Research And Implementation Of 2FSK And QPSK Hybrid Modem Technology

With the integrated development of all-digital modulation technology,the modulation and demodulation chip often needs to be able to complete a variety of modulation methods.In the conventional mode,the modulation mode is selected by the modulation selection modu,le in the chip during modulation,and only one channel of signal modulation and demodulation can be performed.Increases the design cost of the chip,and the system spectrum utilization rate is not high.In order to improve the chip design function and realize the coexistence of two different rate modulation methods,and subtract the modulation selection module of the non-hybrid modulation chip to improve the spectrum utilization,a new hybrid modulation and demodulation mode is designed.In this thesis,the 2FSK and QPSK hybrid modulation and demodulation technology is researched and analyzed,and the feasibility of 2FSK and Q'PSK hybrid modulation and demodulation technology is verified by FPGA platform.Hybrid transmission combines 2FSK and OPSK and transmits at the same time.At the receiver,the 2FSK and QPSK spectral differences are separated by a high-pass filter.Th,e main research content includes the following aspects:(1)The principle of 2FSK and QPSK hybrid modulation and demodulation is analyzed,and the important theory of multi-rate signal processing and digital frequency conversion technology in the design of hybrid modulation and demodulation system is discussed.(2)A hybrid 2FSK and QPSK modulation and demodulation system is designed,and the traditional 2FSK modulation and demodulation method is improved.By separating the two modulation frequencies of 2FSK,peak detection and decision accuracy are optimized.The frequency offset caused by the receiver is corrected to improve the demodulation accuracy.(3)The mathematical model of the whole system is built under the MATLAB simulation platform,and the fixed-point simulation is carried out.The feasibility of the design of the hybrid modulation and demodulation system is demonstrated by the simulation results.The simulation of the noise environment is carried out to simulate the error rate.The system meets both functional and performance requirements.(4)In Quartus II,a hybrid modem system is designed by using Verilog HDL language.The feasibility of the hybrid modem system is verified and the expected results are achieved.In the hybrid modem system,the 2FSK symbol rate is 10 kbps,the QPSK symbol rate is 2 Mbps,and the system clock is 16 MHz.The modulation noise is controlled within 8dB,and the system performance is tested.The BER of 2FSK and QPSK are lower than 0.001,which shows that the system has good anti-jamming ability and can meet the requirements of communication system.It has practical application significance.