Multiple-tuned normal-mode helical antenna

摘要

An antenna includes a conductive coil electrically coupled to a wave launching structure and configured such that a plurality of capacitances act electrically in parallel with a plurality of distinct portions of the conductive coil. The capacitances configure what would otherwise be a conventional normal-mode helical antenna for operation at multiple, closely spaced resonance frequencies. The antenna operates at the multiple resonance frequencies with only a small loss of efficiency relative to the maximum response of a conventional normal-mode helical antenna that has a single resonance frequency. Also, the antenna in accordance with the invention is self-duplexing, eliminating the need for complex and expensive duplexing circuitry.