Band 7 for ALMA Receivers covers the frequency range 275-370 GHz. Our baseline design includes two double side band mixers, i.e. one for each polarization, with waveguide couplers for the local oscillator injection. The polarizations are separated by one grid and the 17 dB crossguide coupler allows LO injection in a compact configuration. The mixers to be used in the cartridge are fixed-tuned across the RF frequency range and low noise for an IF covering 4 to 8 GHz. Future development involves integrated sideband separation mixers in waveguides.
The full report can be found in the ALMA Project book at the following
http://www.tuc.nrao.edu/~ demerson/almapbk/construc/chap5/chap5.pdf, Chapter 5.6.6., p 32.