Calibration of broadband RF field probes using a coaxial conical transmission line

We discuss a new broadband (10 MHz to 40 GHz) RF field standard to be used for calibrating electrically-small electromagnetic field probes. The technique generates a well-defined and uniform TEM mode field between the conductors of an air-filled coaxial transmission line of conical geometry (termed a "co-conical" line) that is terminated in a well-matched, high-power, distributed load. Internal field levels equivalent to power density levels in excess of 10 mW/cm² can be generated using broadband power sources of only 20 watts output. The new system will be capable of rapid, automated and accurate calibration of small field probes and can realize significant savings in both equipment/facility expenses and operational costs.