Combined antenna apparatus and method for receiving and transmitting radio frequency signals

• US 5,678,202 A
• Filed: 12/20/1996
• Issued: 10/14/1997
• Est. Priority Date: 06/08/1995
• Status: Expired due to Term

• Current Assignee: Plantronics, Inc.
• Original Assignee: Plantronics, Inc.
• Inventors: Filimon, Cristian C., Gundavajhala, Anand, Jacobs, Stephen M.
• Primary Examiner(s): Pham, Chi H.
• Application Number:
  US08/771,573
• Time in Patent Office: 298 Days
• Field of Search: 455/89, 455/90, 455/100, 455/107, 455/129, 455/278.1, 455/289, 455/277.1, 343/702, 343/700 MS, 343/718
• US Class Current: 455/575.7
• CPC Class Codes: H01Q 1/242 specially adapted for hand-held use
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H
• CPC Class Codes: H04B 1/3827 Portable transceivers
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/26 using coils

Abstract

An antenna system and method for use in a portable unit of a wireless telephone headset, wireless telephone headset adapter, or other telecommunication device combines a capacitive coupling antenna with an electric field sensitive antenna. The electric field sensitive antenna, such as a monopole antenna, receives and transmits RF signals when the portable unit is located remote from the user. A patch antenna receives and transmits RF signals when the portable unit is located proximate to, for example is worn by, the user. The patch antenna is a conductive surface for capacitively coupling to a user'"'"'s body which acts as a radiating and receiving medium. Both the patch antenna and monopole antenna are coupled to an antenna port by matching circuits to tune each antenna for desired RF characteristics. When worn by the user, the RF effects of the monopole antenna are negligible and the patch antenna operates as the primary antenna. When located remotely from the user, the patch antenna will not be capacitively coupled to a body and the RF effects will be negligible as compared with the RF effects of the monopole antenna. The portable unit of a wireless headset receives and transmits signals when the portable unit is located either proximate to the user or remote from the user.

Claims

1. In a portable unit having a housing, an apparatus for operating on electromagnetic signals comprising:

an antenna port in the portable unit for coupling to a load having a load impedance;

a conductive surface disposed on the housing for capacitively coupling to a conductive body in close proximity with the portable unit;

an electric field antenna disposed on the portable unit;

a first matching circuit coupling the conductive surface to the antenna port and having an impedance that causes the conductive body to operate as the dominant receiving medium as compared to the electric field antenna when the portable unit is in close proximity with the conductive body; and

a second matching circuit for matching the load coupling the electric field antenna to the antenna port.

2. The apparatus of claim 1 wherein:

the first matching circuit comprises a first inductor; and

the second matching circuit comprises a T network including serially coupled inductors and a shunt capacitor connected between the serially coupled inductors.

3. The apparatus of claim 1 wherein the electric field antenna is a monopole antenna.

4. The apparatus of claim 1 wherein the conductive surface is substantially rectangular and has approximately three inch length and approximately two inch width.

5. A method for receiving an electromagnetic signal using a portable unit adapted for use in a first operating environment proximate a body and a second operating environment remote from a body, the portable unit having a combined antenna comprising a capacitive coupling element, an electric field sensitive antenna and an antenna port for coupling to a load having a load impedance, comprising the steps of:

positioning the combined antenna in a first location;

responsive to the first location being in the first operating environment performing the steps of;

capacitively coupling the capacitive coupling element to the body; and

using the body as a dominant receiving medium; and

responsive to the first location being in the second operating environment using the electric field sensitive antenna as a dominant receiving medium.

6. The method of claim 5 further comprising the step of tuning the electric field antenna to match the load impedance.

7. The method of claim 5 further comprising the step of tuning the capacitive coupling element to match the load impedance when using the body as the dominant receiving medium.

8. The method of claim 5 wherein the electromagnetic signal has a transmission frequency of at least 25 MHz.

9. The method of claim 5 wherein the electromagnetic signal has a transmission frequency range of 46-49 MHz.

10. A method for transmitting a transmission signal using a portable unit adapted for use in a first operating environment proximate a body and a second operating environment remote from a body, the portable unit having a combined antenna comprising a capacitive coupling element, an electric field antenna and an antenna port for coupling to a load having a load impedance, comprising the steps of:

coupling the transmission signal to the capacitive coupling element;

coupling the transmission signal to the electric field antenna;

positioning the combined antenna in a first location;

responsive to the first location being in the first operating environment performing the steps of;

capacitively coupling the capacitive coupling element to the body; and

using the body as a dominant radiator; and

responsive to the first location being in the second operating environment using the electric field antenna as a dominant radiator.

11. The method of claim 10 further comprising the step of tuning the electric field antenna to match the load impedance.

12. The method of claim 10 further comprising the step of timing the capacitive coupling element to match the impedance when using the body as the dominant receiving medium.

13. The method of claim 10 wherein the transmission signal has a transmission frequency of at least 25 MHz.

14. The method of claim 10 wherein the transmission signal has a transmission frequency range of 46-49 MHz.