A class of binary FSK direct conversion receivers

Receivers of low power consumption and high dynamic range of typically 60 to 100 dB are key elements in wireless communication systems. This paper deals with a class of direct conversion receivers for binary FSK, involving the class of quotient detectors and an AGC circuit. The members of the class of quotient detectors are circuits of low complexity and do not contain components with excessive power consumption, as e.g. high-speed high-resolution ADCs. Analytical and experimental investigations show the capability of the class of quotient detectors for GMSK signals. So far, for one member of the quotient detectors an inherent dynamic range of 47 dB at a BER of 10^-3 has been achieved. The proposed AGC is realized as a slow low-power ADC, based on a base-band switchable gain amplifier and a two bit power level detector that keeps the mean power level at the detector input within a 12 dB interval. Furthermore, the AGC circuit yields a signal strength information with the received signal resolution of 6 dB. Due to low power consumption, low complexity, and high dynamic range, the proposed class of receiver is well suited for wireless and cordless communication systems such as GSM or DECT