A 930 MHz CMOS DC-offset-free direct-conversion 4-FSK receiver

Although direct-conversion has potential for high integration and low cost, it is plagued by issues ranging from DC offset to flicker noise. While most recent integrated single-chip direct conversion receivers concentrate on wideband applications where flicker noise and DC offset can be filtered out without affecting performance, focus here is on a narrow-band application using CMOS technologies. This effort is to fully integrate RF and baseband circuitry for a narrow-band application such as a high-speed pager, which uses a 4-FSK modulation scheme. The receiver overcomes the problem using a harmonic mixing and a DC-offset cancellation.