This paper presents the shaping optimization of an S-band cylindrical offset reflector antenna with cosecant-squared radiation pattern in elevation plane. The cross section of the antenna is mathematically modeled by a polynomial function and optimized by the genetic algorithm to obtain the desired pattern for both TE and TM polarizations. The physical optics method together with the uniform theory of diffraction is used to efficiently calculate the radiation pattern during the optimization. Numerical results show that the cosecant-squared radiation pattern can be achieved with good accuracy for angular span of 50◦. The computed radiation pattern agrees well with method of moments as well as CST software and deviates less than about 0.7 dB, on average, from the ideal cosecant-squared pattern.

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