| 摘要 |
FIELD: physics. ^ SUBSTANCE: to use coherent accumulation when detecting single or grouped parametric scatterers, a pair of short successive auxiliary radio pulses with identical form and opposite phases is emitted simultaneously with pumping radio pulses at the subharmonic frequency of the pumping radio pulses. One of the radio pulses of the pair is a synchronising radio pulse and for this purpose, said pulse must be emitted in such a way that a pumping radio pulse is emitted during its duration. A receiver is tuned to receive radio pulses of the signal scattered at the subharmonic frequency. The coherent accumulation law is selected beforehand. Pairs of auxiliary radio pulses are emitted in form of an alternative sequence having the least of all possible levels of accumulation in the receiver. The selected sequence is generated due to that the synchronising pulse is either the first or second auxiliary radio pulse depending on whether corresponding current symbols of the alternative and selected encoding laws coincide. The cost of such an engineering solution is a certain violation of synchronism of the scattered radio signals generated in the duration of the pair of auxiliary radio pulses, although this time is significantly shorter than the duration of the pumping radio pulse. To prevent missing a target due to zeroes on the nonlinear back scattering pattern in grouped parametric scatterers, for example arrays of parametric scatterers, a flashing mode is provided. For this, synchronisation of parametric scatterers in a group takes place either from the wave of the probing signal, i.e. from an external synchronisation radio pulse, or from an internal synchronisation source (sources) which is one or more first excited parametric scatterers. In order that the said synchronisation sources are formed, there is need for one or more parametric scatterers having a smaller excitation threshold and the front edge of the pumping radio pulse increases monotonously. ^ EFFECT: high accuracy of detecting parametric scatterers. ^ 6 dwg |
