Antenna assembly for radio circuit and method therefor

• US 5,708,445 A
• Filed: 03/01/1993
• Issued: 01/13/1998
• Est. Priority Date: 01/29/1993
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Moller, Paul J., Schwinghammer, Patrick A., Schwartz, Mark W.
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US08/024,545
• Time in Patent Office: 1,779 Days
• Field of Search: 343/895, 343/702, 343/752, 343/900, 343/901
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/244 extendable from a housing along a given path
• CPC Class Codes: H01Q 1/362 for broadside radiating helical antennas
• CPC Class Codes: H01Q 9/36 with top loading
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface

Abstract

An antenna assembly, and associated method, for a radio, such as a portable radiotelephone, which is of minimal physical dimensions and which is operable over a wide range of frequencies. A length of wire is helically-shaped and includes at least a portion of a winding. A capacitive top-hat is positioned at an end portion of the wire. By increasing the number of windings of the wire, the height of the antenna assembly is reduced, but such reduction also reduces the size of the bandwidth of frequencies over which the antenna assembly is operable. Increase in the size of the surface area of the capacitive top-hat increases the size of the bandwidth over which the antenna assembly is operable. Selection of the top-hat size and the number of windings permits beth physical dimensions of the antenna assembly and the size of the bandwidth to be selected.

Claims

1. An antenna assembly of selected antenna characteristics for a radio having radio circuitry housed within a radio housing body, the antenna assembly comprising:

an electrically-conductive wire positioned in the radio housing body and having at least a portion of a winding formed therein to configure the electrically-conductive wire into a coiled shape, the electrically-conductive wire having a proximal end portion and a distal end portion wherein the proximal end portion is coupled to the radio circuitry;

a top-hat positioned in the radio housing body, the top hat including a first electrical coupling portion coupled to the distal end portion of the wire, wherein the top-hat is of a surface area of a magnitude related to numbers of windings formed in the electrically-conductive wire and is selected such that the number of windings of the wire and the magnitude of the surface area of the top-hat are together determinative of the antenna characteristics, and the top hat including a second electrical coupling portion for electrically coupling the top hat to an antenna associated with a projecting rod, the first and second electrical coupling portions spaced from one another; and

a rod including a rod coil carried thereon, the rod and coil extending through the top hat and out of the radio housing body in an extended position, the rod coil coupled to the top hat at the second electrical coupling portion when the rod is in the extended position, whereby the rod coil is coupled to the radio circuitry via the top hat and the electrically conductive wire when the rod is in the extended position.

2. The antenna assembly of claim 1 wherein the wire comprises a non-integer number of windings.

3. The antenna assembly of claim 2 wherein the proximal end portion and the distal, end portion of the electrically-conductive wire extend in parallel directions.

4. The antenna assembly of claim 3 wherein the proximal end portion and the distal end portion of the electrically-conductive wire each define longitudinally-extending axes, wherein the longitudinally-extending axis defined by the proximal end portion of the wire extends in a direction offset with respect to a direction in which the longitudinally-extending axis defined by the distal end portion of the wire extends.

5. The antenna assembly of claim 1 wherein the wire is of a length comprising a low impedance antenna at a frequency of operation of the radio circuitry of the radio.

6. The antenna assembly of claim 1 wherein the electrically-conductive wire is of a length substantially corresponding to the length of one-quarter wavelength of a signal of a frequency at which the radio circuitry of the radio is operable.

7. The antenna assembly of claim 1 wherein the distal end portion of the wire is coupled to the top-hat by way of an electrical connection therewith.

8. The antenna assembly of claim 7 wherein the distal end portion of the wire abuts against a face surface of the top-hat, thereby to form the electrical connection therewith.

9. The antenna assembly of claim 1 wherein the top-hat is comprised of a drawn sheet of metallic material.

10. The antenna assembly of claim 9 wherein the top-hat defines at least one face surface having at least a portion which extends in a planar direction generally orthogonal to a direction in which the distal end portion of the wire extends.

11. The antenna assembly of claim 10 wherein the top-hat comprises a transversely-extending, domed, cap member.

12. The antenna assembly of claim 10 further comprising a supportive plug member having a support surface permitting supportive seating of a face surface of the at least one face surface of the top-hat thereupon.

13. The antenna assembly of claim 12 wherein the electrically-conductive wire is supported to extend through the supportive plug member to be supported thereat.

14. The antenna assembly of claim 13 wherein the supportive plug member is comprised of a molded, thermoplastic material.

15. The antenna assembly of claim 13 wherein at least a portion of the proximal end portion of the electrically-conductive wire extends beneath the supportive plug member to permit thereby electrical connection of the proximal end portion of the wire with the radio circuitry of the radio.

16. The antenna assembly as defined in claim 1, wherein the second coupling portion of the top hat includes a recess for receiving the rod coil associated with the rod.

17. The antenna assembly as defined in claim 16, wherein the recess includes an aperture which circumscribes the coil and rod.

18. The antenna assembly as defined in claim 17, wherein the second coupling portion aperture is substantially round.

19. In a radio having radio circuitry housed within a radio housing body, a combination with the radio circuitry of an antenna assembly, said antenna assembly comprising:

an electrically-conductive wire positioned in the radio housing body, a portion of the electrically-conductive wire configured in a helical shape and having a proximal end and a distal end portion comprised of portions of the wire extending beyond the helical shaped portion, wherein the proximal end portion of the wire is coupled to the radio circuitry;

a top-hat coupled to the distal end portion of the wire, wherein the top-hat is of a surface area of a magnitude related to numbers of windings of the electrically-conductive wire such that the numbers of windings of the wire and the magnitude of the surface area of the top-hat are together determinative of the antenna characteristics, the top hat including an opening; and

a rod including a rod coil carried thereon, the rod and coil extending through the top hat opening and out of the radio housing body in an extended position, the rod coil coupled to the top hat at the opening when the rod is in the extended position, whereby the rod coil is coupled to the radio circuitry via the top hat and the electrically conductive wire when the rod is in the extended position.