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 ( \varepsilon -{\mathrm{r}}= 3.48 and tan \delta = 0.0037 ). Coax-Thru-hole via array is used to control the signal via impedance to achieve impedance 50~\Omega 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 \vert S-{21}\vert 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.