STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
J.-M Friedt, S. Alzuaga, N. Ratier, N. Vercelloni, R. Boudot, B.
Guichardaz, W. Daniau, V. Laude, S. Ballandras FEMTO-ST/LPMO (Besan¸con, France),
17 septembre 2005
STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
STW resonators
STW display highest QF product (compared to Rayleigh for example).
Can the quality factorQ be improved with an optimized geometry ? p : period=constant over the whole device (cavity, transducers and mirrors)
a : finger width
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STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Asynchronous design for stop-band tuning
0.4965 0.497 0.4975 0.498 0.4985 0.499 0.4995 0.5
468 469 470 471 472 473 474 475
real part (γ) imaginary part (γ)
frequency (MHz)
a/p 0.55 a/p 0.65
STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Realization of the resonators
Dipole and quandripoles designed for resonance at 750 and 1015 MHz were designed and fabricated (FEMTO-ST/LPMO cleanroom : 2.5µm and 3.38µm fingers).
700 to 1000 ˚A thickAl sputtered on AT quartz (3” wafers).
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STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Measurements
Measurements : reflected admittanceY11(f) for dipoles, andS21(f) transmission coefficient for the quadrupoles
1.01 1.015 1.02 1.025
x 109
−50
−45
−40
−35
−30
−25
−20
−15
−10
frequency (Hz)
S21 (dB)
asynchronous
Q~5800−6770 synchronous Q~5100−5800
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
1.012e+009 1.014e+009 1.016e+009 1.018e+009 1.02e+009 1.022e+009
Re[Y11]
frequency (Hz) 1GHz STW resonators
asynch1: Q=4400 asynch 2: Q=4600 synch 1 : Q=5300 synch 2 : Q=4600
⇒asynch. devices display reduced ripples but also loweredQ factor
⇒asynch. devices appear best suited for filter applications while synchronous devices are better suited for frequency source applications
STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Modelling
Simplified mixed matrix based model
• for simulating the response of dipoles and quadrupoles
• including geometrical effects and mass loading but
• excluding bulk modes.
0
@ S1
S2
I 1 A=
0
@
r1 t α1
t r2 α2
−α1 −α2 G+jB 1 A
0
@ E1
E2
V 1 A
r1=r2=−jsin(∆) exp(−jϕ) t= cos(∆) exp(−jϕ) α1=α2=j√
Gexp
„
−jϕ+ ∆ 2
«
B=G sin(ϕ)−sin(∆) cos(∆)−cos(ϕ)
and
|∆|=πfe−fs
fe+fs
ϕ= 2π f fe+fs
G = ys−ye
tan(|∆|)
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STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Synchronous dipole resonators
synchronous designs
Re(Y11)
frequency (MHz)
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
1004 1006 1008 1010 1012 1014 1016
0.3 0.35 0.4 0.45 0.5 0.55
0.65 0.75
0.60.7
An optimum a/p appears to be around 0.7 for which insertion loss are
STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Quadrupoles
Modelling of
• asynchronous devices (a/pmirror constant at 0.7, varyinga/pin transducers+cavity)
• sychronous configurations (negligible effect of the cavity)
-70 -60 -50 -40 -30 -20 -10 0
1004 1006 1008 1010 1012 1014 1016 1018 1020
Mag(S21) (dB)
Frequency (MHz) a/p=0.7 in mirrors, variable in transducers and cavity
a/p=0.75 a/p=0.7 a/p=0.6 a/p=0.5 a/p=0.4 a/p=0.3
-60 -50 -40 -30 -20 -10 0
1004 1006 1008 1010 1012 1014 1016 1018 1020
Mag(S21) (dB)
Frequency (MHz)
Quadrupole resonators with a/p=0.4 in cavity and variable in transducers and mirrors a/p=0.7 a/p=0.6 a/p=0.5 a/p=0.4 a/p=0.3
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STW Resonators for Filters and High Stability Source Applications J.-M Friedt& al
Introduction Experimental results Models Conclusion
Conclusion
• Synchronous and asynchronous STW resonators have been modelled and fabricated
• sideband ripples are strongly attenuated in the asynchronous design
⇒filters
• the quality factor is degraded in the asynchronous design compared to synchronous⇒source
• strong sensitivity to the mass of the fingers (metal thickness). Not systematically investigated here.
• optimuma/pvalues are in the 0.7 range for synchronous dipoles and 0.3 for synchronous quadrupoles⇒spectral purity.
• greatest difference betweena/p of mirrors and transducers leads to sharpest resonances (greatest efficiency of mirrors) in asynchronous quadrupoles.
