METHOD FOR MEASURING ABSOLUTE TRANSMISSION TIME OF SHORT RADIO WAVES IN IONOSPHERE BY MEANS OF RADIO SIGNALS WITH LINEAR-FREQUENCY MODULATION Russian patent published in 2006 - IPC G04C11/02 H04B7/165 H04B7/22 G01S1/22 

FIELD: radio engineering, possible use in radio location and navigation systems.

SUBSTANCE: in the method for measuring absolute transmission time of short radio waves in ionosphere by means of radio signals with linear-frequency modulation, mode structure of ionosphere short-wave channel is determined and alignment of time scales of distributed stations is performed by signals of precise time with precision up to several milliseconds, probing of ionosphere is performed in whole linear-frequency modulation range of radio complex (3-30 MHz). In accordance to synchronized program, transfer to emission/receipt mode is performed at sliding frequency with speed 100 kHz/s in more narrow range of frequencies from f_n to f_k=f_n+100KHz, i.e., "saw" mode is realized with repetition period ΔT=1s. It can be called a synchronization mode. Frequency f_n lies within range of passage frequencies and may be changes in accordance to synchronized program in process of measurements. In time moment t₀ transmitter starts, receiver at other end of radio lines starts in time moment t₀+Δt_dis, where Δt_dis - time of discrepancy of time scales of aforementioned transmitter and receiver. Differential frequency for receiver will be proportional: F₂=(df/dt)Δt_meas, where Δt_meas=t_gr-Δt_dis, where t_gr - time of group transmission from transmitter to receiver; Δt_meas=t_gr-Δt_s=0 and t_gr= Δt_s. Correction is performed during several emission cycles, during which measuring of differential frequency is performed and correction of Δt_dis is performed to provide F₂=0. At next stage in time moment t₀+Δt_s=t₀+t_gr transmitter launches. Supposing routes to be reversible, in time t_gr radio signal is received by receiver. Its differential frequency F₁ equals F₁=2t_gr(df/dt), and time of group transmission is determined as t_gr+F₁/2(df/dt).

EFFECT: possible measurement of absolute transmission time of short-wave radio signals.

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