  In this work, we consider the detection of manoeuvring small objects with
radars. Such objects induce low signal to noise ratio (SNR) reflections in the
received signal. We consider both co-located and separated transmitter/receiver
pairs, i.e., mono-static and bi-static configurations, respectively, as well as
multi-static settings involving both types. We propose a detection approach
which is capable of coherently integrating these reflections within a coherent
processing interval (CPI) in all these configurations and continuing
integration for an arbitrarily long time across consecutive CPIs. We estimate
the complex value of the reflection coefficients for integration while
simultaneously estimating the object trajectory. Compounded with this is the
estimation of the unknown time reference shift of the separated transmitters
necessary for coherent processing. Detection is made by using the resulting
integration value in a Neyman-Pearson test against a constant false alarm rate
threshold. We demonstrate the efficacy of our approach in a simulation example
with a very low SNR object which cannot be detected with conventional
techniques.
