Energy-budget analysis of a 2-D high-frequency radar incorporating optimum beamforming

In a previous paper we reported on a high-frequency line-of-sight radar that was used for satellite ephemeris determination. The radar has been modified and is now configured to look directly upwards compared to the oblique viewing geometries used in previous deployments. The changes include a revised receiver array geometry that is now based on a two-dimensional hexagonal lattice as well as a new mismatched optimum beamformer. The paper discusses the beamformer design, which exploits the non-isotropic distribution of terrestrially propagated noise in the HF band and full receiver array modelling using NEC. We achieve improved target detection of approximately 10dB compared to a conventional beamformer. In addition, we determine exact signal energy and noise spectral density levels (rather than signal-to-noise ratio improvement only) at the output of the optimum beamformer for use in our radar energy budget calculations that are an important step in our system design. The new array geometry and the optimum beamformer combine to provide significant sensitivity improvement for this radar.