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1、Lecture#1,Richard Li,2004,1,Lecture#1:Impedance matching Richard Li,Tel.:001-817-788-8428(USA)86-21-58756314(Shangahi)Email:,4.Impedance measurement o Impedance measured by small signal o The Smith Chart:impedance and admittance coordination o Relationship between the impedance in series and in para
2、llel o Impedance measured by large signal 5.Impedance matching o One part matching network o Recognition of regions in the Smith Chart o Two parts matching network o Two parts upward and downward impedance transformer o Three parts matching network and impedance transformer 6.Some useful schemes for
3、 impedance marching o Designs and tests when ZL is not 50 ohms o Conversion between“T”and“”type matching network o Parts in a matching network o Impedance matching between power transportation units o Impedance matching for a mixer,1.Difference between RF/RFIC and digital circuit design o Case#1:Dig
4、ital circuits with low data rate o Case#2:Digital circuits with high data rate 2.The significance of impedance matching o Power transportation from a source to a load o Maximizing of power transportation without phase shift o Matching network 3.The problems due to impedance un-matched status o Gener
5、al expression of power transportation o Power instability and additional power loss o Quasi-noise and unmatched distortion o Power measurement o Power transportation and voltage transportation o Burning of the device,Lecture#1,Richard Li,2004,2,1.Difference between RF/RFIC and digital circuit design
6、,where R=Transmitted bits per second,fRF=RF frequency.,and,o Case#2:Digital circuits with high data rate,o Case#1:Digital circuits with Low data rate,Lecture#1,Richard Li,2004,3,Why?The answer is*The modulated carrier,a RF signal,can be effectively modulated,transmitted,transported,and de-modulated,
7、only when it has enough power.*In the digital signal processing,only status but not power is transported between circuit blocks.,o Low digital data rate case:,Item RF module/RFICDigital circuit(Low data rate)Impedance Low(50 typically)High(Infinitive ideally)Impedance matching ImportantDont care(usu
8、ally)CurrentHigh(mA)Low(A)Location in the wireless communication system*Rx Front end(Before de-modulation)Back end(After de-modulation)*TxBack end(After modulation)Front end(Before modulation)Transportation typePower(Watt)Status(Voltage),Table 1.1 The difference between RF and digital circuit when d
9、ata rate is low.,Lecture#1,Richard Li,2004,4,Why?The answer is*Without impedance matching,the digital voltage level would be suffered with additional attenuation,additional jitter,additional cross-talk,and eventually additional bit error.*The impedance matching becomes even more important for a digi
10、tal circuit than for a RF circuit if the data rate is the same order as the RF frequency.The reason is that The waveform of digital signal is rectangular pulse while that of RF signal is sinusoidal usually.Consequently,the digital signal is wide band signal while the RF signal is narrow band signal.
11、,o High digital data rate case:,and,Lecture#1,Richard Li,2004,5,2.The significance of impedance matching,The condition to maximize PL is,o To maximize the power transportation from source to load,Then,the condition of impedance matching is,or,or,The power that delivered from source to load resistor
12、is,or,Lecture#1,Richard Li,2004,6,认知压力,6,压力的含义是：第一、它是源自工作/生活中那些使人感到紧张的事件或环境刺激；第二、它是一种主观的内部心理状态；第三、它是人体对需要和威胁的一种生理反应,Lecture#1,Richard Li,2004,7,心理调整技术挑拆技术,挑拆技术基本步骤接受你已经产生的情绪接受拥有这些负面情绪的你确定你需要改变的认知改变你的认知,7,Lecture#1,Richard Li,2004,8,*To maximize the power transportation from source to load,This is ca
13、lled as“neutralization”of reactance between source and load.,o The meaning of impedance conjugate-matching condition is twofold:,*To eliminate the phase shift from source to load,Lecture#1,Richard Li,2004,9,o Matching Network Usually ZS ZL*,a matching network must be inserted between source and load
14、 so that the impedance matching condition can be satisfied as following:When looking from source toward the input of the matching network,when looking from output of the matching network toward the load.and,there is not power consumption in the matching network if the matching network consists of id
15、eal inductors and capacitors.Therefore,Lecture#1,Richard Li,2004,10,3.The problems due to impedance un-matched status,The value of PRL after the first reflection from the load is,Define,o General expression of power transportation,Where S=Power reflection coefficient at source,L=Power reflection coe
16、fficient at load,S=Voltage reflection coefficient at source,L=Voltage reflection coefficient at load,PS,incident=Incident power at source,PS,reflected=Reflected power at source,PL,incident=Incident power at load,PL,reflected=Reflected power at load.,If,where td=the delay time of power transportation
17、 from source to load.,=,=,Lecture#1,Richard Li,2004,11,where td=Delay time from source to load,The general expression of power transportation is a sum of all the reflected powers between source and load,Lecture#1,Richard Li,2004,12,*Power instability*Additional power loss*Additional noise*Additional
18、 distortion,If,Or,It results,where,then,The sum is,Lecture#1,Richard Li,2004,13,o Power instability and additional power loss,*Additional power loss,If td is not neglected,PRL is a time-variable.,*Power instability:,Lecture#1,Richard Li,2004,14,when PL,=0=-30 dBm,%,PRL/PRL,=0,%,PRL,=0.dBm,PRL,dBm,PR
19、L,dBm,Table 1.3 Additional power loss due to un-matched state,0,0.00,-30.00,-Infinitive,-30.00,5,4.76,-30.00,-43.22,-30.21,10,9.09,-30.00,-40.41,-30.41,50,33.33,-30.00,-34.77,-31.76,Lecture#1,Richard Li,2004,15,o Additional noise and additional distortion due to un-matched status,*Assuming that the
20、powers at load,PRL1 and PRL2,are observed at two moments,t and t+2td,respectively,where vS1 is delayed 2td from vS2:.,RS,RL,vS,XL,Figure 1.4 Voltage and power transported from a source to a load when 0,vRL,XS,Lecture#1,Richard Li,2004,16,At the instant(t-td),PRL2(t+2td)becomes the additional noise t
21、o the PRL1(t),that is,*Additional quasi-noise if the frequency 1 is not the same as 2.,Lecture#1,Richard Li,2004,17,Change of SNR,%,SNRRL0,dB,SNRRL,w,2,1+2 SNRRL0,w,1+2 SNRRL0,dB,SNRRL,dB,0,10,10,0.00,1.00,0.00,10.00,5,10,10,0.25,1.03,0.11,9.89,10,10,10,1.00,1.10,0.41,9.59,50,10,10,25.00,3.50,5.44,4
22、.56,Table 1.4 Additional noise due to un-matched state,when SNRRL0=10 dB,Lecture#1,Richard Li,2004,18,*Additional distortion if the frequency 1 is the same as 2.,Lecture#1,Richard Li,2004,19,Table 1.5 Additional distortion due to un-matched state,when DRL0=10%,Lecture#1,Richard Li,2004,20,by power m
23、eter or spectrum analyzer,o Power measurement,Lecture#1,Richard Li,2004,21,(a)Matched case,Tested Block,vS,ZS*,vL,PL,50,ZS,SpectrumAnalyzer,MatchNetwork(ZS*to 50),*Power Measurement by spectrum analyzer(Matched case),Figure 1.5(a)Power measurement by spectrum analyzer,Lecture#1,Richard Li,2004,22,*P
24、ower Measurement by spectrum analyzer(Un-matched case),RS,(ohms)XS(ohms)PL/Po PL/Po,dB00.555556-2.610500.327869-4.8101000.147059-8.310 10000.001993-27.010100000.000020-47.050 01.000000 0.050500.800000-1.050 1000.500000-3.05010000.009901-20.050100000.000100-40.010000.888889-0.5500.800000-1.01001000.6
25、15385-2.110000.019560-17.1100100000.000200-37.01000 00.181406-7.41000500.180995-7.410001000.179775-7.51000 10000.095125-10.21000 100000.001978-27.0 10000 00.019801-17.0 500.019801-17.010000 1000.019800-17.010000 10000.019607-17.110000 100000.009950-20.0,Table 1.6 Calculated values of PL/Po in un-mat
26、ched case(b),Lecture#1,Richard Li,2004,23,*Is it necessary to match LO portion?Some engineers design mixer without matching of LO portion.The reasons are,Instead of power,only voltage is needed to ON/OFF the devices.As long as the runner from LO source to LO injection gate is short enough,the voltag
27、e from source would be directly effective on the gate.Or,one can simply put a 50 on LO injection gate for matching to 50 source.,o Power transportation and voltage transportation,Lecture#1,Richard Li,2004,24,*The answer is:Absolute necessary!The reasons listed above are plausible and wrong!,Assuming
28、 that the impedance at LO port of mixer is,ZL=1000+1/(jC),and thatXL=-XC,then,power and voltage transportation in three matching cases are,Lecture#1,Richard Li,2004,25,o Burning of the device,Lecture#1,Richard Li,2004,26,Q:RF Engineering=Matching Engineering?,A:Not really but it may be the first imp
29、ortant,Lecture#1,Richard Li,2004,27,4.Impedance measurement,When S=L=0,Or,S21=0,Or,S12=0,o S11,S22 measurement,Lecture#1,Richard Li,2004,28,o Smith Chart:Impedance coordination,Figure 1.11 Impedance coordination of Smith Chart,Lecture#1,Richard Li,2004,29,o Smith Chart:Admittance coordination,The y
30、curves can be obtained by rotating of z with 180o because,Lecture#1,Richard Li,2004,30,o Smith Chart:Impedance and admittance coordination together,Figure 1.13 Impedance and admittance coordination of Smith Chart,Solid line,Dashed line,Lecture#1,Richard Li,2004,31,Some scaled parameters are attached
31、 below the Smith Chart:*Reflection coefficient of power,2,*Return loss in dB,-10log(2),*Reflection loss in dB,-10log(1-2),*VSWR(Voltage Standing Wave Ratio),(1+|)/(1-|),*VSWR in dB,20log(1+|)/(1-|),*Transmission loss coefficient,(1+|2)/(1-|2).,o Scales on Smith chart,Lecture#1,Richard Li,2004,32,o R
32、elatively inaccurate and accurate area of Smith Chart,Lecture#1,Richard Li,2004,33,o Transformation of impedance between in series and in parallel,Note:XS and XP could be either inductors or capacitors.,Lecture#1,Richard Li,2004,34,(a)When XS and XP are impedance of inductors,Lecture#1,Richard Li,20
33、04,35,o Impedance measured by means of circulator,Lecture#1,Richard Li,2004,36,o Impedance matching of a mixer:,*Use of circulator,Lecture#1,Richard Li,2004,37,o One part added on Smith chart,Figure 1.20 Moving direction of impedance after LS,CS,LP,or CP is added.,Impedance matching with assistance
34、of Smith Chart,LP:Inductor in parallel Counter-clockwise moved along admittance circle,RP:Resistor in parallel Jumped to smaller admittance circle,CP:Capacitor in parallel Clockwise moved along admittance circle,LS:Inductor in series Counter-clockwise moved along impedance circle,RS:Resistor in seri
35、es Jumped to smaller impedance circle,CS:Capacitor in series Clockwise moved along impedance circle,Lecture#1,Richard Li,2004,38,o Recognition of regions in Smith Chart,Region 1Low resistance&high conductance:r1,-b+,Region 2High impedance&low conductance:r1,-x+,g1,b|0.5|,Region 3Low resistance&low c
36、onductance:r0,g1,b0,Region 4Low resistance&low conductance:r0,PZP=R+jXC,PZP=R+jXL,Figure 1.21 4 regions of impedance in the Smith Chart,Lecture#1,Richard Li,2004,39,*Region 1 and 2 on Smith Chart,o Two parts added for matching(“type of matching),Figure 1.22 Two ways to pull original impedance P to c
37、enter of Smith Chart,O,by addition of two passive parts in region 1 and 2,Lecture#1,Richard Li,2004,40,Figure 1.23 Another two ways to pull original impedance P to center of Smith Chart,O,by addition of two passive parts in region 1 and 2,*Region 1 and 2 on Smith Chart(Continued),Lecture#1,Richard L
38、i,2004,41,Lecture#1,Richard Li,2004,42,Lecture#1,Richard Li,2004,43,For P1 and P2,For P1 or P2:Rm Zo=50 ohmIn series first and in parallel second,First matching part,XS,in series,is to get g=1.If g=1,then,When g=1,then y(g,b)can be pulled to Zo by second part,xm,General formula for impedance and adm
39、ittance,For P3 and P4,the impedance after adding of 1st part,XP,in parallel,For P3 or P4:Rm Zo=50 ohmIn parallel first and in series second,First matching part,XP,in parallel,is to get R=Zo,or r=1,If R=Zo,or r=1,then,When R=Zo,or r=1,then z(r,x)can be pulled to Zo by second part,XS,General formula f
40、or impedance and admittance,+for Ls-for Cs,+for Lp-for Cp,+for Ls-for Cs,+for Cp-for Lp,Lecture#1,Richard Li,2004,44,*Region 3 and 4 on Smith chart,Figure 1.26 Matching path of impedance in Region 3 and 4 of Smith Chart,PZm=Rm+jXm(XC),PZm=Rm+jXm(XL),Lecture#1,Richard Li,2004,45,Figure 1.28 Impedance
41、 matching for region 3 and 4 on Smith ChartZ=R+jX,Y=G+jB=R/(R2+X2)-jX/(R2+X2),Region 3Low resistance&low conductance:r0,g1,b0,Region 4Low resistance&low conductance:r0,CS,Cp,Zo=50 ohm,R m 0,P5,Zo=50 ohm,Rm 50 ohmXm 0,CS,Cp,P5,LP,Ls,Zo=50 ohm,Rm 50 ohmXm 0,P6,Zo=50 ohm,Rm 50 ohmX m 0,LP,Ls,P6,P6:(In
42、capacitive area),Figure 1.27 Impedance matching for region 3 on Smith ChartZ=R+jX,Y=G+jB=R/(R2+X2)-jX/(R2+X2),P5:(In inductive area),Lecture#1,Richard Li,2004,46,Lecture#1,Richard Li,2004,47,For P1 and P2,For P5 or P6:Rm Zo=50 ohmIn series first and in parallel second,First matching part,XS,in serie
43、s,is to get g=1.If g=1,then,When g=1,then y(g,b)can be pulled to Zo by second part,xm,General formula for impedance and admittance,For P3 and P4,the impedance after adding of 1st part,XP,in parallel,For P5 or P6:Rm Zo=50 ohmIn parallel first and in series second,First matching part,XP,in parallel,is
44、 to get R=Zo,or r=1,If R=Zo,or r=1,then,When R=Zo,or r=1,then z(r,x)can be pulled to Zo by second part,XS,General formula for impedance and admittance,+for region 3,Cs-for region 4,Ls,+for region 3,Cp-for region 4,Lp,+for region 4,Lp-for region 3,Cp,+for region 4,Ls-for region 3,Cs,Lecture#1,Richard
45、 Li,2004,48,*Upward impedance transformer:From pure resistor to pure resistor,*Downward impedance transformer:,V,U,E,W,S,N,O,A,Rm,Ro,B,Figure 1.31 Upward and downward impedance transformer,R oXo=0,Figure 1.32 Downward impedance transformer,Figure 1.30 Upward impedance transformer,Lecture#1,Richard L
46、i,2004,49,o Key points in the case of two parts added on Smith chat,*The 1st component is to bring the impedance to the circle with reference resistance or reference admittance.,*Matching network in region 1 is an upward impedance transformer.-It can transfer the impedance from low to high(50 ohm he
47、re).-Usually it is the case of power amplifier design.,*Matching network in region 2 is a downward impedance transformer.-It can transfer the impedance from high to low(50 ohm here).-Usually it is the case of LNA,mixer etc.with CMOS processing.,*Matching network in region 3 and 4 is an simple matchi
48、ng unit with only one type of parts.-In region 3 it can be matched only by capacitors.One is in series and another one in parallel.It doesnt matter to the order of these two capacitors.-In region 4 it can be matched only by inductors.One is in series and another one in parallel.It doesnt matter to t
49、he order of these two capacitors.,*The 2nd component is to bring the impedance to the center of Smith Chart,that is,to the point of the reference resistance and zero reactance,Lecture#1,Richard Li,2004,50,o Three parts added for matching,*Limitation by two parts scheme Impedance on Smith Chart can b
50、e moved to anywhere by three parts*More flexible The values of three parts are adjustable,Lecture#1,Richard Li,2004,51,Topology A,Topology C,Figure 1.33a Topology limitation by two parts matching Exclusive from each other between topology A and C,*Topology limitation by two parts matching Exclusive
