Research And Design Of Ultra-short-wave Radio Based On SDR

In response to the problems of resource waste,increased costs,and poor user experience caused by different technical standards and different hardware platforms in the wireless communication field,software radios with the advantages of universal hardware,software software,and front-end broadband provide designers with new solutions.In the context of project requirements,a radio design scheme based on software radio was proposed,and a baseband signal processing program in FPGA was designed to enable high-quality voice calls in the ultra-short wave band to meet the established functional requirements.The main content of the thesis research includes the following aspects:First,analyze the historical origin of software radio and the current status of research and application at home and abroad.Compare software radio and cognitive radio in principle and analysis of common hardware architectures is carried out.The characteristics of quadrature modulation,non-quadrature modulation,coherent demodulation,and quadrature demodulation methods are studied.Analyze the method to realize the key indicators in engineering development such as useless sideband suppression,local oscillator leakage suppression,IQ imbalance compensation,interference suppression from a theoretical perspective.Second,based on the function and index requirements of a project,a hardware platform design scheme with AD9361 + FPGA as the core is proposed,including the transmission channel and the reception channel.Design the implementation scheme of the core unit function module,in which the working principle,configuration method and FPGA characteristics of the agile transceiver AD9361 are analyzed.Design the front-end unit RF signal transceiver channel,and perform power amplification,filtering,and program-controlled attenuation within the channel.Design a high-fidelity voice signal processing circuit in the audio unit,and complete the codec processing of the voice signal in the AD73311.Accomplish the transmission and exchange of external signals in the interface unit,and isolate and protect the equipment.According to the power demand,the power supply unit supplies power to each module.The data exchange between the units is expected to be completed through the connection of the backplane.Third,complete the design of the AD9361 configuration program in the software part,configure the sampling clock of the data link,and configure the AD9361 initial state parameters in the initialization function.After the host computer issues new parameters,it completes the state switching and performs DC offset and transmit / receive quadrature calibration.Design and implement a FPGA program for baseband processing of transmission and reception.When transmitting,the signal is band-passed,processed by the CIC filter,and multiplied by the NCO parameter,and then output.The quadratic root value of the sum of the squares of the IQ signal is generated during reception and restored after passing through the CIC filter and low-pass filter.At the same time set the working state of AD73311 and the volume value of PGA2310 in FPGA.Fourth,after verifying the reliability of power supply,in accordance with the principle of modular design,each module unit is verified by a combination of software and hardware.After testing,the audio unit has a complete waveform after encoding and decoding at a 16-bit wide 32 Ksps rate.The transceiver channel of the AD9361 works normally.The RF front-end effectively suppresses the out-of-band harmonics and the actual attenuation is consistent with the programmed attenuation.During the test of the whole machine,the power is adjustable at each frequency point of the 25 KHz interval in the frequency bands of 121 MHz ? 124 MHz and 243 MHz ? 248 MHz.The measured values of the 6 test points of the transmission channel in the attenuation of 0 ? 60 d B are the same as the preset values,and harmonic and spurious suppression is above 40 d B.The time waveform of the received IQ signal observed in MATLAB is smooth and orthogonal.The waveform of the baseband signal recovered after FPGA processing is complete and smooth.Audio quality of the AD73311 decoded and restored audio is clear and no obvious noise.The waveform data can be correctly transmitted and restored,indicating that the platform's functions and performance are in line with the requirements of the technical indicators,and it also verifies the correctness of the design scheme of the ultra-short wave radio station based on software radio.The proposed and implemented software radio station in this paper can transmit and receive data at VHF,and has the characteristics of a configurable setting.Combined with the modification of the front-end RF circuit,it can be applied in more frequency bands and scenarios,which have important reference value and significance for software radio technology research and communication product development.