An interference cancelling system for cancelling or minimizing multiple signal components of a received signal in a radio receiver caused by an interfering signal from a radio transmitter which interfering signal follows multiple paths to the radio receiver includes a directional coupler which samples the interfering signal transmitted from the radio transmitter and provides a primary sample signal, a transmission link which defines a primary sample signal path from the radio transmitter to the radio receiver, a power splitter for dividing a portion of the primary sample signal path into a plurality of secondary sample signal paths, a power combiner for combining the plurality of secondary sample signal paths back into the primary signal path, and a 180.degree. hybrid coupled to the primary sample signal path and to the radio receiver. The secondary sample signal paths include delay lines and attenuator pads. The power combiner has an output which provides an adjusted primary sample having signal components corresponding to the secondary sample signals that are substantially equal in amplitude and time delay to the corresponding multiple signal components of the received signal caused by the interfering signal. The hybrid subtracts the adjusted primary sample signal from the received signal so that the signal components of the adjusted primary sample signal cancel or at least minimize the corresponding multiple signal components of the received signal caused by the interfering signal.
The invention concerns a communications system including at least one transmit antenna near at least one receive antenna, transmission producing signals in the receive frequency band. The system includes a transmit neutralizing circuit for supplying a correction signal for eliminating only interfering signals whose frequency is in the receive signal frequency band. The transmit neutralizing circuit is on the input side of an amplifier and comprises means for evaluating, in the wanted receive frequency band, a limited number of parameters of the power amplifier feeding the transmit antenna, this evaluation of parameters being effected on the basis of the input and output signals of the amplifier. The circuit also evaluates the signals causing the interference prior to the input of the amplifier; this evaluation of the interfering signals is based on the calculated parameters and the signal at the input of the amplifier. Application to transmission systems on ships or spacecraft.
A full-duplex radio transceiver, in which cancellation of transmission signals in the receive path is achieved by sampling the transmission signals, and controllably adjusting the gain and phase of the sampled signal, before subtracting the adjusted signal from the received signals in order to minimise the component of the transmission signals appearing in the received signals. Processing is done in a DSP at or near baseband.
The invention relates to a method for attenuating interference in a positioning receiver of an electronic device, in which method a signal transmitted by satellites of a positioning system is received through a second antenna. The electronic device further comprises at least a mobile station and a first antenna to be used at least as a transmission antenna of the mobile station. In the method the strength of at least one interference signal generated in the electronic device is determined, a compensation signal corresponding to the strength of the determined interference signal is produced, and said compensation signal is combined to a signal received through a second antenna. The combined signal is directed to the positioning receiver.
The invention is a repeater for a telecommunications transmission system such as a CDMA wireless system. The repeater reduces leakage by using a feedback signal whose amplitude and phase are adjusted in response to the amplitude and phase of a sampled input signal when a switch turns off the normal output of the repeater for a short period of time. In one embodiment, a pilot signal is transmitted during this time period so that the sampled input is the leakage signal. In another embodiment, the sampled input is the normal transmission signal received during the time period.
A method is provided for obtaining a reference signal for suppressing an interfering signal received by a radio receiver system. The radio receiver system receives the interfering signal on an antenna along with a signal of interest. An electrically conducting structure on which is present an interfering signal corresponding to the interfering signal present on the antenna and close to the antenna is selected and the interfering signal present on the conducting surface is sampled to obtain a reference signal. The reference signal is provided to an interference cancellation system which generates a cancellation signal used to suppress the interfering signal received by the radio receiver system.
