Glenayre Electronics, Inc.

Jay Jui-Chieh Chen

Claudio Gustavo Rey

Robert Richard Leyendecker

Vladimir Pavlovic

David Kent Bonds

Paul Andrew Goud

Derek Stephen Hilborn

Mark A Walker

Patricia Fern Kavanagh

Thomas L Frederick

David E Jones

Charles Brian Cox

Theron Lee Jones

David W Kroeger

Armando Cova Garrido

Desmond Wai Yan

Richard Johnathan Hinkle

Flaviu C Costescu

Ray Mr Sewlochan

Emre Tapucu

Yan Guo

Terry Lee Hinkle

Wayne Douglas Duello

Joel Richard Dierks

A system for linearly transmitting an amplified output signal using predistortion whereby a straight inverse modeling scheme is used to more easily and accurately determine the inverse of the distortion caused by a power amplifier of a RF transmitter. The 'inverse' of the power amplifier is directly modeled by considering the power amplifier as a signal processing block with the input and output ports reversed. As a result, the computationally intensive inversion required by conventional schemes is avoided. The predistorter system stores complex coefficients in a predistorter LUT, which are then used as the tap weights of a digital filter implementing the predistorter. The predistortion is done by a non-linear filter which incorporates both instantaneous and average envelope power or magnitude effects. The predistortion LUT is addressed as a function of the instantaneous envelope power or magnitude and past power or magnitude envelopes. This scheme takes into account the instantaneous envelope power or magnitude of the current sample and a profile of the envelope power or magnitude of previous samples to accurately compensate for modulation envelope memory effects of the power amplifier. The past powers or magnitudes provide an indication of the trajectory of the power or magnitude leading to the current power or magnitude, which enables the predistorter to more accurately compensate for the power amplifier distortion. The predistorter LUT is updated with values that are indexed as a function of the powers or magnitudes of past samples and the power or magnitude of the current sample.

Method and apparatus for linear transmission by direct inverse modeling

A linear transmitter (101) using predistortion includes a modulator (103), a predistorter (107), a digital quadrature modulator (111), an upconverter (113), a power amplifier (115), and an antenna (117). In addition, the transmitter (101) has a feedback loop including a coupler (119), a downconverter (123), a digital quadrature demodulator (125), and a trainer (131). The digital data to be transmitted is provided into the modulator (103), which converts the digital data into in-phase and quadrature component signals. The in-phase and quadrature component signals are then provided to the predistorter (107), which 'predistorts' the component signals prior to amplification. The digital quadrature modulator (111) converts the component signals into a single analog signal. The upconverter (113) upconverts this signal from the predistorter (107) into the desired frequency of transmission, which is provided to the power amplifier (115) and the antenna (117) for amplification and broadcast. The coupler (119) provides a portion of the amplified signal to the analog downconverter (123), which lowers the frequency of this signal to a range that is easily processed. The signal is then provided to the digital quadrature demodulator (125), which outputs the in-phase and quadrature component signals of the signal. These in-phase and quadrature component signals are provided to the trainer (131) which analyzes them with the output signals from the modulator. The trainer (131) compares these signals and updates the predistorter (107) so that the digital quadrature demodulator (125) output signals are substantially equivalent to the modulator (103) output signals.

Linear transmitter using predistortion

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Vancouver, Canada

Jay Jui-Chieh Chen