A SPICE model for passive diode ring mixers

This article describes a macromodel for passive diode ring mixers for frequency range up to 1 GHz. The models are usable for all commercial harmonic balance simulators as well as for the standard SPICE 2G6 simulator. The model structure is very similar to the real topology of a passive mixer. It is characterized according to the RF performance by optimization. Basis for the optimization are the data sheet and measurements. Mixer measurements are performed by an automatic PC based measurement system with a Rohde & Schwarz FSBS network/spectrum analyzer. The mixer model describes as well the transfer characteristics like conversion loss and isolation, the reflection performance as the linearity (compression and third order intermodulation). The procedure of computation of the model parameters is also presented. For effective characterization a semi-automatic test system has been implemented with the MDS simulator from HP. It allows the complete characterization of a passive mixer in a fe w days. Comparisons of a mixer model (SRA-1 from Mini-Circuits) with data sheet and measurements are also presented. The model's performance of conversion gain shows excellent agreement within 0.5 dB. VSWR at the LO and RF port performance is better than 5 per cent.