  Integrated passive radar (IPR) can be regarded as next generation passive
radar technology, which aims to integrate communication and radar systems.
Unlike conventional passive radar, which does not prioritize
communication-centric radar technology, IPR technology places a higher priority
on incorporating specific radar constraints to develop waveforms that are
better suited for radar applications. This paper deals with the problem of
distributed MIMO IPR target detection under uncalibrated surveillance/reference
receivers. We focus on a communication-centric radar system consisting of
several opportunity transmitters non-overlapping in frequency with the same
bandwidth and several spatially separated receivers. Five new detectors are
devised according to the likelihood ratio test (LRT), Rao, Wald, Gradient and
Durbin criteria. Although, it is shown that these detectors are asymptotically
equivalent, they provide different performance in the presence of noisy
reference channels. The invariance principle is applied in this paper to show
that all uncertainties affecting threshold setting can be unified in the
direct-path signal power-to-noise power ratio (DNR) of the reference channels.
To ensure effective detection threshold setting regardless of the DNR values in
the reference channels, we introduce a novel strategy to adjust the level of
the proposed detectors rather than their sizes. Then, we examine false alarm
regulations and detection performance of the fixed-level proposed detectors to
demonstrate their effectiveness compared to several existing detectors. Thus,
we create a unified framework for uncalibrated MIMO IPR target detection in the
presence of noisy reference channels.
