Design and simulations of a nulling interferometer using a single Martin-Puplett interferometer for double-sideband operation

We propose a new quasi-optical setup for a nulling interferometer at short millimeter and submillimeter wavelengths employing a single Martin-Puplett interferometer (MPI) for sideband separation. The new design allows the simultaneous use of both sidebands, thus avoiding the loss of sensitivity from conventional sideband filters. Although intended for solar flare observations, the quasi-optical setup can be applied to cancel any extended circular source, while at the same time preserving the full sensitivity toward a point-like source on or near the extended one. Numerical simulations show that the sinusoidal transmission characteristic of the MPI limits the usable relative bandwidth to one-third of the IF. Compared to an instrument employing lossless sideband filters, an increase of the response to a point-like continuum source by a factor of /spl sim/1.6-2 is expected, depending on the source position and relative bandwidth.