Design and characterization methods for a balanced antenna integrated in a small sensor node

Design and characterization of a dipole antenna at 2.45 GHz is presented. The antenna is fitted within a small space in a body-worn sensor node. The entire node is cylindrical with 30 mm diameter and 7 mm height. The antenna is fed by a differential transceiver which has an optimal load impedance of 115+J180 Omega. A T-match feed of the dipole is used to achieve the proper input impedance. Characterizing a balanced antenna in an electrically small node is difficult. Different passive and active methods for characterization of port impedance and radiation performance are described, and simulations are used for comparison. The presented design has a performance in level with what is normally seen for unbalanced antennas. The results demonstrate that it is possible to implement a dipole within a very small volume, with good electrical performance, and that it is possible to characterize it using the right techniques.