Down/up-conversion apparatus and method

• US 6,611,569 B1
• Filed: 10/02/1998
• Issued: 08/26/2003
• Est. Priority Date: 10/03/1997
• 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): Pham, Chi
• Assistant Examiner(s): TRAN, KHANH C
• Application Number:
  US09/165,644
• Time in Patent Office: 1,789 Days
• Field of Search: 375/271, 375/275, 375/321, 375/322, 375/331, 375/302, 375/335, 375/350, 455/104, 455/109, 455/110, 455/112, 455/118, 455/131, 455/139, 455/147, 455/189.1, 455/190.1, 455/203, 455/204, 455/245.2, 455/324, 455/307, 455/335, 455/339
• US Class Current: 375/322
• CPC Class Codes: H03D 1/24 for demodulation of signals wherein one sideband or the carrier has been wholly or partially suppressed receiver circuits H04B1/302
• CPC Class Codes: H03D 2200/0054 Digital filters
• CPC Class Codes: H03D 2200/0072 by complex multiplication
• CPC Class Codes: H03D 7/161 all the frequency changers being connected in cascade
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H03D 7/166 using two or more quadrature frequency translation stages

Abstract

A down-converter converts an amplitude modulated high frequency signal into a low frequency or baseband signal. A first mixer (30, 32) mixes the high frequency signal into a composite signal having an in-phase component and a quadrature component. A complex bandpass filter (34) bandwidth limits the composite signal into a bandwidth limited signal with an in-phase component and a quadrature component. A second mixer (36, 38) mixes the bandwidth limited signal into an intermediate signal with an in-phase component and a quadrature component, and an adder (40) adds one component of the intermediate signal to the other. A similar up-converter performs the reverse process.

Claims

1. A down-converter for converting a modulated high frequency signal into a low frequency signal, including a first mixer for mixing said high frequency signal into a composite signal having an in-phase component and a quadrature component, said down-converter comprising:

A/D converters for A/D conversion of the components of said composite signal;

a complex bandpass filter, coupled to the output of said first mixer, for bandwidth limiting said composite signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a digital bandpass filter, and wherein said complex bandpass filter is a complex bilinear ladder filter;

a second mixer, coupled to the output of said complex bandpass filter, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component, wherein said second mixer is a digital mixer; and

an adder, coupled to the output of said second mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component, wherein said adder is a digital adder.

2. The down-converter of claim 1, wherein said high frequency-signal is a single sideband signal and said low frequency signal is a bandbased signal.

3. An up-converter for converting a low frequency digital signal into a modulated high frequency signal, including a first digital mixer for mixing said low frequency signal into a composite signal having an in-phase component and a quadrature component, said up-converter comprising:

a complex digital bandpass filter, coupled to the output of said first digital mixer, for bandwidth limiting said composite signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a complex bilinear digital ladder filter;

D/A converters for D/A conversion of the components of said bandwidth limited signal;

a second mixer, coupled to the output of said D/A converters, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component; and

an adder, coupled to the output of said second mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component.

4. An up-converter for converting a low frequency digital signal into a modulated high frequency signal, including a first digital mixer for mixing said low frequency signal into a composite signal having an in-phase component and a quadrature component, said up-converter comprising:

a set of D/A converters for D/A conversion of the components of said composite signal;

a complex bandpass filter, coupled to the output of said D/A converters, for bandwidth limiting said composite signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a complex switched capacitor filter;

a set of A/D converters for A/D conversion of the components of said bandwidth limited signal;

a second mixer, coupled to the output of said A/D converters, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component; and

an adder, coupled to the output of said second mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component.

5. An up-converter for converting a low frequency digital signal into a modulated high frequency signal, including a first digital mixer for mixing said low frequency signal into a composite signal having an in-phase component and a quadrature component, said up-converter comprising;

a first set of D/A converters for D/A conversion of the components of said composite signal;

a complex bandpass filter, coupled to the output of said D/A converters, for bandwidth limiting said composite signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a complex switched capacitor filter;

a second digital mixer, coupled to the output of said complex bandpass filter, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component;

a digital adder;

coupled to the output of said second digital mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component; and

a further D/A converter for D/A conversion of the output signal from said digital adder.

6. An apparatus for reconstructing a low frequency signal from a composite signal having an in-phase component and a quadrature component, comprising:

A/D converters for A/D conversion of the components of said composite signal;

a complex bandpass filter for bandwidth limiting said composite signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a complex bilinear digital ladder filter;

a digital mixer, coupled to the output of said complex bandpass filter, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component; and

a digital adder, coupled to the output of said mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component.

7. The apparatus of claim 6, wherein said low frequency signal is a baseband signal.

8. An apparatus for generating a high frequency signal from a digital composite signal having an in-phase component and a quadrature component comprising:

a complex bandpass filter for bandwidth limiting said component signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a complex bilinear digital ladder filter;

D/A converters for D/A conversion of the components of said bandwidth limited signal;

a mixer, coupled to the output of said D/A converters, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component; and

an adder, coupled to the output of said mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component.

9. The apparatus of claim 8, wherein said high frequency signal is a single sideband signal.

10. An apparatus for generating a high frequency signal from a composite digital signal having an in-phase component and a quadrature component comprising:

a set of D/A converters for D/A conversion of the components of said composite digital signal,

a complex bandpass filter for bandwidth limiting said component signal into a bandwidth limited signal having an in-phase component and a quadrature component, wherein said complex bandpass filter is a complex switched capacitor filter;

a set of A/D converters for A/D conversion of the components of said bandwidth limited signal;

a mixer, coupled to the output of said A/D converters, for mixing said bandwidth limited signal into an intermediate signal having an in-phase component and a quadrature component; and

an adder, coupled to the output of said mixer, for adding (subtracting) one component of said intermediate signal to (from) the other component.