A Compact Linear 60-GHz PA With 29.2% PAE Operating at Weak Avalanche Area in SiGe

This paper presents a 60-GHz SiGe PA with a 29.2% power-added efficiency (PAE), a peak power of 16.8 dBm, and a peak output 1-dB compression (OP_1dB) of 14 dBm. Its measured gain is 13.5 dB at 60 GHz with a corresponding 3-dB bandwidth of 47-74 GHz. The PAE is above 25% with a supply voltage from 2.2 to 4 V. A cascode stage has been analyzed and used as the amplifier core. The high PAE is achieved by pushing the upper transistor of the cascode stage to weak avalanche area and correct transistor sizing. The linearity is achieved by optimizing the input matching and emitter degeneration. Safe operation conditions of heterojunction bipolar transistors at dc and high frequencies have been investigated at weak avalanche area. A safe operation boundary for high frequencies is given based on our experimental results and analytical derivations. Large-signal stress tests have shown there is no performance degradation and have proved the validity of this safe operation boundary.