.30-3000mhz Rf Front-end Development Of General-purpose Receiver

The subject derives from the project of "0.1M~3000MHz universal receiver", which is collaborated with Ministry of Science and Technology of PRC and Chengdu Sine Science and Technology Ltd. undertake the RF front end in this project. The RF front end is divided into two separate parts, the 0.1~30MHz & the 30M~3GHz RF front end. R&D on the later one is the very subject. By means of using the electronically tuned preselector and multiple conversion technology, a wide band receiver with wide dynamic range is basically achieved. The scheme is innovative and original not only in the scheme itself but also in the technology of some sub-circuits.By making full use of favourable narrow-band tracing filter character of PLL and by combining the merits of DDS such as super fine frequency resolution,high frequency accuracy,very fast frequency hoping with it, the PLL/PLL+DDS frequency synthesizer presents wide band high quality source and super small frequency hoping step. While the electronically tuned filter abates the image interference and notably improves the selectivity.The theorem of frequency synthesizer and center-frequency-fixed filter is simply but adequately introduced first in this paper. Subsequently, the technology of the electronically tunable filter is discussed. At last, the circuitry realization,some test data and trouble shooting are presented.