A communications device for sending and receiving an information signal. The communications device comprising an element having an opening defined therein for receiving an antenna, the element comprising first conductive material disposed proximate the opening and comprising transmitting and receiving circuits. The antenna comprises: a dielectric tubular member, second conductive material forming an exterior surface of the tubular member with the second conductive material defining a slot therein, a slot length approximately equal to one-half of a guided wavelength and a feed connected to the transmitting and receiving circuits and disposed proximate the slot for establishing currents in the second conductive material.
1. An antenna for placement in an opening within a first conductive material, the antenna comprising:
a dielectric tubular member;
a second conductive material forming an exterior surface of the tubular member;
the second conductive material defining a slot therein, the slot having a slot length approximately equal to one-half of a guided wavelength and having a slot width, there being no slot present in the tubular member immediately beneath the slot in the second conductive material, wherein a width of the opening defined by the first conductive material is less than a quarter wavelength of the guided wavelength; and
a feed proximate the slot for establishing currents in the second conductive material when the antenna is in a transmitting mode, the currents perpendicular to the slot length.
2. A communications device for sending and receiving an information signal, the communications device comprising:
an element having an opening defined therein for receiving an antenna, the element comprising first conductive material disposed proximate the opening;
transmitting and receiving circuits;
the antenna comprising:
a dielectric tubular member;
second conductive material forming an exterior surface of the tubular member;
the second conductive material defining a slot therein, a slot length approximately equal to one-half of a guided wavelength; and
a feed connected to the transmitting and receiving circuits and disposed proximate the slot for establishing currents in the second conductive material when the antenna is in a transmitting mode.
3. The device of claim 2 wherein the currents are perpendicular to the slot length.
4. The device of claim 2 wherein the slot length is substantially greater than a slot width.
5. The device of claim 2 wherein a dielectric constant of the dielectric tubular member is at least 10.
6. The device of claim 2 wherein the antenna comprises a slotted cylinder antenna.
7. The device of claim 2 wherein a width of the opening for receiving the antenna is less than a quarter wavelength at an operating frequency of the antenna.
8. The device of claim 2 wherein the second conductive material further defines a gap therein, the gap extending a length of the tubular member.
9. The device of claim 2 wherein a cross section of the tubular member comprises one of a D-shaped cross-section, a circular cross-section, a rectangular cross-section and a square cross-section.
10. The device of claim 2 wherein the feed comprises a first conductor connected to the second conductive material and a second conductor extending across a width of the slot from a first edge of the slot to a second edge of the slot and connected to the second edge.
11. The device of claim 2 wherein the element having an opening therein comprises a laptop computer screen or a laptop computer keyboard, and wherein a radiation pattern is substantially omnidirectional relative to a long axis of the slot.
12. The device of claim 2 wherein the antenna exhibits two closely spaced resonant frequencies.
13. The device of claim 2 wherein the antenna comprises at least two slots each separately excited.
14. The device of claim 2 wherein the two slots have a substantially equal resonant frequency and provide antenna diversity for the communications device.
15. The device of claim 2 wherein the slot comprises a J-shaped slot.
16. The device of claim 15 wherein the J-shaped slot comprises a short leg having a first resonant frequency and a long leg having a second resonant frequency.
17. The device of claim 2 wherein the feed comprises a microstrip probe mounted proximate the slot.