Performance of Electrically Small Array Receiving Systems in the Presence of Noise

The performance of broad band electrically small beamed receiving arrays operating in the high-frequency band (3 to 30 MHz) and in a random noise environment is studied. The concepts of system noise figure (SNF) and signal-to-noise ratio improvement factor (SNIF) are proposed as criteria for comparing one array antenna receiving system to any reference antenna system when the conditions of operation are defined. Graphical representations of SNIF for the two- and four-element antenna systems versus a single-element system are presented. SNIF is shown to depend on the geometry of the array, on the phasing network, and on the ratio of atmospheric noise power to internal system noise power.