SE9800039L - Radio antenna for mainly vehicles - Google Patents

Abstract

A single antenna is used to handle the two different frequencies of a twin frequency communications system, achieved using connector wires, coupling plate and earth to transmit signal on either frequency, and using coupling device and coupling unit to create characteristic impedance for both frequencies. The outer module of the antenna includes at least one radiator suitable for one or more frequency bands, which is attached to the outside of the window. A capacitor in the module couples signals through the glass to a coupling device on the inside of the window, positioned centrally beneath the outer module. A lead (6) such as a coaxial cable extends between the radio or telecommunications equipment and the coupling device. The conductive outer sleeve of the conductor is coupled to an earth (13) inside the antenna casing (14). A signal carrier (8) is linked to connector leads (9, 11), where the junction is earthed in a way that enables one of the leads (9) and the coupling via the coupling plate (10) to transmit on a first frequency band, and the other lead (11) and the coupling via the coupling plate to transmit on a second frequency band. The connector leads are both single wires, which in combination with the coupling between the coupling plate and earth all ows signal transmission via the radiator on the first and second frequency bands respectively. The coupling device combines with the coupling unit to form a characteristic impedance for two frequency bands (e.g. 900 MHz and 1800 MHz), optionally including stroke capacitors, flow and leakage inductors and parallel or series-coupled resistors. The degree of impedance is the same as that for the coaxial cable between the antenna housing and the radio or telecommunications equipment.