KEYWORDS: Signal processing, Radio optics, Acousto-optics, Spectrum analysis, Diffraction gratings, Transparency, Modulators, Optical signal processing
The outstanding role of the optical coherent Fourier processor and the instantaneous spectrum computed with is considered when performing spectral-correlation processing of the signals of the radio and optical bands. Within the framework of the performed studies, the spread functions for "real spectral devices in an ideal implementation" are established. The sampling theorem for the instantaneous spectrum is proved. These general theoretical studies are used to develop the theory of a diffraction grating spectral device of the optical range, as well as an acoustooptic (AO) radio signal analyzer, and the coordinated filter and a correlator of radio signals created on its basis.
Further development of stochastic aspect of the harmonic signal analysis theory is considered in this article. The choice of the analyzed signal model in the form of a harmonized finite random process is reasoned. It allows to receive the estimation of energy realization of a random process.
The energy spectrum estimations of a random process have been obtained basis on an instantaneous spectrum of the harmonized random process processing. These estimations have been received both in the form of convolution with the Bartlett spectral window and in the form of reference values.
These reference values are obtained by detecting CCD structures in acousto-optic spectrum analyzer and a diffraction grating spectral device, as well as by narrow-band filtering in a multichannel optical spectrometer.
The acousto-optic modulator as an element of the radio and optical signal processing system is considered. The transparency function of the acousto-optic modulator is established and a procedure for its linearization is proposed. A new generalized superposition principle for the transparency function of a pair of acousto-optic modulators, which located close to each other, is introduced. In the framework of computer simulation, the diffraction divergence of acoustic waves in the non-dissipative and dissipative mediums of acousto-optic interaction is investigated. The criterion of difference of diffracted field from rectangle consists in the increase of plane figure radius of inertia, which describing a one-dimensional diffraction acoustic field, from the radius of inertia of rectangle, which describes a non-diffracted field.
A new, alternative theory of diffraction grating spectral device which is based on the mathematical analysis of the optical signal transformation from the input aperture of spectral device to result of photo detection is proposed.
Exhaustive characteristics of the diffraction grating spectral device - its complex and power spread functions as the kernels of the corresponding integral operator, describing the optical signal transformation by spectral device is obtained. On the basis of the proposed alternative theory the possibility of using the diffraction grating spectral device for calculation of convolution and correlation of optical pulse signals is showed.
The review of the radio pulses acousto-optical correlator allows us to create an algorithm for calculation the correlation functions on the basis of pre-calculated instantaneous spectra of correlated pulse signals and it is given its interpretation in the form of a functional scheme. The new definition of the instantaneous spectrum explaining the operation of real spectral devices: an acousto-optical spectrum analyzer of radio signals and diffraction (lattice) spectral optical analyzer was introduced. Mathematical identity complex spread functions of acousto-optic spectrum analyzer of radio signals and optical diffraction spectral analyzer allows us to put the question about the implementation of the correlation of the optical pulse signals based on diffractive optical spectral analyzers.
We consider the analysis of the spectra of the dynamic signal optical range by the methods of acousto-optics at light diffraction by a traveling acoustic wave excited by a periodic sequence of radio pulses with a rectangular envelope and a linear variation of the instantaneous frequency. The procedure of the linear approximation of the acousto-optic interaction is described. Acousto-optic interaction is thought of as a bilinear transformation of the spectral components, which are radio signal and optical radiation. It is shown that from the bilinear spectral transformation ensue relations, describing the spectral processing or radio or optical signal as a result of diffraction on grating structure formed by traveling acoustic wave. The problem of spectrum analysis of optical signals by optical spectral device based on acoustooptic tunable filter is considered separately. An expression allowing to investigating in detail the possibility of such an optical spectral device is obtained.
In this paper a liquid-crystal phase modulator (LCPM) is investigated, the volt-phase chracteristics being important parameter of this modulator. This LCPM is the most impotent element in acousto-optic scheme of quasi-matched filter, which allows controlling of impulse response. Method of measurement of volt-phase characteristic of LCFM is described. Experimental results that were obtained are considered.
Performance analysis for the space-integrating acousto-optic correlator based on optical interference with external noise and allowance for shot noise of photodetector is presented. Signal-to-noise ratio and dynamic range are obtained in the general form, the results in the graphical form are also presented.
The results of theoretic research a matrix-vector multiplier on base acoustooptic filter with 2D liquid-crystal reference mask are brought in report. Dependencies of dynamic range from real parameters of scheme are presented and analyzed. Also relationship between dynamic range and probability of error on symbol is determined.
The principle of quadrature signal processing was implemented in a space-integrating acousto-optic correlator (SIAOC). A new SIAOC structure for quadrature filtering of phase-shift keyed signals is developed. Performance analysis for this architecture is described.
The principle of quadrature signal processing was implemented in a space-integrating acousto- optic correlator (SIAOC). A new SIAOC structure for quadrature filtering of wideband radio signals was developed. Performance analysis for this architecture is described. Simple experimental results obtained with microwave acousto-optic cell (AOC) are presented.
The capabilities of the video-frequency (VF) space-integrating acousto-optic correlator (SIAOC) are demonstrated for synthesis of VF acousto-optic orthogonal filters. The orthogonal basic set is based on the first type Chebyshev polynomials. The structures of the corresponding reference masks are described. The main advantages of the acousto-optic implementation are emphasized. The results of the experimental research are presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.