Browse Prior Art Database

Differentiate and Dump Receiver Circuitry

IP.com Disclosure Number: IPCOM000038448D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Bustamente, C: AUTHOR [+3]

Abstract

This article describes a circuit arrangement with an active/passive filtering approach for infrared (IR) communication which increases the data rate of the IR media without sacrificing signal amplitude, while reducing the noise of 70 Khz fluorescent bulbs. The worst noise in the IR media is produced by high frequency fluorescent bulbs. They produce 70 Khz IR noise which is effectively filtered out by several stages of high-pass filtering, as illustrated in Fig. 1. It has been shown that compressed pulse position modulation (CPPM) is the most efficient encoding method for IR transmission. The best solution to date is the CPPM encoding scheme together with the filtering shown in Fig. 1. In CPPM, one pulse encodes 4 bits by detecting the arrival of a pulse in one of 16 possible time slots.

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Differentiate and Dump Receiver Circuitry

This article describes a circuit arrangement with an active/passive filtering approach for infrared (IR) communication which increases the data rate of the IR media without sacrificing signal amplitude, while reducing the noise of 70 Khz fluorescent bulbs. The worst noise in the IR media is produced by high frequency fluorescent bulbs. They produce 70 Khz IR noise which is effectively filtered out by several stages of high-pass filtering, as illustrated in Fig. 1. It has been shown that compressed pulse position modulation (CPPM) is the most efficient encoding method for IR transmission. The best solution to date is the CPPM encoding scheme together with the filtering shown in Fig. 1. In CPPM, one pulse encodes 4 bits by detecting the arrival of a pulse in one of 16 possible time slots. The present pulse becomes the time reference for the next pulse. CPPM information is stored in the time between positive pulses. Fig. 2 shows the format of PPM. The width of the pulse 1 is 500 ns. This pulse is followed by a guard time 2 of 1500 ns. After the guard time elapses, the next pulse is expected to follow in one of the 16 500 ns slots 3. This guard time 2 allows the capacitances in Fig. 1 to discharge between pulses, thus eliminating the inter-symbol-interference (ISI). ISI is a type of interference found when the energy of one pulse spills over into the time slot of the next pulse. The circuit disclosed herein eliminates the nee...