Abstract: An optical signal transmission apparatus (1) for a rotating antenna comprising a plurality of optical modulators (6) arranged for receiving a respective plurality of analog RF signals (5) and for modulating a respective plurality of optical signals therewith to produce a plurality of modulated analog optical signals (8). A plurality of opto-electrical converters (14) each converts a respective modulated analog optical signal (13) into an analog electrical signal. The plurality of optical modulators (6) are rotationally coupled in optical communication with the plurality of opto-electrical converters (14) via an optical rotary joint (10) including a reversion prism.

Abstract: According to a first aspect of the present invention, there is provided a duplexer for a radio frequency antenna, comprising: a radio frequency signal transmitter port arranged for connection to a radio frequency signal transmitter; a radio frequency signal receiver port arranged for connection to a radio frequency signal receiver; a switch arranged selectively to adopt either one of: a first state which connects the transmitter port to a common input/output port of the switch arranged for connection to a radio frequency antenna; and a second state which connects the receiver port to the common input/output port; a switch control unit arranged to monitor radio frequency power at the common input/output port and to receive a transmission gate signal; wherein the switch control unit is arranged to control the switch to adopt the first state upon receipt of the transmission gate signal, and, subsequently, to control the switch to adopt the second state when the monitored radio frequency power falls below a thres

Abstract: Methods and apparatus for controlling a bias voltage supplied to an optical modulator, the modulator comprising a biasable component, the biasable component being configurable to be biased by application of the bias voltage (20) such that the modulator operates at quadrature, the method comprising: providing a target for the output power of the modulator, the target for the output power of the modulator being an output power corresponding to the modulator operating at quadrature; applying, to the biasable component, a bias voltage (20) having an initial value of 0V; and, thereafter, varying the bias voltage (20) until the value of the bias voltage (20) is the value that is closest to the initial value and that biases the biasable component so that the output power of the modulator is within a pre-defined range of the target output power.

Abstract: According to a first aspect of the present invention, there is provided a duplexer for a radio frequency antenna, comprising: a radio frequency signal transmitter port arranged for connection to a radio frequency signal transmitter; a radio frequency signal receiver port arranged for connection to a radio frequency signal receiver; a switch arranged selectively to adopt either one of: a first state which connects the transmitter port to a common input/output port of the switch arranged for connection to a radio frequency antenna; and a second state which connects the receiver port to the common input/output port; a switch control unit arranged to monitor radio frequency power at the common input/output port and to receive a transmission gate signal; wherein the switch control unit is arranged to control the switch to adopt the first state upon receipt of the transmission gate signal, and, subsequently, to control the switch to adopt the second state when the monitored radio frequency power falls below a thres

Abstract: Methods and apparatus for finding a bias voltage (20) corresponding to a quadrature point of an optical modulator, the modulator comprising a biasable component which is configurable to be biased by application of the bias voltage (20) such that the modulator operates at quadrature, the method comprising: providing a target for the output power of the modulator which corresponds to quadrature; applying, to the biasable component, a bias voltage (20) having an initial value; thereafter, finding a value for the bias voltage (20) that biases the biasable component such that the output power of the modulator is within a pre-defined range of the target by, starting at the initial value, alternately increasing and decreasing (or decreasing and increasing) the bias voltage (20) with gradually increasing amplitude; and identifying the found value for the bias voltage (20) as a bias voltage corresponding to a quadrature point of the optical modulator.

Abstract: An optical signal transmission apparatus (1) for a rotating antenna comprising a plurality of optical modulators (6) arranged for receiving a respective plurality of analogue RF signals (5) and for modulating a respective plurality of optical signals therewith to produce a plurality of modulated analogue optical signals (8). A plurality of opto-electrical converters (14) each converts a respective modulated analogue optical signal (13) into an analogue electrical signal. The plurality of optical modulators (6) are rotationally coupled in optical communication with the plurality of opto-electrical converters (14) via an optical rotary joint (10) including a reversion prism.

Abstract: Methods and apparatus for finding a bias voltage (20) corresponding to a quadrature point of an optical modulator, the modulator comprising a biasable component which is configurable to be biased by application of the bias voltage (20) such that the modulator operates at quadrature, the method comprising: providing a target for the output power of the modulator which corresponds to quadrature; applying, to the biasable component, a bias voltage (20) having an initial value; thereafter, finding a value for the bias voltage (20) that biases the biasable component such that the output power of the modulator is within a pre-defined range of the target by, starting at the initial value, alternately increasing and decreasing (or decreasing and increasing) the bias voltage (20) with gradually increasing amplitude; and identifying the found value for the bias voltage (20) as a bias voltage corresponding to a quadrature point of the optical modulator.

Abstract: Methods and apparatus for controlling a bias voltage supplied to an optical modulator, the modulator comprising a biasable component, the biasable component being configurable to be biased by application of the bias voltage (20) such that the modulator operates at quadrature, the method comprising: providing a target for the output power of the modulator, the target for the output power of the modulator being an output power corresponding to the modulator operating at quadrature; applying, to the biasable component, a bias voltage (20) having an initial value of 0V; and, thereafter, varying the bias voltage (20) until the value of the bias voltage (20) is the value that is closest to the initial value and that biases the biasable component so that the output power of the modulator is within a pre-defined range of the target output power.