A wideband and low side lobe series fed patch array at 5.8 GHz for radar applications

In this paper a novel series feed patch array working in the 5.8 GHz ISM band for healthcare radar monitoring applications has been proposed. The single patch has been opportunely shaped to solve two critical problems of this antenna topology: reduced bandwidth and high Side Lobe Level (SLL). The bandwidth enhancement has been obtained with a dual band structure, resulting from the superposition of two tapered patches with different lengths. For the side lobes, a non conventional technique, based on the modulation of the power transferred by one patch to the following one has been proposed. An electrical two port model of the single patch has been developed to significantly speed up the design process of longer series feed arrays. The model impedance matrix shows a good agreement with the one extracted from electromagnetic simulations. The designed antenna shows a fractional bandwidth of 5.92% (more than twice the available one at 5.8 GHz) and a SLL of about -20 dB inside all the bandwidth. A prototype has been realized and both return loss and radiation pattern at 5.8 GHz have been measured showing an excellent agreement with simulation results.