Broadband Noncontact Time-Domain Waveform Reconstruction for Near-Field Probing Systems

The time-domain integration method (TDIM) has been widely used for noncontact reconstruction of voltage and current signals on printed circuit board traces. However, its performance is fundamentally constrained by two critical limitations: first, the knee point of the frequency response, which restricts the effective operating bandwidth, and second, frequency response ripples, which degrade measurement accuracy. To overcome these challenges, a novel odd harmonic signal construction Fourier transform method (OHSFM) is proposed for near-field probing systems. The OHSFM addresses the key shortcomings of TDIM in two ways: 1) bandwidth expansion: it eliminates the knee-point limitation, extending the measurable bandwidth by at least tenfold compared to TDIM and 2) enhanced accuracy: it suppresses distortion caused by ripple and knee point, reducing the peak measurement error from 177% (TDIM) to just 3.2% (OHSFM). Experimental results demonstrate that OHSFM excels in high-frequency microwave and transient pulse measurements, particularly for signals with nanosecond-scale rising edges.