CN115149234A - Transmission line structure and transmission line design method - Google Patents
Transmission line structure and transmission line design method Download PDFInfo
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- CN115149234A CN115149234A CN202211068328.8A CN202211068328A CN115149234A CN 115149234 A CN115149234 A CN 115149234A CN 202211068328 A CN202211068328 A CN 202211068328A CN 115149234 A CN115149234 A CN 115149234A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P3/00—Waveguides; Transmission lines of the waveguide type
- H01P3/02—Waveguides; Transmission lines of the waveguide type with two longitudinal conductors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P3/00—Waveguides; Transmission lines of the waveguide type
- H01P3/02—Waveguides; Transmission lines of the waveguide type with two longitudinal conductors
- H01P3/08—Microstrips; Strip lines
- H01P3/081—Microstriplines
Abstract
The invention provides a transmission line structure and a transmission line design method, comprising a transmission line unit, wherein the transmission line unit comprises a first inductor, a second inductor, a first capacitor and a second capacitor; two ends of the first inductor are respectively used as a positive phase input end and a positive phase output end of the transmission line unit; two ends of the second inductor are respectively used as an inverted input end and an inverted output end of the transmission line unit; two ends of the first capacitor are respectively connected with the positive phase input end and the negative phase output end of the transmission line unit; two ends of the second capacitor are respectively connected with the inverting input end and the non-inverting output end of the transmission line unit. The invention has high-pass characteristic in insertion loss, smaller loss, small change of the insertion loss along with the increase of frequency and slow change of the phase along with the increase of frequency; the application range of the functional device realized based on the quarter-wavelength transmission line can be effectively widened; the circuit can be realized through a group of inductors and a group of capacitors, and has the advantages of simple structure, small size and wide working bandwidth.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a transmission line structure and a transmission line design method.
Background
In recent years, with the development of communication technology, microwave and millimeter wave circuits have been developed. The transmission line is one of the most basic circuit elements, and can replace the capacitance required in the circuit besides realizing the inductance characteristic; the transmission line has a very rich realization form, and the simplest transmission line structure can be realized only by one layer of medium and one layer of metal, so the transmission line is widely applied to the design of a radio frequency circuit.
Besides the common replacement of inductance and capacitance devices, many functional circuits based on microstrip line structures have been developed, such as wilkinson power divider, quarter-wavelength impedance transformer, microstrip annular bridge, branch line type power divider, etc., and these functional devices are all implemented based on quarter-wavelength transmission lines. The working bandwidths of the functional circuits are directly related to the phase of the transmission line, while the traditional transmission line is a broadband low-pass structure, and the phase and the working frequency of the traditional transmission line have a linear relation, so that the bandwidths of the functional circuits are directly limited, and the application of the functional circuits is limited to a certain extent. In addition, since the transmission line is a broadband low-pass filter structure, the insertion loss increases with the increase of frequency, which is more obvious especially in a silicon-based integrated circuit with large loss, which causes difficulty in designing the circuit to some extent. Although the operating bandwidth of the circuit can be improved by an improvement in the circuit configuration, such as the use of the multi-node wilkinson configuration, this is accompanied by an increase in the circuit size and an increase in the loss. Therefore, it is important to develop microstrip circuits to find a transmission line structure that can realize broadband, low loss, and small size (especially, quarter wavelength).
It should be noted that the above background description is only for the convenience of clear and complete description of the technical solutions of the present application and for the understanding of those skilled in the art. Such solutions are not considered to be known to the person skilled in the art merely because they have been set forth in the background section of the present application.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a transmission line structure and a transmission line design method, which are used to solve the problems of narrow bandwidth, high loss, large size, etc. of the transmission line in the prior art.
To achieve the above and other related objects, the present invention provides a transmission line structure, comprising:
the transmission line unit comprises a first inductor, a second inductor, a first capacitor and a second capacitor;
one end of the first inductor is used as a positive phase input end of the transmission line unit, and the other end of the first inductor is used as a positive phase output end of the transmission line unit; one end of the second inductor is used as an inverting input end of the transmission line unit, and the other end of the second inductor is used as an inverting output end of the transmission line unit; one end of the first capacitor is connected with the positive phase input end of the transmission line unit, and the other end of the first capacitor is connected with the negative phase output end of the transmission line unit; one end of the second capacitor is connected with the inverting input end of the transmission line unit, and the other end of the second capacitor is connected with the non-inverting output end of the transmission line unit.
Optionally, the inductance values of the first inductor and the second inductor are the same.
Optionally, the capacitance values of the first capacitor and the second capacitor are the same.
Optionally, the transmission line structure implements a quarter-wavelength transmission line characteristic.
More optionally, the transmission line structure is composed of at least two transmission line units, each transmission line unit is cascaded in sequence, and the characteristic impedances of the transmission line units are the same.
To achieve the above and other related objects, the present invention provides a transmission line design method, which at least includes:
1) Determining target characteristic impedance, target phase and target working frequency of the transmission line structure according to requirements;
2) Acquiring the transmission line structure, and acquiring initial values of all inductors and all capacitors in the transmission line structure;
3) Respectively adjusting parameters of each inductor and each capacitor in the transmission line structure so as to enable the characteristic impedance of the transmission line structure to reach a target characteristic impedance at a target working frequency and enable the phase of the transmission line structure to reach a target phase; at the moment, the parameters of each inductor and each capacitor of the transmission line structure are design values;
4) And obtaining each inductor and each capacitor with the design values, and building the transmission line structure.
Optionally, the method for obtaining the initial values of the inductors and the capacitors includes:
21a) Obtaining inductance values of all inductors and capacitance values of all capacitors when the transmission line structure has target characteristic impedance characteristics according to a Smith chart;
22a) Obtaining the phase of the transmission line structure under the target working frequency by scaling the inductance value of each inductor and/or the capacitance value of each capacitor;
23c) The inductance value of each inductor is used as the initial value of the corresponding inductor, and the capacitance value of each capacitor is used as the initial value of the corresponding capacitor.
Optionally, when the inductance values of the inductors and the capacitance values of the capacitors in the transmission line structure are the same, the method for obtaining the initial values of the inductors and the capacitors includes:
21b) Calculating inductance values of inductors and capacitance values of capacitors in the third-order low-pass filter based on a design principle of the third-order low-pass filter, so that the third-order low-pass filter has target characteristic impedance and phases under target working frequency;
22b) And taking the inductance value of the inductor in the third-order low-pass filter as the initial value of the inductor in the transmission line structure, and taking the capacitance value of the capacitor in the third-order low-pass filter as the initial value of the capacitor in the transmission line structure.
Optionally, the method for adjusting the parameters of each inductor and each capacitor in step 3) includes:
31 Adjusting the inductance value of each inductor and/or the capacitance value of each capacitor in the transmission line structure according to the Smith chart to obtain the transmission line structure with target characteristic impedance characteristics;
32 Obtaining a phase at a target operating frequency by scaling an inductance value of the inductor and/or a capacitance value of the capacitor;
33 Completing parameter adjustment if the characteristic impedance of the transmission line structure reaches a target characteristic impedance and the phase of the transmission line structure reaches a target phase; otherwise, returning to step 31) until the characteristic impedance of the transmission line structure reaches the target characteristic impedance and the phase of the transmission line structure reaches the target phase.
More optionally, the target phase is 90 ° ± 10 °.
As described above, the transmission line structure and the transmission line design method of the present invention have the following advantages:
1. the transmission line structure of the invention has high-pass characteristic in insertion loss, has smaller loss, and the insertion loss does not change greatly along with the increase of frequency; and the phase change becomes slower as the frequency increases, so that a more broadband quarter-wave transmission line characteristic can be realized. The application range of functional devices (including but not limited to Wilkinson power dividers, quarter-wavelength impedance converters, microstrip annular bridges and branch line type power dividers) realized based on quarter-wavelength transmission lines can be effectively expanded.
2. The transmission line structure can be realized through a group of inductors and a group of capacitors, and has the advantages of simple structure, small size and wide working bandwidth.
Drawings
Fig. 1 is a schematic diagram of a transmission line structure according to the present invention.
Fig. 2 is a schematic diagram showing an equivalent circuit of a third-order low-pass filter.
Fig. 3 is a schematic diagram of a quarter-wave transmission line structure according to the present invention.
Fig. 4 is a schematic diagram of an artificial transmission line with a fifth-order lumped structure.
Fig. 5 is a schematic diagram showing a comparison of insertion loss performance of the transmission line structures of fig. 3 and 4.
Fig. 6 is a diagram showing a comparison of simulation results of phase shift characteristics of the two structures of fig. 3 and 4.
Fig. 7 is a diagram showing a comparison of simulation results of reflectance characteristics of the two structures of fig. 3 and 4.
Fig. 8 shows another schematic diagram of the transmission line structure of the present invention.
Description of the element reference numerals
1-transmission line structure; 11-a transmission line element; 11 a-first transmission line unit; 11 b-a second transmission line element; 11 c-third transmission line element.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1 to 8. It should be noted that the drawings provided in this embodiment are only for schematically illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings and not drawn according to the number, shape and size of the components in actual implementation, and the form, quantity and proportion of each component in actual implementation may be arbitrarily changed, and the component layout may be more complicated.
The traditional transmission line structure is mainly realized in a distributed mode, and the simplest transmission line structure can be realized by using a signal line, a reference ground plane and a medium. The transmission line has simple structure and stable performance, and is widely applied to the design of microwave and millimeter wave circuits. The transmission line characteristics are similar to an ultra-wideband low-pass filter, with the phase increasing linearly with frequency and linearly with the length of the transmission line, and the loss increasing with frequency and with the length of the transmission line. With the development of rf circuits, many miniaturization techniques have been developed, and one development is to replace the transmission line structure with a few lumped elements, which can greatly reduce the size of the transmission line. Meanwhile, in many process scenarios, especially in the integrated process on a silicon substrate, the loss of the transmission line increases rapidly with the frequency, so methods for reducing the loss of the transmission line have been developed, for example, the size of the transmission line can be reduced while the loss of the transmission line is reduced by using a slow-wave structure.
Although transmission line theory has been developed for many years, there are few structures capable of realizing broadband phase characteristics, and especially in application scenarios with requirements on transmission line phase, such as application of quarter-wavelength transmission line, it is necessary to keep the phase of the transmission line at about 90 ° to realize specific functions, so the characteristic that the phase of the transmission line increases linearly with frequency directly limits the bandwidth of the function, and although the bandwidth can be increased by cascading multiple sections of functional devices or other ways, the loss and the structure complexity increase are accompanied therewith, which greatly increases the cost and the development difficulty.
The invention provides a transmission line structure which is wide in bandwidth, small in size and suitable for a quarter-wavelength transmission line, and can well solve the problems.
Example one
As shown in fig. 1 to 7, the present embodiment provides a transmission line structure 1, where the transmission line structure 1 includes:
the transmission line unit 11 includes a first inductor ind1, a second inductor ind2, a first capacitor cap1, and a second capacitor cap2. In this embodiment, the transmission line structure 1 realizes a 90 ° phase shift at a target characteristic impedance, so as to obtain a quarter-wavelength transmission line. In practical use, the phase of the transmission line structure 1 can be set as required to obtain a transmission line with a corresponding wavelength, which is not described herein again.
Specifically, as shown in fig. 1, one end of the first inductor ind1 serves as a positive-phase input end of the transmission line unit 11, and the other end serves as a positive-phase output end of the transmission line unit 11; one end of the second inductor ind2 serves as an inverting input terminal of the transmission line unit 11, and the other end serves as an inverting output terminal of the transmission line unit 11. The first capacitor cap1 is cross-connected with the second capacitor cap 2; one end of the first capacitor cap1 is connected to the positive-phase input end of the transmission line unit 11, and the other end is connected to the negative-phase output end of the transmission line unit 11; one end of the second capacitor cap2 is connected to the inverting input terminal of the transmission line unit 11, and the other end is connected to the non-inverting output terminal of the transmission line unit 11. The positive phase input end of the transmission line unit 11 is used as the positive phase input end IP of the transmission line structure 1, the negative phase input end of the transmission line unit 11 is used as the negative phase input end IN of the transmission line structure 1, and the positive phase input end IP and the negative phase input end IN of the transmission line structure 1 are differential ports. The positive phase output end of the transmission line unit 11 is used as the positive phase output end OP of the transmission line structure 1, the negative phase output end of the transmission line unit 11 is used as the negative phase output end ON of the transmission line structure 1, and the positive phase output end OP and the negative phase output end ON of the transmission line structure 1 are differential ports.
Specifically, in this embodiment, the inductance values of the first inductance ind1 and the second inductance ind2 are the same; the capacitance values of the first capacitor cap1 and the second capacitor cap2 are the same; as an example, the input port and the output port of the transmission line structure 1 have symmetry. In practical use, the inductance values of the first inductor ind1 and the second inductor ind2 may be different, and the capacitance values of the first capacitor cap1 and the second capacitor cap2 may also be different, so as to further improve the required performance by properly introducing asymmetry, which is not described herein again.
The transmission line structure 1 of the present embodiment can realize a broadband miniaturized quarter-wavelength transmission line only by using a pair of inductors and a pair of capacitors, and has a simple structure.
The present embodiment further provides a transmission line design method, which determines device parameters of the transmission line structure 1 of the present embodiment. The transmission line design method comprises the following steps:
1) And determining the target characteristic impedance, the target phase and the target working frequency of the transmission line structure according to requirements.
Specifically, the target characteristic impedance of the transmission line structure is set based on different application scenarios, mainly for achieving impedance matching.
Specifically, the phase of the transmission line structure determines the bandwidth, so that the target phase of the transmission line structure 1 can be determined according to the relative bandwidth requirement, in this embodiment, in order to implement a quarter-wavelength transmission line, the target phase is set to be about 90 °, and as an example, the target phase is located in a range of 90 ° ± 10 °, including but not limited to a left-right deviation ± 5 °, ± 10 °, ± 15 ° with 90 ° as a middle value, which is not described herein again.
Specifically, the target operating frequency of the transmission line structure and the center frequency point of the target operating frequency are set based on actual application requirements.
2) And acquiring initial values of all inductors and all capacitors in the transmission line structure.
As an implementation manner of this embodiment, the method for obtaining the initial values of the inductors and the capacitors in the transmission line structure 1 includes:
21a) The inductance values of the inductors and the capacitance values of the capacitors with the target characteristic impedance characteristics are obtained according to the Smith chart based on the transmission line structure 1.
Specifically, the smith chart is a calculated graph obtained by plotting a normalized input impedance equivalent circle family on a reflection system dispersion plane, and is mainly used for impedance matching of a transmission line; the Smith chart is composed of three circle systems, so as to avoid complicated operation and obtain the target characteristic impedance. When the target characteristic impedance is met, each inductor and each capacitor in the transmission line structure 1 have corresponding values, and the inductance values of the inductors can be set to be the same or different according to requirements; similarly, the capacitance values of the capacitors can be set to be the same or different according to needs.
22a) And obtaining the phase of the transmission line structure 1 under the target working frequency by scaling the inductance value of each inductor and/or the capacitance value of each capacitor.
Specifically, in this example, the coarse relationship based on the linear frequency response is scaled on the basis of the inductance and capacitance values obtained in step 21 a); the scaling ratios of the inductors and the capacitors can be the same or different, and are set according to actual requirements.
23a) And taking the inductance value of each inductor as an initial value of the corresponding inductor, and taking the capacitance value of each capacitor as an initial value of the corresponding capacitor.
Specifically, the inductance and capacitance values obtained in step 22 a) are used as initial values of the corresponding devices.
As another implementation manner of this embodiment, when the inductance values of the inductors in the transmission line structure are the same and the capacitance values of the capacitors are the same, the method for obtaining the initial values of the inductors and the capacitors in the transmission line structure 1 includes:
21b) And calculating the inductance value of an inductor and the capacitance value of a capacitor in the third-order low-pass filter based on the design principle of the third-order low-pass filter, so that the third-order low-pass filter has target characteristic impedance and a phase at a target working frequency.
Specifically, as shown in fig. 2, the equivalent circuit of a common third-order LC low-pass filter is shown, in which the inductance of the two inductors is L 1 The capacitance value of the two-terminal capacitor is C 1 The capacitance value of the capacitor at the intermediate node is 2C 1 Establishing a relation between inductance values and capacitance values of the inductors and phase, characteristic impedance and frequency, and satisfying the following formula as an example:
where θ is the target phase, Z 0 F is a target characteristic impedance and a target working frequency; and corresponding the target phase, the target characteristic impedance and the target working frequency to the above formula to obtain each inductance value and each capacitance value in the third-order low-pass filter.
22b) And taking the inductance value of the inductor in the third-order low-pass filter as an initial value of the inductor in the transmission line structure, and taking the capacitance value of the capacitor in the third-order low-pass filter as an initial value of the capacitor in the transmission line structure.
Specifically, the inductance and capacitance values obtained in step 22 b) are used as initial values of corresponding devices in the transmission line structure 1.
It should be noted that initial values of each inductor and each capacitor in the transmission line structure 1 may also be set at will, and at this time, the workload of adjusting parameters of each inductor and each capacitor in step 3) is relatively large, so that two ways of determining the initial values in the present invention may limit an approximate range, and further reduce the workload in step 3).
3) Respectively adjusting parameters of each inductor and each capacitor in the transmission line structure 1, so that the characteristic impedance of the transmission line structure 1 reaches a target characteristic impedance at a target working frequency, and the phase of the transmission line structure 1 reaches a target phase; at this time, the parameters of the inductors and the capacitors of the transmission line structure 1 are designed values.
Specifically, adjusting the parameters of each inductor and each capacitor in an iterative adjustment manner includes:
31 The inductance values of the inductors and/or the capacitance values of the capacitors in the transmission line structure 1 are adjusted according to the smith chart, so as to obtain the transmission line structure with the target characteristic impedance characteristic.
32 By scaling the inductance of the inductor and/or the capacitance of the capacitor to obtain the phase at the target operating frequency, scaling may be based on a simple coarse relationship of linear frequency response, as an example.
33 Completing parameter adjustment if the characteristic impedance of the transmission line structure 1 reaches a target characteristic impedance and the phase of the transmission line structure 1 reaches a target phase; otherwise, returning to step 31) until the characteristic impedance of the transmission line structure 1 reaches the target characteristic impedance and the phase of the transmission line structure 1 reaches the target phase.
It should be noted that, in step 31), as the inductance value of each inductor and/or the capacitance value of each capacitor in the transmission line structure 1 changes, the phase of the transmission line structure 1 determined in step 2) changes. In step 32) the characteristic impedance of the transmission line structure 1 determined in step 31) changes as the inductance values of the inductances and/or the capacitance values of the capacitances in the transmission line structure 1 change. And through the step 33), the parameters of the inductor and/or the capacitor are iteratively adjusted for multiple times to achieve convergence of the characteristic impedance and the phase, and further the target characteristic impedance and the target phase are obtained.
4) And obtaining inductors and capacitors with design values, and building the transmission line structure 1.
Specifically, the parameters of the respective devices in the transmission line structure 1 are determined based on design values.
Based on the above design method, a quarter-wavelength microstrip line is designed using a lossy inductor with a Q value (quality factor) of 12 and an ideal capacitor, where the inductance values of the first inductor and the second inductor are 2195pH, and the capacitance values of the first capacitor and the second capacitor are 115fF, as shown in fig. 3. Fig. 4 shows a conventional artificial transmission line structure implemented by using a fifth-order lumped structure, in which the inductance of each inductor is 820pH, the capacitance of the capacitors at two ends is 80fF, and the capacitance of the capacitor at the middle node is 197F. Compared with the traditional artificial transmission line structure, the broadband miniaturized quarter-wave transmission line has more compact layout, greatly reduced area, greatly reduced number of required devices and simpler design. FIG. 5 is a comparison of the insertion loss performance of the two transmission line structures of FIGS. 3 and 4, wherein dB (S (2, 1)) is the transmission function of the insertion loss; FIG. 6 is a comparison of simulation results of phase shift characteristics for the two structures of FIGS. 3 and 4, where phase (S (2, 1)) is the transfer function of the phase shift; FIG. 7 is a comparison of simulation results of reflection coefficient characteristics for the two configurations of FIGS. 3 and 4, where dB (S (1, 1)) is a function of the emission coefficient. In fig. 5, 6 and 7, the thin solid line represents the simulation characteristics of the transmission line structure 1 of the present embodiment, and the thick solid line represents the simulation characteristics obtained by the fifth-order lumped structure artificial transmission line. Therefore, the insertion loss of the transmission line structure is obviously improved compared with the insertion loss of the artificial transmission line with the fifth-order integrated structure (the insertion loss of the transmission line structure is closer to 0), and the insertion loss of the transmission line structure is less changed (basically keeps a constant value) around a 90-degree phase shift frequency band and is not increased along with the increase of frequency; the phase change of the transmission line structure in a frequency band near 90-degree phase shift is obviously slower than that of the artificial transmission line of the traditional five-order integrated structure, the working bandwidth of 80-100-degree phase shift is increased by 66.7%, and the transmission line structure has obvious advantages; compared with the artificial transmission line with the fifth-order integrated structure, the transmission line structure has smaller reflection coefficient and is basically not influenced by frequency.
The broadband miniaturized quarter-wavelength transmission line structure provided by the invention can be realized by only one group of inductors and one group of capacitors, has a simple structure and a smaller size, and has larger working bandwidth compared with the traditional five-order lumped transmission line; the phase changes more slowly with frequency than conventional structures and thus a wider bandwidth of quarter-wave transmission line characteristics can be achieved. The advantages can be applied to most transmission line circuit designs, not only provides a solution for broadband quarter-wavelength transmission lines, but also can realize the reduction of loss and size, effectively improve the performance of the circuit, reduce the cost, and can be widely applied to wireless communication systems of radio frequency/microwave/millimeter wave frequency bands.
Example two
As shown in fig. 8, the present embodiment provides a transmission line structure 1, which is different from the first embodiment in that the transmission line structure 1 of the present embodiment includes at least two transmission line units.
Specifically, in the present embodiment, three transmission line units are set, which are respectively denoted as a first transmission line unit 11a, a second transmission line unit 11b, and a third transmission line unit 11c, and the structure of each transmission line unit is the same as that of the transmission line unit 11 in the first embodiment, which is not repeated herein.
Specifically, the transmission line units are cascaded in sequence, and the characteristic impedance of each transmission line unit is the same. Namely, the positive phase input terminal of the first transmission line unit 11a is used as the positive phase input terminal IP of the transmission line structure 1, and the negative phase input terminal of the first transmission line unit 11a is used as the negative phase input terminal IN of the transmission line structure 1; the positive phase input end of the second transmission line unit 11b is connected to the positive phase output end of the first transmission line unit 11a, and the negative phase input end of the second transmission line unit 11b is connected to the negative phase output end of the first transmission line unit 11 a; the positive-phase input end of the third transmission line unit 11c is connected to the positive-phase output end of the second transmission line unit 11b, and the negative-phase input end of the third transmission line unit 11c is connected to the negative-phase output end of the second transmission line unit 11 b; the non-inverting output terminal of the third transmission line unit 11c is used as the non-inverting output terminal OP of the transmission line structure 1, and the inverting output terminal of the third transmission line unit 11c is used as the inverting output terminal ON of the transmission line structure 1.
In practice, the number of the transmission line units can be set according to the requirement, and is not limited to this embodiment. In addition, the structure of each transmission line unit and the design principle of the transmission line structure are referred to in the first embodiment, which is not described herein again.
In summary, the present invention provides a transmission line structure and a transmission line design method, including: the transmission line unit comprises a first inductor, a second inductor, a first capacitor and a second capacitor; one end of the first inductor is used as a positive phase input end of the transmission line unit, and the other end of the first inductor is used as a positive phase output end of the transmission line unit; one end of the second inductor is used as an inverting input end of the transmission line unit, and the other end of the second inductor is used as an inverting output end of the transmission line unit; one end of the first capacitor is connected with the positive phase input end of the transmission line unit, and the other end of the first capacitor is connected with the negative phase output end of the transmission line unit; one end of the second capacitor is connected with the inverting input end of the transmission line unit, and the other end of the second capacitor is connected with the non-inverting output end of the transmission line unit. The transmission line structure of the invention has high-pass characteristic in insertion loss, has smaller loss, and the insertion loss does not change greatly along with the increase of frequency; and the phase change becomes slower as the frequency increases, so that a wider band quarter-wave transmission line characteristic can be realized. The application range of functional devices (including but not limited to Wilkinson power dividers, quarter-wave impedance converters, microstrip annular bridges and branch line type power dividers) realized based on the quarter-wave transmission lines can be effectively expanded. The transmission line structure can be realized through a group of inductors and a group of capacitors, and has the advantages of simple structure, small size and wide working bandwidth. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A transmission line structure, characterized in that the transmission line structure at least comprises:
the transmission line unit comprises a first inductor, a second inductor, a first capacitor and a second capacitor;
one end of the first inductor is used as a positive phase input end of the transmission line unit, and the other end of the first inductor is used as a positive phase output end of the transmission line unit; one end of the second inductor is used as an inverting input end of the transmission line unit, and the other end of the second inductor is used as an inverting output end of the transmission line unit; one end of the first capacitor is connected with the positive phase input end of the transmission line unit, and the other end of the first capacitor is connected with the negative phase output end of the transmission line unit; one end of the second capacitor is connected with the inverting input end of the transmission line unit, and the other end of the second capacitor is connected with the non-inverting output end of the transmission line unit.
2. The transmission line structure according to claim 1, characterized in that: the inductance values of the first inductor and the second inductor are the same.
3. The transmission line structure according to claim 1, characterized in that: the capacitance values of the first capacitor and the second capacitor are the same.
4. The transmission line structure according to claim 1, characterized in that: the transmission line structure achieves a quarter-wavelength transmission line characteristic.
5. The transmission line structure according to any one of claims 1-4, characterized by: the transmission line structure is composed of at least two transmission line units, the transmission line units are sequentially cascaded, and the characteristic impedance of each transmission line unit is the same.
6. A transmission line design method, characterized in that the transmission line design method at least comprises:
1) Determining target characteristic impedance, target phase and target working frequency of the transmission line structure according to requirements;
2) Obtaining initial values of inductors and capacitors in a transmission line structure according to any one of claims 1 to 5;
3) Respectively adjusting parameters of each inductor and each capacitor in the transmission line structure so as to enable the characteristic impedance of the transmission line structure to reach a target characteristic impedance and the phase of the transmission line structure to reach a target phase at a target working frequency; at the moment, the parameters of each inductor and each capacitor of the transmission line structure are designed values;
4) And obtaining each inductor and each capacitor with the design values, and building the transmission line structure.
7. The transmission line design method of claim 6, wherein: the method for acquiring the initial values of the inductors and the capacitors comprises the following steps:
21a) Obtaining inductance values of all inductors and capacitance values of all capacitors when the transmission line structure has target characteristic impedance characteristics according to a Smith chart;
22a) Obtaining the phase of the transmission line structure under the target working frequency by scaling the inductance value of each inductor and/or the capacitance value of each capacitor;
23a) And taking the inductance value of each inductor as an initial value of the corresponding inductor, and taking the capacitance value of each capacitor as an initial value of the corresponding capacitor.
8. The transmission line design method of claim 6, wherein: when the inductance values of the inductors in the transmission line structure are the same and the capacitance values of the capacitors in the transmission line structure are the same, the method for acquiring the initial values of the inductors and the capacitors comprises the following steps:
21b) Calculating inductance values of inductors and capacitance values of capacitors in the third-order low-pass filter based on a design principle of the third-order low-pass filter, so that the third-order low-pass filter has target characteristic impedance and phases under target working frequency;
22b) And taking the inductance value of the inductor in the third-order low-pass filter as the initial value of the inductor in the transmission line structure, and taking the capacitance value of the capacitor in the third-order low-pass filter as the initial value of the capacitor in the transmission line structure.
9. The transmission line design method of claim 6, wherein: the method for adjusting the parameters of each inductor and each capacitor in the step 3) comprises the following steps:
31 Adjusting the inductance value of each inductor and/or the capacitance value of each capacitor in the transmission line structure according to the Smith chart to obtain the transmission line structure with target characteristic impedance characteristics;
32 Obtaining a phase at a target operating frequency by scaling an inductance value of the inductance and/or a capacitance value of the capacitance;
33 Completing parameter adjustment if the characteristic impedance of the transmission line structure reaches a target characteristic impedance and the phase of the transmission line structure reaches a target phase; otherwise, returning to step 31) until the characteristic impedance of the transmission line structure reaches the target characteristic impedance and the phase of the transmission line structure reaches the target phase.
10. The transmission line design method according to any one of claims 6 to 9, characterized in that: the target phase is 90 ° ± 10 °.
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