Electrographic position location apparatus and method

• US 6,661,405 B1
• Filed: 05/19/2000
• Issued: 12/09/2003
• Est. Priority Date: 04/27/2000
• Status: Expired due to Fees

• Current Assignee: Knowledge Kids Enterprises, Inc.
• Original Assignee: LeapFrog Enterprises, Inc. (VTech Holdings Ltd.)
• Inventors: Flowers, Mark
• Primary Examiner(s): Chow, Dennis-Doon
• Assistant Examiner(s): ENGLISH, ALECIA DIANE
• Application Number:
  US09/574,499
• Time in Patent Office: 1,299 Days
• Field of Search: 345/173-178, 345/169
• US Class Current: 345/173
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: G06F 3/046 by electromagnetic means
• CPC Class Codes: H01Q 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence

Abstract

An apparatus for use in an electrographic position sensing system comprises an antenna system and a signal strength detector. In one embodiment, the antenna system comprises two antennas. The detector measures the signal strength from each antenna. A microprocessor contains an algorithm to calculate the position of the detector near the antennas.

Claims

1. A method for locating a user selected position over an antenna apparatus comprising the steps of:

a) providing a first transmitting antenna, the first antenna comprising a first voltage divider having at least two electrical contacts coupled to it, and a plurality of spaced apart, substantially parallel, electrically conductive, finger elements coupled to the first voltage divider between the at least two electrical contacts;

b) providing an electrical insulator to separate the first transmitting antenna from a second transmitting antenna;

c) providing the second transmitting antenna comprising a second voltage divider having at least two electrical contacts coupled to it, and a plurality of spaced apart, substantially parallel, electrically conductive, finger elements coupled to the second voltage divider between the at least two electrical contacts, the second transmitting antenna oriented so that the area defined by its finger elements overlay a portion of the area defined by the finger elements of the second antenna, and the finger elements of the first antenna form a non-zero angle with the finger elements of the second antenna;

d) providing a processor coupled to a user interface and further coupled through other electronics to the first voltage divider at two or more electrical contacts and coupled to the second voltage divider at two or more electrical contacts;

e) providing a drive signal transmitter coupled between the processor and through amplifiers to the first voltage divider at two or more electrical contacts and through amplifiers to the second voltage divider at two or more electrical contacts, the transmitter capable of receiving commands from the processor and transmitting signals to the first and second voltage dividers independently;

f) providing a receiving antenna coupled to an amplifier, the amplifier coupled to the processor;

g) providing a signal detector coupled between the receiving antenna amplifier and the processor;

h) providing a signal receiver coupled between the signal detector and the processor, the signal receiver further coupled to the drive signal transmitter;

i) placing the receiving antenna at a position over the area where the finger elements of the first and second antenna overlap;

j) causing the processor to send commands to the drive signal transmitter, the commands causing the transmitter to send a sequence of five drive-signal states to the first and second voltage dividers independently, the five states being;

i) applying zero voltage to the first and the second voltage dividers;

ii) applying a gradient voltage to the voltage divider of the first, top, antenna and zero voltage to the second, bottom, antenna;

iii) applying a constant voltage to the voltage divider of the first, top, antenna and zero voltage to the second, bottom, antenna;

iv) applying a gradient voltage to the voltage divider of the second, bottom, antenna and zero voltage to the first, top, antenna; and

v) applying a constant voltage to the voltage divider of the second, bottom, antenna and zero voltage to the first, top, antenna;

k) receiving a signal measurement from the receiving antenna during each drive state;

l) detecting a magnitude of the measured signal data from the receiving antenna and sending to the signal receiver;

m) synchronizing the received signal data with timing data obtained from the drive signal transmitter; and

n) calculating the position of the receiving antenna from the measured signal data.

2. The method of claim 1 wherein the position of the receiving antenna is calculated according the following steps:

a) subtracting the signal magnitude data measured at state (i) from the signal magnitude measured at each of the four other states, to yield;

P_Top-G=the signal magnitude measure at state (ii) less the signal magnitude data measured at state (i);

P_Top-C=the signal magnitude measure at state (iii) less the signal magnitude data measured at state (i);

P_Bottom-G=the signal magnitude measure at state (iv) less the signal magnitude data measured at state (i);

P_Bottom-C=the signal magnitude measure at state (v) less the signal magnitude data measured at state (i);

b) obtaining a single data point relating to the measurements taken from the top antenna, P_Top, by calculating the ratio of P_Top-G/P_Top-C;

c) obtaining a single data point relating to the measurements taken from the bottom antenna, P_Bottom, by calculating the ratio of P_Bottom-G/P_Bottom-C; and

d) determining the positional meaning of P_Top and P_Bottom based on a model of a field radiated by the transmitting antennas.

9. The method of claim 2 further comprising the step of shaping the first and second transmitting antennas and insulator substantially into a hemisphere and orienting the finger elements of the first antenna to substantially encircle the hemisphere along a latitude and orienting the fingers of the second antenna to substantially lie along longitudes of the hemisphere.

3. The method of claim 3 wherein the position of the receiving antenna is calculated by the additional step of compensating for variance in resistance in each voltage divider after P_Top and P_Bottom are calculated.

4. The method of claim 3 further comprising the step of compensating for nonlinear variation along any voltage divider by providing an algorithm in the processor, the algorithm containing correction parameters for a one-dimensional voltage divider.

5. A method for locating a user selected position over an antenna apparatus wherein one antenna has a loop voltage divider, comprising the steps of:

a) providing a first transmitting antenna, the first antenna comprising a first voltage divider having at least two electrical contacts coupled to it, the first, and a plurality of spaced apart, electrically conductive, finger elements coupled to the first voltage divider between the at least two electrical contacts;

b) providing an electrical insulator to insulate the components of the first transmitting antenna from a second transmitting antenna;

c) providing the second transmitting antenna, the second antenna comprising a second voltage divider shaped in a loop and having at least three electrical contacts at intervals along the loop, and a plurality of spaced apart, low resistance, finger elements coupled to the second voltage divider at intervals between each two of the at least three contacts, such that the electrical potential along a each element is substantially uniform and the elements are oriented at a substantially a constant angle with a tangent of the loop where each element couples to the loop;

d) orienting the finger elements of the first antenna to define the area enclosed by the loop of the second voltage divider, and orienting the fingers of the second antenna to lie within the loop of the second voltage divider, wherein the first antenna is oriented so that the area defined by the finger elements of the first antenna overlay a portion of the area defined by the finger elements of the second antenna; and

the finger elements of the first antenna form a non-zero angle with the finger elements of the second antenna;

e) providing a processor coupled to a user interface and further coupled through other electronics to the first voltage divider at two or more electrical contacts and coupled to the second voltage divider at three or more electrical contacts;

f) providing a drive signal transmitter coupled to the processor and through amplifiers to the first voltage divider at two or more electrical contacts and coupled through amplifiers to the second voltage divider at three or more electrical contacts, the transmitter capable of receiving commands from the processor and transmitting signals to the first and second voltage dividers independently;

g) providing a receiving antenna coupled to an amplifier, the amplifier coupled to the processor;

h) providing a signal detector coupled between the receiving antenna amplifier and the processor;

i) providing a signal receiver coupled between the signal detector and the processor, the signal receiver further coupled to the drive signal transmitter;

j) placing the receiving antenna at a position over the area where the finger elements of the first and second antenna overlap;

k) causing the processor to send commands to the drive signal transmitter, the commands causing the transmitter to send a sequence of six drive-signal states to the first and second voltage dividers independently, the six states being;

i) applying zero voltage to the first and the second voltage dividers;

ii) applying a gradient voltage to the voltage divider of the first, top, antenna and zero voltage to the second, bottom, antenna;

iii) applying a constant voltage to the voltage divider of the first, top, antenna and zero voltage to the second, bottom, antenna;

iv) applying a first gradient voltage to two or more of the at least three contacts of the voltage divider of the second, bottom, antenna and applying zero voltage to the first, top, antenna;

v) applying a second gradient voltage to two or more of the at least three contacts of the voltage divider of the second, bottom, antenna and applying zero voltage to the first, top, antenna;

vi) applying a constant voltage to the voltage divider of the second, bottom, antenna and zero voltage to the first, top, antenna;

l) receiving a signal measurement from the receiving antenna during each drive state;

m) detecting a magnitude of the measured signal data from the receiving antenna and sending to the signal receiver;

n) synchronizing the received signal data with timing data obtained from the drive signal transmitter; and

o) calculating the position of the receiving antenna from the measured signal data.

6. The method of claim 5 wherein the position of the receiving antenna is calculated according the following steps:

a) subtracting the signal magnitude data measured at state (i) from the signal magnitude measured at each of the five other states, to yield;

P_Top-G=the signal magnitude measure at state (ii) less the signal magnitude data measured at state (i);

P_Top-C=the signal magnitude measure at state (iii) less the signal magnitude data measured at state (i);

P_Bottom-G1=the signal magnitude measure at state (iv) less the signal magnitude data measured at state (i);

P_Bottom-G2=the signal magnitude measure at state (v) less the signal magnitude data measured at state (i);

P_Bottom-C=the signal magnitude measure at state (vi) less the signal magnitude data measured at state (i);

b) obtaining a single data point relating to the measurements taken from the top antenna, P_Top, by calculating the ratio of P_Top-G/ P_Top-C;

c) obtaining two data points relating to the measurements taken from the bottom antenna, P_Bottom-G1 and P_Bottom-G2 by calculating the ratios of P_Bottom-G1/P_Bottom-C and P_Bottom-G2/P_PBottom-C respectively; and

d) determining the positional meaning of P_Top, P_Bottom-G2, and P_Bottom-G1, based on a model of a field radiated by the transmitting antennas.

7. The method of claim 6 wherein the position of the receiving antenna is calculated by the additional step of compensating for variance in resistance in each voltage divider after P_Top and P_Bottom are calculated.

8. The method of claim 6 further comprising the step of compensating for nonlinear variation along any voltage divider by providing an algorithm in the processor, the algorithm containing correction parameters for a one-dimensional voltage divider.