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RF - IQ Demodulator Slide 6
The traditional Super Heterodyne is a common receiver architecture that has been implemented in the past. The main facets of the design include: high-Q RF and IF filters that cannot be integrated; two mixer stages; high selectivity and image rejection; and Quadrature separation done in the digital domain (giving near perfect I and Q gain and phase matching). Great performance comes with high component count and cost. The Direct Conversion receiver is a more modern architecture that will be discussed in depth throughout this presentation. This design features a single quadrature down conversion to DC or low-IF. When downconversion is to DC, the performance burden on the ADC is not great since sampling is done on a signal centered at DC. Quadrature down conversion with the IQ demodulator is key, specifically the gain, phase matching, and DC offsets on I and Q channels. Furthermore, component count is lower than for heterodyne receivers.
PTM Published on: 2010-03-31