Fig. 2 (b) Stack-up of the probe
as the induced end in the front of the probe, mainly to increase the contact area with the tangential electric field to enhance the sensitivity of this probe. The end of the resonator is connected with the dipole and the other end is connected to the coupled balun which converts the differential mode voltage into the common mode voltage. The other end of the coupled balun is connected with the strip line which is connected to conductor-backed coplanar waveguide CB-CPW through a signal via. The current generated at the probe tip through the electromagnetic field to be measured, and then flows to the SMA connector through the resonator, the coupled balun, the signal via and the CB-CPW.
A. Resonator: Compared with the broadband probe, the electric field probe with resonator has higher sensitivity working at narrow-band frequency [8]. The capacitor and inductor are the parts of the resonator, open-circuited and short-circuited transmission line can be used for the resonator which has a high quality factor. The resonator shown in Fig. 3 is loaded into the probe designed in the paper, the function of open-circuited stub is equivalent to capacitor, and the function of short-circuited stub is equivalent to inductor. The length of open-circuited stub and short-circuited stub can be used to tune the resonant frequency. Fig. 3 shows the specific dimensions of open-circuited stub and short-circuited stub when the probe works at 1.320 GHz resonant frequency. The initial value is set to be less than\(\lambda/8\) and the specific values can be obtained by sweeping parameters to achieve specific resonance in HFSS.