Research Of Mm-wave Transmitter For One Point To Multiple Addresses

As spectrum resources become more and more tense,the millimeter-wave band is receiving more and more attention due to the rich spectrum resources.Due to the large space loss of the millimeter wave,it is easy to obtain better confidentiality for short-distance communication.A widely used and promising millimeter wave communication method is one-point multi-access millimeter wave communication(digital transmission),also known as point-to-multipoint millimeter wave communication.Due to the high price of components in the millimeter wave band,the research of low-cost millimeter wave one-point multi-access digital transmission system has important engineering practical significance.This paper first introduces the basic concepts of millimeter wave point multiple access data transmission system and the development status at home and abroad;then clarifies the related technical theory of multiple access digital transmission system: including multiple access,modulation and demodulation,receiver theory;These technical theories,followed by the overall scheme design,and detailed description from three different levels of hardware,antenna,software;Finally,the program is tested and verified.The hardware part can be divided into RF circuit and baseband signal processing circuit according to the working frequency,and can be divided into data transmission link and data receiving link according to functions.The core of the data transmission link is a phase-locked loop.By switching the frequency division ratio of the phase-locked loop,the phase-continuous 2FSK modulated signal is finally obtained;the data receiving link is composed of RF low-noise,quadrature downconverter,filtering,the variable gain amplifier,the analog-to-digital converter,and the FPGA.The modulated 2FSK signal is converted into two orthogonal signals after passing through the orthogonal down-converter.After filtering,amplifying,and analog-to-digital conversion,the FPGA runs 2FSK.The digital quadrature demodulation algorithm recovers the transmitted data.The antenna section uses an easy-to-machine,small-sized patch antenna with a design gain of 13 dB.The software part can be divided into three parts: 2FSK demodulation program,chip driver,and Labview host computer.Firstly,the principle of 2FSK orthogonal demodulation algorithm is introduced in detail,and the influence of key parameters is discussed by Matlab simulation.Secondly,a brief introduction to the design process of the chip driver,including analog-to-digital converter,digital-to-analog converter,and phase-locked loop driver.Finally,the Labview host computer is designed in a graphical language to monitor the important intermediate results of the FPGA program and assist in the analysis and debugging of the program.The final test results show that for the transmit link,the output power is not less than 1.5dBm in the transmission frequency range of 23.998~24.002GHz;the phase noise at the center frequency of 24 GHz is-74dBc/Hz@100kHz.For the receive link,the 2FSK modulated signal with an input power range of-28~-48 dBm can be demodulated.The measured patch antenna gain is 12.41 dB,and the first sidelobe level is-18.39 dB.The measured data transmission is stable when the transmission distance is 1.2~7.8 meters.