  We present interferometric observations with resolution of ~3 arcsecs of the
isolated, low-mass protostellar double cores CG30 and BHR71 in the N2$H+(1-0)
line and at 3mm dust continuum, using the Australian Telescope Compact Array
(ATCA). The results are complemented by infrared data from the Spitzer Space
Telescope. In CG30, the 3mm dust continuum images resolve two compact sources
with a separation of ~21.7 arcsecs (~8700 AU). In BHR71, strong dust continuum
emission is detected at the position of the mid-infrared source IRS1, while
only weak emission is detected from the secondary mid-infrared source IRS2.
Assuming optically thin 3mm dust continuum emission, we derive hydrogen gas
masses of 0.05--2.1 $M_\odot$ for the four sub-cores. N2H+(1-0) line emission
is detected in both CG30 and BHR71, and is spatially associated with the
thermal dust continuum emission. We derive the velocity fields and find
symmetric velocity gradients in both sources. Assuming that these gradients are
due to core rotation, we estimate the specific angular momenta and ratios of
rotational energy to gravitational energy for all cores. We also find that the
N2H+ emission is strongly affected by the outflows, both in terms of
entrainment and molecule destruction. $Spitzer$ images show the mid-infrared
emission from all four sub-cores. All four sources appear to drive their own
outflows. Based on the ATCA and $Spitzer$ observations, we construct spectral
energy distributions (SEDs) and derive temperatures and luminosities for all
cores. Based on the morphology and velocity structure, we suggest that the
sub-cores in CG30 were formed by initial fragmentation of a filamentary
prestellar core, while those in BHR71 could originate from rotational
fragmentation of a single collapsing protostellar core.
