Inter-Site Fluctuation Mechanics, Sampling Jitter, and Quantization Noise in Direct-Sampling ADCs and Software-Defined Radio (SDR) Front-Ends

Modern radio astronomy instrumentation and software-defined radio (SDR) architectures—spanning RTL-SDR dongles, USRP transceivers, and high-performance FPGA direct-sampling backends—rely heavily on high-speed Analog-to-Digital Converters (ADCs) to digitize wideband RF spectra. However, ultimate dynamic range, spurious-free dynamic range (SFDR), and spectral baseline stability are frequently constrained by transistor flicker noise in sampling switches, aperture clock jitter, and non-linear quantization noise floors that standard stationary quantization models fail to resolve. In this work, we extend our first-principles inter-site fluctuation mechanics to the sampled-data electrodynamic transport regime of high-speed ADCs. We formulate a stochastic master equation coupling quantum zero-point phase dispersion in sampling gate transistors with clock-tree phase noise. We derive the exact non-stationary aperture jitter spectral density and its convolution with inter-site resistance fluctuations in CMOS/SiGe sampling switches, establishing how sub-sample voltage errors manifest as anomalous low-frequency noise in spectral line and pulsar observations. Finally, we outline a MATLAB simulation architecture to validate jitter-induced noise floors across operational regimes.