  As a logical next step in improving the radio-to-submm spectral index as a
redshift indicator (Carilli & Yun 1999), we have investigated a technique of
using the entire radio-to-FIR spectral energy distribution (SED) for deriving
photometric redshifts for dusty starburst galaxies at high redshift. A dusty
starburst SED template is developed from theoretical understanding on various
emission mechanisms related to massive star formation process, and the template
parameters are selected by examining the observed properties of 23 IR selected
starburst galaxies: $T_d=58$ K, $\beta=1.35$, and $f_{nth}=1$. The major
improvement in using this template SED for deriving photometric redshifts is
the significant reduction in redshift uncertainty over the spectral index
technique, particularly at higher redshifts. Intrinsic dispersion in the radio
and FIR SEDs as well as absolute calibration and measurement errors contribute
to the overall uncertainty of the technique. The derived photometric redshifts
for five submm galaxies with known redshifts agree well with their
spectroscopic redshifts within the estimated uncertainty. Photometric redshifts
for seven submm galaxies without known spectroscopic redshifts (HDF850.1,
CUDSS14.1, Lockman850.1, SMM J00266+1708, SMM J09429+4658, SMM J14009+0252,
FIRBACK J1608+5418) are derived.
