Virtually every RF receiver use a superhetereodyne receiving scheme. QUOTE]
This is bit off your point, but to be precise, most mobile phones produced in the last couple of years have used direct conversion topologies for receiving. Mobile phones account for an awful lot of the world's RF receivers, and I wouldn't be surprised if most RFID receivers are direct conversion as well. Not sure about TVs and stereos, but I wouldn't be suprised if they are moving over to DC receivers too. And lots of base stations have been moving to software defined structures, sometimes with a direct conversion front end. The technology commonly used in radio has been changing quickly in the last few years, thanks mainly to the mobile phone.