Stylus antenna

• US 6,262,684 B1
• Filed: 06/27/2000
• Issued: 07/17/2001
• Est. Priority Date: 06/27/2000
• Status: Expired due to Fees

• Current Assignee: 3Com Corporation (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Prestwich, Sy, Jones, Jeffrey L., Forte, Steven Lo, Stewart, Kurt
• Primary Examiner(s): PHAN, THO GIA
• Application Number:
  US09/604,713
• Time in Patent Office: 385 Days
• Field of Search: H01/Q.124, 343/702, 343/850, 343/852, 343/888, 343/889, 343/900, 343/901, 345/179, 345/180, 345/181, 178/18.01, 178/18.03, 178/18.04, 178/19.01, 178/19.04
• US Class Current: 343/702
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
• CPC Class Codes: G06F 1/1683 for the transmission of signal or power between the different housings, e.g. details of wired or wireless communication, passage of cabling
• CPC Class Codes: G06F 1/1698 the I/O peripheral being a sending/receiving arrangement to establish a cordless communication link, e.g. radio or infrared link, integrated cellular phone details of antennas disposed inside a computer H01Q1/2266
• CPC Class Codes: G06F 2200/1632 Pen holder integrated in the computer
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: H01Q 1/10 Telescopic elements
• CPC Class Codes: H01Q 1/24 with receiving set
• CPC Class Codes: H01Q 1/244 extendable from a housing along a given path

Abstract

The present invention discloses antenna structures for portable digital devices that continuously receive radio signals in both the extended and the retracted antenna positions. In addition, the disclosed antenna structures tune the antenna based on the position of the antenna to achieve good impedance matching, which is particularly useful in reducing the noise and interference, while maximizing the available power for radiation from the portable digital devices. More specifically, a multiple position stylus antenna is disclosed that incorporates an antenna into a stylus for use with a Personal Digital Assistant (PDA). The stylus antenna uses one radiating element tuned for optimal performance in the extended position and synthesizes a compensation impedance to match the impedance of the feeding transmission line in the retracted position.

Claims

1. A stylus antenna structure connected to a transmission feed line on a digital device, the stylus antenna structure comprising:

a radiator element for receiving and transmitting electromagnetic energy, the radiator element having an extended and a retracted position;

a termination module located within the digital device electrically connected to the radiator element and the transmission feed line, the termination module synthesizing a termination impedance for optimal power transfer between the transmission feed line and the radiator element; and

a stylus comprising a molded tip and a non-conductive cylinder with an upper and lower end, the molded tip used predominately for data entry on a touch sensitive screen on the digital device and the non-conductive cylinder protecting the radiator element located substantially within the non-conductive cylinder in the retracted position, the stylus being formed to selectively mechanically couple with the digital device via the insertion into a stylus socket on the digital device such that the stylus socket aligns the stylus to electrically couple the radiator element to the termination module.

2. The stylus antenna structure as recited in claim 1, wherein a first stylus antenna comprises the radiator element and the stylus, the first stylus antenna can be replaced with a second stylus antenna, wherein the first stylus antenna is tuned for use with a first wireless protocol and the second stylus antenna is tuned for use with a second wireless protocol.

3. The stylus antenna structure as recited in claim 1, wherein the retracted position is any position less than the extended position.

4. The stylus antenna structure as recited in claim 3, wherein the termination module only synthesizes the termination impedance for optimal power transfer between the transmission feed line and the radiator element in the retracted position.

5. The stylus antenna structure as recited in claim 1, wherein the stylus antenna structure further comprises:

an upper metal sleeve attached to the upper end of the non-conductive cylinder, the upper metal sleeve being electrically connected to the radiator element in the extended position and selectively electrically coupled to the digital device when the stylus is mechanically coupled to the digital device; and

a lower metal sleeve attached to the lower end of the non-conductive cylinder, the lower metal sleeve being electrically connected to the termination module, the radiator element in the retracted position, and selectively electrically coupled to the digital device when the stylus is mechanically coupled to the digital device.

6. The stylus antenna structure as recited in claim 1, wherein the stylus antenna structure further comprises:

a lower connection clip in electrical communication with the radiator element in the retracted position, the lower connection clip being selectively electrically coupled to a lower conductive clip on the digital device; and

an upper connection clip in electrical communication with the radiator element in the extended position, the upper connection clip being selectively electrically coupled to a upper conductive clip on the digital device.

7. A stylus antenna for use with a wireless enabled digital device, the digital device having an antenna interface with a characteristic impedance, the stylus antenna comprising:

a stylus facilitating data entry to the digital device, the stylus selectively coupling with a stylus socket on the digital device that electrically aligns the antenna interface with the stylus;

a radiator element to transmit and receive electromagnetic energy in the form of radio waves with the antenna interface, the radiator element having an extended position with an extended impedance tuned for the antenna interface to maximize the available power for radiation and a retracted position with a retracted impedance, the radiator element being operably attached to the stylus; and

an impedance synthesis module that generates a compensation impedance to be electrically combined with the retracted impedance of the radiator element in the retracted position creating an impedance combination that matches the characteristic impedance of the antenna interface so as to maximize the available power for radiation when the radiator element is in the retracted position.

8. The stylus antenna as recited in claim 7, wherein the radiator element is frequency independent to provide equal transceiving performance over a broad frequency band.

9. The stylus antenna as recited in claim 7, wherein the retracted position is any radiator element position less than the extended position and the retracted impedance varies according to the retracted position.

10. The stylus antenna as recited in claim 9, further comprising a position detection module connected to the stylus and radiator element, the position detection module for determining an actual position of the radiator element and transmitting the actual position to the impedance synthesis module.

11. The stylus antenna as recited in claim 10, wherein the impedance synthesis module further comprises a processor and a voltage controlled variable LC circuit impedance source, the processor receiving the actual position, calculating the compensation impedance, and sending a corresponding voltage to the impedance source for generating the compensation impedance.

12. The stylus antenna as recited in claim 10, wherein the impedance synthesis module and the position detection module comprises a potentiometer tuned to generate the compensation impedance based on the received actual position of the radiator element.

13. The stylus antenna as recited in claim 10, wherein the position detection module comprises:

a magnet on the radiating element that moves when the radiating element is extended or retracted; and

magnetic sensors positioned next to the radiating element to detect the position of the magnet.

14. The stylus antenna as recited in claim 10, wherein the position detection module comprises:

an optical sensor array configured to emit optical signals at positional increments less than the extended position; and

an optical inhibitor attached to the radiating element so that when the radiating element is moved the inhibitor blocks the optical signal next to the position of the optical inhibitor.

15. The antenna as recited in claim 9, wherein the position detection module further comprises a collar affixed to the radiator element;

and the impedance synthesis module further comprises a variable resistor mechanically attached to the collar and electrically attached to the radiating element, the variable resistor generating the compensation impedance based on the position of the collar.

16. A method for matching the impedance of a stylus antenna to the feeding transmission line so as to maximize the available power for radiation when the stylus antenna is in different positions between and including an extended and a retracted position, the method comprising the steps of:

determining the characteristic impedance of the feeding transmission line;

detecting the position of the extendable portion of the stylus antenna;

calculating the stylus antenna impedance based in part on the position of the extendible portion of the stylus antenna and based in part on a unit impedance of the stylus antenna; and

generating a compensation impedance such that the combination of the stylus antenna impedance and the compensation impedance creates a matched impedance to the feeding transmission line.

17. The method for matching impedance as recited in claim 16, wherein the step of detecting the position uses a collar fixed to the extendable portion of the antenna.

18. The method for matching impedance as recited in claim 17, wherein the collar fixed to the extendable portion of the antenna is attached to a potentiometer that generates the matched impedance based on the position of the collar in the extendable portion.

19. The method for matching impedance as recited in claim 17, wherein the collar fixed to the extendable portion of the antenna is attached to a variable resistor calibrated to generate the matching impedance of the transmission line when the variable resistor is used in combination with the antenna.

20. The method for matching impedance as recited in claim 17, wherein the collar fixed to the extendable portion of the antenna is a magnet, so that the magnet moves when the antenna is extended or retracted and the position is detected by magnetic sensors placed next to the extendable portion.

21. The method for matching impedance as recited in claim 16, wherein the extendable portion is a radiating element having a balanced impedance characteristic.

22. The method for matching impedance as recited in claim 16, wherein the unit impedance is based in part on the dielectric constants of material used in the extendable portion of the stylus antenna.