1. J. Chan-Wai, B. Lawrence, V. Proulx
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

2. Team Members
Jason Chan Wai
Brian Lawrence
Valerie Proulx

3. Conventional Envelope Detector
Envelope detectors are used to obtain the envelope of an AM modulated signal.

4. 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.

5. 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

6. Application: Hearing Aids and Cochlear Devices

7. Original Control Path
Control path proposed in referenced research paper

8. 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

9. Simulation
Simulation was performed on researched control path using PSpice

10. Simulation Results 1 Output when input signal is 3V (large)
Circuit functions as intended

11. Simulation Results 2
At small voltages (300mV) the proposed control path does not function properly!

12. 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)

13. Primary Goal Secondary Goals
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

14. Optimized Control Path
Proposed design utilizes active components in the input network!

15. Simulation Results 1
Output of proposed control path with 300mV, 2kHz input signal

16. Simulation Results 2
Output of proposed control path with 300mV 500Hz input signal

17. 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!

18. 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

19. 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

20. 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

21. Followed Schedule

22. References
[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
[2] Communication Systems Tutorial: Envelope Detection, Utah State University:
[3] Advanced frequency division bat detector:
[4] RAMALINGAM, RAVI RAMALINGAM Choice of hearing aids. The HINDO Newspaper:

23. متشکرم 谢谢！ Ευχαριστώ Dankie ありがとう！ Urakoze Asante DMnvwd WAD MAHAD
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