Did you know that NPS thesis papers are published for public access?

Here is a fantastic paper on Over-The-Horizon Radar, or OTHR.

It includes detailed overviews of OTHR systems, the effect the ionosphere plays in OTHR systems, and current systems in use, to include the Chinese Type 110R shown in the photo.

The paper’s abstract follows:

“The basic concept of the structure and properties of the ionosphere are discussed to explain how the performance of the over-the-horizon radar (OTHR) system is affected. An overview of the OTHR system characteristics and performance are presented along with some applications currently used around the world, including their geographic location and historical background. The waveforms used for the OTHR systems include simple pulse, pulse Doppler, phased-coded pulse, frequency modulated continuous wave (FMCW), and frequency modulated interrupt continuous wave (FMICW). Other characteristics such as target detection methods and the skywave OTHR range equation are also discussed.

A model of the maximum detection range for the Chinese FMCW OTH backscatter (OTH-B) radar was developed in MATLAB. An intercept receiver maximum interception range is also analyzed. Simulation results indicate that the minimum required input signal-to-noise ratio (SNR) for a target with 100 m2 cross section at 3,500 km footprint range is 52.4−dB at cf=14.5 MHz. In addition, a non-cooperative intercept receiver requires a minimum input SNR of 94 dB for a square law detector and 97 dB for a linear detector for interception at a footprint range of 3,500 km at cf=14.5 MHz. A ray tracing technique is also used in PROPLAB to present a more detailed analysis. The analysis includes the electron density profile, the maximum usable frequency, the critical frequency of the layers, the skip zone, and the signal quality. The simulations focused on the Chinese OTH-B radar system are to investigate the Chinese surveillance capabilities.”

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