April 3, 2013 Introduction to Surface Acoustic Wave (SAW) Devices

105 Pages·2015·2.6 MB·English

April 1, 2015
Introduction to Surface
Acoustic Wave (SAW) Devices
Part 1: What is SAW Device?
Ken-ya Hashimoto
Chiba University
[email protected]
http://www.te.chiba-u.jp/~ken
Contents
•SAW Transversal Filter
•SAW Unidirectional IDT Filters
•SAW Resonator Filters
•Duplexers
•Oscillators
•SAW Wireless Tags and Sensors
Contents
•SAW Transversal Filter
•SAW Unidirectional IDT Filters
•SAW Resonator Filters
•Duplexers
•Oscillators
•SAW Wireless Tags and Sensors
Surface Acoustic Wave
Bulk Acoustic Wave
(BAW):
•Longitudinal Wave
(Primary Wave)
•Transverse Wave
(Share Wave,
Secondary Wave)
Surface Acoustic
Wave (SAW):
Propagation of
(Rayleigh SAW)
Seismological Waves
Surface Acoustic Wave (SAW) Device
Interdigital Transducers (IDT)
SAW
V
in
V
out
Piezoelectric substrate
• Mass Production by Photolithography
• Low loss, Miniature & Low price
• Operation inVHF-UHF ranges
Line width /4=0.5m (f=2GHz)
SAW Transversal Filters
Impulse Response
• Independent Control of Amplitude
and Phase Responses
Impulse Response Frequency Response
t f
t f
t
f
 
h(t)   H ( f ) exp(2jft)df H ( f )   h(t) exp(2jft)dt
 
Why Acoustic Wave Devices?
• Temperature Stability
1 sec.
For watch,
 10 ppm
1 day
cf. For Si, 3000ppm/oC
I  I [exp(qV / kT ) 1]
0
Trade-Off Between Temp. Stability & Bandwidth
T drift

(a) Wider Transition Bandwidth
T drift

(b) Narrower Transition Bandwidth
Efficient Use of Frequency Resources  Narrow
Transition Bandwidth (Or Improve Production Yield)
Fourier-Transform-Based Design
5
1
0 B
0.8
B
d
d
-5
0.6 n

n
i
i
-10 0.4 n
n
o
o
i
i -15 0.2 t
t c
c n
n -20 u
0
u
f
f
r
-25 -0.2
r e
e f
f s
-30 -0.4
s n
n
a
a r
-35 -0.6
r T
T
-40 -0.8
-45
-1
-0.2 -0.1 0 0.1 0.2
Relative Frequency
Ripple due to truncation [Gibb’s Phenomenon]