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US 6,215,828 B1Granted
Signal transformation method and apparatus
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorsSvante Signell, Thorsten Schier
Life of this patent
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Abstract
A base station in a radio communication system uses complex bandpass filters Ω1, Ω2, . . . ,ΩN and down-sampling to channelize a wideband signal containing many channels or channel groups.
Claims11
An apparatus for transforming a real digital wideband high-frequency signal into a set of complex digital baseband signals, comprising:
- a set of complex digital bandpass filters for filtering the real digital wideband high frequency signal into a corresponding set of complex signals, each complex signal having an I component and a Q component, wherein each complex digital bandpass filters is formed by a real digital lowpass filter that has been transformed into a complex digital bandpass filter through a transformation of its digital lowpass filter transfer function into a complex digital bandpass filter transfer function, and has substantially non-overlapping narrow passbands for separating said real digital wideband high-frequency signal into a set of complex digital narrowband high-frequency signals;
- and
- means for converting said set of complex digital narrowband high-frequency signals into said set of complex digital baseband signals by first down-sampling and then low-pass filtering each complex digital narrowband high-frequency signal into a corresponding complex digital baseband signal.
A signal transformation method, including the steps of:
- A/D converting a real analog wideband high frequency bandpass signal into a real digital wideband high-frequency bandpass signal;
- forming a set of complex digital narrowband high-frequency signals, each complex signal having an I component and a Q component, by filtering said real digital wideband high-frequency bandpass signal through a set of complex digital bandpass filters having substantially non-overlapping narrow passbands;
- and
- down-sampling said set of complex digital narrowband high-frequency signals to form a set of low-frequency digital signals having I- and Q-components;
- and
- subsequent to the step of down-sampling, low-pass filtering each low-frequency digital signal into a corresponding digital baseband signal having I- and Q-components.
3 more elements
A signal transformation apparatus, including:
- an A/D converter converting a real analog wideband high frequency bandpass signal into a real digital wideband high-frequency bandpass signal;
- a set of complex digital bandpass filters having substantially non-overlapping narrow passbands for separating said real digital wideband high-frequency bandpass signal into a set of complex digital narrowband high-frequency signals, each complex signal having an I component and a Q component;
- and
- down-sampling means for converting said set of complex digital narrowband high-frequency signals into a set of low-frequency digital signals having I- and Q-components;
- and
- means for low-pass filtering each low-frequency digital signal into a corresponding digital baseband signal having I- and Q-components.
3 more elements
Dependencies are inferred from the claim text.