Douglas E Bowman

US Patent:

6349116, Feb 19, 2002

Filed:

Oct 12, 2000

Appl. No.:

09/689340

Inventors:

Ronald J. Hash - Rogersville TN
Douglas C. Bowman - Capitola CA

Assignee:

Wherenet Corp. - Santa Clara CA

International Classification:

H04B 300

US Classification:

375258, 375272, 375276

Abstract:

A non-propagating magnetic field-based communication system transmits and receives digital data within a limited coverage area environment. The system includes a compact transmitter unit, such as that contained in an âtrackingâ tag affixed to an object, and a digital detector/demodulator unit. In order to generate and FSK-modulate a non-propagating magnetic field in accordance with modulation signals representative of the digital data, the transmitter unit contains a magnetic field coil and one or more capacitors controllably switched in circuit with the coil in accordance with the data, so as to change the resonant frequency of an inductor-capacitor transmitter resonant circuit. The receiver unit includes a magnetic field-sensing coil in circuit with a capacitor, to form a receiver resonant circuit that resonates at a frequency between the FSK frequencies modulated by the transmitter unit. A digital receiver/demodulator detects whether received frequencies are valid FSK frequencies and derives digital data using differences between valid detected FSK frequencies.

US Patent:

6476719, Nov 5, 2002

Filed:

Mar 6, 2001

Appl. No.:

09/800079

Inventors:

Donald K. Belcher - Rogersville TN
John A. Eisenberg - Los Altos CA
Ronald J. Hash - Rogersville TN
Douglas C. Bowman - Capitola CA

Assignee:

Wherenet Corp. - Santa Clara CA

International Classification:

G08B 1314

US Classification:

3405721, 340525, 342126

Abstract:

The unwanted influence a noise-source environment upon a modulated (e. g. , FSK-encoded) magnetic field-based communication system is diminished by a non-modulated AC magnetic field communication scheme that uses a demodulatorless magnetic field detector. When installed in a tag to be tracked by a geolocation system, the demodulatorless detector responds when the tag comes within a prescribed proximity of the field generator producing the non-modulated AC magnetic field. The received signal is downconverted to baseband and processed to detect a valid AC magnetic field tone and indicate whether the tag is within a prescribed proximity of the AC magnetic field source.