Antenna system for multipath diversity in an indoor microcellular communication system
First Claim
1. In a microcellular digital communication system having one or more mobile transceivers and at least one stationary transceiver with at least one antenna element comprising a set of antennas for sending and receiving a data signal having a carrier frequency propagated between any of said mobile transceivers and said stationary transceiver through a channel having a plurality of paths, a method for limiting the maximum signal fading loss duration in said propagation channel to a predetermined threshold value, said method comprising the steps of:
- coupling together said set of antennas creating a radiation pattern thereof; and
modulating said radiation pattern of said set of antennas at a predetermined rate so as to average power of said data signal sent and received over said plurality of paths by said set of antennas, said predetermined rate being selected to reduce said signal fading loss duration below said predetermined threshold value over any of said plurality of paths in said system.
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Abstract
A system for mitigating the effect of fading in a digital communication system. Deep signal nulls occur when signals from multiple paths are precisely aligned in amplitude and phase canceling the signal at the receiving antenna and creating a fade. In an indoor system, moving either transmitter or receiver a short distance can shift a fade away from the frequency of interest. This invention provides an actual or perceived movement of an antenna such that the effects of fading can be averaged over a time interval. The signal processing capability of modern digital transceivers can correct errors due to the time varying fades using the present invention. Thus, a dual-antenna element using the system of this invention can provide diversity receive and transmit paths to maintain capacity. The present invention may also provide improved capacity to due enhanced stability in power control.
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Citations
10 Claims
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1. In a microcellular digital communication system having one or more mobile transceivers and at least one stationary transceiver with at least one antenna element comprising a set of antennas for sending and receiving a data signal having a carrier frequency propagated between any of said mobile transceivers and said stationary transceiver through a channel having a plurality of paths, a method for limiting the maximum signal fading loss duration in said propagation channel to a predetermined threshold value, said method comprising the steps of:
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coupling together said set of antennas creating a radiation pattern thereof; and modulating said radiation pattern of said set of antennas at a predetermined rate so as to average power of said data signal sent and received over said plurality of paths by said set of antennas, said predetermined rate being selected to reduce said signal fading loss duration below said predetermined threshold value over any of said plurality of paths in said system. - View Dependent Claims (2, 3, 4, 5)
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6. The method of claim I wherein said modulating step comprises the step of moving the position a first antenna of said set of antennas relative to a second antenna of said set of antennas at said predetermined rate.
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7. A microcellular cellular digital communications system in which information signals are communicated between a fixed location and one or more mobile transceivers, said system comprising:
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at least one stationary transceiver, positioned at said fixed location, having at least first and second antennas for sending and receiving an encoded data signal having a carrier frequency propagated over a channel between each said mobile transceiver and said at least one stationary transceiver; and a time varying phase shifter coupled between said at least said first and second antennas for varying phase therebetween so as to average power of said encoded signal transmitted and received, by said first and second antennas, over a plurality of paths of said channel. - View Dependent Claims (8, 9, 10)
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Specification