Design of Asynchronous STW Resonators for Filters and High Stability
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. @.
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications J.-M Friedt & al Introduction Experimental results
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
Models Conclusion
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
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Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
STW resonators
J.-M Friedt & al Introduction
STW display highest QF product (compared to Rayleigh for example).
Experimental results Models Conclusion
Can the quality factor Q be improved with an optimized geometry ? p : period=constant over the whole device (cavity, transducers and mirrors) a : finger width
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Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
Asynchronous design for stop-band tuning
J.-M Friedt & al Introduction
0.5 Experimental results
0.4995
Models Conclusion
imaginary part (γ)
real part (γ)
0.499 0.4985 0.498 0.4975 a/p 0.55
0.497
a/p 0.65 0.4965 468
469
470
471 472 frequency (MHz)
473
474
475
Increasing the finger width in the mirror enhances the reflection coefficient 3/9
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
Realization of the resonators
J.-M Friedt & al Introduction Experimental results Models Conclusion
Dipole and quandripoles designed for resonance at 750 and 1015 MHz were designed and fabricated (FEMTO-ST/LPMO cleanroom : 2.5 µm and 3.38 µm fingers). 700 to 1000 ˚ A thick Al sputtered on AT quartz (3” wafers).
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Design of Asynchronous STW Resonators for Filters and High Stability Source Applications J.-M Friedt & al
Measurements Measurements : reflected admittance Y11 (f ) for dipoles, and S21 (f ) transmission coefficient for the quadrupoles
⇒ asynch. devices display reduced ripples but also lowered Q factor ⇒ asynch. devices appear best suited for filter applications while synchronous devices are better suited for frequency source applications (high Q needed) 5/9
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
Modelling
J.-M Friedt & al Introduction Experimental results Models Conclusion
Simplified mixed matrix based model • for simulating the response of dipoles and quadrupoles • including geometrical effects and mass loading but • excluding bulk modes. 0
10 1 α1 E1 A @ E2 A α2 G + jB V fe − fs fe + fs f ϕ = 2π fe + fs ys − ye G = tan(|∆|)
|∆| = π and
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Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
0.16
Introduction
0.14
Experimental results
synchronous designs
0.12
Models
Re(Y11)
Conclusion
0.75
0.6
J.-M Friedt & al
0.7 0.65
Synchronous dipole resonators
0.55
0.1
0.5
0.08
0.45
0.06
0.4
0.04
0.35 0.3
0.02 0 1004
1006
1008
1010
frequency (MHz)
1012
1014
1016
An optimum a/p appears to be around 0.7 for which insertion loss are lowest and Q highest. 7/9
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
Quadrupoles
J.-M Friedt & al
Models Conclusion
Modelling of • asynchronous devices (a/p mirror constant at 0.7, varying a/p in transducers+cavity) • sychronous configurations (negligible effect of the cavity) a/p=0.7 in mirrors, variable in transducers and cavity
Quadrupole resonators with a/p=0.4 in cavity and variable in transducers and mirrors
Design of Asynchronous STW Resonators for Filters and High Stability Source Applications
Conclusion
J.-M Friedt & al Introduction
• Synchronous and asynchronous STW resonators have been
modelled and fabricated
Experimental results Models
• sideband ripples are strongly attenuated in the asynchronous design
Conclusion
• • • •
⇒ 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. optimum a/p values are in the 0.7 range for synchronous dipoles and 0.3 for synchronous quadrupoles ⇒ spectral purity. greatest difference between a/p of mirrors and transducers leads to sharpest resonances (greatest efficiency of mirrors) in asynchronous quadrupoles.