1 Low Phase Noise Oscillators for MEMS inductors Sofia Vatti Christos Papavassiliou.
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Transcript of 1 Low Phase Noise Oscillators for MEMS inductors Sofia Vatti Christos Papavassiliou.
1
Low Phase Noise Oscillators
for MEMS inductors
Sofia Vatti
Christos Papavassiliou
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Summary
Two sets of oscillator circuits prototyped for EPSRC-STEP FASTSAN:• Fixed frequency single phase Oscillators for MEMS integration• Voltage controlled Oscillators for MEMS integration• Quadrature Oscillators for MEMS integration • MEMS characterisation test patterns• Same circuits with planar inductors provided by the process
Extensive on-chip calibration facilities:• MEMS inductor characterisation pattern• Monolithic inductor characterisation pattern• RF wafer probe calibration structures
All oscillator circuits ESD protected
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Measurements on “chip2” (novel VCO, AMS 0.35)
Proposed topology:- oscillates at 1.952 GHz- phase noise as State of the Art- extra tunability through internal
loop supply (+varactors)
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measurements - 1: frequency tuning
Varactor control: 100 MHz
Reference Supply Control: VDD2
30 MHz tunability ---- linearity improved
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measurements – 2 phase noise
Varactor control
Reference Supply Control: VDD2
- Phase Noise performance maintained when tuning via VDD2.- Integrated inductor Q=3 @ 2GHz (low compared to literature)
- Power consumption = 50mW (high compared to literature)
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FastSAN “chip 3”micrograph
MEMS Inductor Integration pad
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Oscillator exampleDC probe card (10 needles) :
Power & frequency band switching
RF probes
Calibration patterns
UMC 0.18 micron CMOS
200um
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VCO Measurements: circuit
- No varactors in the tank
- Control voltages switch in caps C0-C4 to change frequency bands
- 3nH foundry inductor
Breaking the loop with Caps provides access to gates of NMOS. AC is still coupled.
DC gate bias is set from M3-M5, M4-M6, by controlling VDD2.
VDD2 control from 0.8V-1.8V provides up to 300MHz tuning.
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VCO measurements: tuning range
VCO Tuning Range
3.8003.9004.0004.1004.2004.3004.4004.5004.6004.7004.8004.9005.0005.1005.2005.3005.400
0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
VDD2 (V)
Fre
qu
ency
(G
Hz)
- 1.5GHz total range: 3.8 to 5.3 GHz
- Switch-in capacitor approach
- 5 coarse-tuning regions
- Fine tuning (200 to 300MHz) provided by bias mechanism
- No varactors used
Reference Supply Control
Gradually switching in the caps: 5 switches
Phase noise: <-70dBc/Hz @100kHz
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Conclusions
• Collaboration with OSD Group• CAS role:
– Electronic Design for CMOS – MEMS co-integration– Novel LC oscillator topologies have been prototyped and tested– Performance comparable to state of the art
• OSD role:– Develop Hetero-Integration Technology
• Project status:– Final stages of CMOS+MEMS assembly