Design of Downconverter for 870 MHz to 2.0 GHz Using MMIC

Abstract: The performance of signal processing circuits at very high frequencies is very poor. At such higher frequencies that is in the order of GHz range active components like transistors cannot deliver much gain. Therefore, the signal is shifted to lower frequency band. Another problem is that higher frequency signal needs waveguides and strip lines. If we use intermediate frequency, signal can be easily carried through ordinary coaxial cable. The lower frequency transistors generally have higher gains so fewer stages are required. It's easier to make sharply selective filters at lower fixed frequencies. RF upconverters and RF downconverters are integrated assemblies that convert microwave signals to another frequency range for further processing. Generally, they are designed to produce an output signal frequency for a particular frequency band. RF upconverters are designed to convert microwave signals to a higher frequency range. By contrast, RF downconverters are designed to convert microwave signals to lower frequency range. In this paper we present a downconverter for frequency range of 870 MHz - 2000 MHz. This downconverter will convert 870 MHz to 2GHz frequency to 45 MHz to 870MHz using MMIC.

Keywords: upconverter, downconverter, intermediate frequency, mixer etc.