  In this letter, the problem of spectrum sensing is addressed for noncircular
(NC) signal in cognitive radio networks with uncalibrated multiple antennas.
Specifically, by taking both the standard covariance and complementary
covariance information of the NC signal into account, a new robust spectrum
sensing method called NC covariance (NCC) is proposed, which can fully reap the
statistical property of the NC signals. Meanwhile, we derive the asymptotic
distribution of the NCC statistic under the signal-absence hypothesis and
obtain the theoretical decision threshold of the NCC method. Simulation results
demonstrate that the proposed method is capable of outperforming
state-of-the-art methods.
