Method of reducing d.c. offset
AssigneeFuture Waves UK Limited
InventorMark Dawkins
Life of this patent
Estimating the term…
Abstract
A method of reducing d.c. offset comprises comparing the a first variable signal with a second variable signal, producing a control signal in dependence upon the comparison, providing the control signal to a charge pump for generation of a feedback signal, and varying the first signal and/or the second signal in dependence upon the feedback signal thereby reducing any difference between the d.c. level of the first signal and the d.c. level of the second signal.
Claims23
A method of reducing d.c. offset, the method comprising:
- comparing a variable first signal with a variable second signal;
- producing a control signal dependent upon the comparison;
- providing the control signal to a charge pump for generation of a feedback signal;
- and varying the first signal and/or the second signal in dependence upon the feedback signal thereby to reduce any difference between the d.c. level of the first signal and the d.c. level of the second signal.
A method according to any preceding claim, wherein the first signal and the second signal are each obtained from the same input signal.
A method according any preceding claim, wherein the first signal and the second signal are each obtained by downconversion of a received radio-frequency signal, preferably a received radio-frequency DAB signal.
A method according to any preceding claim, wherein the first signal is out of phase with the second signal, and preferably the first signal is around 180° out of phase with the second signal.
A method according to any preceding claim wherein the first signal comprises the signal on the positive path of an in-phase or quadrature channel of a DAB receiver and the second signal comprises the signal on the negative path of the channel.
A method according to any preceding claim, further comprising producing the feedback signal in dependence upon at least one earlier value of the feedback signal as well as in dependence upon the comparison.
Apparatus for reducing d.c. offset, comprising:
- amplification means adapted to vary a variable first signal and/or a variable second signal;
- means adapted to compare the first signal and the second signal and to produce a control signal in dependence upon the comparison;
- and means for producing a feedback signal and for passing the feedback signal back to the amplification means, the means for producing the feedback signal being adapted to receive the control signal and including a charge pump;
- the amplification means being further adapted to receive the feedback signal and to vary the first signal and/or the second signal in dependence on the feedback signal so as to reduce any difference between the d.c. level of the first signal and the d.c. level of the second signal.
Dependencies are inferred from the claim text.