Patent Number: 6,169,912

Title: RF front-end with signal cancellation using receiver signal to eliminate duplexer for a cordless phone

Abstract: A fully duplex cordless telephone has a transmitter and a receiver connected to a common antenna. A broad-band antenna coupler such as a ferrite-core hybrid transformer may replace a more costly duplexer with filters. Since all characteristics of the transmit signal are known, the transmit signal removes itself from the receiver by signal cancellation. The canceling signal is extracted from the composite signal from within the receiver front end, after the antenna coupler and low noise amplifier. This composite signal is coupled to the first input of a difference amplifier, and the output of this amplifier is coupled to the remainder of the receiver. The composite signal is coupled to the second input, after its smaller receive component has been further suppressed, and its remaining transmit signal has been adjusted by two feedback control systems to restore its phase and amplitude to be equal to the transmit component of the composite signal. Obtaining the canceling signal from the receiver, instead of the transmitter, relieves the control systems of correcting for the rapid signal phase introduced by variable proximity of objects to the short antenna.

Inventors: Zuckerman; Lawrence H. (Pleasanton, CA)

Assignee: Pericom Semiconductor Corp.

International Classification: H04B 1/52 (20060101); H04B 1/50 (20060101); H04B 1/12 (20060101); H04M 001/00 ()

Expiration Date: 01/02/2018