Optimization of control path for low-ripple fast
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Transcript Optimization of control path for low-ripple fast
Envelope Detector Control Path
Enhancements for Low-Power
Medical Applications
J. Chan-Wai, B. Lawrence, V. Proulx
ELG 4135 Electronics III
Dr. Riadh Habash
November 24th 2006
Team Members
Jason Chan Wai
Brian Lawrence
Valerie Proulx
Conventional Envelope Detector
•
Envelope detectors are
used to obtain the
envelope of an AM
modulated signal.
Relevant Research
Envelope Detector Proposed in Research Paper
[1] Alegre, J.P., Celma, S., Sanz, M.T., and Garcia del Pozo.
‘Low-ripple fast-settling envelope detector’, Electronics Letters,
2006, 42, (18), pp. 1-2.
Application:
Hearing Aids and Cochlear Devices
We are interested in
engineering for
medical applications
Hearing aids are
designed for
frequencies ranging
from 250 to 4,000 Hz
Application:
Hearing Aids and Cochlear Devices
Original Control Path
Control path proposed in referenced research
paper
Problems
Cannot receive low voltage signals
High-pass filter
No amplification
Hearing aids require low voltage and low
frequency signals
Noise amplified due to three stage MOSFET
inverters
Two separate control paths (180° out of
phase) required to minimize the effect of
noise
Simulation
Simulation was performed on researched
control path using PSpice
Simulation Results 1
Output when input signal is 3V (large)
Circuit functions as intended
Simulation Results 2
At small voltages (300mV) the proposed
control path does not function properly!
Simulation Results
Input
signal not strong enough to drive
MOSFET inverters
Therefore, control path is unable to
properly switch the peak hold circuits at
a peak in the input signal
Problematic with low frequency signals
(due to high-pass filter)
Primary Goal
Enhance
the circuit’s response to weak,
low frequency signals to ensure that
they can switch the CMOS inverters and
therefore properly detect signal peaks
Secondary Goals
Minimize
output noise
Eliminate the need for a second control
path
Optimized Control Path
Proposed design utilizes active components
in the input network!
Simulation Results 1
Output of proposed control path with 300mV,
2kHz input signal
Simulation Results 2
Output of proposed control path with 300mV
500Hz input signal
Simulation Results
Capable
of receiving low voltage input
signals within the desired frequency
band
Number of CMOS stages reduced
(lower output noise)
Single control path now capable of
driving two control signals, eliminating
the need for a second control circuit!
Analysis Comparison: Passive Circuit
PROS
Energy efficient
Passive input network requires no power
Speed
CONS
Inability to receive low frequency, low voltage
signals
Requires two control paths
Analysis Comparison: Active Circuit
PROS
Ability to receive low frequency, low voltage
signals
Single control path required
Lower output noise
CONS
Active stage requires more power usage than
passive equivalent
Conclusion
Researched envelope detector employing passive
control path proves to be inadequate when utilized in
hearing aids and cochlear devices
Control path implementing active stage demonstrates
acceptable performance for low voltage, low
frequency signal reception as required in Audio
Sensory Medical (ASM) devices
Recommended future work – define an alternative
implementation to the op-amp that provides
equivalent performance at lower power consumption
Followed Schedule
References
[1] Alegre, J.P., Celma, S., Sanz, M.T., and Garcia del Pozo.: ‘Low-ripple fastsettling envelope detector’, Electronics Letters, 2006, 42, (18), pp. 1-2
[2] Communication Systems Tutorial: Envelope Detection, Utah State University:
http://images.google.ca/imgres?imgurl=http://www.engineering.usu.edu/classes/
ece/5660/lab2/envdetpic.jpg&imgrefurl=http://www.engineering.usu.edu/classes/
ece/5660/lab2/lab2.html&h=144&w=324&sz=7&hl=en&start=11&tbnid=Z7GdbY9
TXA0qoM:&tbnh=50&tbnw=114&prev=/images%3Fq%3Denvelope%2Bdetector
%2Bcircuit%26svnum%3D10%26hl%3Den%26lr%3D
[3] Advanced frequency division bat detector:
http://images.google.ca/imgres?imgurl=http://bertrik.sikken.nl/bat/pix/envlop1.gif
&imgrefurl=http://bertrik.sikken.nl/bat/advdiv.htm&h=108&w=269&sz=2&hl=en&s
tart=6&tbnid=tGVJMzfqre9kUM:&tbnh=45&tbnw=113&prev=/images%3Fq%3De
nvelope%2Bdetector%2Bcircuit%26svnum%3D10%26hl%3Den%26lr%3D
[4] RAMALINGAM, RAVI RAMALINGAM Choice of hearing aids. The HINDO
Newspaper: http://www.hinduonnet.com/2001/08/12/stories/1312048d.htm
谢谢!
ありがとう!
متشکرم