Multiband Television/Communications Antenna

The invention relates to multiband antennas and particularly to a multiband unitary antenna unit for receiving television signals and for transmitting and receiving 2-way communication signals like in mobile cellular telephones.

With the increasing popularity of cellular telephones, a need has arisen for antennas to be used on automobiles and the like vehicles. Previously, television antennas have been provided for automobiles in a winged, ornamental housing as shown in Des. Pat. No. 245,778 wherein a dipole antenna folded in the shapes of both wings. Cellular telephone antennas have typically included rectilinear elements commonly referred to as 3 dB antennas. With the use of a television and a cellular phone in one vehicle, the need for multiple antennas on the vehicle has arisen. The mounting of more than one antenna on a vehicle gives a cluttered appearance. While it is desirable to eliminate multiple antennas on a vehicle, it is not always simple or practical from a technical and aesthetic view point.

A folded antenna consisting of a plurality of dipoles connected end to end in a generally J-shaped pattern, commonly referred to as a folded Franklin antenna, has been known and used typically for business (emergency, police, etc.) and marine bands and vertically polarized.

Accordingly, an important object of the invention is to provide a multi-element antenna capable of operating at multiple bands from a compact unitary housing for vehicular use.

Another object of the invention is to provide a multiband antenna unit which may be used for receiving television and 2-way communication.

Another object of the invention is to provide a compact vehicle antenna capable of efficiently operating in the television and cellular telephone frequency bands in a unitary housing without interference from one another.

The above objectives are accomplished according to the present invention by providing a unitary housing which houses a television antenna having a horizontally polarized radiation pattern and a 2-way communications antenna having a vertically polarized radiation pattern. The communications antenna includes a first radiating element connected to a second radiating element by a phasing coil. A current null point is formed adjacent the phasing coil. The two antennas are incorporated in the housing so that a horizontal plane in which the television antenna lies intersects the current null point of the communications antenna so the cross-coupling and interference is reduced. Preferably, the television antenna is provided by a folded generally J-shaped antenna which creates three radiating elements radiating at three resonant frequencies for effective reception of VHF and UHF television signals. The communications antenna is in the form of a cellular telephone antenna which transmits and receives. The second radiating element of the cellular telephone antenna extends outwardly from a boomerang shaped upper portion of the housing in which the horizontal television antenna lies. A compact unitary multiband antenna is provided having plural antennas effectively operating at dual polarity.

The construction designed to carry out the invention will hereinafter be described, together with other features thereof.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown and wherein:

FIG. 1 is a side elevation illustrating a vehicle with a multiband antenna constructed in accordance with the present invention.

FIG. 2 is a perspective view of the multiband antenna;

FIG. 3 is a perspective view of the multiband antenna with the housing shown in phantom lines to illustrate multiple antenna elements for a unitary multiband antenna according to the invention;

FIG. 4 is a side elevation of the multiband antenna with the housing shown in phantom lines;

FIG. 4A is a schematic illustration of the cellular antenna element and current null current with intersection of the horizontally polarized television antenna;

FIG. 5 is a schematic view illustrating a theoretical configuration and wave length of a cellular phone antenna for use with a multiband antenna according to the invention;

FIG. 6 is a schematic view illustrating the size and configuration of a television antenna for use in a multiband antenna according to the invention; and

FIG. 7 is an illustration of theoretical radiation patterns of the multiband antenna of the present invention.

Referring now in more detail to the drawings, a multiband antenna is designated generally at A which includes a housing 10 in the form of a winged antenna housing having a widened horizontal portion consisting of a pair of wings 12, 14 in a boomerang shape supported on a narrow pedestal base 16. Base 16 may be fastened directly onto a vehicle such as a trunk 18 of an automobile.

In accordance with the invention, multiband antenna A includes a television receiving antenna B and a 2-way communication antenna C for cellular telephone reception and transmission. Television antenna B includes antenna elements constructed from any suitable conductor such as round copper or aluminum wire. Preferably, antenna B is arranged in a folded Franklin configuration which results in multiple resonant frequencies, and is carried in housing 10 in a horizontal plane for horizontal polarization. As can best be seen in FIGS. 3 and 6, there is a first radiating antenna element 20 and a second, half radiating antenna element 22. Each of these elements acts individually and also together in phase. Element 20 operates individually at a first resonant frequency in a high VHF band of generally 172 to 214 megahertz for reception of VHF channels 8-13. Element 22 operates at a second resonant frequency generally within a 410 to 900 megahertz band for UHF reception of channels 14-83. In the UHF mode of operation, the antenna acts as a long wire antenna resulting in some gain. Elements 20 and 22 operate together as a third radiating element, at a third resonant frequency within a low VHF band for reception of channels 2-7, generally between 54 and 88 megahertz. A feed point 24 of antenna B is connected to a coaxial cable 26 which may be routed to the interior of the vehicle for connection to a television amplifier or television receiver 28, as can best be seen in FIG. 3.

Multiband antenna A includes a fourth, monopole radiating element 30 and a fifth, monopole radiating element 32 of 2-way communication antenna C. The 2-way antenna is preferably a cellular phone antenna element C. The 2 monopole antennas 30,32 are connected by a phasing coil 34. Antenna elements 30 and 32 may be any suitable conductors such as copper or aluminum wire. Phasing coil 34, is of a suitable number of turns, diameter, and length, in order to achieve proper phasing between antenna elements 30 and 32. Radiating element 30 may be approximately 6" in length and may be made from copper or aluminum wire or other suitable conductive material. Element 30 extends at an angle of 0 to 30 degrees to vertical for effective vertical polarization. Radiating element 30 is half-wave antenna element which produces a half wave signal 36 (FIG. 5). Radiating element 32 may be approximately 3" long and a quarter-wave antenna element which produces a quarter wave signal 38. Phasing coil 34 also produces a full half-wave signal, the net effect of which places the half-wave and quarter-wave signals 36 and 38 in phase to produce a three-quarter wave antenna in phase for gain. Quarter wave element 32 has a nominal 50 ohm impedance designed to match the impedance of a coaxial cable 40 connected to antenna element C at a feed point 42. It will be noted that the vehicle 18 acts as a ground plane, and in this sense acts as a quarter wave antenna with element 32. Alternately, cable 40 may be provided with a coaxial sleeve when antenna A is mounted to vehicles having non-conductive bodies. Coaxial cable 40 is connected to a cellular telephone unit 44 inside the vehicle (FIG. 3).

In accordance with the invention, antennas B and C are enclosed in a compact unitary housing to provide multiband antenna A. Housing 10 is preferably formed from a nonconductive, plastic material. An important feature of multiband antenna A is that a current null point 50 of communication antenna C, created by phasing coil 34, is located within housing 10 with respect to the horizontal plane of television antenna B so that interference between antenna elements B and C is minimized. As can best be seen in FIG. 4, horizontal antenna element B is disposed in a horizontal plane 52 which intersects antenna C at current null point 50 so that both antennas may be accommodated in housing 10 without significant cross coupling, interaction, and interference. Antenna element B is a horizontally polarized and antenna element C is vertically polarized.

For purposes of illustration only, and not limitation, FIG. 7 illustrates generally a theoretical radiation pattern of antenna elements B and C. Antenna element C radiates a generally toroidal shaped, vertically polarized pattern 54 having its center about the generally vertical antenna. Antenna element B radiates a generally toroidal shaped, horizontally polarized pattern 56.

While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.