Introduction to Surface Acoustic Wave (SAW) Devices

Transcription

1 Introduction to Surface Acoustic Wave (SAW) Devices Part 1: What is SAW Device? Ken-ya Hashimoto Chiba University

2 Contents SAW Transversal Filter SAW Unidirectional IDT Filters SAW Resonator Filters SAW Wireless Tags and Sensors

3 Contents SAW Transversal Filter SAW SAW Unidirectional IDT Filters SAW SAW Resonator Filters SAW SAW Wireless Tags and Sensors

4 Surface Acoustic Wave Bulk Acoustic Wave (BAW): Longitudinal Wave (Primary Wave) Transverse Wave (Share Wave, Secondary Wave) Propagation of Seismological Waves Surface Acoustic Wave (SAW): (Rayleigh SAW)

5 Surface Acoustic Wave (SAW) Device Interdigital Transducers (IDT) V in SAW V out Piezoelectric substrate Mass Production by Photolithography Low loss, Miniature & Low price Operation invhf-uhf ranges Line width λ/4=0.5μm (f=2ghz)

6 SAW Transversal Filters Impulse Response Independent Control of Amplitude and Phase Responses

7 Impulse Response Frequency Response t f t f t f + h ( t) = H ( f )exp( + 2πjft) df + H ( f ) = h( t)exp( 2πjft) dt

8 Why Acoustic Wave Devices? Temperature Stability GSM Bandwidth (200kHz) GSM1900 Center Freq. (1.9GHz) 100ppm cf. For Si, 3000ppm/ o C I = I0[exp( qv / kt) 1] For watch, 1sec. 1day 10 ppm

9 Trade-Off Between Temp. Stability & Bandwidth T drift (a) Wider Transition Bandwidth ω T drift (b) Narrower Transition Bandwidth Efficient Use of Frequency Resources Narrow Transition Bandwidth (Or Improve Production Yield) ω

10 Transfer function in db Fourier-Transform-Based Design Relative Frequency Transfer function in db Ripple due to truncation [Gibb s Phenomenon]

11 Influence of Truncation h d (t) t Convolution Relation w(t) t H + w ( f ) H d ( ξ ) W ( ξ f ) = dξ h d (t)w(t) t

12 Window Functions t f t f Hamming:w(t)= cos(2πt/T) Blackmann:w(t)= cos(2πt/T) +0.08cos(4πt/T) Blackmann-Harris:w(t)= cos(2πt/T) cos(4πt/T) cos(6πt/T)

13 1 0.8 Weight Hamming Blackmann Blackmann-Harris Relative Position

14 Frequency Response of Window Functions with same T Amplitude in db rectangular Hamming Blackmann Blackmann-Harris Relative frequency

15 Design by Fourier Transform + Window Function Transfer function in db Relative frequency Transfer function in db

16 Ref. 15dB 10 db/div 1 db/div 50ns/div FREQUENCY (MHz) FREQUENCY (MHz) SAW Transversal Filter for CATV

17 SAW IF Filter for IS-95 Insertion loss in db Simulation Experiment Effects of Diffraction (2D SAW Propagation) Frequency in MHz Courtesy of Fujitsu Labs.

18 (a) For Wide Aperture (b) Narrow Aperture Variation with Aperture Size For Weighted IDT

19 Low Frequency Design CD player Amp. DAT High Z in and Low Z out for Minimum Interference High Frequency Design Power source Load Power source Load R S E S R L R S E S? R L R L =R S for Maximum Power Transfer How about for this case?

20 Triple Transit Echo (TTE) Interdigital Transducers (IDT) Mechanical Reflection + Electrical Regeneration Mutual-Connection Dependent Trade-Off: TTE Insertion Loss Intrinsic for Bidirectional IDTs

21 Insertion loss in db Influence of TTE Relative Frequency S 21 S 0 21

22 Bragg Reflection Single-Electrode IDT Bragg Condition p p=nλ/2 Double-Electrode IDT

23 Transversal SAW Filter absorber absorber Guard electrode Absorbers for Suppression of Reflection at Substrate Edges Dummy Electrode for Suppression of Reflection and Charge Concentration at Edges Guard Electrode for Suppression of EM Feedthrough

24 Contents SAW SAW Transversal Filter SAW Unidirectional IDT Filters SAW SAW Resonator Filters SAW SAW Wireless Tags and Sensors

25 Heterodyne Transceiver Antenna Duplexer LNA RF-BPF IF-BPF φ A/D Q A/D I PLL/VCO PLL/VCO PLL/VCO PA D/A I RF-BPF IF-BPF φ D/A Q Red:SAW Devices

26 Single Phase Unidirectional Transducer (SPUDTs) (a) Combination with Reflector (Simple but Narrowband) (b) Inlayed Reflector (Complex but Wideband) TTE Suppression Low Loss Frequency Response Weighting for Excitation Profile Reflection Bandwidth < IDT Bandwidth Reflector Weighting Independent Weighting to both Excitation and Reflection

27 Unidirectional Condition C r C t C r C t C t : Excitation Center C r : Reflection Center p I Δ X For +X Direction, For -X Direction 2 βδ + Γ = 2mπ 2 β ( Δ) + Γ = (2n + 1)π p I Unidirectional Cond. Γ = ± π / 2, Δ = ± λ / 8

28 For Independent Weighting to Excitation and Reflection (a) Excit.-Less, Ref.-Less (b) With Excit., Ref.-Less (c) Excit.-Less, With Ref. (d) With Excit. & Ref. EWC(Electrode-Width-Control)/SPUDT

29 Filter Response with Reduced TTE Scattering Coefficient (db) L I =20p I L T =50p I κp I =0.02π ψ=90 o ψ=0 o Relative Frequency Low Loss and Suppressed TTE

30 Resonant SPUDT (R-SPUDTs) Reversed Reflection Weighting Direct Pulse Multiple Echoes Extension of Impulse Response

31 With Reflection ω Without Reflection Skirt Characteristics are Defined by Impulse Response Length Out-of-Band Characteristics are Defined by Excitation Profile

32 Designed Example Scattering Coefficient (db) L I =34p I L T =0 S 21 κp I max =0.1π τ Relative Frequency Sharp Passband Shape + Flat Group Delay Group Delay τ/τ p

33 Optimized weighted function Weighting Function Excitation Forward Reflection Relative Position

34 Weak Resonant SPUDT Filter Courtesy of EPCOS AG

35 Strong Resonant SPUDT Filter Courtesy of EPCOS AG

36 Contents SAW SAW Transversal Filter SAW SAW Unidirectional IDT Filters SAW Resonator Filters SAW SAW Wireless Tags and Sensors

37 Homodyne Transceiver Antenna Duplexer LNA RF-BPF φ A/D Q A/D I PLL/VCO PLL/VCO PA RF-BPF D/A I φ D/A Q Circuit Simplification Reducing Component Number No Image Signal Relaxing Specs to RF Filters

38 SAW Resonator (a) 1-Port Resonator (b) 2-Port Resonator Filter

39 Application of Electric Field to Piezoelectric Material, + - M i dv dt + ηv + k vdt = F V v k -1 M Piezoelectric Material C m L m C 0 V F η C 0 R m (a) Electric + Mechanical Circuit (b) Electrical Equiv. Circuit Analogies between V F and I v reduce to M L, h R, k 1/C

40 k η C m L m M C 0 R m k 0 (a) Electrical Equiv. Circuit F (b) Equiv. Mechanical Circuit Resonance Frequency ω r =1/ C m L m Anti-Resonance Frequency ω a =1/ L m (C -1 m +C -1 0 ) -1 Resonance Q (Steepness of Resonance) Q=ω r L m /R m Determine Insertion Loss and Skirt Characteristics Capacitance Ratio (Weakness of Piezoelectricity) γ=c 0 /C m =[(ω a /ω r ) 2-1] -1 Determine Insertion Loss and Bandwidth

41 f r f a Admittance [S] Frequency [GHz] Resonance Frequency ω r =1/ C m L m Anti-Resonance Frequency ω a =1/ L m (C m -1 +C 0-1 ) -1

42 Transverse Mode Admittance G In-harmonic Resonance B Frequency ω r ω a

43 Ladder-Type SAW Filter Low Loss High Power Durability Moderate Out-of-Band Rejection Topology

44 Insertion Loss (db) ω r ω a Frequency ω Series-Connection Y s Insertion Loss (db) ω r ω a Frequency ω Parallel-Connection Y p Insertion Loss (db) ω r p p s ω a =ω r Frequency ω π-connection Y p s ω a Y s Y p Null Generation at Both Sides

45 Performance of Ladder-Type SAW Filter Scattering Parameter S 21 (db) Tx Rx Frequency (MHz) Scattering Parameter S 21 (db) W-CDMA-Rx Fujitsu FAR-F6CP-2G1400-L21M

46 Antenna Duplexer for US PCS Tx Band strip line λ/4 SAW filter, TX TX-port Antennaport Rx Band strip line λ/4 SAW filter, RX RX-port 0 Attenuation [db] Tx band Rx band Frequ ency [M H z] Courtesy of Fujitsu Labs.

47 Temperature Compensation (1) Bonding with Small Thermal Expansion Coef. J.Tsutsumi, et al., Proc. IEEE Ultrason. Symp. (2004) pp Fujitsu Labs.

48 Temperature Compensation (2) Depositing SiO 2 with Negative Temp. Coef. M.Kadota, et al., Proc. IEEE Ultrason. Symp. (2004) pp Murata MFG

49 Double Mode SAW (DMS) Filter Symmetrical & Antisymmetrical Resonances Electrically Isolated I/O Insertion loss (db) ωs r Frequency ωa r ω Good Out-of-Band Rejection Balun Function Transformer Function Low Loss Lower Power Durability

50 Structure of Pitch-Modulated IDT & Reflector Conventional Structure Pitch-Modulated Structure Gap Controlled Modulated REFECTOR IDT IDT Presented at IEEE 2004 UFFC Conf. Modulated

51 DMS Filter with Modulated Structure Scattering parameter. S 21 [db] Frequency [MHz] Scattering parameter. S 21 [db] Fujitsu FAR-F5EB-942M50-B28E

52 Integrated RF Circuit (a) Balanced I/O (b) Unbalanced I/O Current Antenna and RF Stage are Unbalanced

53 Discrete SAW Filter & Balun Front-end BPF LNA Inter-stage BPF Balun Mixer IF-BPF IF-Amp SAW Filter with Balun Function Front-end Inter-stage BPF LNA BPF Mixer IF-BPF IF-Amp

54 DMS Filter (Ideally No Common Signal) Acoustically Coupled but Electrically Isolated V in V out+ V out- Common Signal Generation by Parasitics

55 Z-conversion by DMS Filter V out+ V in V out- V in V out+ V out-

56 Contents SAW SAW Transversal Filter SAW SAW Unidirectional IDT Filters SAW SAW Resonator Filters SAW Wireless Tags and Sensors

57 Quartz Micro-Balance (QMB) Mass Loading AT-cut Quartz Temperature Stability Phase (or Frequency) Output High Resolution Low Price Sensor Applications: Physical (Film Thickness, Pressure), Chemical(Gas, Liquid), Bio

58 SAW Sensor IDT V in SAW V out Piezo-Substrate High f (Δ f = K f 02 Δm) High Sensitivity Moderate Temperature Stability Surface Protection (Packaging)? Area 1 mm 2 & f 0 =1 GHz give K f 0 ~ 10 7 / kg 1 ppm of f deviation=resolution 0.1 pg.

59 SAW Sensor Configuration Frequency Detection Δf ~ Δm Phase Detection Δφ~ Δm

60 SAW Chemical Sensor Frequency Deviation [Hz] Time [min] Content [ppm] Sensitive Layer: A calixarene (10 nm) Object: tetrachloroethene f 0 : 434 MHz

61 Pattern Recognisition with Sensor Array Sensor Array A B C D p-xylene m-xylene humidity Sensor : Sensitive Film A Calix[4]resorcinearene 1 B Calix[4]resorcinearene 2 C Cyclodextrine-functiona- D lized polymer 1 Cyclodextrine-functionalized polymer 2

62 What is SAW ID-TAG? Antenna Transceiver Wireless, Batteryless Large Group Delay (Separation with Environmental Echoes)

63 Separation of SAW Signal in Time Domain Excited Signal RF Response Environmental Echo Sensor Echo time

64 Which Frequency? 5.2 GHz (ISM Band) Wideband (100MHz), Short Accessible Distance (<1m), Hard to Realize SAW Devices 2.45 GHz (ISM Band) Wideband(22MHz), Short Accessible Distance (2-3m), Price of SAW Devices? MHz (RKE Band) Narrowband(1.7MHz), Long Accessible Distance (>10m), Low SAW Device Cost

65 SAW ID Tag with 5 reflectors in one track (f 0 = 2.45 GHz) using pulse position coding Pulse position coding schema Antenna Possible coding position of 1st reflector Possible coding position of 2nd reflector Tag by 1st reflecor 2nd reflector

66 Baumer Ident (2.45 GHz ISM) OIS - W

67 Brake temperature of a train entering a station reader antenna 100,00 Brake (with attached SAW temperature transponder, not seen) Temperature C 90,00 80,00 70,00 60,00 Time

68 SAW Torque Sensor Rx antennas Tx antennas phase difference in deg strain in SAW sensors measurement set-up rotating shaft The dynamic range of monitoring the torque with SAW can be up to several tenths of khz

69 antenna SAW pressure diaphragm sensor adhesive cover-plate closed cavity with reference-pressure pressure [Bar] :30:55 14:30:59 14:31:04 14:31:09 14:31:13 14:31:18 Two Track Railway Crossing 14:31:22 14:31:27 Adjacent Water Channel 14:31:32 14:31:36 time 14:31:41