Browse Prior Art Database

Impedance Optimized Multiple Photodiode Optical Receiver

IP.com Disclosure Number: IPCOM000109880D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Arai, Y: AUTHOR [+2]

Abstract

Disclosed herein is a high sensitivity optical beam sensor/receiver to be used in diffuse optical communication, such as infrared wireless local area networks (LANs).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Impedance Optimized Multiple Photodiode Optical Receiver

       Disclosed herein is a high sensitivity optical beam
sensor/receiver to be used in diffuse optical communication, such as
infrared wireless local area networks (LANs).

      One of the key difficulties of diffuse optical communication is
signal to noise (S/N) ratio since the optical beam is diffused out
when the distance increases.  As a receiver side solution, a
parallel-connected multiple photodiode receiver is often used to
increase equivalent area of detection, as shown in Fig. 1.  But, this
technique creates a new problem of impedance mismatch between
photodiodes and the amplifier since impedance of the photodiode
itself is quite low at high frequency due to the capacitance of the
large detection area.  This limits the S/N ratio improvement.

      Fig. 2 shows a basic embodiment of this disclosure where
multiple photodiodes are in parallel and serially connected to
achieve optimum impedance to the amplifier.  Resistors within the
network are for DC current bleeding for bias voltage stabilization.
The optimum topology may range from full parallel to full serial
depending upon the device characteristics and carrier frequency.