On target distance estimation by passive radar under far-tropospheric radio wave propagation

Subject and Purpose. The progress in the development of communication means requires a brand-new radar-component base and state-of-the-art technologies of signal processing. Last years, passive radar systems have become increasingly important. Yet such a shortcoming as poor estimation of the target distance takes place when the signal reception is only provided by a single station. The present work suggests a concept of the object distance determination by passive radar means under far-tropospheric radio wave propagation upon that the statistical parameters of amplitude fluctuations of the target reflection beyond the radiohorizon are distance dependent.  

Methods and Methodology. The basic mechanism of radio wave propagation beyond the radiohorizon is a phenomenon of tropospheric scatter on tropospheric heterogeneities in the upper tropospheric layers. These heterogeneities continuously change form and size and move through the space. The resulting electromagnetic field at the reception point represents additively combined radio wave powers scattered by all heterogeneities in the illuminated area that varies its height depending on the distance so that the statistical parameters of received signal fluctuations are distance dependent. After statistical processing of received signal fluctuations, the target distance can be determined. The present work examines radiowave propagation of the 3 cm and 50 cm waves over the Sea of Okhotsk with target distances up to 500 km.

Results. For the target distance estimation by passive radar means, the standard deviation value, s, of the received signal amplitude can be employed.

Conclusion. The distance dependence of the statistical parameters of amplitude fluctuations of the target signal allows the target distance to be estimated by a passive radar in the centimeter, decimeter and meter wave ranges.