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High Gain, Wide Field of View, Optical Antenna

IP.com Disclosure Number: IPCOM000101374D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 112K

Publishing Venue

IBM

Related People

Carri, S: AUTHOR [+2]

Abstract

This article describes a high gain optical antenna which can be used for optical data transmission in free space. The antenna uses a collection of "ideal optical concentrators" to form an antenna which has high gain over a wide field of view.

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This is the abbreviated version, containing approximately 52% of the total text.

High Gain, Wide Field of View, Optical Antenna

       This article describes a high gain optical antenna which
can be used for optical data transmission in free space.  The antenna
uses a collection of "ideal optical concentrators" to form an antenna
which has high gain over a wide field of view.

      Wireless data transmission systems using infrared (IR)
radiation can be either directional, semidirectional or
nondirectional.  In a directional optical system a narrow beam from
the transmitter is aimed directly at the receiver. At the receiver an
optical system, consisting of either a lens or light collector is
used to concentrate as much power on the photodetector as possible.
For a directional system this works well, and long range (> 1 mile)
high speed data transmission using low power (< 1W) IR devices has
been demonstrated. In the semidirectional system a wider beam is
produced at the transmitter, and a wider field of view (FOV) optical
system is used at the receiver.  As the spread of the beam at the
transmitter is increased, a corresponding decrease in maximum range
occurs.  One way to possibly combat this decrease in range is to
increase the optical system's cross-sectional area to the light beam.
However, a measure of the maximum concentration ratio arising from
the second law of thermodynamics states that the maximum possible
concentration in a three-dimensional system is

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 where n1 is the index of
refraction inside the light concentrator, n2 is the index of
refraction outside the light concentrator, r1 is the maximum exit
angle from the light concentrator, and r2 is the maximum acceptance
angle, i.e., FOV, of the light concentrator.  The C3d equation
indicates that as the FOV is increased, the concentration of
collected light decreases.  This works against the requirements of
wide FOV in a nondirectional IR data transmission system.  In this
article we present a technique which uses multiple light
concentrators to...