Research And Implementation Of π/4-DQPSK And GMSK Modulator Based On DSP

Digital Modulation Technology is an important part of the Mobile Communication Systems.π/4-DQPSK and GMSK modulation have been widely adopted for many Mobile Communication systems and Satellite Communication systems because of many advantages, such as better spectral efficiency, stronger anti-interference performance , lower Bit Error Rate, and so on. Currently, though there exsits various solutions to carry out Digital Modulation Technology, DSP solution is still in researching and developing. Therefore, the resreach ofπ/4-DQPSK and GMSK modulation base on DSP solution is of great significance.In this paper, firstly, the development and resreach progress ofπ/4-DQPSK and GMSK modulation technologies both at home and abroad are introduced. Then, the principle ofπ/4-DQPSK and GMSK are presented, and the DSP and Quadrature Modulation solution which adopt for this paper is proposed. Secondly, the hardware of Modulator is designed accronding to the system's requirements, the principle and design of each part is given in detail. Meanwhile the densign of software based on CCS2．0 including flow chart and realization of system program and function program are given too, Finally, the performance of system is tested and some experiment results are presented and analyzed. Through test and actual operation, both of the functions and technical specifications meet the design requirements.This system is an all-digital realization, various problems in analog arrroach, such as any I/Q imbalance (phase or amplitude) results in poor side-band suppression and carrier feed-through are eliminated. Other advantages of the DSP solutions including the ability to easily software update to accommodate different data rates, modulation schemes and filter Specifications, etc. In addition, the modulator is also flexible and adoptable too.