Measurements of Structure in the Cosmic Background Radiation with the Cambridge Cosmic Anistropy Telescope

We have observed a 2 deg x 2 deg area of sky at frequencies of 15.5 and 16.5 GHz with the Cambridge Cosmic Anisotropy Telescope (CAT). Comparison with earlier measurements at 13.5 GHz shows that the observed structure at 16.5 GHz arises predominantly from the cosmic microwave background. The broadband power, averaged over spherical harmonic multipole orders between 330 and 680, is ( Delta T/T) = 2.0^{+0.4}_{-0.4} x 10-5, which is consistent with the predictions of a standard COBE-normalized, cold dark matter model.