InGaAs-based MM-wave integrated subharmonic mixer exhibiting low input power requirement and low noise characteristics

Low-power, low-noise mixer diodes are required for a variety of applications such as receivers operating from tens of GHz to one THz. At millimeter-wave frequencies, the expense of LO power (P_LO) has encouraged the use of subharmonic mixers, especially antiparallel planar GaAs, to halve the required LO frequency. This paper describes the use and application of InGaAs-InP technology to subharmonic mixer diodes which demonstrate significant reduction in P_LO and have performance comparable to planar GaAs technology with no DC bias requirement. Single-ended mixers, based on similar technology, have demonstrated excellent performance at 94 GHz as described previously by the authors. The subharmonic InGaAs mixer, described here, requires integration of two antiparallel connected Schottky diodes. Due to the inherent properties of this scheme, mixing is performed at twice the LO signal frequency. This halving in LO frequency reduces the cost of providing LO. An integrated antenna-mixer, having an antiparallel Schottky diode pair, is described and characterized at 180 GHz. First, the mixer layer and antenna design are presented. Next, the diode´s I-V curves are discussed. Then the mixer characterization methods and millimeter-wave performance are discussed. Theoretical analysis, based on experimentally evaluated anode capacitance (C_j0) and I-V characteristics of real 2 μm diameter InGaAs diodes, is then used to investigate subharmonic mixer performance as a function of LO power and imbedding impedance. Finally, the InGaAs subharmonic mixer´s conversion loss and noise temperature are compared to those of state-of-the-art GaAs antiparallel diode pairs