Joint optimisation of supply and bias modulation

Abstract

A radio frequency amplifier system is disclosed in which the amplifier bias supply and power supply voltages are instantaneously modulated with signals derived from the envelope voltage of the input signal. Separate non-linear mapping functions are used to derive the supply and bias voltages. The two mapping functions are optimised jointly to achieve particular system performance goals, such as optimum efficiency, constant gain, constant phase, or minimum spectral spreading. An optimisation of particular interest is that which achieves best RF amplifier power added efficiency subject to achieving constant amplifier gain. In this way the need for pre-distortion linearization may be reduced or eliminated.

1 . A method of controlling an amplification stage, comprising:
 a. selecting a linearity objective for the amplification stage;   b. in dependence on an input signal to said amplification stage, determining a combination of supply input and bias input for the amplification stage in order to meet said linearity objective; and   c. in dependence on there being more than one combination of supply input and bias input for meeting the linearity objective, selecting the combination that optimises efficiency for the amplification stage.   
     
     
         2 . (canceled) 
     
     
         3 . The method according to  claim 1  wherein the supply input and bias input vary in dependence on a variation in the input signal. 
     
     
         4 . The method according to  claim 1  wherein the supply input and the bias input vary in dependence on a variation in the envelope of the input signal or the power of the input signal. 
     
     
         5 . The method according to  claim 1  further comprising:
 a. measuring at least one amplifier dependent characteristic in dependence on at least one amplifier independent characteristic; and 
 b. determining a preferred combination of bias and supply inputs to achieve the specific system performance objective based on said measurements. 
 
     
     
         6 . The method according to  claim 4  wherein the step of determining a preferred combination is based on an instantaneous value of the input signal. 
     
     
         7 . The method according to  claim 5  further comprising the step of measuring a plurality of amplifier dependent characteristics in dependence on a plurality of amplifier independent characteristic. 
     
     
         8 . The method according to  claim 5  further comprising:
 a. creating a searchable database of said amplifier dependent and independent characteristics; and 
 b. searching said database to simultaneously determine the optimum combination of bias and supply voltage at each input power over the measurement range to achieve specific system performance objectives; 
 c. wherein step of applying the supply voltage and the bias voltage is based on said determined combinations. 
 
     
     
         9 . The method according to  claim 5  further comprising:
 a. measuring a plurality of amplifier dependent characteristics in dependence on a plurality of amplifier independent characteristics; 
 b. creating a model of the amplifier operating for emulation of said measured amplifier characteristics; and 
 c. determining from said model the optimum combination of bias and supply voltage at each input power over the measurement range to achieve specific system performance objectives; 
 d. wherein step of applying the supply voltage and the bias voltage is based on said determined combinations. 
 
     
     
         10 . The method according to  claim 9  wherein said model is in real-time or non-real-time. 
     
     
         11 . The method according to  claim 9  further comprising simultaneously applying a modulated RF waveform and the determined optimum combination of bias and supply voltage to said amplifier. 
     
     
         12 . The method according to  claim 5  wherein the plurality of amplifier independent characteristics are from the group comprising bias voltage; supply voltage; input power; input phase; temperature; device periphery; and load impedance. 
     
     
         13 . The method according to  claim 5  wherein the plurality of amplifier dependent characteristics are from the group comprising: output power; output phase; gain; supply current; adjacent channel power; error vector magnitude; and correlation coefficient. 
     
     
         14 . The method according to  claim 9  wherein the inputs to the model are from the group comprising bias voltage; supply voltage; input power; input phase; temperature; device periphery; and load impedance. 
     
     
         15 . The method according to  claim 9  wherein the outputs from the model are from the group comprising: output power; output phase; gain; supply current; adjacent channel power; error vector magnitude; and correlation coefficient. 
     
     
         16 . The method according to  claim 5  wherein said system performance objectives comprise highest power added efficiency; highest drain efficiency; constant gain; constant phase; lowest adjacent channel power; lowest error vector magnitude; and highest correlation coefficient. 
     
     
         17 . The method according to  claim 1  wherein the supply and bias inputs are selected in dependence upon one or more previous input signal values. 
     
     
         18 . An amplification stage for amplifying an input signal, the amplification stage having a supply voltage input and bias voltage input, comprising:
 a. detection means for detecting the input signal to the amplifier; and   b. voltage selection means for determining a combination of supply input and bias input for the amplification stage in dependence on the detected input signal, wherein the combination of supply input and bias input is selected in order to meet a linearity objective for the amplification stage; and further wherein in dependence on there being more than one combination of supply input and bias input for meeting the linearity objective, the voltage selection means is adapted to select the combination that optimises efficiency for the amplification stage.   
     
     
         19 . The amplification stage according to  claim 18  wherein the voltage selection means comprises:
 a. a non-linear mapping element for receiving the detected input signal and generating the supply input; and 
 b. a non-linear mapping means for receiving the detected input signal and generating the bias input. 
 
     
     
         20 . The amplification stage according to  claim 19  wherein each of the respective non-linear mapping means is adapted to approximate an idealised mapping for the detected input signal to meet the specific system performance objective. 
     
     
         21 . The amplification stage according to  claim 19  wherein each of said respective non-linear mapping means is a digital linear mapping means. 
     
     
         22 . The amplification stage according to  claim 19  wherein each of said respective non-linear mapping means is a digital linear mapping means. 
     
     
         23 . The amplification stage according to  claim 18  wherein the non-linear mapping means are configured in accordance with measured results for the amplification stage performance. 
     
     
         24 . The method according to  claim 1 , wherein the linearity objective is a constant gain objective. 
     
     
         25 . The amplification stage according to  claim 18 , wherein the linearity objective is a constant gain objective.