Abstract
The noise characteristics of multichannel systems of forming signals based on hybrid frequency synthesizers with automatic compensation of phase distortions of direct digital synthesizers, which are used in the composition of georadars with synthesized aperture, are investigated. It is established that the phase noise of the output signals of the formers at the 1 kHz detuning from the carrier oscillation at the output frequencies of the devices in the range from 500 to 3500 MHz is characterized by a level of minus 100 - minus 130 dB. In this case, the circuit of the signal former based on a hybrid frequency synthesizer with direct digital synthesizer as a reference oscillator of a phase locked loop is characterized by the worst noise characteristics but with the highest degree of autocompensation (about 13 dB). Conversely, the circuit of the signal former based on a hybrid frequency synthesizer with direct digital synthesizer as a support generator of the phase-locked loop has the best phase noises level from the considered variants of devices and least degree of autocompensation (about 6 dB).
Highlights
Georadar subsurface probing is one of the most effective methods of nondestructive testing
Modeling and comparative analysis of noise characteristics of the proposed variants of construction of channels for signal formation based on hybrid frequency synthesizers with automatic compensation for phase distortions (ACPD) of the direct digital synthesizers (DDS) of georadars with synthesized aperture are carried out
As the phase locked loops (PLL) was used the parameters of the ADF5355 synthesizer, which has the slope of the modulation characteristic of the VCO KVCO of 15 MHz/V, the steepness of the detector characteristic KPD = 1, and the cutoff frequency of the LPF fLPF = 10 MHz
Summary
Georadar subsurface probing is one of the most effective methods of nondestructive testing. One of the options for its implementation is holographic ultrawideband probing, based on the use of georadars (GPR) with a synthesized aperture [3,4,5,6,7] The idea of this radar technique with respect to subsurface probing is based on the emission of ultra-wideband signals and recording the results of their reflection from objects located under the frontier of probed media having differences in the permittivity. With this type of probing, the reflected signals contain the most complete information about the properties of the inhomogeneities of the medium. The processing of reflected signals obtained as a result of successive scanning of the surface under research allows one to reconstruct the three-dimensional distribution of inhomogeneities under the interface of the probed media
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