Wide band instantaneous coverage receiver concept for ALMA

We propose concept of frequency array receiver. Receiver input beam will be quasi-optically frequency multiplexed on several mixer pixels. All individual mixers will be operated simultaneously creating very large input bandwidth covering several atmospheric windows in high frequency resolution. This system allows to combine large bandwidth advantage of direct detecting with high frequency resolution of heterodyne system. We will discuss initial system concept, and report on mixer designs and their performance for building elements. In particularly we report DSB noise temperature below hf/k level at 260GHz mixer prototype. Sensitivity of such system in presents of atmospheric background will be evaluated.