Synthesis of array antennas to produce near-field contoured patterns for RFID reader applications

An efficient procedure is developed to synthesize the radiation pattern of a planar antenna array in the near zone of array aperture, which can be used for the applications of RFID reader as illustrated in Fig. 1 [1,2]. In this case, the objects under detection may locate in the near zone of antenna. The presented work appears to be more effective than a conventional near-field focused array antenna [3] because the field distribution in the target zone can be optimized, and can help to reduce the interferences. In this synthesis scheme, we utilize a global basis set to span the array excitation as previously proposed in [4], where each basis's excitation will radiate a near-field focused spot beam in the target area, and serves as local basis functions to synthesize the contoured pattern in the target area. The unknown coefficients of array's basis set are then found via a MLSE technique. It is found that only a small number of basis functions are sufficient to resemble the radiation pattern, and make the present approach very fast.