A Simple Wideband Differential Magnetic Probe Loaded With Out-of-Phase Balun and Parasitic Loop

In this communication, a simple ultrawideband magnetic-field probe loaded with out-of-phase balun and parasitic loop is proposed. The magnetic-field probe is composed of a U-shaped sensing loop as a driven element, a U-shaped loop as a parasitic element, a pair of interconnected via, several rows of via fences, and an integrated out-of-phase balun. Initially, the U-shaped sensing loop is employed to detect differential electromagnetic signals. Then, in order to enhance the detection sensitivity, the parasitic U-shaped loop is utilized to sense more electromagnetic signals. Furthermore, an integrated out-of-phase balun functions as a bandpass filter, allowing the transmission of differential electromagnetic signal into a single reception port while suppressing the common electromagnetic signal. Finally, the numerous rows of via fences situated adjacent to these loops serve to prevent the occurrence of unwanted electromagnetic modes. To substantiate the benefits of this design, the proposed probe was developed, simulated, fabricated, and evaluated. Test results demonstrate that the new probe possesses a broad operational bandwidth, ranging from 4 to 12 GHz, and exhibits high detection sensitivity near -30 dB within this range.