A SiGe frequency quadrupler for M-QAM carrier recovery

In this paper a frequency quadrupler circuit, integrated with a commercially available SiGe HBT technology (f
T
/f
max
≈80/90 GHz) is presented. The quadrupler consists of two Gilbert cell mixers stacked as squarers. The measured maximum conversion gain is 0.6 dB for an input level of −9 dBm. The circuit is optimized for M-QAM carrier recovery, and the performance was tested by applying QPSK and 16QAM modulated signals with 4 Gbit/s data rate at the input. Both experimental and simulated results are presented. The fully integrated chip is operated from a single 2.5V DC supply and draws 22.3mA current.