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

Introduction Experimental results

1GHz STW resonators −10

Models

asynchronous Q~5800−6770

0.08

synchronous Q~5100−5800

asynch1: Q=4400 asynch 2: Q=4600 synch 1 : Q=5300 synch 2 : Q=4600

0.07

−15

−20

0.06

−25

0.05 Re[Y11]

S21 (dB)

Conclusion

−30

−35

0.04

0.03

−40

0.02

−45

0.01 −50 1.01

1.015

frequency (Hz)

1.02

1.025 9

x 10

0 1.012e+009

1.014e+009

1.016e+009 1.018e+009 frequency (Hz)

1.02e+009

1.022e+009

⇒ 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

1 0 S1 r1 @ S2 A = @ t I −α1

t r2 −α2

r1 = r2 = −j sin(∆) exp(−jϕ) t = cos(∆) exp(−jϕ) « „ √ ϕ+∆ α1 = α2 = j G exp −j 2 sin(ϕ) − sin(∆) B=G cos(∆) − cos(ϕ)

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

0

0 a/p=0.75 a/p=0.7 a/p=0.6 a/p=0.5 a/p=0.4 a/p=0.3

-10

a/p=0.7 a/p=0.6 a/p=0.5 a/p=0.4 a/p=0.3

-10

-20 -20 Mag(S21) (dB)

Experimental results

Mag(S21) (dB)

Introduction

-30

-40

-30

-40 -50

-50

-60

-70 1004

1006

1008

1010

1012 1014 Frequency (MHz)

1016

1018

1020

-60 1004

1006

1008

1010

1012 1014 Frequency (MHz)

1016

1018

1020

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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.

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