Investigations On Frequency Synthesizer For Broadband Wireless Communication System

With the promotion of broadcast networks, telecommunications networks and Internet, broadband is required in transceiver for communication system. As the reference source of the frequency transceiver, the frequency oscillator is an important part of the radio frequency transceiver. Therefore, it makes sense to design the ultra-wideband, high stability, low phase noise and low spurious performance frequency synthesizer.First of all, the phase locked loop linear mathematical model is elaborated to analyze the noise thransfer in PLL structure and the phase noise and spurious performance are discussed. For the miniaturization of the model, the frequency synthesizer integrated with inter VCO is designed. It covers the range from 137.5MHz to 4.4GHz using a TCXO reference. Besides, the PC software is developed to meet the need of the control of the output power and frequency. Also, an optimized frequency synthesizer is designed covering the range 31.25MHz to 8GHz with a reference of OCXO. It consists of three parts:the PLL part, AGC unit, frequency divider circuit and frequency multiplier circuit.The results show the integrated frequency synthesizer covers the range 137.5MHz to 4GHz,its typical phase noise is-95.1dBc/Hz@ 1kHz,-99.26dBc/Hz@ 10kHz,-142.6dBc/ Hz@ 1MHz and spurious is better than -90dBc normalized to 1GHz;the optimized frequency synthesizer covers the frequency range from 31.25MHz to 8GHz, theoretical frequency resolution is 0.6Hz, typical phase noise is -102.01dBc/Hz@100Hz,-114.01dBc/Hz@1kHz,-131.29dBc/Hz@11MHz.Finally, the results are analyzed and future work is prospected.