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Radio transmitter with power amplifier linearizer
| Details |
Inventors: Horowitz, Ilan; Ayun, Moshe Ben; Shamsian, Roni; Grabsky, Nachman; Rozental, Mark;
Assignee: Motorola, Inc. (Schaumburg, IL)
Primary Examiner: Eisenzopf; Reinhard J.
Assistant Examiner: Banks-Harold; Marsha D.
Attorney, Agent or Firm: Doutre; Barbara R.
This invention relates to a radio transmitter having a power amplifier and a linearizer arrangement, for example Cartesian feedback, for compensating for non-linearity in the power amplifier. A training signal is applied to the amplifier (36) and the linearizer arrangement is adjusted during a training mode of operation. In one embodiment, a look-up table (23) is provided for storing predetermined operating condition adjustment parameters. According to an operating condition input (e.g. frequency, temperature) control means (21) select operating condition adjustment parameters during the training mode and adjust the training signal to compensate for loop gain variations during the training mode. Automatic gain control (26) may be provided in the amplifier loop for activation during at least a portion of the training mode of operation to maintain constant closed loop gain. |
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DETAILED DESCRIPTION According to the a first aspect of the present invention, a radio transmitter is provided comprising: a power amplifier; linearizer means coupled to the amplifier for compensating for non-linearity in the power amplifier; feedback means for feeding a signal from an output of the power amplifier to the linearizing means, whereby said amplifier, feedback means and linearizer means form an amplifier loop having a varying loop gain, and training means for applying a training signal to the amplifier and adjusting the linearizer means during a training mode of operation.
The arrangement is characterized by: a look-up table for storing predetermined operating condition adjustment parameters and control means having an operating condition input, said control means being coupled to the look-up table for selecting operating condition adjustment parameters according to the operating condition input during the training mode and adjusting the training signal to compensate for loop gain variations during the training mode.
In this manner, more accurate and consistent training can be achieved for varying operating conditions (e.
g.
temperature and frequency).
The training means preferably comprise switching means for opening and closing the amplifier loop and means for applying a phase training signal to the amplifier when the loop is open, wherein the control means adjust the phase training signal to adjust for open loop gain variations.
In this manner, the phase training signal can be adjusted to perform phase training at, for example, a consistent predetermined output power level (e.
g.
average output power) irrespective of the open loop gain at the operating conditions.
A temperature sensor may be provided and the look-up table may comprise temperature adjustment parameters.
Alternatively or in addition, the operating condition input may comprise a frequency selection input and the look-up table may comprise frequency adjustment parameters, with the control means being responsive to the frequency selection input to select one or more frequency adjustment parameters and to adjust the phase training signal according to the one or more frequency adjustment parameters
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Audio Signal Processing 
