  This article presents a two-stage approach for the processing of
frequency-stacked mobile subbands. The frequency stacking is performed in the
analog domain to enable the use of a wideband analog-to-digital converter
(ADC), instead of employing multiple narrowband ADCs, to support multiple
antenna elements for digital satellite beamforming. This analog front end
provides a common broadband digital interface to the on-board processor and can
be configured to support multiple satellite missions, reducing the cost of
commissioning a digital processor for individual satellite missions. This
article proposes a framework on the specification of digital prototype filter
for the analysis of frequency-stacked mobile subbands. The computational
complexity of the analysis operation, with two digital filter alternatives, are
evaluated. A series of results, taken from our European Space Agency sponsored
project, are presented here to demonstrate the applicability of the proposed
two stage approach, reporting on the savings in power consumption when an
Nth-band all-pass-based recursive filter having an infinite impulse response is
used as the digital prototype filter.
