Low-Scattering Chopped Dipole for Secondary Surveillance Radar

A periodically loaded, low-scattering dipole suitable for the secondary surveillance radar, particularly for identification-friend-or-foe antenna, is presented along with the methods to design such an antenna. The dipole is chopped into the pieces with length that minimizes scattering at 10 GHz, i.e., at the operation frequency of the primary antenna. In addition, optimal inductive loading is found to connect the pieces together so that the formed entity can radiate at 1 GHz, i.e., at the operation of frequency of the secondary antenna. Two meander-line designs are presented to realize the required inductances, and the proposed structures are realized on a printed circuit board. Designed prototypes are analyzed through simulations and measurements, which are in good agreement. The reduction in radar cross section at 10 GHz with the inductively loaded dipoles is at best more than 15 dB, when compared to the reference half-wave dipole. As a consequence, the radiation efficiency at 1 GHz decreases by 0.4 dB with the inductively loaded dipoles.