Signal transformation method and apparatus

• US 6,546,061 B2
• Filed: 02/05/2001
• Issued: 04/08/2003
• Est. Priority Date: 10/02/1996
• Status: Expired due to Term

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Schier, Thorsten, Signell, Svante
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US09/775,820
• Publication Number:
  US 20010050966A1
• Time in Patent Office: 792 Days
• Field of Search: 375/316, 375/298, 375/261, 375/279, 375/295, 375/320, 375/329, 375/350, 375/229, 329/304, 329/305, 329/306, 329/310, 332/103, 332/104, 332/105
• US Class Current: 375/316
• CPC Class Codes: H03H 17/0202 Two or more dimensional filters; Filters for complex signals multidimensional convolutions G06F17/153
• CPC Class Codes: H04J 1/05 using digital techniques
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A base station in a radio telecommunication system, transforms real digital wideband high-frequency signals into a set of complex digital baseband signals and vice versa. The base station receives a set of complex digital baseband signals having an “I” and a “Q” components. A portion of these signals are modulated and then converted into complex digital high-frequency signals. The complex digital high-frequency signals are then filtered via bilinear digital ladder bandpass filters to retrieve real digital narrowband high-frequency signals. The outputs of these filters are the same corresponding “I” and “Q” components at the narrowband frequencies. These signals are further combined to form real digital wideband high-frequency signals. Finally, the combined signals are converted through a D/A converter to real analog wideband high-frequency bandpass signals.

Claims

1. A signal transformation method, comprising the steps of:

modulating at least a set of complex digital baseband signals;

up-sampling the set of complex digital baseband signals, each having an I component and a Q component, to form a set of complex digital high-frequency signals, each having a corresponding I component and a Q component;

forming a set of real digital narrowband high-frequency signals by filtering said set of complex high-frequency signals through a corresponding set of complex digital bandpass filters having substantially non-overlapping narrow passbands;

combining said real narrowband high-frequency signals to form a real digital wideband high-frequency signal; and

D/A converting the real digital wideband high-frequency bandpass signal into a real analog wideband high-frequency bandpass signal.

2. An apparatus for transforming a set of complex digital baseband signals into a real digital wideband high-frequency signal, comprising:

means for converting said set of complex digital baseband signals, each having an I component and a Q component, into a set of complex digital high-frequency signals, each having a corresponding I component and a corresponding Q component, by up-sampling each complex digital baseband signal into a corresponding complex digital high-frequency signal;

a set of complex digital bandpass filters having substantially non-overlapping narrow passbands for filtering said set of complex digital high-frequency signals, with respective I and Q components, into a set of real digital narrowband high-frequency signals, the complex digital bandpass filters being 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

means for adding said real digital narrowband high-frequency signals for forming said real digital wideband high-frequency signal.

3. The apparatus of claim 2, wherein said converting means includes modulators for modulating at least some of said complex digital baseband signals before up-sampling.

4. The apparatus of claim 2, wherein said complex digital bandpass filters are formed by bilinear digital ladder filters with complex transfer functions.

5. The apparatus of claim 2, wherein the apparatus is used in a base station operating in a radio communication system for transforming a set of complex digital baseband signals into a real digital wideband high-frequency signal.

6. A signal transformation apparatus, including:

a modulator for modulating at least a set of complex digital baseband signals;

an up-sampler for converting the set of said complex digital baseband signals, each having an I component and a Q component, into a set of complex digital high-frequency signals, each having a corresponding I component and a Q component;

a set of complex digital bandpass filters having substantially non-overlapping narrow passbands for filtering said set of complex high-frequency signals into a set of real digital narrowband high-frequency signals;

a signal combiner for adding said real digital narrowband high-frequency signals to form a real digital wideband high-frequency signal; and

a D/A converter for converting the real digital wideband high-frequency bandpass signal into a real analog wideband high-frequency bandpass signal.

7. The apparatus of claim 6, wherein each of said 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.

8. The apparatus of claim 7, wherein said complex digital bandpass filters are formed by bilinear digital ladder filters with complex transfer functions.

9. The apparatus of claim 6, wherein the apparatus is used in a base station operating in a radio communication system for transforming a set of complex digital baseband signals into a real analog wideband high-frequency signal.