berkeley sensor & actuator center smart dust active laser transmitter (salt) matthew last, kris...
TRANSCRIPT
Berkeley Sensor & Actuator Center
Smart dust Active Laser Transmitter (SALT)
Matthew Last, Kris PisterBerkeley Sensor and Actuator Center
http://www.eecs.berkeley.edu/~mattlast
Berkeley Sensor & Actuator Center
• Free-space Communication • Low-frequency Beam Steering (DC -> 1kHz)
Smart dust Active Laser Transmitter (SALT)
Berkeley Sensor & Actuator Center
Free-Space Communication using Agile Beamsteering• What do we gain over RF?
– High Antenna Gain• Excellent performance: low power, long range, high bit rate• 1mrad, 1mW beam = 318 kW/steradian• Isotropic 1mW radiator = 80 W/steradian Antenna gain of 152 dB for typical laser
– No spectrum regulation issues– SDMA (Space-Division, Multiple Access) with imaging
receivers– Only simple baseband modulation necessary (OOK)
Berkeley Sensor & Actuator Center
Free-Space Communication using Agile Beamsteering (2)• When to use?
– Need Line of Sight– Need Clear Weather (no fog)
• At what cost?– Tight alignment tolerances– Only point-to-point networks (no broadcasting)– Unidirectional links yield asymmetrical networks
Berkeley Sensor & Actuator Center
Long Range, Low Power Crosslinks
(a) 5.2 km Berkeley Marina
(b) 15.3 km Coit Tower
(c) 21.4 km Twin Peaks
3 mW optical power:
And plenty of power to go further…
Berkeley Sensor & Actuator Center
Current Work
Berkeley Sensor & Actuator Center
Performance:
Mechanical Angle of
Deflection
Unactuated
(Probe Tip)
Actuated
(Thermal)
In-plane 45 degrees 11 degrees
Out-of-plane Untested 28 degrees
Berkeley Sensor & Actuator Center
Actuation Power - 1st Generation
Power vs Mechanical Deflection Angle
0
50
100
150
200
250
300
350
0 10 20 30 40
degrees
actu
ato
r p
ow
er (
mW
)
1st DOF
2nd DOF
Berkeley Sensor & Actuator Center
Actuation Power – 2nd Generation
Power vs Mechanical Deflection Angle: 1st DOF, torsion mirror
0
50
100
150
200
250
0 2 4 6
degrees
mW 1st DOF
Berkeley Sensor & Actuator Center
2nd Generation Mirror Pictures:
Berkeley Sensor & Actuator Center
Ongoing Projects:
• Lenses and lens systems– vary lens diameter– lens quality evaluation?
• Laser diode mount• Prototype laser transmitter system (laser diode ->
collimating lens -> 2-DOF mirror)
Berkeley Sensor & Actuator Center
More Pictures:
Berkeley Sensor & Actuator Center
Fun Numbers:
• divergence = 1.22 /d– 1mm aperture @ 650nm .79 mrad divergence– 1mrad divergence @ 650nm .79mm aperture
• 1mW 1mrad emitter puts out 40 times more power/steradian than a 100 W bulb