Signal transformation method and apparatus
First Claim
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1. 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.
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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.
163 Citations
11 Claims
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1. An apparatus for transforming a real digital wideband high-frequency signal into a set of complex digital baseband signals, comprising:
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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. - View Dependent Claims (2, 3, 4)
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5. A signal transformation method, including the steps of:
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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. - View Dependent Claims (6)
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7. A signal transformation apparatus, including:
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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. - View Dependent Claims (8, 9, 10, 11)
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Specification