Synchronous telemetry channel

• US 5,608,390 A
• Filed: 02/23/1994
• Issued: 03/04/1997
• Est. Priority Date: 02/23/1994
• Status: Expired due to Term

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: AT&T Global Network Services LLC (AT&T, Inc.), Symbios Logic Incorporated (Broadcom, Inc.), Hyundai Electronics America Incorporated (SK Hynix Inc.)
• Inventors: Gasparik, Frank
• Primary Examiner(s): Hofsass, Jeffrey
• Assistant Examiner(s): MANNAVA, ASHOK K
• Application Number:
  US08/200,721
• Time in Patent Office: 1,105 Days
• Field of Search: 341/22, 341/34, 364/174, 364/175, 178/18, 178/19, 178/20, 381/13, 381/6, 381/4, 345/179, 455/206, 455/306, 375/350, 375/376, 340/870.01, 340/870.02, 340/870.03, 340/870.1
• US Class Current: 340/870.01
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

The invention concerns pen-based computers, wherein a pen, or stylus, is positioned on a display of the computer, and produces a signal which allows the computer to detect the position of the stylus. The stylus produces a second signal, which is used as a carrier for telemetry, to transmit data from the stylus to the computer.

Claims

1. In a digitizing tablet which receives signals from a stylus, the improvement comprising:

a first filter having a passband centered at a first frequency f1, and zeroes at other frequencies, which filters a first received signal; and

a second filter having a passband centered at a second frequency f2, which coincides with a zero of the first filter, which filters a second received signal.

2. In combination:

a stylus which transmits two signals at two different frequencies; and

a receiver for one of the signals, comprising

a rectifier for rectifying the signal;

an integrator for periodically integrating the rectified signal; and

phase-locked-loop means for synchronizing the period of integration with one of the signals.

3. In combination:

a stylus which transmits two signals which may drift in frequency; and

filter means for

tracking one of the signals,

maintaining a pass band centered on the tracked signal, and

maintaining a ZERO centered on the other signal.