A Directly Matched PA-Integrated $K$-Band Antenna for Efficient mm-Wave High-Power Generation

A K-band slot antenna element with an integrated gallium nitride power amplifier (PA) is presented. It has been optimized through a circuit-electromagnetic codesign methodology to directly match the transistor drain output to its optimal load impedance (ℤ
_opt
= 17 + j46 Ω), while accounting for the over-the-air coupling effects in the vicinity of the transition between the PA and antenna. This obviates the need for using a potentially lossy and bandwidth-limiting output impedance-matching network. The measured PA-integrated antenna gain of 15 dBi with a 40% total efficiency at 28 dBm output power agrees well with the theoretically achievable performance targets. The proposed element is compact (0.6 × 0.5 × 0.3 λ
³
) and, thus, well suited to meet the high-performance demands of future emerging beamforming active antenna array applications.