Design Of EBPSK Demodulation Circuits Based On CMOS Technology

With the development of high quality and high speed data communication, the occupation of the wireless spectrum resources is increasing, and the spectrum resource is in short, which has seriously hindered the development of wireless communication. How to maximize the spectrum utilization has become a hot topic in the field of wireless communication, and the modulation and demodulation circuit is an important part of the communication system. Therefore, it is of great practical significance to study the demodulation circuit of high efficiency modulation system.This paper designs an EBPSK demodulation chip for three special modulation modes(reverse modulation mode, MCM modulation mode and narrow pulse modulation mode).), and there is almost no research achievements in this regard. Therefore on the basis of the theoretical study of EBPSK,this topic innovatively designs an EBPSK analog demodulation chip.In this design, the EBPSK signals are entered in the down-conversion mixer, then low pass active filter with high stopband attenuation filters out the useful signal, at last, baseband signals are recovered by the timing recovery circuit to complete the demodulation. As we can see, the main modules of the EBPSK demodulation system are mixer, LPF and related auxiliary circuit. Down-conversion mixer consists of double-balance Gilbert Mixer. As for the implementation of LPF, it is a 6-order Butterworth active-RC filter by cascading three Tow-Thomas biquad. The core module of the LPF is the OPA which is a two-stage operational amplifier with a Miller-pole-zero compensation. In addition, the capacitor array with external digital control is chosen to achieve the function of frequency tuning and bandwidth adjustment. The system-level design of the EBPSK demodulation circuit and the design of the auxiliary circuit are also given.The EBPSK demodulation circuit uses TSMC 0.18 CMOS process and has been taped-out. The post simulation results indicate that the EBPSK demodulation circuit can achieve the demodulation function in three modulation modes in the 1.8V power supply, the carrier frequency ranges from 10MHz to 2.4GHz.