideal value no matter a real part or an imaginary part is near the working frequency point.
TABLE 2
TABLE 3
The difference from table 1 is that tables 2 and 3 are used to estimate impedance values of the NFC antenna near the operating frequency points (13.56 MHz, 12.56MHz, and 14.56 MHz) by using the antenna equivalent models of the method one, the method two, and the method three for the other two NFC antennas. Observing tables 2 and 3, results quite similar to those of table 1 can be obtained, i.e. method three is closest to the ideal value (simulated value) and method one is the most apart from the ideal value.
In general, in designing the antenna 100, it is necessary to consider the problem of impedance matching between the chip and the antenna 100, and when the impedance is more matched, the lower the reflected signal generated when the signal enters the antenna 100 from the chip, the higher the power output from the chip to the antenna 100, and the higher the efficiency. In order to achieve impedance matching, a matching network is further provided between the antenna 100 and the chip, and values of each device in the matching network are tuned, so that the antenna 100 and the matching network become an antenna network. According to the circuit principle, the network impedance of the antenna network changes along with the change of the signal source frequency, the network impedance of the antenna network is pure resistance at certain specific frequency points, the output power to the antenna network is the highest, and the radiation magnetic field of the antenna is the strongest. Tuning is to make the network impedance of the antenna network a pure resistance at the operating frequency.
In a general tuning method, values of each tuned device need to be calculated by using antenna equivalent lumped parameters, and therefore, the antenna equivalent lumped parameters need to be estimated before tuning. In addition, when calculating the Q value of the antenna, it is also necessary to use equivalent lumped parameters, such as the Q value of the antenna 100
Therefore, it can be known that accurate antenna equivalent lumped parameters are the crucial premise for the design of the antenna 100, when the antenna equivalent lumped parameters and actual values are input and output, the impedance matching effect of the designed antenna network is not as good as expected, and meanwhile, the estimation of the antenna Q value is misaligned, which results in the actual Q value and target of the finally designed antenna 100The Q value has a difference.
The application provides an estimation method of equivalent lumped parameters of the antenna, and different methods are compared. Not only can let the user know how to estimate antenna equivalent lumped parameter, more importantly, can also select more accurate mode to estimate antenna equivalent lumped parameter for antenna matching and antenna Q value calculation are more accurate, have reduced the cost of later stage debugging.
Although the above description and the accompanying drawings describe the calculation of equivalent lumped parameters of an antenna by taking a differential driving method with positive and negative input terminals as an example, those skilled in the art can determine that the method is also applicable to a single-ended driving method.
The foregoing description has set forth briefly the features of certain embodiments of the present application so that those skilled in the art may more fully appreciate the various aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should understand that they can still make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.
Claims (12)
1. A method for estimating equivalent lumped parameters of an antenna, wherein the antenna operates at an operating angular frequency ω, the antenna comprises a positive input terminal and a negative input terminal, and an equivalent model of the antenna comprises: a capacitor is equivalently coupled between the positive input terminal of the antenna and the negative input terminal of the antenna; and a resistor and an inductor which are equivalently connected in series between the positive input end of the antenna and the negative input end of the antenna, wherein the equivalent lumped parameter of the antenna comprises a capacitance value C of the capacitor a Resistance value R of said resistor a And inductance value L of the inductor a Characterized in that the method comprises:obtaining the antenna at the working angular frequency omega from the positive input end of the antenna and
impedance value Z of the negative input end looking into the antenna a (ii) a And
according to the impedance value Z a To obtain a resistance value R a 。
2. Method according to claim 1, characterized in that the impedance value Z is dependent on a Obtaining the resistance value R a Comprises the following steps:
obtaining a self-resonant angular frequency ω of the antenna r (ii) a And
according to the impedance value Z a The working angular frequency omega and the self-resonant angular frequency omega r Obtaining the resistance value R a 。
3. The method of claim 2, further comprising:
according to the impedance value Z a The working angular frequency omega and the self-resonant angular frequency omega r Obtaining the inductance value L a And the capacitance value C a 。
4. The method of claim 3, wherein the resistance value R is a ＝X(a 2 +b 2 ) In which
Wherein X is the impedance value Z a Y is the impedance value Z a An imaginary part of (c).
5. The method of claim 4, wherein the inductance value is
And the capacitance value
6. The method of claim 1, wherein said varying is dependent on said impedance value Z a Obtaining the resistance value R a Comprises the following steps:
obtaining the angular frequency omega of the antenna at the preset low frequency 1 The impedance value Z looking into the antenna from the positive input end and the negative input end of the antenna 1 Wherein the preset low-frequency angular frequency ω 1 Closer to 0 rad/sec, less close to the operating angular frequency;
obtaining the self-resonant angular frequency omega of the antenna r (ii) a And
according to the impedance value Z a The working angular frequency ω, the self-resonant angular frequency ω r The preset low-frequency angular frequency omega 1 And the impedance value Z 1 Obtaining the resistance value R a 。
7. Method according to claim 6, characterized in that the impedance value Z is dependent on a The working angular frequency ω, the self-resonant angular frequency ω r The preset low-frequency angular frequency omega 1 And the impedance value Z 1 Obtaining the resistance value R a Comprises the following steps:
according to the preset low-frequency angular frequency omega 1 And the impedance value Z 1 Obtaining said inductance value
According to the inductance value L a Obtaining the capacitance value
And
according to the impedance value Z a The operating angular frequency ω and the capacitance value C a Obtaining the resistance value
8. Method according to claim 6, characterized in that said preset low-frequency angular frequency ω is such that it is equal to ω 1 Is 2 pi.10 6 Radians/second.
9. Method according to claim 1, characterized in that the impedance value Z of the antenna looking into the antenna from the positive and negative input of the antenna at the operating angular frequency ω is obtained a Comprises the following steps:
measuring the impedance value Z by using a vector network analyzer a 。
10. Method according to claim 1, characterized in that the impedance value Z of the antenna looking into the antenna from the positive and negative input of the antenna at the operating angular frequency ω is obtained a Comprises the following steps:
performing a simulation with a computing unit to obtain the impedance value Z a 。
11. Method according to claim 6, characterized in that said antenna is obtained at said preset low angular frequency ω 1 The impedance value Z looking into the antenna from the positive input end and the negative input end of the antenna 1 Comprises the following steps:
measuring the impedance value Z by using a vector network analyzer 1 。
12. Method according to claim 6, characterized in that said antenna is obtained at said preset low frequency angular frequency ω 1 The impedance value Z looking into the antenna from the positive input end and the negative input end of the antenna 1 Comprises the following steps:
performing simulation by using a computing unit to obtain the impedance value Z 1 。
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| CN202110377736.0A CN115207647A (en) | 2021-04-08 | 2021-04-08 | Estimation method of equivalent lumped parameter of antenna |
| PCT/CN2021/137742 WO2022213650A1 (en) | 2021-04-08 | 2021-12-14 | Method for estimating equivalent lumped parameter of antenna |
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| WO2013011702A1 (en) * | 2011-07-20 | 2013-01-24 | 株式会社フジクラ | Antenna and wireless tag |
| CN103185838B (en) * | 2011-12-29 | 2016-06-15 | 国民技术股份有限公司 | A kind of method of measuring coil antenna match capacitance parameter |
| CN105958584A (en) * | 2016-06-02 | 2016-09-21 | 恒宝股份有限公司 | Wearable device integrated with wireless charging function, and charging method thereof |
| CN106130091A (en) * | 2016-06-02 | 2016-11-16 | 恒宝股份有限公司 | A kind of micro radio charger and method of work thereof |
| CN109873618A (en) * | 2019-04-10 | 2019-06-11 | 中国科学院上海微系统与信息技术研究所 | A kind of high-power lamped element power splitter with -45 ° of phase delay |
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