Design Of The Hardware Platform Of The IF System In The Broad Band Down Link Based On OFDM Technique

Orthogonal Frequency Division Multiplexing (OFDM) technique has alreadybecome one of today’s research hotspots in wireless communication because of itsadvantages such as good performance under narrow-band interference, effectivesuppression of the effect of inter-symbol-interference(ISI) and high spectrumeffectiveness. However, OFDM system is very sensitive to frequency offset, timingerror and phase noise, and OFDM signal always has a wide band and highpeak-to-average power ratio (PARR), which requires better performance of thehardware circuits in the OFDM system.In the dissertation, the background and the meaning of the research are introduced,the development history and research actuality of OFDM technology are reviewed, andthe basic principle of OFDM is also expatiated briefly. On the background of the projectof the broad band down link based on OFDM technique, the structures of the IF receiverand IF transmitter are proposed respectively. The necessity of the modules in thestructures is proved from the point of signal processing and data convertion theory. Thecircuits of the IF receiver and IF transmitter are designed based on the structures. TheADC circuits along with the analog circuits before ADC of the receiver, and theup-conversion circuits and the DAC circuits of the transmitter are discussedemphatically in this thesis. The power requirements in the system including the voltagesneeded and the current every voltage must provide are analyzed. DC/DC regulator andline regulator are compared to each other for their advantages and disadvantages. Basedon the results of the analysis of the power requirements and the characteristics ofDC/DC regulators and line regulators, the power supply schemes of receiver andtransmitter are respectively proposed, and the power system circuits are designed.The test results of the power circuits, the analog circuits and the ADC circuits of thereceiver, and the up-conversion circuits and the DAC circuits of the transmitter aregiven. Finally, the waveforms of the demodulated data by the receiver in systemdebugging are given. The results show that the design requirement of the system is metbasically.