Optimal Allocation of Noise Floor among the Blocks in Analog Signal Chains

Abstract:
The noise floor allocation of analog signal chains is optimized. Optimization models are built for 2 and 3 stage cases whose optimum solutions are, then, acquired by a rigorous mathematical derivation. The results are generalized to a case where an arbitrary number of blocks are cascaded. It is found that the optimum analog signal chain is reached when the noise ratio between each two consecutive blocks is equal to the geometric mean of the in-band and out-or-band gains of the preceding block or, equivalently, when the SNDR (and power dissipation) ratio between each two consecutive blocks is equal to the geometric mean of the in-band gain and the out-of-band attenuation (inverse of the out-of-band gain) of the preceding block. This simple conclusion provides the analog designers who want to optimize the noise floor and power budget allocation of their designs with an easily applicable rule-of-thumb.