Subsampling Architecture for Low Power Receivers

GNSS Signals Acquisition and Tracking in Unfavorable Environment

“…The first variant acquisition and tracking procedure, of our proposed method, consists of acquiring BOCsin/cos(α,β) modulated signals with α ˃ β, and more specifically with α >> β, after undergoing a transformation based on undersampling process. The latter technique relies on sampling one desired signal with a frequency that is lower than twice the highest signal frequency (Shannon frequency) [51], [52], [53], [54]. The main purpose of such processing, which does not meet the Nyquist condition, is to bring closer the main lobes of BOCsin/cos(α,β) signals and provide, thus signals similar to those of BOCsin/cos(α,α).…”

De-Interleaved Subsampling Architecture for Homodyne Receivers

“…The last topology, which is reviewed in this paper is based on subsampling technique [6][7][8]14]. In this topology, the RF signal is down-sampled with a sampling rate much smaller than the RF carrier frequency.…”

“…In the subsampling technique one of the replicas at lower frequency is used as an IF signal to extract the baseband I and Q signals. In order to avoid possible aliasing, the sampling rate should be considered according to the following boundaries [8]:…”

“…However, this simple topology is not yet feasible, mostly due to limitations in designing high-resolution ADCs with high sampling rates of several Gigahertzes (GHz). More realistic receiver topologies, such as direct conversion [4], low intermediate frequency (low-IF) [5], and subsampling receivers [6][7][8] have also been proposed. In the direct conversion receiver, the radio frequency (RF) input signal is directly down-converted to complex baseband signals designated as in-phase (I) and quadrature (Q) signals.…”

“…Sampling the RF signal at a rate lower than double rate of the RF will fold the signal to lower frequencies, where these replicates of the RF signal at baseband or IF are used to extract the baseband signal [6][7][8]. Receivers designed based on this architecture suffer generally from higher noise floors.…”