  Microwave photonic systems are compelling for their ability to process
signals at high frequencies and over extremely wide bandwidths as a basis for
next generation communication and radar technologies. However, many
applications also require narrow-band $(\sim\text{MHz})$ filtering operations
that are challenging to implement using optical filtering techniques, as this
requires reliable integration of ultra-high quality factor $(\sim 10^8)$
optical resonators. One way to address this challenge is to utilize long-lived
acoustic resonances, taking advantage of their narrow-band frequency response
to filter microwave signals. In this paper, we examine new strategies to
harness a narrow-band acoustic response within a microwave-photonic signal
processing platform through use of light-sound coupling. Our signal processing
scheme is based on a recently demonstrated photon-phonon emitter-receiver
device, which transfers information between the optical and acoustic domains
using Brillouin interactions, and produces narrow-band filtering of a microwave
signal. To understand the best way to use this device technology, we study the
properties of a microwave-photonic link using this filtering scheme. We
theoretically analyze the noise characteristics of this microwave-photonic
link, and explore the parameter space for the design and optimization of such
systems.
