  In this letter, we apply previous array receiver architecture which employs
time-domain sub-Nyquist sampling techniques to jointly estimate frequency and
direction-of-arrival(DOA) of narrowband far-field signals. Herein, a more
general situation is taken into consideration, where there may be more than one
signal in a subband. We build time-space union model, analyze the
identification of the model, and give the maximum signal number which can be
classified. We also proof that the Cramer-Rao Bound (CRB) is lower than that of
which employs Nyquist sampling. Simulation results verify the capacity to
estimate the number of sources. Meanwhile, simulations show that our estimation
performance closely matches the CRB and is superior for more sources than
sensors, especially when the minimum redundancy array (MRA) is employed.
