Leveraging Integration

The scaling of silicon (Si)-based technologies has led to transistors with maximum frequencies of oscillation (fmax) surpassing 400 GHz in volume production processes [1]. As a result, operating frequencies in the millimeter-wave (mm-wave) region (+30-300 GHz) have become achievable with Si-based integrated circuits (ICs), with significant commercial development at 60 GHz for high-bandwidth, short-range communications and at 77 GHz for automotive radar systems [2]. However, as device-critical dimensions approach the 10-nm regime, device breakdown voltages are greatly reduced, resulting in reduced maximum operating voltages and amplifier output voltage swings. Therefore, a major challenge in Si RF microelectronics has been to achieve acceptable transmitter linearity for digitally modulated mm-wave signals. At the same time, RF power amplifiers (PAs) in Si technologies historically suffer from low efficiencies, raising the parallel challenge of high-efficiency Si-based transmitter design. On the other hand, today's Si technologies provide an ultrahigh level of integration, which enables the leveraging of complex circuit designs to improve transmitter output power, power efficiency, and linearity, while offering economies of scale for low-cost volume fabrication. Significant technical challenges include the development of high-efficiency Si PA circuits (e.g., Class E, Class F, etc.) at mm-wave frequencies, mixed-signal linearization circuits, and novel circuit designs for increasing output power (e.g., breakdown voltage multiplication, power combining, etc.). © 2000-2012 IEEE.