A number oF radio applications are starting to reach beyond 100 GHz. These systems are looking to leverage silicon technologies for their high yield, high levels of integration, and co-integration with analog and digital signal-processing blocks. Because they can take advantage of continued device scaling, millimeter-wave systems in complementary-metal-oxide-semiconductor (CMOS) technologies are particularly garnering interest. Recently, a 150-GHz amplifier in digital 65-nm CMOS was presented by Munkyo Seo from Teledyne Scientific and Imaging, Basanth Jagannathan from IBM SRDC, John Pekarik from STMicroelectronics, and Mark J.W. Rodwell from the University of Santa Barbara.
To reduce matching loss and extend bandwidth, a simple topology was used for this amplifier. It has no DC-block capacitor, shunt-only tuning, and radial stubs for AC ground. Dummy-prefilled microstrip lines serve as a compact, density-rulecompliant matching element. These lines enable explicit yet efficient dummy modeling. At 150 GHz, the transistor layout with parallel gate feed yields 5.7 dB of maximum saturated gain. The amplifier exhibits 8.2 dB of gain while delivering +6.3 dBm of saturated output power, +1.5 dBm output power at 1-dB compression, and a 3-dB bandwidth of 27 GHz. It consumes 25.5 mW at 1.1 V.
The researchers chose a simple amplifier topology to reduce matching loss and modeling uncertainties. They also chose a FET layout that minimizes extrinsic gate resistance. This work suggests that dummy-prefilled lines can be used beyond 200 GHz. See "A 150 GHz Amplifier with 8 dB Gain and +6 dBm PSAT in Digital 65 nm CMOS Using Dummy-Prefilled Microstrip Lines," IEEE Journal Of Solid-State Circuits, December 2009, p. 3410.
