《微带电路》ppt课件

1、Basics of microstrip circuitAddressed by Xinhua Yu.1.1 The development of the microstrip line1.1.1 The transmission line The transmission line is used to guide electromagnetic wave to travel in a certain direction and to form many kinds of microwave elements , such as filters and dividers. It consis

2、ts of a system constructed with conductor and dielectric. Its common forms are parallel lines, coax, waveguide, strip line, microstrip and so on.Coaxial cable (coax) rectangular waveguide parallel linesMicrostripCoplanar stripsFigure 1.1 Several transmission structuresstriplinecoplanar waveguide(CPW

3、).Parallel lines are suitable to transmit low frequency signal and unsuitable high frequency signal due to large radiation losses at high frequencies. This situation results in the advent of coax and waveguide. .Coax and waveguide are discarded in the integrated circuit for their large size and heav

4、y! So its the microstrips turn to work in the integrated circuit. The microwave integrated circuit can be divided two types: The Lumped integrated circuit : dimension far smaller than the operational wavelength; Its elements are all lumped type; 1.1.2 The transmission line typeThe trend of minimizin

5、g the communication system made the advent of microwave integrated circuits. . The distributed integrated circuit (referred to as micro- strip circuit): Its dimension is at the same level as the o-perational wavelength; Its elements consist of distribut-e d parameter microstrip;1.2 Microstrip Figure

6、 1.2 Configuration of a microstrip line.Figure 1.3 Conceptual evolution of a microstrip from a two-wire line.Figure 1.4 Microstrip configuration The configuration open at the top makes a microstrip very convenient for use in MICs where discrete lumped devices(active or passive)must be mounted in the

7、 integrated circuit.Figure 1.5 Various transmission lines derived from a microstrip02468100246810Y Axis TitleX Axis Title #02468100246810Y Axis TitleX Axis Title #02468100246810Y Axis TitleX Axis Title #02468100246810Y Axis TitleX Axis Title #rr2 Inverted microstrip Suspended microstripSlot microstr

8、ipMicrostrip with double-layer dielectric.1.2.1 Microstrip field configurationa microstrip Structure cannot support a pure TEM wave. Continuity of the tangential component of the electric field along a dielectric-air interface yields|xdxaEEDielectric side of the interfaceAir side of the interface(1.

9、1)Figure 1.6 Microstrip configurationUsing Maxwells equations, one may thus write.() |() |xdrxaHH(1.2) Expanding (1.2) and using the continuity of the normal component of the magnetic flux, we obtain (for the case when ) 1r|(1)yzzrardrHHHyyz(1.3) As r is not equal to unity and Hy0, (1.3) implies tha

10、t the expression on the left-hand side should be a nonzero quantity, which can only be true if Hz is nonzero. Thus we note that for Maxwells equations to hold good for the configuration of Figure 1.6, the longitudinal component of H must exist. Similar arguments can be advanced to show that Ez, the

11、longitudinal component of the electric field, is also a nonzero quantity.The fringing components Ex and Hx at the dielectric-air interface that lead to the non-TEM nature of the microstrip mode.微波线中存在的是TE-TM混合波场，其纵向场分量主要是由介质-空气分界面处的边缘场Ex和Hx引起的，由于微带线基片厚度h远小于传输波长，因此纵向场分量与导体带和接地板之间的横向分量场相比很小，所以微带线中传输模的

12、特性与TEM模相差很小，称之为准TEM 模。xzFigure 1.7 Microstrip field configurationy.1.2.2 Methods of Microstrip Analysis The analysis methods are aimed at determining the characteristic impedance and propagation constant (phase velocity and attenuation constant).Figure 1.8 Various methods of microstrip analysis *pur

13、e TEM considered only*Suitable to circuit at lower frequencies (below X-band)Hybrid nature of the mode of propagation considered.Quasi-static methodPure TEM mode，introduce homogeneous medium with effective dielectric constant e to replace the hybrid medium of a micostrip.Modes propagating in a micro

14、strip are quasi-TEM mode and high order modes including waveguide mode and surface wave modes which must be suppressed.Figure 1.9 Field configuration of microstrip .wteh0000,ekkbewm e=0;pgeecvllee=Figure 1.10 Field configuration of microstrip Figure 1.11 Microstrip with homogenous dielectricMain par

15、ameter: the characteristic impedance and the phase velocity.01/22608ln0.25111220.041 122errehwZwhhwwheeee-骣=+桫轾骣骣+-犏鼢珑=+-鼢珑犏鼢珑桫桫犏臌01/21201 /1.3930.667ln( /1.4444)1111222erreZw hw hhwpeeee-=+骣+-=+桫( t = 0 )/1w h/1w h(1-1)(1-2)1.2.3 Microstrip Analysis using quasi-static method.When0t th/2tWThe effect

16、 of non-zero thickness can be representedby broader width We under the conditionWe can be decided by1.2521 lneWWtxhhhtWhere12122WhhxWWh(1-3)(1-4).28e1.52e2120.611 ln(21)ln(1)0.391.522AArrrAWhBBBA 0200110.11(0.23)6021377602rrrrrrZABZZWhere When and are given, the width W can be got by0Zr1.2.4 Microst

17、rip design using quasi-static method(1-5)(1-6).t/h=0t/h=0.01t/h=0.1t/h=0t/h=0.01t/h=0.1Z0( ) eZ0( ) eZ0( ) eZ0( ) eZ0( ) eZ0( ) e0.100.10192.25 1.87 190.51 1.87 158.16 1.90 108.90 5.83 107.89 5.8489.12 5.971.001.0089.41 1.9988.61 1.9984.58 2.0049.50 6.4949.04 6.5046.73 6.562.002.0062.15 2.0761.79 2.

18、0759.89 2.0833.96 6.9333.76 6.9332.69 6.972.502.5054.15 2.1053.87 2.1052.44 2.1029.46 7.0929.30 7.0928.50 7.122.702.7051.52 2.1151.27 2.1149.98 2.1127.98 7.1427.84 7.1527.12 7.182.802.8050.30 2.1150.06 2.1148.84 2.1227.30 2.1727.17 2.1726.48 7.202.902.9049.14 2.1248.92 2.1247.75 2.1226.65 7.2026.53

19、7.2025.87 7.233.003.0048.04 2.1247.82 2.1246.71 2.1326.03 7.2225.91 7.2325.29 7.26W/h r=2.55 r=9.6Table 1-1. Example 1: Get the width and length of a microstrip to result in a phase shift of 90 degrees at 2.5GHz. The substrates parameters are and the characteristic impedance of the microstrip is 50

20、ohms. 01. 0,55. 2,27. 1tmmhr0rFigure 1.12 Microstrip with Example 1.Solution： For microstrip with a characteristic impedance 50W，by consulting Table 1.2 or calculating by 1-2,3,4， t/h=0.01,/2.825;2.11eWhe=3.59Wmm=So the length of the 900 phase shift line can obtain bymmklmcfklklee64.20235.52/220100T

21、hus,.例2 试计算复合介质微带电路50欧姆传输线宽度W。知r=9， h=1mm， t=0.01mm。解：采用1.3式计算。 A=2.057 B=3.948 W/h=1.06W=1.06mm t/h=0t/h=0.01t/h=0.1t/h=0t/h=0.01t/h=0.1Z0( ) eZ0( ) eZ0( ) eZ0( ) eZ0( ) eZ0( ) e0.100.10192.25 1.87 190.51 1.87 158.16 1.90 108.90 5.83 107.89 5.8489.12 5.971.001.0089.41 1.9988.61 1.9984.58 2.0049.50

22、6.4949.04 6.5046.73 6.562.002.0062.15 2.0761.79 2.0759.89 2.0833.96 6.9333.76 6.9332.69 6.972.502.5054.15 2.1053.87 2.1052.44 2.1029.46 7.0929.30 7.0928.50 7.122.702.7051.52 2.1151.27 2.1149.98 2.1127.98 7.1427.84 7.1527.12 7.182.802.8050.30 2.1150.06 2.1148.84 2.1227.30 2.1727.17 2.1726.48 7.202.90

23、2.9049.14 2.1248.92 2.1247.75 2.1226.65 7.2026.53 7.2025.87 7.233.003.0048.04 2.1247.82 2.1246.71 2.1326.03 7.2225.91 7.2325.29 7.26W/h r=2.55 r=9.6. The compared with waveguide are the generally lower power handling capacity, and higher losses. Also, unlike waveguide, microstrip is not enclosed, an

24、d is therefore susceptible to cross-talk and unintentional radiation. Microwave components such as antennas, couplers, filters, power dividers etc. can be formed from microstrip, the entire device existing as the pattern of metallization on the substrate.1.2.5 Disadvantages of microstrip 1.2.6 Application