Quadrature modular with adaptive suppression of carrier leakage

Claim 2

A carrier leakage suppression circuit for adaptively suppressing carrier leakage in a signal processing device which modulates a carrier signal with a baseband signal to generate a radio frequency (RF) output signal, the carrier leakage suppression circuit comprising: means for imparting a signature to the baseband signal prior to modulation of the carrier signal, such that after modulation the RF output signal includes a carrier leakage component that carries said signature; means for isolating and measuring in the RF output signal said carrier leakage component by correlating the RF output signal with said signature; means for generating as a function of said measurement of said carrier leakage component an offset signal; and means for combining the baseband signal with said offset signal to thereby suppress carrier leakage due to the baseband signal.

Claim 3

A carrier leakage suppression circuit for adaptively suppressing carrier leakage in a signal processing device which modulates a carrier signal with an in-phase baseband signal and a quadrature baseband signal to generate a radio frequency (RF) output signal, the carrier leakage suppression circuit comprising: means for imparting a first signature to the in-phase baseband signal and a second signature to the quadrature baseband signal prior to modulation of the carrier signal, such that after modulation the RF output signal includes an in-phase carrier leakage component that carries the first signature and a quadrature carrier leakage component that carries the second signature; means for isolating and measuring in the RF output signal said in-phase and quadrature carrier leakage components by respectively correlating the RF output signal with said first and second signatures; means for generating as a function of said measurement of said in-phase and quadrature carrier leakage components an in-phase offset and a quadrature offset, respectively; and means for combining the in-phase baseband signal with said in-phase offset and the quadrature baseband signal with said quadrature offset to thereby suppress carrier leakage due to the in-phase baseband signal and the quadrature baseband signal.

Claim 4

A carrier leakage suppression circuit for adaptively suppressing carrier leakage in a signal processing device which modulates a carrier signal with an in-phase baseband signal and a quadrature baseband signal to generate a radio frequency (RF) output signal, the carrier leakage suppression circuit comprising: means for imparting a first signature to the in-phase baseband signal and a second signature to the quadrature baseband signal prior to modulation of the carrier signal, such that after modulation the RF output signal includes an in-phase carrier leakage component that carries the first signature and a quadrature carrier leakage component that carries the second signature; means for isolating and measuring in the RF output signal said in-phase and quadrature carrier leakage components by respectively correlating the RF output signal with said first and second signatures; means for generating as a function of said measurement of said in-phase and quadrature carrier leakage components an in-phase offset and a quadrature offset, respectively; and means for combining the in-phase baseband signal with said in-phase offset and the quadrature baseband signal with said quadrature offset to thereby suppress carrier leakage due to the in-phase baseband signal and the quadrature baseband signal.

Claim 5

The carrier leakage suppression circuit of claim 2, wherein said imparting means comprises: a pseudo-noise (PN) generator for generating a first PN sequence representing said first signature and a second PN sequence representing said second signature, said first PN sequence being non-correlative relative to said second PN sequence; a first combiner to combine said first PN sequence with the in-phase baseband signal; and a second combiner to combine said second PN sequence with the quadrature baseband signal.

Claim 6

The carrier leakage suppression circuit of claim 2, wherein said isolating and measuring means comprises: a directional coupler to sample the RF output signal; a diode detector to detect a power spectrum of the sampled RF output signal; a first multiplier to multiply the detected power spectrum of the sampled RF output signal with said first signature to thereby generate an in-phase direct current (DC) signal corresponding to said in-phase carrier leakage component; and a second multiplier to multiply the detected power spectrum of the sampled RF output signal with said second signature to thereby generate a quadrature DC signal corresponding to said in-phase carrier leakage component.

Claim 7

The carrier leakage suppression circuit of claim 4, wherein said generating means comprises: a first integrator for integrating over said in-phase direct current (DC) signal to adjust a value of said in-phase offset; and a second integrator for integrating over said quadrature direct current (DC) signal to adjust a value of said quadrature offset.

Claim 8

The carrier leakage suppression circuit of claim 2, wherein said combining means also combines said first and second signatures with the in-phase baseband signal and the quadrature baseband signal, respectively.

Claim 9

The carrier leakage suppression circuit of claim 2, wherein the signal processing device is a quadrature modulator.

Claim 10

The carrier leakage suppression circuit of claim 2, wherein the signal processing device is a single sideband upconverter.

Claim 13

The method of claim 9, wherein step (1) comprises the steps of: generating a first PN sequence representing said first signature and a second PN sequence representing said second signature, said first PN sequence being non-correlative relative to said second PN sequence; combining said first PN sequence with the in-phase baseband signal; and combining said second PN sequence with the quadrature baseband signal.

Claim 14

The method of claim 9, wherein step (2) comprises the steps of: sampling the RF output signal; detecting a power spectrum of the sampled RF output signal; multiplying the detected power spectrum of the sampled RF output signal with said first signature to thereby generate an in-phase direct current (DC) signal corresponding to said in-phase carrier leakage component; and multiplying the detected power spectrum of the sampled RF output signal with said second signature to thereby generate a quadrature DC signal corresponding to said in-phase carrier leakage component.

Claim 15

The method of claim 11, wherein step (3) comprises the steps of: integrating over said in-phase direct current (DC) signal to adjust a value of said in-phase offset; and integrating over said quadrature direct current (DC) signal to adjust a value of said quadrature offset.

Claim 16

The method of claim 9, wherein step (4) also comprises the step of combining said first and second signatures with the in-phase baseband signal and the quadrature baseband signal, respectively.