Kenneth Corbett
Endowment
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Design an optical communication Integrated
Circuit (IC) chip that will allow full-duplex
transmission of wireless data at a bandwidth
of 100kbit/s over a distance of several meters
using a Field Programmable Gate Array
(FPGA) interface.
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Undergraduate Seniors pursuing a B.S.E.E.
Markus Chris Pin-Jen
Geiger Goodale Wang
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Consulting Faculty
Dr. Ken Noren
Dr. Suat Ay
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Product applications
Technical constraints and design goals
Simplified block diagram
General design considerations
Major design decisions
Integrated Circuit Design
FPGA interface
Final Product
Demonstration platform
Specifications
Project cost
Future work
References
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Directional, highly secure wireless transmission
 Control/monitor sensitive
information/infrastructure eg. wireless traffic
monitoring, wireless money transfer via cellphone,
etc.
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Alternative to WiFi (Wireless Fidelity), which is
based on the IEEE 802.11 standard
 Electro Magnetic (EM) safe
 Unregulated wireless spectrum
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Wireless sensor networks
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 Transmitter (TX) requirements
▪ Pdp_max = 500mW
▪ V_bias = 1.5V (+/- 100mV)
 Receiver (RX) requirements
▪ Pdp_typ = 100mW
▪ V_bias = -5V
 Transmission distance through air
▪ limited by power output of light-emitting diode (LED)
and beam half angle
▪ Power decreases through air with
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Preliminary Specifications:
 100kbit/s signal transmission
 Range of 2+ meters
 Custom transmission protocol
 Total power dissipation of TX circuitry < 500mW
 Total power dissipation of RX circuitry < 10mW
 5V single-ended power supply
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High gain
trans
impedance
amplifier
(TIA)
Comparator
to digitize
the signal
Transmitter
Light
emitting
element
(transmitter)
Common Drain amplifier to
provide sufficient current
MCPnano Transceiver IC
Encoder that
processes the
received signal
Decoder that
processes binary
input according to
a communication
standard
User
Photo
sensitive
element
(receiver)
user interface
Free space
Receiver
FPGA
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Off the shelf components
 LED to transmit data (IR or visible light)
 Photo-diode to receive data (PIN or Avalanche)
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MCPnano Integrated Circuit (IC) Design
 Amplifier / Comparator stages for the receiver circuit
 Transmitter circuitry consisting of repeaters and FET
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System integration/interface with FPGA
 Connectivity/User-interface
 Encoding/Decoding schemes
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INFRARED (IR) LED
VISIBLE LIGHT LED
Wavelength: 390nm to 780nm
Very susceptible to
interference from ambient
light (need for a versatile filter
system & noise cancellation
system)
 May use solid-state lighting
(more compact system, ease of
deployment)
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Wavelength: 780 nm to 950 nm
limits interference due to
ambient light
 Need for separate transmission
circuitry
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Vishay High Speed IR LED
890nm:
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PHOTO
TRANSISTOR
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Slow response
time (~500ns+
rise & fall)
Not feasible for
our com.
System
Inherent gain of
the NPN
transistor
Low cost
(50c/piece)
fff
PIN PHOTO-DIODE
Fast rise/fall
times (5 to 50ns
typ.)
 5V typ. rev. bias
 Low cost (eg.
50c/piece)
 Osram Photo
diode 900nm
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AVALANCHE
PHOTO-DIODE
Fast rise/fall
times (1ns typ.)
 Highly sensitive
 High gain (self
multiplication
‘avalanche’
mechanism)
 40V typ. rev.
bias
 High cost
($50+/piece)
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PIN PHOTODIODE
IR LED
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Design environment: Cadence 6.1.5
Process: ONSemi’s 0.5mm process (C5)
Tapeout Date: November 28th, 2011
Cost:$960
IC Design Effort
 Receiver design (TIA, comparator)
 Transmitter design (LED driver)
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Bias voltages to be set externally (adjustability)
 Allows use of different diodes
 Debugging
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Feedback resistor/potentiometer located off
chip
 impractical to implement 5MOhm resistor on-chip
 Flexibility, various distances possible
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Reference current set through off-chip variable
resistor (adjustable gain of opamp if needed)
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Custom VHDL code that implements the
following protocol
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Special Thanks to Dr. James Frenzel (aka Dr. J)
for supplying us with two Digilent BASYS2
boards
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back
front
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Specifications:
 100kbit/s signal transmission
 Maximum range of 3 meters
 Custom transmission protocol (FPGA in VHDL)
 Total power dissipation of TX < 500mW
 Total power dissipation of RX < 10mW
 5V single-ended power supply (battery pack)
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Compact IC transceiver unit on a PCB
Datasheet/Documentation of transceiver
 TX: LED
 RX: Photo-diode
 IC: TIA, Comparator, LED driver
 Discrete level shifter
 Custom Communication Protocol (VHDL)
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Parts
$ 180.00
Fabrication and packaging – 20 parts (11/28/11)
$ 960.00
Poster for presentation
$ 100.00
Total cost
$ 1,240.00
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Incorporate the transmission protocol (using
shift registers, etc.) onto the Integrated
Circuit
 VHDL description may be used to create the
layout using automated place & route tools
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Improve the comparator design on the IC
(accomplish hysteresis)
Design for higher speed transmission
(500kbit/s +)
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FSO applications / outlook into the future
 http://www.bu.edu/smartlighting/files/pdf/May808_slides_Little_FSO_Commun1.pdf
IR vs. RF
 https://www.audiolinks.com/articles/rfvsir/
Vishay High Speed IR LED 890nm:
 http://www.mouser.com/Search/ProductDetail.aspx?qs=%2fjqivxn91cfAnyW9i5Zlpg%3
d%3d
Osram Photo diode 900nm:
 http://www.mouser.com/ProductDetail/Osram-Opto-Semiconductor/SFH-2500-FAZ/?qs=K5ta8V%252bWhtarQtPwL45qKw%3d%3d
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