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Microwave Devices - Microwave Passive Devices I - 2

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Presentation on theme: "Microwave Devices - Microwave Passive Devices I - 2"— Presentation transcript:

1 Microwave Devices - Microwave Passive Devices I - 2
2008 / 1 학기 서 광 석

2 전송선의 길이가 l 인 경우 phase shift
Transmission Line U U U V V V V V V Lossless 전송선 의 경우 : (R=G=0) 전송선의 길이가 l 인 경우 phase shift  delay: C     delay 줄임

3 Microwave Transmission Line
1.coaxial cable 2.waveguide 3.planar transmission line * Ref : Practical Microwaves, Chap. 3 1. coaxial cable z Dielectric material - PTFE(polytetrafluroethylene) : r = 2.1 Mode : TEM mode (Ez=Hz=0) TE mode (Ez=0) TM mode (Hz=0) a b

4 Coaxial Cable (1) For f < fC (TE11 mode, , where a and b in inches ), - TEM mode exists. (no cut-off frequency for TEM mode) - Zo: independent of frequency 0.9 fC 까지 coaxial cable을 사용하는 것이 일반적으로 추천됨. high freq.용의 경우 fC   a , b  (Example)  0.085” semi - rigid cable ( ~ 40만원 / 2feet) a = ”, b = 0.066”  ZO = 49.47 r = fC = 60GHz (50GHz까지 사용)  0.047” semi - rigid cable  fC = 110GHz (m precision machining 필요, connector 가격 ~ 수백$ ) * a,b 가 작을 경우  attenuation loss증가 , power handling 감소 , 가격 상승

5 Coaxial Cable (2) Attenuation coefficient ” cable dB/ft @10GHz 0.25” cable dB/ft @10GHz (line length가 클 경우,optical fiber로 대체 필요) Coaxial cable의 장점 : dc to fc 까지 동작 (TEM mode 로 인해) 2. frequency independent 3. Radiation loss 없음 Coaxial cable의 Type - flexible cable : outside conductor, high loss - semi-rigid cable : outside conductor – metal (Ag-coated Cu), 1번만 bent 가능  Micro–coaxial cable Dielectric filled MEMS 기술로 제작 가능 - high cost process metal substrate

6 Waveguide 2. waveguide - Standard : a=2b
- 경계 조건 : tangential E field = 0 at metal walls  mode 발생 b a z Hx Ey (Ez=0,Hz0) TE10 mode Air-filled waveguide 의 경우 (TEmn mode) dominant node: TE10 mode (a=2cm) - fC10 에서 TM11 mode 의 cut -off 까지 사용가능 - 각 주파수 별로 사용되는 wave-guide size 결정 * dielectric filled에 비해 air - filled가 사용 주파수에서 a ,b 증가

7 Modes in Waveguide Ref : D. M. Pozar, “Microwave Engineering”, Chap. 3

8 Planar Transmission Line
a. Microstrip 로 인해 TEM mode 가 존재하지 않으나 quasi-TEM mode로 approximation GND Via connection b. Coplanar Wave Guide (CPW) - GND가 표면에 있으므로 shunt connection 용이 - transmission line 구조가 넓은 면적 차지 GND s ( c. Coplanar Strip (CPS) d. Slot - line GND ( (c,d : antenna-feed에 주로 사용)

9 Microstrip Transmission Line
< dielectric의 종류에 따라  결정 > (loss tangent) h dielectric  ZO = = 50  의 경우 w  1. compact한 구조 가능, loss 증가 2. w가 너무 작은 경우 공정 제어 문제 GND  glass substrate MIC - 미국 M/A–COM 사의 low cost 기술, 0.7 ~ 4.2GHz 대역에 응용 - borosilicate glass 를 기판으로 사용  SiO2 substrate MIC : 텔레퍼스 (KAIST venture) – cost problem 습식 에칭  porous Si conducting Si ~30m Si conducting Si Metal 대용 산화 공정

10 Dielectrics for Microstrip Transmission Line
Dielectric Loss low freq. (~10GHz) medium freq. high freq. (~60GHz) Ref : Practical Microwaves, Chap. 1

11 FR4 & Duroid FR4 for PCB (PWB) - Low Frequency Applications
Alkali-free glass cloth impregnated with an epoxy resin under pressure and heat Flame retardant properties, easily machined and die cut & very low cost Duroid - Higher Frequency Applications (

12 PCB Substrate – FR4

13 Materials for MCM-L Material Comparison $ per 18x24 core
Added Process $ FR4 $4-6 (1.0x) 1.0x FR5 (Hi Tg FR4: FR406, etc) $5-7 ( x) x FR408 $7-11 ( x) x Ro3003 $28-35 (4.5-6x) x Ro4350 $24-30 (3.5-5x) x

14 Relative Raw Material Cost Multiplier
Performance Polymer Thick Film Thin Film LTCC & Photo

15 Substrate material ~ 50m
Various PCB Materials Substrate material ~ 50m

16 50 Microstrip Attenuation
Frequency, (GHz) Thick & Thin Film on Alumina 4 8 12 16 20 0.5 1.0 1.5 2.0 Multilayer Thick Film FR-4 Advanced PWB LTCC PTFE PWB (wide lines) Attenuation (dB/Inch)

17 Microstrip Analysis (1)
- pure TEM mode 존재 안함 - full wave analysis - low freq.경우: TEM mode로 가정하여 해석 – quasi-TEM analysis - 2=0  L,C 계산 w h (air) (substrate) Ca, La C, L= La air (1st estimate q = ½ , correction q > ½ )

18 Microstrip Analysis (2)
w  (q  1) : 기판 (r) 에 대부분 field 분포 . high frequency ( w/ )  ( q  1 ) : q (f) : function of frequency (frequency dispersion) d quasi-TEM analysis air ( /c ) Dispersion diagram freq. dispersion의 영향이 심각해지는 frequency

19 Microstrip Analysis(3)
freq. dispersion이 중요한 영역: where fd : GHz, h : cm low frequency에서는 quasi-TEM approximation where = h for w > h/2 2w for 2t < w < h/ w ( t : metal thickness, weff : equivalent metal width ) conformal mapping 에 의한 microstrip 해석 – ”Foundation for Microwave Engineering”, R.E Collin

20 Characteristic Impedance of Microstrip

21 Microstrip for GaAs MMIC
microstrip on GaAs substrate w/h ~ 0.8 일때 (r = 12)  Zo  50  fd ~ 10 GHz fd를 높이기 위해 h 필요 ( -strip based 광대역 증폭기 MMIC  freq. dispersion 효과 발생이 가능) h가 작을 경우 fragile , thermal conduction 증가 w GaAs (r ~12) 100 m (h) GND - GaAs wafer의 초기 두께 ~ 600 m m  표면 process 후에 backside lapping에 의한 wafer thinning - h : 25 ~100 m in microstrip MMIC ( ~25 m : power MMIC에서 사용 ) - w/h  for Zo=50  : h, w 가 작을 경우 line 저항 증가  transmission line 의 conductor loss 증가

22 Higher Order Modes in Microstrip
w - fundamental mode – HEO mode - transverse resonant mode – HE1 mode E E GHz where w , h in inches (HE1 mode) h = 100 m, ZO=50   fT  200 GHz h = 100 m, fT= 94 GHz  w = 16 mil , ZO = 18  Zo,min 결정 : higher order mode excitation  ZO가 작아지면 high freq.까지 사용못함. - 상용 microwave CAD tool : r, eff(f) , ZO(f) 포함 full- wave analysis결과를 curve-fitting한 eq. 사용 (Ref. K.C. Gupta, pp.102~109)

23 Modified Microstrip Lines (1)
1. thin –film microstrip w signal dielectric h GND substrate ( small h : 210 m )  small h  small w for constant ZO , compact MMIC (NTT)  too small w  excessive conductance loss (c) 이 경우 dielectric 의 r 을 감소시켜 w를 증가  c  * small r dielectric : BCB (r =2.6), air (r =1)

24 Modified Microstrip Lines (2)
2. Air-filled microstrip  X -ray lithography 용 mask 제작과 동일한 process stress stress control 이 중요함 (yield problem) U. Michigan 의 Prof. Katehi thin dielectric Si Etching에 의한 Air Gap (Si3N4 , 수천 Å) Si 기판 * metal cover gap  3h 일때 효과 없음 Air Gap thin membrane Si Si Si Air Gap Si h Air Gap ( membrane coaxial cable)

25 Microwave Packages package용 case cover
hermetic package -- high frequency 용 soldering air Metal cover Si Air Gap MMIC MMIC chip 접착제 ceramic substrate (ceramic or Si) * plastic package -- low frequency 용 (up to 수 GHz) (Micro machined Si의 package에의 응용)  Ref. “Novel Micromachined Approach”, MTT-S p.1145


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