Wide-band matching of a small disk-loaded monopole

A wide-band, electrically small, disk-loaded antenna, comprising of a disk, 0.26 wavelength (at midband) in diameter, located 0.097 wavelength above a ground plane, has been designed and tested. A unique experimental procedure was used to determine the parameters of the impedance matching network, which consists of a conductive biconical center post and two structural side posts located in the space under the disk. The resulting antenna has a maximum voltage standing-wave ratio (VSWR) of 2:1 over a frequency bandwidth ratio of approximately 2:1. A second model, designed using the same technique, has a maximum VSWR of 3:1 over a frequency bandwidth ratio of 3:1. This antenna was compared to a multi-element disk-loaded antenna (with the same size profile) designed by Dr. Georg Goubau. This multi-element antenna also has a maximum VSWR of 2:1 over a frequency band of approximately 2:1. The comparison shows that the simple disk-loaded antenna, with fixed double tuning, achieves the same low VSWR as the multi-element disk-loaded antenna with fixed triple tuning. Therefore, an increase in bandwidth could be achieved in the simple disk-loaded antenna by applying higher order tuning.