Feed equations for phased array multiport antennas

This paper derives equations associated with multi-port antenna elements used in phased array antennas. Each multi-port element requires a feed circuit. For a scanned transmitting array, element reflections are predominantly absorbed in the isolation resistors of this feed circuit. Results show that the element mismatch loss is far larger than the mismatch at the feed circuit input. Hence system loss is determined by element mismatch, not feed circuit input mismatch. Equations are derived for the element mismatch loss, the dissipation in the feed isolation resistors and the feed circuit input return loss.