Low Profile Antenna Performance Study. Part 1. Efficiency and Bandwidth Characteristics

The bandwidth and efficiency of antennas whose dimensions do not exceed one-tenth of a wavelength are discussed. A brief review of the Armys present VHF antenna capability is given. The distinction between small and low-profile is made and some basic principles relating to the efficiency and bandwidth of stub and loop antennas are studied. Top-loading and loading elements in the antenna structure well-known techniques that have been used over the years are most effective for improving the efficiency and bandwidth of small antennas. It was found that the configuration of the tuning and matching network plays an important role in determining the instantaneous bandwidth of a system. In particular, it is shown that the parallel-input, two-element L- network provides wider bandwidth than does the series input L-network. In addition, it was found that the first element in the L-network, i.e., that nearest the antenna, is the primary source of constraints on the achievable instantaneous bandwidth.