Powerwave Technologies, Inc.

Christian G Luke

Ian Robert Johnson

Steven Andrew Wood

Mark Cope

Adrian Richard Mansell

Adrian Mansell

A system and method for controlling the gain in the forward signal path of a digital predistortion linearizer is disclosed. The loop gain of the predistortion system is driven to unity, where a separately controlled constant-gain observation path allows accurate gain control of the forward path. This is divided into digital gain from the predistortion function and analog gain from a Voltage Variable Attenuator (VVA) in the transmitter. The invention balances the distribution between these two domains in order to maximize dynamic range and minimize noise in the forward signal path. In order to distribute the forward path gain accurately, the characteristic of the VVA must be well known. Since these devices tend to be non-linear, with variable characteristic over temperature and batch, the invention compensates for this non-linear behavior by tracking the varying transfer characteristic of the VVA, giving a predictable local characteristic. Another aspect of the disclosed invention is the ability to operate with very low transmit power and loop gain levels, allowing accurate gain control during such scenarios as cell initialization, that require operation over a wide dynamic range.

System and method for forward path gain control in a digital predistortion linearized transmitter

A system and method for rapidly correcting the time difference between two signals is disclosed. In particular, a system and method for very rapidly correcting timing errors to the very high degree of accuracy required for digital predistortion adaptation is disclosed. The method is a signal processing technique, which can be performed in either hardware or software, which employs a correlation computation. The correlation results are processed in a manner that enables very rapid and accurate estimation of the time difference between the two signals.

System and method for digital timing error correction in a communications system utilizing adaptive predistortion

A system and method for compensating for the time delay between the in-phase I and the quadrature Q paths of a digitally modulated transmitter incorporating an analog quadrature modulator is disclosed. The time delay between the in-phase I and the quadrature Q paths is computed and used to calibrate a set of interpolation filters in the forward path that compensate for this delay, reducing the frequency dependent degradation in performance of the analog quadrature modulator. The disclosed system and method provides improved compensation of gain, phase and DC offsets in the analog quadrature modulator over a broader bandwidth. Fractional delay interpolation filters may be used to estimate the delay between the in-phase and quadrature paths. This eliminates the need for a factory calibration procedure, speeding up manufacture and reducing costs.

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Bristol, United Kingdom

Christian G Luke