On Robustness Properties of Beta Encoders and Golden Ratio Encoders

TL;DR

This paper demonstrates that beta and golden ratio encoders for analog-to-digital conversion are robust against hardware imperfections, allowing precise recovery of the encoding base despite component inaccuracies.

Contribution

It introduces a method to accurately approximate the base beta in beta and golden ratio encoders despite hardware imprecisions, enhancing their robustness.

Findings

Exponential precision in approximating beta is achievable.

Robustness of encoders against component imperfections is demonstrated.

Method applies to both beta and golden ratio encoders.

Abstract

The beta-encoder was recently proposed as a quantization scheme for analog-to-digital conversion; in contrast to classical binary quantization, in which each analog sample x in [-1,1] is mapped to the first N bits of its base-2 expansion, beta-encoders replace each sample x with its expansion in a base beta satisfying 1 < beta < 2. This expansion is non-unique when 1 < beta < 2, and the beta-encoder exploits this redundancy to correct inevitable errors made by the quantizer component of its circuit design. The multiplier element of the beta-encoder will also be imprecise; effectively, the true value beta at any time can only be specified to within an interval [ beta_{low}, beta_{high} ]. This problem was addressed by the golden ratio encoder, a close relative of the beta-encoder that does not require a precise multiplier. However, the golden ratio encoder is susceptible to integrator leak in the delay elements of its hardware design, and this has the same effect of changing beta to an unknown value. In this paper, we present a method whereby exponentially precise approximations to the value of beta in both golden ratio encoders and beta encoders can be recovered amidst imprecise circuit components from the truncated beta-expansions of a "test" number x_{test} in [-1,1], and its negative counterpart, -x_{test}. That is, beta-encoders and golden ratio encoders are robust with respect to unavoidable analog component imperfections that change the base beta needed for reconstruction.