Monolithic microwave integrated circuit developer Custom MMIC of Westford, MA, USA has announced a new technical brief detailing its progress in boosting linearity by using passive MMIC mixers based on gallium nitride (GaN) technology.
For decades, gallium arsenide (GaAs) has been the process of choice for passive mixers fabricated on MMIC technologies. However, in terms of linearity, GaAs mixers tend to have input third-order intercept points (IP3) that reach +20-24dBm, which is typically only 3-8dB above the applied LO drive. This level of ‘linear efficiency’, which is newly defined as the difference between IP3 and LO drive level, is one reason why higher IP3 levels have generally been unachievable in GaAs.
Over the past year, mixer experts at Custom MMIC have been exploring the use of GaN processes as the basis for extremely linear RF mixers. Deducing that the high linearity performance of GaN power amplifiers may cross-over to other critical microwave components, the firm has gone through several iterations of GaN mixer technologies and topologies with several of its key foundry partners.
Ultimately, this has led to passive GaN mixer designs that surpass all gallium arsenide (GaAs) passive mixer designs in terms of the ratio of input third-order intercept point (IIP3) to local oscillator (LO) drive - a figure-of-merit that Custom MMIC is coining linear efficiency. From S-band to K-band (2GHz to 19GHz) the new passive GaN mixers are demonstrating IIP3 figures well above 30dBm, LO drive levels around 20dBm, and linear efficiencies above 10dB.