A Wideband Tangential Electric Field Probe and a New Calibration Kit for Near-Field Measurements

A wideband tangential electric field ( $E$ -field) probe with operating frequency of 4–15 GHz is proposed. The $E$ -field probe is designed on a four-layer printed circuit board (PCB) with high-performance Rogers substrate. A wideband balun based on a microstrip-to-slotline transition structure is integrated into the probe to realize balanced–unbalanced transform in a wide frequency band through field conversion. Numerical simulations show that the magnitude imbalance and the phase imbalance of the balun are below 1 dB and 1 ^° , respectively. To reduce the interference of the normal $E$ -field component to the calibration result, the slotline is used as a calibration kit to generate the standard field because of its excellent field distribution characteristics. The tangential $E$ -field probe placed at the center of a slotline for calibration captures the symmetrical $E$ -field, while the normal component regarded as interference can be suppressed by the wideband balun. The performance of proposed probe is demonstrated with simulation and laboratory experiments.