High-performance compact HF antenna for radar and communication applications

Over the years there have been many systems developed in the area of HF Surface Wave Radars (HFSWR) and Over the Horizon Radars (OTHR). The increased emphasis on applications such as maritime surveillance for national security and enforcement of Economic Exclusion Zones (EEZs) continues to drive the need for efficient yet mobile and low cost HFSWR and OTHR systems. For the HFSWR systems, propagation characteristics are based on vertically polarized, high frequency (3 to 30 MHz) electromagnetic waves and this provides distinct advantages when used in medium and long range coastal surveillance type operations. The high conductivity of seawater results in relatively low attenuation of vertically polarized radio waves thus allowing for effective long range HFSWR systems. OTHR systems, on the other hand, achieve long range propagation by utilizing the refractive properties of the ionosphere. Large changes in ionospheric layers between day and night cycles cause corresponding changes in the effective radar ranges. OTHR systems cover much longer ranges than HFSWR systems while HFSWR receivers have to handle the increased noise and signal clutter during periods of increased ionospheric activity.