2 TO 18 GHz Triple Balanced Mixer for MMIC Implementation

Multioctave Triple Balanced Mixers are circuits characterized by inherent ability to isolate the three signals for a very wide frequency range. Usually, this characteristic has been achieved by "suspended substrate" structures, on duroid or on allumina, involving double side mask alignement tecniques, expensive assembly procedures and, consequently, high production costs. Moreover, two ring quads of diodes are requested to implement the circuits. At our knowledge, the only alternative proposal for such an item has been done by the autor of this conference contribution few years ago, based on uniplanar technology on allumina. But even this circuit was not completely uniplanar, as long as the IF out-put circuit was implemented in "bifilar line". The MMIC circuit we intend to present is, on the contrary, fully uniplanar, that means the IF output circuit has been implemented on the same surface of the GaAs substrate of the other items. The circuit uses only four diodes, and shows much more performant electrical characteristics compared to the previous one implemented on allumina: this excellent result has been achieved thanks to LIBRA non linear simulation and SONNET e.m. analysis. The advantage in production costs and production reliability is pretty evident; the design is intended to be implemented in ELTA's GaAs foundry in the near future.