CN110555228A - impedance matching design method for transmission line - Google Patents
impedance matching design method for transmission line Download PDFInfo
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- CN110555228A CN110555228A CN201910590368.0A CN201910590368A CN110555228A CN 110555228 A CN110555228 A CN 110555228A CN 201910590368 A CN201910590368 A CN 201910590368A CN 110555228 A CN110555228 A CN 110555228A
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Abstract
The transmission line impedance matching design method comprises the following steps of determining the size of a microstrip line, calculating characteristic impedance Z 0 and transmission delay T pd of the microstrip line, determining strip line impedance Z 1 and transmission delay T pd1 according to the calculated impedance value, calculating the size of the strip line according to the strip line impedance Z 1, and achieving matching of the transmission line impedance when the transmission line is switched between a printed board surface layer and an inner layer by using a simple algorithm, so that reflection and distortion of signals are effectively inhibited, and transmission quality of the signals is improved.
Description
Technical Field
the invention relates to a transmission line impedance matching design method.
background
The transmission line is divided into a microstrip line and a strip line, the line width is not changed when the traditional wiring mode is layer changing, the impedance of the transmission line is not continued at the moment, signal reflection and distortion are generated, and the phenomena of crosstalk between signals, power supply and ground ripple waves and the like are easily caused. In order to keep signals stable and not to cause malfunction in high-speed signal transmission, improvement in control accuracy of characteristic impedance of a printed board to be used and continuity of transmission line impedance are required.
For example, a digital signal impedance matching circuit design method disclosed in publication No. CN105653752A is to design a PCB board layer required by a circuit according to the complex situation of the circuit, each layer defining different characteristics; the adopted impedance matching circuit designs a schematic diagram in a simulation system and activates the input or output characteristics between each device; different matching effects are simulated by inputting different impedance, capacitance, inductance and wiring length values, but the method needs to preset the size of the transmission line in advance by depending on experience and perform experiments on a simulation platform, and the method is complex and has no practicability.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a transmission line impedance matching design method.
The invention is realized by the following technical scheme.
The invention provides a transmission line impedance matching design method, which comprises the following steps:
S1, determining the size of the microstrip line;
S2, calculating the characteristic impedance Z of the microstrip line0And a transmission delay Tpd；
S3, determining the strip line impedance Z according to the calculated impedance value1And a transmission delay Tpd1；
s4, according to the strip line impedance Z1The stripline dimensions are calculated.
The microstrip line impedance Z0A transmission delay TpdThe calculation formulas are respectively
Wherein w is the microstrip line width, t is the microstrip line thickness, h is the dielectric thickness, epsilonrIs the dielectric constant of the medium.
The strip line impedance Z1A transmission delay Tpd1The calculation formulas are respectively
In the formula w1Is the width of the strip line, t1Is the thickness of the strip line, h1Is the thickness between conductive planes,. epsilonrIs the dielectric constant of the medium.
The microstrip line impedance Z0And the stripline impedance Z1Are equal.
The medium is an FR-4 copper-clad plate.
The microstrip line is attached to the surface of the medium.
the strip lines lie in two conductive planes and the strip lines are surrounded by a dielectric.
The invention has the beneficial effects that: the impedance matching of the transmission line can be achieved by using a simple algorithm when the transmission line is switched between the surface layer and the inner layer of the printed board, the reflection and distortion of signals are effectively inhibited, and the transmission quality of the signals is improved.
Drawings
Fig. 1 is a schematic size diagram of a microstrip line of the present invention;
FIG. 2 is a schematic of the stripline dimensions of the present invention;
FIG. 3 is a diagram of a printed board laminate structure of the present invention;
Fig. 4 is a transmission line signal reflection diagram.
Detailed Description
The technical solution of the present invention is further described below, but the scope of the claimed invention is not limited to the described.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
a transmission line impedance matching design method comprises the following steps:
S1, determining the size of the microstrip line;
S2, calculating the characteristic impedance Z of the microstrip line0And a transmission delay Tpd；
S3, determining the strip line impedance Z according to the calculated impedance value1And a transmission delay Tpd1；
S4, according to the strip line impedance Z1The stripline dimensions are calculated.
Microstrip line impedance Z0A transmission delay TpdThe calculation formulas are respectively
As shown in FIG. 1, w is the width of the microstrip line, t is the microstrip lineThickness, h is the thickness of the medium, epsilonrIs the dielectric constant of the medium.
Stripline impedance Z1A transmission delay Tpd1The calculation formulas are respectively
As shown in FIG. 2, wherein w1Is the width of the strip line, t1Is the thickness of the strip line, h1Is the thickness between conductive planes,. epsilonrIs the dielectric constant of the medium.
Calculating the time order microstrip line impedance Z0And the stripline impedance Z1The impedance of the transmission line is equal when the transmission line is switched between the surface layer and the inner layer of the printed board, and the distortion phenomenon of circuit signals is reduced.
The medium is FR-4 copper clad laminate, the base material is generally classified by the insulation part of the substrate, the common raw materials are bakelite board, glass fiber board, and various plastic boards, and the manufacturer of PCB generally presses the insulation part composed of glass fiber, non-woven material, and resin, and then epoxy resin and copper foil into "adhesive sheet" (prepreg).
The FR-4 copper-clad plate has higher mechanical property and dielectric property, better heat resistance and moisture resistance and good machinability. The electric insulation performance is stable, the flatness is good, the surface is smooth, no pit is formed, the thickness tolerance standard is met, and the electric insulation material is suitable for products with high-performance electronic insulation requirements, such as FPC reinforcing plates, PCB drilling base plates, glass fiber mesons, potentiometer carbon film printed glass fiber plates, precision planetary gears (wafer grinding), precision test plates, electric (electrical) equipment insulation stay baffles, insulation base plates, transformer insulation plates, motor insulation pieces, grinding gears, electronic switch insulation plates and the like. The FR-4 epoxy glass fiber cloth substrate is a substrate which takes epoxy resin as an adhesive and takes electronic grade glass fiber cloth as a reinforcing material. The bonding sheet and the inner core thin copper-clad plate are important base materials for manufacturing the multilayer printed circuit board.
The microstrip line is attached to the surface of the medium, the strip line is located in the two conductive planes, and the strip line is surrounded by the medium.
Example 1:
when the transmission line transmits signals from the upper microstrip line to the lower microstrip line, the structure diagram of the printed board stack shown in fig. 3 shows that the width w of the toplayer microstrip line is 0.3mm, t is 0.035mm, and epsilonrWhen h is 4.2, 0.08+0.19+0.08 is 0.35mm, the characteristic impedance is calculatedtransmission delay Tpd144.41ps/inch, the width w of the stripe when transferred through the aperture to the SIG1 layer1Calculated to be 0.109mm, characteristic impedance Z1Is 74.03 omega, the impedance can be made continuous.
And (3) calculating: strip lineWherein h is1＝0.08+0.19+0.08+0.3-0.035＝0.615mm，εr＝4.2,t1＝0.035mm。
Example 2:
When the transmission line transmits signals from the lower layer strip line to the upper layer strip line, a printed board lamination structure diagram is shown in fig. 3, namely when the strip line on the SIG2 layer is transferred to the micro strip line model on the bomlayer layer through a via hole, wherein w is1＝0.2mm，t1＝0.035mm，εr＝4.2，h10.08+0.19+0.08+0.3-0.035 mm, and the characteristic impedance Z of the strip line is calculated153.07 omega, when it is transferred to the bomlayer through the via, t is 0.035mm, epsilonr4.2, h is 0.08+0.19+0.08 is 0.35mm, and when the line width w of the microstrip line is calculated to be 0.593mm, Z0The impedance matching can be made continuous, 53.07 Ω.
When a signal is transmitted on a transmission line, each step on the path of the signal has corresponding transient impedance, if the impedance of the interconnection line is controllable, the transient impedance is equal to the characteristic impedance of the transmission line, no matter what reason the transient impedance is changed, part of the signal is reflected along the direction opposite to the original propagation direction, the other part of the signal is continuously propagated, but the amplitude is changed, and the amount of reflection is determined by the sudden change of the transient impedance.
As shown in fig. 4, if the transient impedance in the first region is Z1 and the transient impedance in the second region is Z2, the ratio of the amplitude of the reflected signal to the amplitude of the incident signal is:
Wherein vreflex: a reflected voltage; vincidient: an incident voltage; zb: transient impedance of the signal as it enters region 2; and Za: transient impedance of the area where the signal is initially located; ρ: a reflection coefficient. The larger the difference in impedance between the two regions, the larger the amount of reflected signal, which is generated to reconcile two important boundary conditions. When the signal reaches the interface between two regions of different transient impedance (regions 1 and 2), there is only one voltage and current loop in the conductors of the signal and return loops, and the voltage and current are the same across the interface. No voltage discontinuity can occur at the boundary surface, otherwise there would be an infinite electric field; it is also not possible to have a current discontinuity, otherwise there will be an infinite magnetic field.
in order to make the whole system harmoniously stable, region 1 generates a voltage which is reflected back to the source. The only purpose of the reflection is to absorb the mismatch of voltage and current between the incident and transmitted signals. Therefore, the voltage and the current on the two sides of the interface can be equal, the voltage and the current at the interface are continuous, and the whole system is balanced. As long as transient impedance changes on a signal transmission path, signals can be reflected, so that the invention effectively avoids the change of transient impedance by adjusting the line width of the transmission line when the transmission line changes in practical application, and the signals can not be reflected in the transmission process.
The invention is applied to a PWM output circuit of a programmable universal controller of certain engineering machinery, realizes signal integrity transmission and has no phenomena of distortion, emission and the like.
Claims (7)
1. A transmission line impedance matching design method is characterized by comprising the following steps:
S1, determining the size of the microstrip line;
s2, calculating the characteristic impedance Z of the microstrip line0And a transmission delay Tpd；
S3, determining the strip line impedance Z according to the calculated impedance value1and a transmission delay Tpd1；
S4, according to the strip line impedance Z1The stripline dimensions are calculated.
2. A transmission line impedance matching design method as claimed in claim 1, characterized in that: the microstrip line impedance Z0A transmission delay TpdThe calculation formulas are respectively
wherein w is the microstrip line width, t is the microstrip line thickness, h is the dielectric thickness, epsilonrIs the dielectric constant of the medium.
3. A transmission line impedance matching design method as claimed in claim 1, characterized in that: the strip line impedance Z1A transmission delay Tpd1The calculation formulas are respectively
In the formula w1Is the width of the strip line, t1Is the thickness of the strip line, h1Is the thickness between conductive planes,. epsilonrIs the dielectric constant of the medium.
4. A transmission line impedance matching design method as claimed in claim 1, characterized in that: the microstrip line impedance Z0And the stripline impedance Z1Are equal.
5. A transmission line impedance matching design method as claimed in claim 1, characterized in that: the medium is an FR-4 copper-clad plate.
6. A transmission line impedance matching design method as claimed in claim 1, characterized in that: the microstrip line is attached to the surface of the medium.
7. A transmission line impedance matching design method as claimed in claim 1, characterized in that: the strip lines lie in two conductive planes and the strip lines are surrounded by a dielectric.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910590368.0A CN110555228A (en) | 2019-07-02 | 2019-07-02 | impedance matching design method for transmission line |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910590368.0A CN110555228A (en) | 2019-07-02 | 2019-07-02 | impedance matching design method for transmission line |
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| CN110555228A true CN110555228A (en) | 2019-12-10 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114696861A (en) * | 2020-12-28 | 2022-07-01 | 深南电路股份有限公司 | Circuit board impedance adjusting method and device |
| CN115345108A (en) * | 2022-08-31 | 2022-11-15 | 苏州浪潮智能科技有限公司 | Transmission line structure determination method, system, electronic device and readable storage medium |
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| CN1964595A (en) * | 2006-11-27 | 2007-05-16 | 华为技术有限公司 | A matching capacitor and PCB using same and impedance matching device |
| CN102201607A (en) * | 2010-03-25 | 2011-09-28 | 周建明 | Microstrip and strip line transformation based on low temperature co-fired ceramic (LTCC) technology |
| CN104039075A (en) * | 2014-06-13 | 2014-09-10 | 杭州华三通信技术有限公司 | Pcb circuit |
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2019
- 2019-07-02 CN CN201910590368.0A patent/CN110555228A/en active Pending
Patent Citations (3)
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|---|---|---|---|---|
| CN1964595A (en) * | 2006-11-27 | 2007-05-16 | 华为技术有限公司 | A matching capacitor and PCB using same and impedance matching device |
| CN102201607A (en) * | 2010-03-25 | 2011-09-28 | 周建明 | Microstrip and strip line transformation based on low temperature co-fired ceramic (LTCC) technology |
| CN104039075A (en) * | 2014-06-13 | 2014-09-10 | 杭州华三通信技术有限公司 | Pcb circuit |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114696861A (en) * | 2020-12-28 | 2022-07-01 | 深南电路股份有限公司 | Circuit board impedance adjusting method and device |
| CN115345108A (en) * | 2022-08-31 | 2022-11-15 | 苏州浪潮智能科技有限公司 | Transmission line structure determination method, system, electronic device and readable storage medium |
| CN115345108B (en) * | 2022-08-31 | 2023-11-03 | 苏州浪潮智能科技有限公司 | Transmission line structure determining method, system, electronic device and readable storage medium |
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Application publication date: 20191210 |