Active probes for creating H-field probes for flat frequency response

This paper presents an approach to obtain a flat frequency response from the first order derivative behavior of an electrically small loop and electrically short electric field probe by using them in combination with active oscilloscope probes. An H-field probe made in flex circuit technology was designed to operate up to about 5 GHz. These probes have loop dimensions as small as 3 times 3 mil and trace widths in the order of 1.75 mils. The H-field probe terminals are connected to the differential amplifier of the active oscilloscope probe which functions as an integrator to achieve a flat frequency response. The integrator behavior compensates for the first order derivative response of the flex circuit probes. The E-field probe utilizes the high input impedance of the browser attached to the active probe for achieving a flat frequency response.