Research And Realization Of A RF Module For DMR Digital Terminal

Along with the development of digital telecommunication technologies, the disadvantage of analog telecommunication is more and more obvious and the development from analog to digital technology is also an inevitable trend of the trunking communication system in the future. DMR (Digital Mobile Radio) protocol is the latest global and open digital wireless standard which European Telecommunication Standards Institute (ETSI) puts forward and the protocol continues to remain perfect. DMR system has many advantages such as advanced technology, low cost product and the support of the transition from analog to digital, so it has high theoretical research value and market application value.This paper has studied on the RF module of DMR digital trunking telecommunication system hand-held terminals, it has presented and improved a RF (Radio Frequency) solution. Transmitter uses the way of two-point injection type direct FM, and phase-locked frequency synthesizer generates high frequency carrier wave, baseband signal directly controls VCO oscillation frequency, and then the power amplifier circuit magnifies its power before it was transmitted. Receiver uses specialized superheterodyne structure with twice down conversion, and at last the baseband signal is output by using frequency-demodulator device. This improvement of PLL chip adopts LMX2485E and finishes two independent PLL designs. One is used to produce carrier wave for transmitter, and the other offers the vibration signal for receiver. Finally, the paper introduces the testing of the design and analysis of test result.