Cosecant‐Squared Pattern Synthesis for Compact Antenna Arrays Based on Regional Root Allocation

ABSTRACT To meet the communication and sensing demands of unmanned aerial vehicles in urban low‐altitude airspace, this letter proposes a low‐sidelobe, cosecant‐squared pattern synthesis method based on a compact antenna array. By employing a 0.25‐wavelength element spacing, the array provides increased degrees of freedom for radiation pattern synthesis. A root‐moving method with complex‐plane, regional root allocation is introduced and combined with the cuckoo search (CS) algorithm to synthesize low‐sidelobe, cosecant‐squared radiation patterns. A compact 32‐element magnetic dipole antenna array is designed and fabricated for the U6G band, capable of switching between a wide‐angle scanning beam and a cosecant‐squared shaped beam. Results show that the array achieves a scanning range greater than 130° and a peak gain of 19.5 dBi for the scanning beam pattern. For the cosecant‐squared pattern, it achieves a maximum sidelobe level (SLL) of −27.5 dB and a main lobe gain of 17.0 dBi.