Joint optimisation of supply and bias modulation

Abstract

There is disclosed a technique for controlling at least one amplification stage, comprising: selecting a linearity objective for the amplification stage; 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 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 a further system performance objective for the amplification stage. The further system performance objective may be one or more of: an efficiency objective; an envelope signal bandwidth objective; or a robustness to production tolerance objective.

1 . A method of controlling at least one 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 a further system performance objective for the amplification stage.   
     
     
         2 . A method according to  claim 1 , wherein the further system performance objective is one or more of: an efficiency objective; an envelope signal bandwidth objective; or a robustness to production tolerance objective. 
     
     
         3 . A 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 and the step of determining a preferred combination is based on an instantaneous value of the input signal. 
     
     
         4 . A method according to  claim 1  further comprising the steps of:
 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. 
 
     
     
         5 . A method according to  claim 4  further comprising the steps of:
 a. creating a searchable database of said amplifier dependent and independent characteristics; 
 b. searching said measurement 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. 
 
     
     
         6 . A method according to  claim 4  further comprising the steps of:
 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; 
 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. 
 
     
     
         7 . A method according to  claim 6  wherein said model is in real-time or non-real-time. 
     
     
         8 . A method according to  claim 4  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. 
     
     
         9 . A method according to  claim 4  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; correlation coefficient. 
     
     
         10 . A method according to  claim 6  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. 
     
     
         11 . A method according to  claim 6  wherein the outputs from the model are from the group comprising: output power; output phase; gain; supply current; adjacent channel power; error vector magnitude; correlation coefficient. 
     
     
         12 . A method according to  claim 4  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; highest correlation coefficient. 
     
     
         13 . A method according to  claim 1  wherein the supply and bias inputs are selected in dependence upon one or more previous input signal values. 
     
     
         14 . 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;   b. voltage selection means for selecting a supply input and bias input set for the amplification stage in dependence on the detected input signal, wherein the selected supply and bias inputs are selected to meet a linearity objective for the amplification stage; and further wherein in dependence on there being more than one supply input and bias input set for meeting the linearity objective, selecting the set that optimises a further system performance objective for the amplification stage.   
     
     
         15 . The amplification stage of  claim 14  wherein the further system performance objective is one or more of: an efficiency objective; an envelope signal bandwidth objective; or a robustness to production tolerance objective. 
     
     
         16 . An amplification stage according to  claim 14  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. 
 
     
     
         17 . An amplification stage according to  claim 16  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. 
     
     
         18 . An amplification stage according to  claim 16  wherein each of said respective non-linear mapping means is a digital linear mapping means. 
     
     
         19 . An amplification stage according to  claim 16  wherein each of said respective non-linear mapping means is a digital linear mapping means. 
     
     
         20 . An amplification stage according to  claim 14  wherein the non-linear mapping means are configured in accordance with measured results for the amplification stage performance.