Abstract: Disclosed herein is a temperature compensated crystal oscillator, TCXO, comprising: a crystal oscillator arrangement configured to generate an output signal of the temperature compensated crystal oscillator; and a temperature sensor arranged to generate a temperature sensor signal, wherein the output signal of the crystal oscillator arrangement is controlled in dependence on the temperature sensor signal; wherein: the temperature sensor comprises a plurality of transistor circuits; each transistor circuit comprises a transistor and a bias circuit; each transistor circuit is arranged to output a temperature signal that is dependent on the temperature of the transistor comprised by the transistor circuit; each bias circuit is configured such that the noise level in each output temperature signal is low; and the plurality of transistor circuits are arranged so that the temperature sensor signal is dependent on each of the plurality of output temperature signals.

Abstract: Disclosed herein is a temperature compensated crystal oscillator, TCXO, comprising: a crystal oscillator arrangement configured to generate an output signal of the temperature compensated crystal oscillator; and a temperature sensor arranged to generate a temperature sensor signal, wherein the output signal of the crystal oscillator arrangement is controlled in dependence on the temperature sensor signal; wherein: the temperature sensor comprises a plurality of transistor circuits; each transistor circuit comprises a transistor and a bias circuit; each transistor circuit is arranged to output a temperature signal that is dependent on the temperature of the transistor comprised by the transistor circuit; each bias circuit is configured such that the noise level in each output temperature signal is low; and the plurality of transistor circuits are arranged so that the temperature sensor signal is dependent on each of the plurality of output temperature signals.

Abstract: Temperature compensated oscillators are provided. The oscillator comprises an oscillator circuit and a temperature compensation module. The temperature compensation module reduces temperature induced errors in the frequency of oscillation of the oscillator by providing a temperature compensation signal to the oscillator circuit based on a temperature sensor output. The temperature compensation module comprises a low pass filter configured to reduce noise in the temperature compensation signal. The low pass filter is such that, using Laplace representations of transfer functions, the transfer function H(s) of the filter is equivalent to the transfer function of a closed loop configuration in which a module having an open loop transfer function G(s) is configured to generate an output from the closed loop configuration by applying the open loop transfer function G(s) to an error between an input to the closed loop configuration and the output from the closed loop configuration.

Abstract: Temperature compensated oscillators are provided. The oscillator comprises an oscillator circuit and a temperature compensation module. The temperature compensation module reduces temperature induced errors in the frequency of oscillation of the oscillator by providing a temperature compensation signal to the oscillator circuit based on a temperature sensor output. The temperature compensation module comprises a low pass filter configured to reduce noise in the temperature compensation signal. The low pass filter is such that, using Laplace representations of transfer functions, the transfer function H(s) of the filter is equivalent to the transfer function of a closed loop configuration in which a module having an open loop transfer function G(s) is configured to generate an output from the closed loop configuration by applying the open loop transfer function G(s) to an error between an input to the closed loop configuration and the output from the closed loop configuration.

Abstract: A tuning arrangement for a resonant circuit, the tuning arrangement having an output reactance dependent upon a plurality of input applied signals one of which is an input tuning signal, and including: an array of tuning circuits connected in a network whose output reactance is used to control the resonance frequency of the resonant circuit, each tuning circuit having a control input and having a reactance which varies in dependence upon the value of a control signal applied to the control input; elements for generating a plurality of different control signals for application to the control inputs of the tuning circuits; and each such control signal varying substantially linearly with the input tuning signal throughout a predetermined range specific to that control signal, so that the frequency response of the resonant circuit to the input tuning signal is substantially linear throughout a desired range of the input tuning signal.

Abstract: An oscillator includes resonator portions each mounted to a substrate via one or more mountings at one end and having an active resonance region defined between a set of electrodes. Each resonator portion has a longitudinal axis directed along the resonator portion from the mounted end to a free end. The resonator portions are mounted such that their longitudinal axes are directed in different directions, e.g. an anti-parallel arrangement, so that acceleration sensitivity vector components aligned with the longitudinal axis cancel each other out.

Abstract: This invention relates to an oscillator having reduced sensitivity to acceleration. The oscillator includes a plurality of asymmetrically mounted resonator portions each having an active resonance region. The asymmetric mounting of the resonator portions means that each resonator portion has an axis passing through its active resonance region along which the acceleration sensitivity vector is dominant, i.e. the sensitivity to acceleration along the direction defined by one axis is much greater than the sensitivity to acceleration in other directions. The resonators are mounted in an oscillator such that their dominant axes are directed in different directions, e.g. an anti-parallel arrangement, which means that the dominant acceleration sensitivity vectors can cancel each other out.

Abstract: This invention relates to an oscillator having reduced sensitivity to acceleration. The oscillator includes a plurality of asymmetrically mounted resonator portions each having an active resonance region. The asymmetric mounting of the resonator portions means that each resonator portion has an axis passing through its active resonance region along which the acceleration sensitivity vector is dominant, i.e. the sensitivity to acceleration along the direction defined by one axis is much greater than the sensitivity to acceleration in other directions. The resonators are mounted in an oscillator such that their dominant axes are directed in different directions, e.g. an anti-parallel arrangement, which means that the dominant acceleration sensitivity vectors can cancel each other out.

Abstract: A circuit for use in a current source or a proportional to absolute temperature sensor or in a bandgap regulator, the circuit comprising at least two PTAT cells the operating Voltages of whose components overlap, the PTAT contribution to the output including the sum of the outputs of the two PTAT cells.

Abstract: A tuning arrangement for a resonant circuit, the tuning arrangement having an output reactance dependent upon a plurality of input applied signals one of which is an input tuning signal, and comprising: an array of tuning circuits connected in a network whose output reactance is used to control the resonance frequency of the resonant circuit, each tuning circuit having a control input and having a reactance which varies in dependence upon the value of a control signal applied to the control input; means for generating a plurality of different control signals for application to the control inputs of the tuning circuits; and each such control signal varying substantially linearly with the input tuning signal throughout a predetermined range specific to that control signal, so that the frequency response of the resonant circuit to the input tuning signal is substantially linear throughout a desired range of the input tuning signal.

Abstract: Apparatus (1) for generating a control signal for a tunable circuit (3) sensitive to temperature receives an input control signal and predistorts it in a distortion circuit (4), so that the output (5) of the tunable circuit (3) will be substantially corrected for non-linearities in the tunable circuit (3). The distortion circuit (4) includes a linear non-distortion circuit element (9), which may be a linear temperature compensation element, and one or more non-linear distortion circuit elements (12, 13, 14), each of which distort the input control signal according to a different function. The outputs of the distortion circuit elements are passed to variable gain elements (17, 18, 19, 20) to produce weighted components. The weighted linear and non-linear components are then combined in a combination circuit element (8) to provide a predistorted control signal to the tunable circuit (3).

Abstract: Apparatus (1) for generating a control signal for a tunable circuit (3) sensitive to temperature receives an input control signal and predistorts it in a distortion circuit (4), so that the output (5) of the tunable circuit (3) will be substantially corrected for non-linearities in the tunable circuit (3). The distortion circuit (4) includes a linear non-distortion circuit element (9), which may be a linear temperature compensation element, and one or more non-linear distortion circuit elements (12, 13, 14), each of which distort the input control signal according to a different function. The outputs of the distortion circuit elements are passed to variable gain elements (17, 18, 19, 20) to produce weighted components. The weighted linear and non-linear components are then combined in a combination circuit element (8) to provide a predistorted control signal to the tunable circuit (3).

Abstract: A system for the transmission of television signals comprising a light emitter diode or diodes feeding an optical transmission line, the light output from the optical transmission line being applied to light sensitive semiconductor devices for re-conversion to analogue television signals.