IMPROVEMENTS IN OR RELATING TO AUTOMATIC GAIN CONTROL OF RADIO DEVICES

摘要

A method of operating a RF device having a first RF gain stage (34) comprising a programmable attenuator (36) coupled to a RF amplifier (38) and a second narrowband gain controlled amplifying stage (24) for amplifying a signal in a wanted bandwidth, comprises selecting a gain setting of the first RF gain stage to maximise the signal-to-noise (SNR) by minimising the total noise in a wanted signal and a gain setting of the second narrowband amplifying stage to provide a substantially constant level output. In order to select the gain setting of the first RF gain stage, the RF device includes a control stage (40) which takes into account the gain settings of the first RF stage and the second gain controlled amplifying stage, the distortion noise (referred to the RF input) and the thermal noise (referred to the RF input) when selecting a gain setting to be applied to the programmable attenuator to minimise the total noise.