Airnet Communications Corporation

Spectrian Corporation

Stephen J Foley

Thomas R Schmutz

Michael A Komara

Jeffrey Wilson Smith

Armando C Cova

Emil James Crescenzi, Jr

Augustin P Chang

A hybrid multicarrier RF power amplifier linearization architecture combines ACT and feed-forward amplifier stages to achieve high output distortion rejection and enhanced amplifier linearity. A carrier cancellation loop is coupled with a main RF power amplifier stage having parallel RF power amplifiers coupled via intermod-complementing predistortion paths. The carrier cancellation loop is coupled to a feed-forward loop containing a feed-forward RF power amplifier, to produce a composite amplified output signal having very reduced intermodulation products. Vector modulators in the main amplifier and feed-forward amplifier stages are controlled by a digital signal processor, using outputs from various monitoring subsystems, including pilot tone detection, correlator, distortion and power detector circuits.

High linearity multicarrier RF amplifier

In a conventional Time Division Multiple Access (TDMA) wireless system, the specified distance between a mobile unit and the base transceiver system (BTS) cannot exceed predetermined distances because of time slot synchronization constraints. Furthermore, varying distances between mobile units and the BTS, as well as Rayleigh fading, caused by destructive interference effects between direct and reflected signals, create extreme signal strength variations in the initial uplink signal from the mobile stations. The use of spatially-diverse antennas for receiving uplink signals provides diversity gain and mitigates deep fades. Furthermore, selecting the stronger of the spatially-diverse uplink signals mitigates deep fades and reduces frequency usage in the backhaul frequency band. In this approach to extending TDMA system coverage, in-band translator components are located in the center of remote cells which would normally contain a base transceiver system (BTS). The in-band translators include delay elements to implement slot-by-slot selective spatial diversity and automatic level control in a predictive feedforward fashion. The selective diversity mitigates deep Rayleigh fades, while the dynamic automatic level control drastically reduces the uplink backhaul dynamic range to allow for greater backhaul distances. Predictive feedforward automatic level control also eliminates overload and saturation of the backhaul high power amplifier, normally caused by wide variations in uplink power levels.

Method and apparatus employing delay elements in multiple diversity

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Santa Clara, CA, United States of America

Stephen J Foley