Time domain sensors for radiated impulsive measurements

Discussion of various sensors and radiators commonly used for time domain antenna measurements is presented. The sensors and radiators discussed here are passive and analog devices which convert the electromagnetic quantity of interest to a voltage or current at their terminal ports. Moreover they are primary standards in the sense that their transfer functions can be calculated from their geometries and are flat (constant) across a wide frequency range. One of the major requirements for these sensors and radiators is that the electromagnetic far field, transmitted or received, is a replica or high fidelity derivative of the original pulse. Note that the transmitting transfer function of an antenna is proportional to the time derivative of the receiving transfer function of the same antenna, which follows from the reciprocity theorem. For electric field strength measurements, linear antennas loaded nonuniformly and continuously with resistance, or with both resistance and capacitance are discussed. Also, a conical antenna and an asymptotic conical antenna are discussed from the standpoint of improved characteristics. For an improved directivity, various types of transverse electromagnetic (TEM) horns are considered, e.g., a conducting TEM horn, and a resistively loaded TEM horn.