Direct IF sampling Digital IF sampling would simplify the design greatly, the amount of phase-locked oscillators would be reduced to one. To get the same performance we have now, we need at least a one gigasample per second, 2-bit sampler. Of course, five-gigasample 4 to 8 bit sampler would be nice, if we intend to do signal processing. Fortunately, out there is an industry that makes high-speed samplers. They call them digital oscilloscopes and bundle the sampler with a screen and lots of knobs.
Digital oscilloscopes are relatively inexpensive.
Of course, these oscilloscopes would need some modifications, but these should not be very difficult. The Japanese have succeeded in doing this in their Giga-bit VLBI system. Here is an excerpt of Yasuhiro Koyama s conference paper. One of the 4 quantization bits is extracted from the digital oscilloscope and is connected to the sampler interface unit. The sampler interface unit demultiplexes the 1024 Mbps of serial data stream to 32 parallel lines.