Patent ID: 9054774
Filing Date: 2015-06-09
Classification: H04B

Abstract:
1. A communication system for transmitting signals having frequencies that lie within a transmission band and for receiving signals having frequencies that lie within a reception band, the communication system comprising: a duplexer; and an antenna wherein the duplexer comprises a transmission branch and a reception branch the transmission branch comprising a transmission filter, a transmission phase shifting network and a transmission matching network, and the reception branch comprising a reception filter, a reception phase shifting network and a reception matching network, wherein the transmission matching network and the reception matching network have predominately constant phase shifts over frequencies within the reception band and within the transmission band, respectively, wherein the antenna is coupled to the transmission matching network and to the reception matching network and shows a predominantly reactance-only impedance variation over frequencies in the transmission band and over frequencies in the reception band, wherein the antenna has a negative reactance at frequencies in the transmission band and has a positive reactance at frequencies in the reception band, and wherein the transmission matching network comprises one of a series inductor and series capacitor and the reception matching network comprises the other of the series inductor and series capacitor, and wherein: in the transmission matching network comprising the series inductor a reactance of the inductor is selected to cancel the negative reactance of the antenna at frequencies in the transmission band; in the reception matching network comprising the series capacitor a reactance of the capacitor is selected to cancel the positive reactance of the antenna at frequencies in the reception band; in the transmission matching network comprising the series capacitor a reactance of the capacitor is selected to cancel the negative reactance of the antenna at frequencies in the transmission band; and in the reception matching network comprising the series inductor a reactance of the inductor is selected to cancel the positive reactance of the antenna at frequencies in the reception band.