Abstract

A time-domain chemical-recognition system for classifying gases and analyzing gas mixtures is presented. We analyze the free induction decay exhibited by gases excited by far-infrared (terahertz) pulses in the time domain, using digital signal-processing techniques. A simple geometric picture is used for the classification of the waveforms measured for unknown gas species. We demonstrate how the recognition system can be used to determine the partial pressures of an ammonia–water gas mixture.

© 1996 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. P. R. Smith, D. H. Auston, M. C. Nuss, IEEE J. Quantum Electron. 24, 255 (1988).
    [CrossRef]
  2. M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Technol. 38, 1684 (1990).
    [CrossRef]
  3. I. Brener, D. Dykaar, A. Frommer, L. N. Pfeiffer, J. Lopata, J. Wynn, K. West, M. C. Nuss, Opt. Lett. 21, 1924 (1996).
  4. M. van Exter, Ch. Fattinger, D. Grischkowsky, Opt. Lett. 14, 1128 (1989).
    [CrossRef]
  5. H. Harde, S. Keiding, D. Grischkowsky, Phys. Rev. Lett. 66, 1834 (1991).
  6. R. A. Cheville, D. Grischkowsky, Opt. Lett. 20, 1646 (1995).
    [CrossRef] [PubMed]
  7. R. G. Brewer, R. L. Shoemaker, Phys. Rev. A 6, 2001 (1972).
  8. L. Rabiner, B.-H. Juang, in Fundamentals of Speech Recognition, A. V. Oppenheim, ed. (Prentice- Hall, Englewood Cliffs, N.J., 1993), p. 97.
  9. J. Makhoul, Proc. IEEE 63, 561 (1975).
    [CrossRef]
  10. J. G. Proakis, D. G. Manolakis, Digital Signal Processing, Principles, Algorithms, and Applications (Prentice-Hall, Englewood Cliffs, N.J., 1996).
  11. H. M. Pickett, R. L. Poynter, E. A. Cohen, Sub-millimeter, Millimeter, and Microwave Spectral Line Catalog, accessed from the Jet Propulsion Laboratory, Pasadena, California, via the World Wide Web ( http://spec.jpl.nasa.gov ).

1996

1995

1991

H. Harde, S. Keiding, D. Grischkowsky, Phys. Rev. Lett. 66, 1834 (1991).

1990

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Technol. 38, 1684 (1990).
[CrossRef]

1989

1988

P. R. Smith, D. H. Auston, M. C. Nuss, IEEE J. Quantum Electron. 24, 255 (1988).
[CrossRef]

1975

J. Makhoul, Proc. IEEE 63, 561 (1975).
[CrossRef]

1972

R. G. Brewer, R. L. Shoemaker, Phys. Rev. A 6, 2001 (1972).

Auston, D. H.

P. R. Smith, D. H. Auston, M. C. Nuss, IEEE J. Quantum Electron. 24, 255 (1988).
[CrossRef]

Brener, I.

Brewer, R. G.

R. G. Brewer, R. L. Shoemaker, Phys. Rev. A 6, 2001 (1972).

Cheville, R. A.

Dykaar, D.

Fattinger, Ch.

Frommer, A.

Grischkowsky, D.

R. A. Cheville, D. Grischkowsky, Opt. Lett. 20, 1646 (1995).
[CrossRef] [PubMed]

H. Harde, S. Keiding, D. Grischkowsky, Phys. Rev. Lett. 66, 1834 (1991).

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Technol. 38, 1684 (1990).
[CrossRef]

M. van Exter, Ch. Fattinger, D. Grischkowsky, Opt. Lett. 14, 1128 (1989).
[CrossRef]

Harde, H.

H. Harde, S. Keiding, D. Grischkowsky, Phys. Rev. Lett. 66, 1834 (1991).

Juang, B.-H.

L. Rabiner, B.-H. Juang, in Fundamentals of Speech Recognition, A. V. Oppenheim, ed. (Prentice- Hall, Englewood Cliffs, N.J., 1993), p. 97.

Keiding, S.

H. Harde, S. Keiding, D. Grischkowsky, Phys. Rev. Lett. 66, 1834 (1991).

Lopata, J.

Makhoul, J.

J. Makhoul, Proc. IEEE 63, 561 (1975).
[CrossRef]

Manolakis, D. G.

J. G. Proakis, D. G. Manolakis, Digital Signal Processing, Principles, Algorithms, and Applications (Prentice-Hall, Englewood Cliffs, N.J., 1996).

Nuss, M. C.

Pfeiffer, L. N.

Proakis, J. G.

J. G. Proakis, D. G. Manolakis, Digital Signal Processing, Principles, Algorithms, and Applications (Prentice-Hall, Englewood Cliffs, N.J., 1996).

Rabiner, L.

L. Rabiner, B.-H. Juang, in Fundamentals of Speech Recognition, A. V. Oppenheim, ed. (Prentice- Hall, Englewood Cliffs, N.J., 1993), p. 97.

Shoemaker, R. L.

R. G. Brewer, R. L. Shoemaker, Phys. Rev. A 6, 2001 (1972).

Smith, P. R.

P. R. Smith, D. H. Auston, M. C. Nuss, IEEE J. Quantum Electron. 24, 255 (1988).
[CrossRef]

van Exter, M.

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Technol. 38, 1684 (1990).
[CrossRef]

M. van Exter, Ch. Fattinger, D. Grischkowsky, Opt. Lett. 14, 1128 (1989).
[CrossRef]

West, K.

Wynn, J.

IEEE J. Quantum Electron.

P. R. Smith, D. H. Auston, M. C. Nuss, IEEE J. Quantum Electron. 24, 255 (1988).
[CrossRef]

IEEE Trans. Microwave Theory Technol.

M. van Exter, D. Grischkowsky, IEEE Trans. Microwave Theory Technol. 38, 1684 (1990).
[CrossRef]

Opt. Lett.

Phys. Rev. A

R. G. Brewer, R. L. Shoemaker, Phys. Rev. A 6, 2001 (1972).

Phys. Rev. Lett.

H. Harde, S. Keiding, D. Grischkowsky, Phys. Rev. Lett. 66, 1834 (1991).

Proc. IEEE

J. Makhoul, Proc. IEEE 63, 561 (1975).
[CrossRef]

Other

J. G. Proakis, D. G. Manolakis, Digital Signal Processing, Principles, Algorithms, and Applications (Prentice-Hall, Englewood Cliffs, N.J., 1996).

H. M. Pickett, R. L. Poynter, E. A. Cohen, Sub-millimeter, Millimeter, and Microwave Spectral Line Catalog, accessed from the Jet Propulsion Laboratory, Pasadena, California, via the World Wide Web ( http://spec.jpl.nasa.gov ).

L. Rabiner, B.-H. Juang, in Fundamentals of Speech Recognition, A. V. Oppenheim, ed. (Prentice- Hall, Englewood Cliffs, N.J., 1993), p. 97.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig. 1
Fig. 1

Two-dimensional representation of a codebook. The vectors a1 and a2 represent two different gas species. From these vectors two orthogonal vectors, b1 and b2, are constructed. Vector a corresponds to a mixture that contains the fraction x1 of species 1 and the fraction x2 of species 2.

Fig. 2
Fig. 2

THz waveform for HCl vapor at 13 kPa and a reference waveform measured for an evacuated gas cell. The HCl waveform has been shifted by 1.5 nA for clarity. The occurrences at 17, 29, and 47 ps are due to reflections in the setup.

Fig. 3
Fig. 3

Power spectrum estimated from a LPC analysis of order M = 50 (thick solid curve) and from a Fourier analysis (dashed curve) for H2O vapor at 2.8 kPa. The thin solid curve and the dotted curve represent the integrated power spectral density for the LPC and the Fourier analysis, respectively.

Fig. 4
Fig. 4

Result of chemical recognition of mixtures of NH3 and H2O. For each mixture we plot a single point representing the estimated partial pressure of the two gas species. The inset shows the estimated versus the measured pressure from a single-species recognition of HCl.

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

s ( n ) = k = 1 M a k s ( n - k ) + e ( n ) ,
S ( z ) = k = 1 M a k z - k S ( z ) + E ( z ) ,
S ( z ) = H ( z ) E ( z ) ,
H ( z ) = 1 1 - k = 1 M a k z - k .

Metrics