Research On Key Techniques Of Radio Resource Allocation In Relay-enhanced Cellular Networks

The frequency synthesizer is a key component of frequency converter in SatelliteCommunication, whose performance affects the final performance of thecommunication directly. With the development of the Ka band Satellite Communication,the usable bandwidth is widen to2GHz. So the demand of research on frequencysynthesizers with excellent performances is imminently, such as high frequency stability,low phase noise, low spurious and wider bandwidth etc.The thesis is mainly to solve the above problems. Under the analysis of trends offrequency synthesis technology and the basic theory of frequency synthesis, the noveland improved algorithms and structures of frequency synthesis are proposed:1. A novel frequency synthesis method based on the offset source to achieve widefrequency coverage and low phase noise is proposed. In this method, the phase noiseand the bandwidth are depended on the offset source. The offset source solves the keyproblem such as low noise and wideband by employed sampling phase-locked loop+4bands switch CRO.2. A novel reference source synthesis method based on frequency multiplier+VCOCXO+PLL is proposed, which improves the near and far phase noise of the50MHz reference source.3. A VCO frequency presetting circuit based on PFD is proposed. The circuit isimplemented by a switch and a digital PLL chip compared with the traditional PLL. Thepreset of VCO frequency is realized by the formidable frequency capture ability of PFD.This method can solve the problem that the loop can’t be locked.4. A phase locked frequency synthesis method to achieve wide frequency coverageand low phase noise is proposed. By adjusting the gain of PFD in the PLL tocompensate the nonlinear behavior of voltage controlled oscillator and keep the loopbandwidth of PLL approximately constant, both of low phase noise and low spurious ofsynthesizer over the output bandwidth can be ensured.