ISOLATED ANTENNA BASES

Abstract: An antenna base, integral to the antenna, which is capacitively coupled to the bodywork or panel of a metal vehicle, or any other form of metal or substitute material groundplane, by any appropriate method comprising of a dielectric or material of suitable permeativity. The antenna is thereby connected to ground enabling alternating current to pass in the form of radio frequency, but not allowing direct current to pass and thus isolating it. The capacitive coupling and d.c. isolation is achieved by the antenna base itself so that no other structure is required between the base and the vehicle to which it is attached.

Description: Description Isolated antenna bases This invention is a range of antenna bases, integral to the antenna, using the same technical principle. When a mobile communication antenna is fitted to a vehicle, the vehicle normally becomes a parI ol " t_hc antenna circuit and this part of the antenna circuit is called the groundplane. Usually the antenna base is fitted by drilling a nc_e and the car is connected to the antenna circuit by way of the mechanical structure of the antenna base itself. For many years, this has presented a number of problems, two of the most significant of these are: first, that it may not be practical to drill a hole in the car - second, that if the vehicle has an insulated return electrical system and is used in the petro-chemical industry to carry volatile liquids or explosives, cr it has a highly sophisticated, computerised electrical system, the connecting of the antenna earth coulα make it dangerous, becoming a serious fire risk cr causing malfunction in the computer with serious probable consequences. The present invention overcomes both of these problems, because it does not require a hole to be drilled and it does not connect the antenna earth to the vehicle directly, but capacitively. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which:- Figure 1 the antenna base is shown in cross-section attached to the vehicle panel or bodywork, irrespective of the location. The coaxial cable 8 which connects the transmitter/ receiver to the antenna is terminated within the antenna base body moulding section 4. The antenna earth or return which is the screened part of the cable is terminated at 7, directly in contact with the capacitive plate 5. The centre 3 or hot part of the antenna cable 2 is connected to 1 where any suitable antenna can be affixed. The connecting of the antenna earth or braid side of the coaxial cable to plate 5 could be magnetic, providing dielectric 6 is a suitable material and the vehicle surface 9 is of a ferrous material, thus allowing a magnetic flux with 5. Plate 6 could be of any alternative suitable material offering itself as a capacitor plate, providing dielectric 6 is also adhesive on both sides. When the radio signal is induced into the antenna base, it is connected to the antenna affixed to 1 and to the vehicle capacitively through plate 5 and dielectric 6, due to the alternating current of the radio signal, but at no time will the vehicle be directly connected to the antenna earth. The cable 8 will also be of sufficiently small diameter to practically run through extremities of the vehicle without causing problems, i.e. doors, boot lid, hatch back, door etc.

Claims: Claim An antenna base, integral to the antenna, which is capacitively coupled to the bodywork or panel of a metal vehicle, or any other form of metal or other substitute material groundplane, which is fastened, attached or secured via any suitable method, comprising of dielectric or material of suitable permeativity, which thus isolates it from direct current (DC), but which allows an alternating current (ΛC) to pass. The antenna base, integral to the antenna, achieves the capacitive coupling soley through the antenna ' s mechanical design and is not dependent upon structures additional to the vehicle to which it is attached.

Inventors: WALLEN LESLIE JAMES, WALLEN, LESLIE, JAMES
Applicants: WALLEN MANUFACTURING LIMITED, LES WALLEN MANUFACTURING LIMITED
Application year: 1991
Main classification: H01Q1
IPC codes: H01Q1