Method for noise reduction of a FM signal
AssigneeSony Deutschland GmbH
InventorJens Wildhagen
Life of this patent
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Abstract
A compander for noise reduction of a FM signal is described, wherein a group delay (τ) linked to the generation of the compressor gain (cc(t)) is equalised during generation of the multiplex signal (m(t)), and a group delay (τ) linked to the generation of the expander gain (ce(t)) is equalised during generation of the sum signal (us(t)) and the expanded difference signal (ue(t)). Alternatively or additionally the compressor gain and/or the expander gain is controlled by an auxiliary signal on the basis of a combination of sum signal and difference signal of the FM signal. Such companders avoid overmodulation in the transmitter.
Claims18
A method for noise reduction of an audio signal transmitted as a FM multiplex signal including a sum signal and a difference signal, comprising:
- companding the difference signal and transmitting a compressed difference signal within a multiplex signal controlling a compressor gain and/or an expander gain based on an auxiliary signal;
- equalizing a group delay linked to a generation of the compressor gain during generation of the multiplex signal;
- and
- equalizing a group delay linked to a generation of the expander gain during generation of the sum signal and the expanded difference signal.
A method for noise reduction of an audio signal transmitted as a FM multiplex signal including a sum signal and a difference signal, comprising:
- companding the difference signal and transmitting a compressed difference signal within the multiplex signal;
- and
- controlling a compressor gain and/or the expander gain on basis of a combination of the sum signal and the difference signal.
A FM transmitter, comprising:
- a compressor configured to compress a difference signal;
- and
- a first delay element arranged in a signal path of the difference signal preceding said compressor to introduce a group delay linked to a generation of a compressor gain.
A FM transmitter, comprising:
- a compressor configured to compress a difference signal said compressor including
- a control circuit configured to receive a sum signal (s(t)) and the difference signal to set a compressor gain on basis of a combination of both the sum and difference signals.
A FM receiver comprising:
- an expander configured to expand a received compressed difference signal which is transmitted within a received FM signals;
- and
- a first delay element arranged in a signal path of the compressed difference signal preceding said expander to introduce a group delay linked to a generation of an expander gain.
A FM receiver, comprising:
- an expander configured to expand a received compressed difference signal which is transmitted within a received FM signal, said expander including
- a control circuit configured to receive a sum signal and a difference signal of the received FM signal to set an expander gain on basis of a combination of both the sum and difference signals.
Dependencies are inferred from the claim text.