A Dual-Band Feed Network for Highly Integrated K-/Ka-Band Phased Array Front-Ends

This paper presents a dual-band feed network for K-/Ka-Band phased array transceiver modules. It is intended to interface receive and transmit beamformer chips and the antenna elements with the remaining front-end circuitry. The whole arrangement consists of two printed circuit boards (PCBs) which are mounted on both sides of an aluminum 1:4 rectangular waveguide (RWG) power divider/combiner. It includes transitions from grounded coplanar waveguide (GCPW) to RWG. These are self-diplexing and thus an integral part of the whole feed network. Due to the RWG aluminum body, this integration approach offers adequate heat transfer capabilities and increased space for surface mount devices (SMDs). Because of its high frequency selectivity, image reject filters in the Rx-path can be dispensed with. The manufactured passive demonstrator exhibits reflection coefficients below -10 dB from 18.7 GHz to 20.5 GHz (Rx-band) and from 29.2GHz to 30.5 GHz (Tx-band) and an insertion loss of 3.9 dB < IL < 4.8 dB and 2.8 dB < IL < 3.6 dB at these frequencies. Although the Rx- and the Tx-paths share the same RWG divider/combiner, they are diplexed with an isolation of more than 30 dB in both bands.