A 77 GHz CMOS power amplifier module using multi-layered redistribution layer technology

This paper presents a new millimeter-wave module concept, which is an integration of CMOS monolithic microwave integrated circuits (MMICs) and passive devices fabricated using a redistribution layer (RDL) technology. To realize a low-loss passive circuit, we introduced a multi-metal-layer for the RDL. The first metal layer was used as ground to shield from substrates. The upper metal layers form passive RF components such as a thin film microstrip line (TFMSL), a spiral inductor, a balun, a power combiner, and an antenna. Detailed measurements and characterizations are presented, and we show their applicability in the millimeter-wave region. Moreover, this concept was applied to an integrating millimeter-wave module consisting of four identical CMOS power amplifiers and RDL power combiners to increase the output power. The module exhibited a saturation power of 15 dBm, which is almost four-times higher than that obtained from the single PA. The measured small-signal gain of the PA module was 5.4 dB. The total chip size was 2.2 × 1.5 mm
²
. The power consumption of the PA module was 800 mW.