Abstract: A radio receiver is suitable for use in an OFDM wireless communications system, in which it is necessary to identify a timing point at a start of a frame. In order to ensure optimum performance of the receiver in multipath environments, it should be synchronised with the first received multipath component, although one or more of the delayed multipath components may be stronger than the first component. A method of determining the time position of the first received multipath component, determines a correlator function from the received signal, and determines the required timing point from a falling edge in a derivative of the correlator function.

Abstract: A Cartesian loop system for radio transmitters in which at least part of the baseband processing is carried out in the digital domain. Digital processing circuitry (250) combines a baseband input signal with a Cartesian feedback signal (206,207) to generate a forward signal. Analog circuitry (221, 201, 203, 204) converts the forward signal into a transmission output signal and generates the Cartesian feedback signal. Preferably the digital processing circuitry applies a phase shift process (208) to the Cartesian feedback signal before combination with the baseband input signal. The system is programmable allowing a single device to be used in a range of transmitters under different radio standards.

Abstract: 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.

Abstract: An image-reject mixer includes a process for adding a signal to a RF input signal. Any imbalance in the mixer circuitry, which would lead to imperfect image suppression, is corrected by detecting any resulting local oscillator component in the mixer output signal, and adjusting the balance to minimize the size of the local oscillator component.