University of Bristol

British Technology Group Limited

Stmicroelectronics Gmbh

National Research Development Corporation

Mark Anthony Beach

Joseph P McGeehan

Peter Blakeborough Kenington

Andrew Bateman

Philip G Mattos

Ross James Wilkinson

Andrew Robert Nix

Christopher Williams

Wycliffe Timothy Slingsby

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.

Synchronisation in a receiver

A Cartesian loop transmitter for transmitting baseband signals is disclosed. The disclosed Cartesian loop includes a forward path having a first input for receiving the baseband signals and a second input and a feedback path having an input from the forward path. The forward path including an upconverter to upconvert the input signals to a signal to be transmitted, an attenuator having selectable attenuation and a plurality of power amplifier stages. The feedback path including a pin diode attenuator having selectable attenuation and a downconverter to downconvert the input from the forward path. The feedback path provides an error signal indicative of the non-linearity of the forward path to the second input of the forward path.

Cartesian loop transmitter

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.

Full-duplex radio transmitter/receiver

The present invention relates to a radio receiver, particularly to a receiver for use in single-frequency applications, such as GPS, and to a frequency generator, which may be used in such a radio receiver, or elsewhere. The frequency generator comprises a tuned circuit connected between the emitter of the transistor and ground, such that a voltage signal at the basic frequency appears on the emitter terminal of the transistor. This arrangement has the advantage that the two frequencies appear on separate ports, and provides a radio receiver including radio receiver circuitry for connection to digital signal processing circuitry, reducing the complexity of the overall circuit. Additionally, there is a radio receiver wherein separate first and second local oscillator signals are generated from the terminal of s single transistor, avoiding the need for cascade multiplication stages, again reducing the size and complexity of the overall circuit. Further, circuitry is included generating an oscillator signal whereby the signal processing means tolerates the resulting frequency errors, and a single frequency direct downconversion receiver, comprising means for sub-sampling and one-bit coding the demodulated signal, and a transistor capable of decoding a microwave local oscillator signal and a digital signal processor with a clock signal for tolerating frequency errors.

Radio receiver and frequency generator for use with digital signal

Image-reject mixers

Method and apparatus for signal processing using reference signals

Broadband amplifiers which are intended to be linear suffer from distortion and although many techniques have been devised to overcome this problem significant improvements are required especially at frequencies above 100 MHz. An error signal is formed from the output of the amplifier 4 by comparison in a subtractor 11 with its input and the error signal is combined in a coupler 17 with the amplifier output to reduce distortion. The present invention provides automatic amplitude and phase control of the signals forming the error signal by means of components 24 and 25 in a multi-channel input and in the error signal by means of components 13 and 14. These components receive control signals from feedback networks 18' and 20' which each process two of three input signals from: couplers 34, 36 before the subtractor 11, a coupler 22 which passes the error signal and a coupler 21 after the coupler 17. Preferably the two input signals used by a feedback network are used to form in-phase and quadrature signals by a 90.degree. phase shifter 41 and mixers 42 and 43. These signals are each amplified 46, 47 and integrated 48, 49 to provide the control signals. The input signals from the feedback networks may be reduced in frequency and applied to a DSP which then provides the control signals.

Apparatus and method for reducing distortion in amplification

Broadband amplifiers which are intended to be linear suffer from distortion and although many techniques have been devised to overcome this problem significant improvements are required especially at frequencies above 100 MHz. An error signal is formed from the output of an amplifier by comparison in a subtractor with its input and the error signal is combined in a coupler with the amplifier output to reduce distortion. The present invention provides automatic amplitude and phase control of the signals forming the error signal by two groups of adjustment means, one group in a multi-channel input path and one group in the error signal path. These groups receive control signals from respective feedback networks which each process two of three input signals from: couplers before the subtractor, a coupler which passes the error signal and a coupler situated after the coupler which combines the amplifier output signal and the error signal. Preferably the two input signals used by a feedback network are used to form in-phase and quadrature signals using a 90.degree. phase shifter and two mixers. These signals are each amplified and integrated to provide the control signals. The input signals from the feedback networks may be reduced in frequency and applied to a DSP which then provides the control signals.

Growing community of inventors

Bristol, United Kingdom

Mark Anthony Beach