0 ~ 3.6 Ghz Spectrometer Key Techniques Of Rf Front End

The Spectrum analyzer has been widely used in many areas, such as mobile communication, radar navigation, electronic countermeasure and electromagnetic compatibility (EMC) design. It is an important testing instrument in the field of signal analysis. The design of the radio frequency (RF) front-end is the key technology in spectrum analyzer. Its performance plays an important part in the overall performance of spectrum analyzer.In this thesis, an low-cost and high-performance RF front-end of spectrum analyzer was presented. The high-IF method is used to in the design and high-performance VCO(Voltage Controlled Oscillator) replacing YTO(YIG-tuned oscillator) used in Local Oscillator (LO), in which performance is guaranteed and miniaturization is reached. Its parameters is following as, input frequency range cover0-3.6GHz,-120-20dBm dynamic range, minimum sensitivity lower than-120dBm, noise factor lower than10, a range of-110～-1OdBm on3rd IF, and its phase noise factor is better than-90dBc/Hz@10kHz or-94dBc/Hz@100kHz.Firstly, a high-IF heterodyne architecture and tuning equation were proposed according to analysis of elated technical indexes and restraining ability to mirror frequency was analyzed. Secondly, simulations of our system are made by simulator ADS2008, including noise factor,1dB compression,3rd order inter-modulation intercept, etc. The three-stage LO, IF filter and mixer were the key parts in system RF front-end. The first LO is implemented with the application of Fractional-N technology. The frequency of first LO is from4.1GHz to7.8GHz and phase noise is better than-90dBc/Hz@10kHz. The step size of minimum frequency is3Hz. In the design of the filter, according to the theory of network synthesis and coupling resonance, simulations and optimization of each filter are made in the simulator IE3D and HFSS.Finally, the hardware design of the RF front-end was completed. The LO output and3rd IF output had been tested. According to the results of test, the proposed system meets the requirements of the RF front-end in the spectrum analyzer.