A Miniature Ultrawideband Electric Field Probe Based on Coax-Thru-Hole via Array for Near-Field Measurement

In this paper, a miniature electric field probe with an ultrawideband of 9 kHz-20 GHz is proposed, fabricated, and tested. The electric field probe is fabricated on a four-layer printed circuit board using high-performance and low-loss Rogers material (ε r = 3.48 and tanδ = 0.0037). Coax-thru-hole via array is used to control the signal via impedance to achieve impedance 50 Ω match over the whole working band, reducing the harmful influence on the probe's characteristic. The ground vias, called via fence, are utilized to suppress the resonance caused by the parallel-plate mode of conductor-backed coplanar waveguide (CB-CPW), expanding the working frequency band. Experimental result shows |S 21 | rather smooth in operation band, demonstrating the working frequency band is up to 9 kHz-20 GHz. The electric field probe has a 2-3 mm spatial resolution, which has a good ability to locate the interference source.