System of and method for reducing or eliminating the unwanted sideband in a signal derived from the output of a quadrature modulator
First Claim
Patent Images
1. A system for reducing or eliminating any unwanted baseband component in the output of a quadrature modulator comprising:
- a quadrature modulator for receiving a baseband signal, the baseband signal having I and Q components in a phase relationship, and quadrature modulating a local oscillator signal with the baseband signal to provide a modulator output;
an unwanted sideband detector for detecting an unwanted sideband component in and responsive to the modulator output, and outputting a signal representative thereof; and
a correction circuit for iteratively adjusting the phase relationship of the I and Q components of the baseband signal responsive to a signal derived from the signal output by the unwanted sideband detector until either the detected unwanted sideband component is reduced to an acceptable level or the adjusted phase relationship of the I and Q components is about a quadrature relationship, wherein the unwanted sideband detector is an envelope detector.
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Abstract
A system of and method for reducing or eliminating any unwanted sideband component in a signal derived from the output of a quadrature modulator. An unwanted sideband detector detects the unwanted sideband in the output of the quadrature modulator, and responsive thereto, a correction circuit corrects a baseband signal prior to inputting it to the quadrature modulator. In one embodiment, the unwanted sideband detector is an envelope detector.
19 Citations
31 Claims
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1. A system for reducing or eliminating any unwanted baseband component in the output of a quadrature modulator comprising:
a quadrature modulator for receiving a baseband signal, the baseband signal having I and Q components in a phase relationship, and quadrature modulating a local oscillator signal with the baseband signal to provide a modulator output;
an unwanted sideband detector for detecting an unwanted sideband component in and responsive to the modulator output, and outputting a signal representative thereof; and
a correction circuit for iteratively adjusting the phase relationship of the I and Q components of the baseband signal responsive to a signal derived from the signal output by the unwanted sideband detector until either the detected unwanted sideband component is reduced to an acceptable level or the adjusted phase relationship of the I and Q components is about a quadrature relationship, wherein the unwanted sideband detector is an envelope detector.- View Dependent Claims (2, 3, 4, 5, 13)
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6. A system for reducing or eliminating any unwanted sideband component in the output of a quadrature modulator comprising:
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a quadrature modulator for receiving a baseband signal having I and Q components in a phase relationship, and modulating a local oscillator signal with the baseband signal to provide an output signal, the output signal having an envelope;
an envelope detector for detecting the envelope of the modulator output signal, and outputting a signal representative thereof; and
a correction circuit configured to iteratively adjust the phase relationship of the I and Q components of the baseband signal responsive to a signal derived from the signal output by the envelope detector until either the output of the envelope detector reaches an acceptable level or the adjusted phase relationship of the I and Q components is about a quadrature relationship. - View Dependent Claims (14, 15, 17)
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7. A method of reducing or eliminating any unwanted sideband in the output of a quadrature modulator comprising the steps of:
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quadrature modulating a local oscillator signal responsive to a baseband signal to provide an output signal, the baseband signal having I and Q components in a phase relationship;
detecting an unwanted sideband in and responsive to the output signal; and
iteratively adjusting the phase relationship of the I and Q components of the baseband signal responsive to a signal derived from the detected unwanted sideband until either the detected unwanted sideband is reduced to an acceptable level or the adjusted phase relationship of the I and Q components is about a quadrature relationship, wherein the output signal has an envelope, and the detecting step comprises detecting the envelope of the output signal. - View Dependent Claims (16)
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8. A method for reducing or eliminating any unwanted sideband in a signal derived from the output of a quadrature modulator comprising the steps of:
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quadrature modulating a local oscillator signal responsive to a baseband signal to provide an output signal, the baseband signal having I and Q components in a phase relationship, and the output signal having an envelope;
detecting the envelope of the output signal; and
iteratively adjusting the phase relationship of the I and Q components of the baseband signal responsive to a signal derived from the detected envelope until either the detected envelope reaches an acceptable level or the adjusted phase relationship of the I and Q components is about a quadrature relationship. - View Dependent Claims (9, 10, 11)
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12. A method of reducing or eliminating any unwanted sideband in a signal derived from an output of the quadrature modulator, comprising the steps of:
quadrature modulating a local oscillator signal with a baseband signal to form an output signal, the baseband signal having I and Q components in a phase relationship, the output signal having an envelope;
detecting the envelope in and responsive to the output signal;
adjusting the phase relationship of the I and Q components of the baseband signal responsive to a signal derived from the detected envelope; and
repeating the foregoing process until either the signal derived from the detected envelope reaches an acceptable level or the adjusted phase relationship of the I and Q components is about a quadrature relationship.
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18. A system for reducing or eliminating any unwanted sideband component in the output of a quadrature modulator comprising:
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a quadrature modulator for quadrature modulating a complex carrier signal with a complex baseband signal to provide a complex output signal, the complex baseband signal having I and Q components and one or more parameters including a phase relationship between the I and Q components thereof;
an unwanted sideband detector for detecting an unwanted sideband component in and responsive to the modulator output, and outputting a signal representative thereof, wherein the unwanted sideband detector includes an envelope detector; and
a correction circuit for iteratively adjusting one or more of the parameters of the complex baseband signal responsive to a signal derived from the output of the unwanted sideband detector until either the detected unwanted sideband component is reduced to a predetermined level or the phase relationship of the I and Q components is about a quadrature relationship. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A method of reducing or eliminating any unwanted sideband component in the output of a quadrature modulator comprising:
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quadrature modulating a complex carrier signal with a complex baseband signal to provide a complex output signal, the complex baseband signal having I and Q components and one or more parameters including a phase relationship between the I and Q components;
detecting an unwanted sideband component in and responsive to the complex output signal, and outputting a signal representative thereof; and
iteratively adjusting one or more of the parameters of the complex baseband signal responsive to a signal derived from the signal representative of the unwanted sideband component in the complex output signal until the detected unwanted sideband component is reduced to a predetermined level or the phase relationship of the I and Q components is about a quadrature relationship, wherein the detecting step includes detecting the envelope of the complex output signal, and outputting a signal representative thereof. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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Specification