ERIEYE and Blind Spots

The ERIEYE radar claims 360 degrees coverage, but the information from Ericsson review shows that it is actually 300 degrees.

Source:
Ericsson review. Volume: 72 Issue: 2, 1995
Article Author: Ahlbom, S.; Andersson, P.; Lagerlof, R.
Article Title: A Swedish airborne early warning system based on the Ericsson ERIEYE radar

Erieye Antenna Characteristics

Scanning Area of Erieye

Antenna Aperture

Antenna System

Cross-Section of Dorsal Unit

Phase Increment & Scan Angle Relation

Compare the above mentioned antenna specs[from 1995] with following from 1990.

Source:
Military microwaves ’90 : conference proceedings, Wednesday 11th to Friday 13th July 1990, Wembley Conference Centre, London
Article Author: Affiliated with Ericsson.
Article Title: A phased array radar antenna for airborne early warning

Old Antenna Min. Perf. Specs

even here it is claimed that it 120 degrees on each side was the minimum they wanted to attain. They eventually were able to optimize it for 150 degrees on each side by 1995.

And since it is clearly a simple planar phased array, the performance after 120 degrees would be severely limited. So, there will be drastic degradation at the extremes 15 degrees of the coverage.