Daniel, Yes, with some little modification your idea [1] might work.
1. Add a LC resonator at the antenna input. Tune the resonator at the frequency f(LOIN)/4. 2. Feed back the output of the AND logic to the resonator. In this way you get a bandpass sigma delta converter. The AND logic outputs a baseband version of the band that is passed by the resonator, in an oversampled (digital) form. You can decimate this high bitrate in software to a practical sample rate, or you can send these bits through a analog RC filter to get the analog signal. 73, Guido [1] http://groups.yahoo.com/group/soft_radio/files/KA9RZA/AND Gate QSD.gif <http://groups.yahoo.com/group/soft_radio/files/KA9RZA/AND%20Gate%20QSD.gif>
