	US 7,541,890 B2
	Quasi active MIMIC circulator
Siu K. Cheung, Storrs, Conn. (US); Willam H. Weedon, III, Warwick, R.I. (US); and Timothy Philip Halloran, Watertown, Mass. (US)
Assigned to Applied Radar, Inc., North Kingstown, R.I. (US)
Filed on Oct. 29, 2007, as Appl. No. 11/978,252.
Prior Publication US 2009/0108954 A1, Apr. 30, 2009
Int. Cl. H03H 11/02 (2006.01)

U.S. Cl. 333—117 [333/24 R]

13 Claims

1. A circulator capable of simultaneous transmit and receive operations, high frequency, high isolation and broadband performance comprising:

an antenna port;

a transmission port;

a receiving port;

wherein each port is connected to a 90 degree combiner/divider for splitting an input signal into two output components, the said output components have a ninety degrees relative phase difference to each other;

each of said 90 degree combiner/dividers in addition to the connection to the above mentioned ports has at least two output connections each of which are connected to a Y-junction and if a fourth connection, said fourth connection is attached to a matching load circuit;

this arrangement of circuits allows the portion of the phase shifted signals from the transmit port to enter the antenna 90 degree combiner/divider and be recombined in phase at the antenna port, while the rest of the signal enters the receive 90 degree combiner/divider and are phase cancelled;

said arrangement simultaneously allows the receive signal entering the antenna port and proceeding to the antenna 90 degree combiner/divider to enter the receive 90 degree combiner/divider and to be combined in phase at the receive port.