Abstract: A method and system for calculating the range between a source which emits electromagnetic energy having an unknown frequency and a first receiver of electromagnetic energy at at least three points along a portion of a source trajectory. The source trajectory portion is a substantially straight line which has two end points. The first receiver moves along a first, substantially straight-line receiver trajectory so that the frequency of the electromagnetic energy is Doppler-shifted. The first receiver measures the Doppler-shifted frequency at at least three predetermined times. Next, at least two ratios of frequencies are calculated, the ratios being functions of the Doppler-shifted frequencies and bearing angles. Finally, the range between the first receiver and the source is calculated from the frequency ratios at the at-least-three points. In a first preferred embodiment the source is stationary.

Abstract: A monopole antenna or the like including a sleeve antenna and a stub antenna having means for decoupling the antenna from surrounding electrically conductive elements. Such elements may consist, for example, of the conductive skin of an aircraft and, typically, of other antennas mounted on this skin, or they may comprise conductive portions of a ship. In order to provide the decoupling, a radial transmission line is disposed at the base of the antenna and concentric with the coaxial transmission line used to excite the antenna. The radial transmission line includes an upper and a lower electrically conductive plate, each having a small central opening and means for electrically interconnecting the plates about the opening. The antenna may be fed by a coaxial transmission line extending through the conductive element and the central opening. The inner conductor of the coaxial transmission line may extend beyond the radial transmission line to form a monopole antenna.