This contribution deals with a frontend for interleaved receive (Rx)-/transmit (Tx)-integrated phased arrays at K-/Ka-band. The circuit is realized in printed circuit board technology and feeds dual-band Rx/Tx- and single-band Tx-antenna elements. The dual-band element feed is composed of a substrate-integrated waveguide (SIW) diplexer with low insertion loss, a low-noise amplifier (LNA), a bandpass filter, and several passive transitions. The compression properties of the LNA are identified through two-tone measurements. The results dictate the maximum allowable output power of the power amplifier. The single band feed consists of a SIW with several transitions. Simulation and measurement results of the individual components are presented. The frontend is assembled and measured. It exhibits an Rx noise figure of 2 dB, a Tx insertion loss of ~ 2.9 dB, and an Rx/Tx-isolation of 70 dB. The setup represents the unit cell of a full array and thus complies with the required half-wave spacing at both Rx and Tx.
