A Wideband Transformer-Coupled CMOS Power Amplifier for $X$-Band Multifunction Chips

This paper presents a wideband transformer-coupled CMOS power amplifier (PA). On-chip transmission-line transformers are used as key components of matching networks at output, input, and interstage. The wideband on-chip transformer is harnessed without any additional inductive devices so that a wideband power characteristic can be achieved. The PA is fabricated using a 0.18-
$\mu{\hbox {m}}$
CMOS process. It provides a saturated output power of 21.5 dBm with the power-added efficiency (PAE) of 20.3%, and the output 1-dB gain-compressed power
$(P_{1\ {\rm {dB}}})$
is 20.2 dBm with the PAE of 14.8% at 9.5 GHz, respectively. The small-signal gain is 25.3 dB and the 3-dB bandwidth is 6.5 GHz (6.5–13 GHz). The die area is 1.34 mm
$\times$
0.47 mm. Among the reported
$X/Ku$
-band CMOS PAs, this amplifier achieves the highest figure of merit, and also shows suitable performances for phased-array systems.