A Direct Down-conversion System Using Sub-harmonic Mixer with Microstrip Lines

Abstract

Abstract-The purpose of this paper is to design a direct downconversion system using sub-harmonic mixer with microstrip lines, it is also called a zero intermediate frequency system. By utilizing the direct conversion configuration, it can not only avoid to use an additional voltage controlled oscillator and phaselocked loop which resulted from twice down conversions so as to simplify the configuration and reduce cost, but also suppress the mirror image frequency, and thus to diminish non-linear conversion distortion and to increase the receive dynamic range. The LO-RF and LO-IF isolations of sub-harmonic mixer with microstrip lines are greater than 60 dB, and the conversion loss is about 14 dB; the phase noise of VCO with spiral-shaped defected ground structure (DGS) is -96 dBc/Hz at 10 kHz. We have succeeded to develop a direct down-conversion system.