A Ka-Band Mutual Coupling Resilient Balanced PA with Magnetic Coupling Self-Cancelling Inductor Achieving 21.2dBm OP1dBand 27.6% PAE1dB

The performance and robustness of millimeter-wave (mm-wave) power amplifiers (PAs) define the quality of a high-data-rate communication system to a large extent [1]. However, the performance of the PAs is strongly affected by mutual coupling among the close element in the phased-array antenna, yielding a beam-steering angle-dependent and time-varying loading or VSWR condition rather than ideal
$50\Omega$
as shown in Fig. 1 (top). Furthermore, mm-wave communication systems typically demand PAs with high output power and power-added efficiency (PAE), worsening the output reflection coefficient
$(\Gamma_{\mathrm{P}\mathrm{A}})[2-7]$
. Therefore, the unwanted “element to element” coupled signals reflect back to the antenna, deteriorating the phased array beam pattern and the linearity of PAs. Recently, a method of tuning the output matching network (self-healing) based on load mismatch detection has been proposed to deal with this problem [8]. However, this method requires a reconfigurable and inevitably lossy output matching network, which will degrade the performance of PAs. Besides, the design of PA with high output power and efficiency meets many challenges as the operating frequency moves into the mm-wave range mainly due to breakdown issues when high voltages are handled, especially in modern downscaled CMOS technologies. In addition, the increased routing parasitic when increasing the device size results in higher loss and makes the design of matching networks more difficult due to a high impedance transformation ratio.