A direct conversion radio receiver takes a high frequency input signal, often in the 800MHz to 3GHz frequency range, and utilizes one mixer/demodulator stage to convert the signal to baseband without going through an intermediate frequency (IF) stage. The resulting low frequency (baseband) signal spectrum has useful information at frequencies from DC to typically a few tens of MHz. Designing these receivers requires the use of very high performance analog ICs. High performance direct conversion radio receiver signal chains for applications such as cellular infrastructure and RFID readers require high linearity, low noise fi gure (NF), and good matching between the in-phase and quadrature (I and Q) channels.
High Linearity Components Simplify Direct Conversion Receiver Designs
Design Note 418