A constant gain radio transmitter for temperature and the different levels of input signal

Since the system performance of a code division multiple access (CDMA) mobile communication system is very sensitive to the power control, a final output of the RF transmitter is very important. A common high power amplifier (HPA) has a temperature characteristic and its output level is not linearly amplified with the input level. A general power detector of a HPA using transistors has also a temperature characteristic. We suggest an intelligent control strategy to compensate the temperature characteristic and the effect of the input signal level to the HPA. An artificial neural network (ANN) is used to estimate the actual output power of the HPA based on power detection voltage for the given temperature and also to keep the open loop gain (HPA gain with a variable gain) constant. The stability problem, which is a hard issue when a system is non-linear, is also discussed