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Audio Analog Chaos Modulator IC for Secure Communications
Team: Manuel Delgado-Restituto and
Angel Rodríguez-Vázquez
Date: 1996
| Physical Data |
- 2.4µ m CMOS n-well, double poly,
double metal.
- 1904µ m
X 2620µ
m (excluding pads)
- 890 transistors.
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Electrical Data |
- 5V@1.8mW.
- Electrically-controlled operation.
- Natural frequencies in the audio band.
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Design Technique: |
- Analog full-custom.
- gm-C circuits:
- Linearization through cross-coupled
differential pairs with RHP zero cancellation.
- Stacked cascode current mirrors.
- Nonlinear voltage-to-current transformation
using current shaping.
- Control of natural frequencies through
correlated biasing for keeping range.
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Features and Applications: |
- Based on Chua's oscillator.
- The model has been obtained (through
a systematic optimization procedure) for an increased robustness
against techological parameter deviations.
- It allows noise-band signal encryption,
by means of the vector field modulations approach.
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Experimental observations and theoretical
analyse have demonstrated that interconnected chaotic cells may evolve
in phase, in spite of their intrinsically irregular behavior and large
sensitivity to the initial conditions. This phenomenon of chaotic synchronization
shows promise of applications for the secure communication of data. The
basic idea is to exploit the noise-like appearance of a chaotic carrier
to hide an information-bearing signal at the emitter site, and make use
of the synchronization property to recover the information at the receiver.
This chip has been designed to be used as
the basic building block for chaotic modulation and demodulation. It realizes
the following nonlinear state equations,
where the nonlinearity (Fig 3) is given by,
The parameters m0
and m1 in the this nonlinearity are controllable
trough external bias current. Thus, a bifurcation sequence can be transversed,
and cryptographiced keys for chaotic encryption can be set-up.
More details are available in the following
papers:
References:
- [Delg95] M. Delgado-Restituto, A. Rodríguez-Vázquez,
R. López Ahumada and M. Liñán: "Chaotic Synchronization
using Monolithic Chua oscillators". Int. J. Electronics, Vol. 79,
pp. 775-785, 1995.
- [Delg96a] M. Delgado-Restituto, M. Liñán
and A. Rodríguez-Vázquez: "IC Design for Spread Spectrum
Communication Exploiting Chaos". Proceedings of IEEE ISCAS, Atlanta,
USA, Vol. 3, pp. 178-181, 1996
- [Delg96b] M. Delgado-Restituto, M. Liñán
and A. Rodríguez-Vázquez: "A CMOS 2.4mm Chaotic Oscillator:
Experimental Verification of Chaotic Encryption of Audio". Electronics
Letters, Vol. 32, pp. 795-796, 1996.
Images List:
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