Pilot symbol driven monitoring of electrical degradation in RF transmitter systems using model anomaly diagnosis

Abstract

Modern RF circuits suffer from increased electrical degradation induced by electrical stress and thermal effects due to the high speeds of operation and the effects of technology scaling. Detection of such degradation is important, particularly in wireless basestations which must operate round-the-clock with high dependability. In this paper, a new approach for detecting degradation in RF transmitter systems using pilot symbols is proposed and is superior to prior algorithms because degradation can be monitored on a frame-to-frame basis independent of the data being transmitted. The response of the RF transmitter to known pilot symbols is captured at the output of the RF power amplifier using an envelope detector and is fitted to a third order transmitter model using a model-parameter solving algorithm. It is shown that the computed model parameters deviate away from their nominal values, exhibiting model anomalies once nonidealities due to electrical degradation start affecting transmitter behavior. The amount of the degradation is proportional to the magnitude of this deviation as measured by a distance metric and is easily computed using simple algorithms running on the baseband processor. Preliminary results indicate the feasibility and low cost of the proposed approach.