Digitally Assisted Built-In Tuning Using Hamming Distance Proportional Signatures in RF Circuits

摘要

In this paper, a novel built-in tuning technique to compensate for process variability-induced imperfections in RF circuits is proposed. The yield improvement methodology proposed is a generic and self-contained tuning method that does not require a digital signal processor as in prior software-based methods or the use of a tester. The technique uses digital logic that can be synthesized on-chip along with the analog/RF tuning circuitry to performing self-tuning. An optimized digital bitstream (stimulus) is used to stimulate the RF device, and the response of the device is downconverted to the low-frequency domain using a sensor. The resulting signal is mapped to a digital signature, in such a way that the Hamming distance between the observed and the reference signatures represents the degree by which the device specifications differ from the nominal specifications. A logic-driven algorithm is used to minimize this Hamming distance to optimize multiple RF specifications concurrently. The presented methodology incurs minimal area overhead, and the tuning time is in the order of milliseconds. Results obtained by tuning the power amplifier of a 2.4-GHz transmitter show up to 16% yield improvement. To validate the proposed yield improvement concept on hardware, results obtained from experimentation on an industrial transmitter are presented.