METHOD OF DETERMINING FREQUENCY OF RADIO SIGNALS IN ACOUSTO-OPTIC RECEIVER-FREQUENCY METRE IN STRONG SIGNAL MODE Russian patent published in 2011 - IPC G02F1/33 

FIELD: physics.

SUBSTANCE: analysed radio signal is transmitted to the electrical input of an acousto-optic deflector where it is converted to an acoustic signal and then to an optical signal which then undergoes Fourier transformation with recording of its intensity distribution using an N-element line of photodiodes. Further, video signals are generated at outputs of said photodiodes, after which frequency of the radio signal is calculated, which matches the abscissa of the axis of symmetry of intensity distribution of the light signal which is discretised by the photodiodes. A threshold is set in the top part of the linear section of the amplitude characteristic of the photodiodes and the level of signals lower than thresholds on four photodiodes with levels closest to the threshold is determined. Further, signal levels on these photodiodes are denoted y_A, y_B, y_C and y_D, and frequencies corresponding to these levels are denoted f_A, f_B, f_C and f_D in ascending order of the frequencies. It is then ascertained that frequencies f_A and f_B are lower than the frequency of the signal limiting section formed by the threshold, and frequencies f_C and f_D - are higher. Further, signals on photodiodes are compared and if y_A>y_C, frequency f₀ is calculated using the formula f₀=(f_C+f_A-Δf₁)/2, where Δf₁=ΔF(y_A-y_C)/(y_A-y_B), otherwise frequency f₀ is calculated using the formula f₀=(f_C+f_A+Δf₂)/2, where Δf₂ =ΔF(y_C-y_A)/(y_C-y_D) where ΔF if the frequency interval between photodiodes.

EFFECT: method increases accuracy of measuring frequency of radio signals in strong signal mode.

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