A car phone antenna

Abstract: An antenna comprises a radiating element and a cone-shaped ground plate the relative distance between which can be altered thus altering the resonant frequency of the antenna and a base. The resulting antenna is a wideband quarter-wave vertical antenna which can be employed for testing in the 1.8 GHz frequency range and for temporary use in all car phones as well as in fixed stations.

Description: The invention relates to an antenna for a car phone. Car phone antennas according to the prior art, which are used in testing in the 1.8 GHz frequency range, are not user friendly. They are very difficult to install and require a ground plate. In addition, their resonance frequency and radiation pattern as well as the impedance of the input point vary due to differences in installation methods. US 5,132,698 describes an antenna for landline satellite communications in which the angle of the radiation beam maximum is controlled by changing the length of the monopole over the ground plane. US 4, 851, 859 describes a tunable discone antenna. According to the present invention there is provided a wideband quarter-wave vertical antenna for testing and temporary use of a car phone comprising a radiating element and a truncated cone-shaped conducting ground plate, wherein the ground plate and the radiating element are mechanically coupled via an adjustable element comprising a screw thread which mates with a complementary threaded nut which is disposed between the radiating element and the cone-shaped ground plate such that by manipulation of the adjustable element the position of the radiating element relative to the ground plate can be adjusted, thereby enabling the antenna's resonance frequency to be altered. The wideband quarter-wave vertical antenna in accordance with the invention can be employed for testing in the 1.8 GHz frequency range and for temporary use in all car phones as well as in fixed stations. An advantage of the present invention is the provision of an antenna for car phones, which operates in the 1.8 GHz frequency range and offers a way of solving or mediating the above-presented deficiencies and problems. Preferably the impedance of the antenna's input point can be adjusted to a constant level by means of a ground plate in the form of a truncated cone. Also preferably the truncated cone-shaped ground plate extends substantially away from the radiating element, the lower part of the radiating element forming a connection means which extends into the truncated cone. The connection means is provided with adjustment means by the manipulation of which the relative distance between the radiating element and the base plan can be adjusted. The base plate and antenna are releasably connected to the magnetic base by locable attachment means. The antenna is attached to the magnetic base in such a way that the antenna equipped with a magnetic base can easily be installed, for example, on a car roof. Also, the resonance frequency can be set to the desired level by manipulating the adjustable element, and the antenna's radiating element and the cone-shaped ground plate can be easily attached to the magnetic base by means of an attachment element. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 presents the construction of an antenna for a car phone in accordance with the invention; Figure 2 presents an alternative mode of installation of the antenna of Figure 1; and Figure 3 presents the detailed construction of the antenna of Figure 1. Figure 1 presents the construction of a car phone antenna in accordance with the invention. The antenna comprises a radiating element 1 and a cone-shaped ground plate 2. In Figure 1 the antenna has been installed on a magnetic base 3. The antenna equipped with the magnetic base 3 according to Figure 1 can be easily installed, for example, on a car roof by merely placing the magnetic base 3 on the car roof once the antenna and ground plate have been attached to the magnetic base 3. Figure 2 presents an alternative mode of installation of the car phone antenna in accordance with the invention. In the alternative mode of installation, the antenna comprises a base tube 4 in addition to the radiating element 1 and the cone-shaped ground plate 2. An antenna equipped with the base tube 4 can be used, for example, in a fixed station. Figure 3 presents the detailed construction of the car phone antenna in accordance with the invention. The antenna comprises an adjusting element 5 between the radiating element 1 and the cone-shaped ground plate 2; in this case, the adjusting element 5 is a nut which has a corresponding thread to that of the threaded part of element 1 and can be manipulated so as to set the resonance frequency to the desired level by relative movement of the antenna with respect to the base plate. The antenna also comprises an attachment element 6 by means of which the antenna's radiating element 1 and the cone-shaped ground plate 2 can easily be attached to the magnetic base 3. The antenna in accordance with the invention operates without a separate ground plate because its cone-shaped element 2 functions as a ground plate. The impedance of the input point of the antenna according to the invention can be adjusted to a constant level (for example, 50 ohms) by means of the cone-shaped ground plate 2.

Claims: A wideband quarter-wave vertical antenna for testing and temporary use of a car phone comprising a radiating element (1) and a truncated cone-shaped conducting ground plate, wherein the ground plate (2) and the radiating element are mechanically coupled via an adjustable element (5) comprising a screw thread which mates with a complementary threaded nut which is disposed between the radiating element and the cone-shaped ground plate such that by manipulation of the adjustable element the position of the radiating element relative to the ground plate can be adjusted, thereby enabling the antenna's resonance frequency to be altered. An antenna as claimed in claim 1, wherein the truncated cone-shaped ground plate extends substantially away from the radiating element, the lower part of the radiating element forming a connection means which extends into the truncated cone. An antenna as claimed in claim 2, wherein the part of the connection means (6) is provided with adjustment means by the manipulation of which the relative distance between the radiating element and the base plan can be adjusted. An antenna as claimed in any previous claim, further comprising a magnetic base. An antenna as claimed in claim 4, wherein the base plate and antenna are releasably connected to the magnetic base by lockable attachment means (6). An antenna as claimed in claim 5, wherein the attachment means are in the form of a coaxial bayonet fitting. An antenna as claimed in any of claims 1 to 3, wherein the mounting element is constituted by a base tube extending downwards from the cone-shaped ground plate.

Inventors: MOILANEN MIKKO, MOILANEN, MIKKO
Applicants: NOKIA MOBILE PHONES LTD, NOKIA MOBILE PHONES LTD.
Application year: 1993
Main classification: H01Q9
IPC codes: H01Q1, H01Q9