Abstract
Low frequency (LF) broadcast system is not only an essential platform for the operation of radio watches but also a potential system for various applications such as disaster warning. The front-end IC of the LF receivers is a key component. A low-power, low-noise receiver with complete function and realized in SiGe BiCMOS technology for low frequency (77.5 kHz) time signal broadcast system is presented in this work. For the use at LF, flicker noise usually dominates the system noise floor. The receiver designed in this work uses SiGe HBT to reduce flicker noise. The receiver incorporates a variable gain amplifier (VGA) to adjust the signal amplitude, and the demodulation function is built in the automatic gain control (AGC) system. Under 3.3 V power supply, the receiver only consumes 0.343 mW when working. Stand-by mode has been implemented to save even more energy. The chip occupies an area of 1300 μm x 908 μm. Another design in CMOS technology is also proposed to enhance the function of receiver. The frequency band of this version is expanded to accommodate multi-frequencies (40 kHz, 60 kHz, and 68.5 kHz). In this design, not only the crystal select circuit was inserted, but also the system of AGC was altered to break through the limitation of the VGA gain range. The chip area of the latter receiver is 1867 μm x 1899 μm.