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US 7,480,348 B2Granted
I/Q demodulation circuit
AssigneeSharp Kabushiki Kaisha
InventorYoshiaki Nakano
Life of this patent
Estimating the term…
Abstract
In an I/Q demodulation circuit, an offset amount determined in an offset detection mode is previously stored so that, in a normal reception mode, an offset is corrected for based on the data thus stored. With this configuration, a DC offset and a phase offset can be corrected for without a delay in an I/Q demodulation operation.
Claims12
An I/Q demodulation circuit comprising:
- an I/Q demodulator for producing an analog I/Q signal by multiplying an input signal by a local oscillation signal;
- an analog-to-digital converter for converting the analog I/Q signal into a digital I/Q signal;
- a reference sinusoidal-wave signal generator for producing a predetermined reference sinusoidal-wave signal;
- a selector for selecting and feeding to the I/Q demodulator one of an external input signal and the reference sinusoidal-wave signal;
- an offset amount detection circuit for detecting a DC offset amount and a phase offset amount of the digital I/Q signal obtained when the reference sinusoidal-wave signal is selected;
- a storage circuit for storing a result of detection by the offset amount detection circuit or a correction value with which to correct for the result;
- and
- an offset correction circuit for correcting for, based on data stored in the storage circuit, a DC offset and a phase offset of the digital I/Q signal obtained when the external input signal is selected,
- wherein the offset amount detection circuit includes:
- a delay circuit for producing a delayed inverted signal by delaying, of two versions of the digital I/Q signal differentially fed thereto, an inverted digital I/Q signal by a half period;
- and
- a subtraction circuit for determining the DC offset amount by subtracting the delayed inverted signal from a non-inverted digital I/Q signal.
9 more elements
An I/Q demodulation circuit comprising:
- an I/Q demodulator for producing an analog I/Q signal by multiplying an input signal by a local oscillation signal;
- an analog-to-digital converter for converting the analog I/Q signal into a digital I/Q signal;
- a reference sinusoidal-wave signal generator for producing a predetermined reference sinusoidal-wave signal;
- a selector for selecting and feeding to the I/Q demodulator one of an external input signal and the reference sinusoidal-wave signal;
- an offset amount detection circuit for detecting a DC offset amount and a phase offset amount of the digital I/Q signal obtained when the reference sinusoidal-wave signal is selected;
- a storage circuit for storing a result of detection by the offset amount detection circuit or a correction value with which to correct for the result;
- and
- an offset correction circuit for correcting for, based on data stored in the storage circuit, a DC offset and a phase offset of the digital I/Q signal obtained when the external input signal is selected,
- wherein the offset amount detection circuit includes:
- a voltage comparison circuit for comparing, with respect to two versions of the digital I/Q signal differentially fed thereto, an I signal with an inverted signal thereof and a Q signal and an inverted signal thereof;
- a zero-cross point detection circuit for determining a time point at which an output signal of the voltage comparison circuit becomes equal to zero;
- and
- a calculation circuit for determining the phase offset by comparing a zero-cross point of the I signal and a zero-cross point of the Q signal shifted by half a period.
10 more elements
An I/Q demodulation circuit comprising:
- an I/Q demodulator for producing an analog I/Q signal by multiplying an input signal by a local oscillation signal;
- an analog-to-digital converter for converting the analog I/Q signal into a digital I/Q signal;
- a reference sinusoidal-wave signal generator for producing a predetermined reference sinusoidal-wave signal;
- a selector for selecting and feeding to the I/Q demodulator one of an external input signal and the reference sinusoidal-wave signal;
- an offset amount detection circuit for detecting a DC offset amount and a phase offset amount of the digital I/Q signal obtained when the reference sinusoidal-wave signal is selected;
- a storage circuit for storing a result of detection by the offset amount detection circuit or a correction value with which to correct for the result;
- an offset correction circuit for correcting for, based on data stored in the storage circuit, a DC offset and a phase offset of the digital I/Q signal obtained when the external input signal is selected;
- and
- a ½ frequency divider for producing two signals having half a frequency of the reference sinusoidal-wave signal and having a phase difference of 90 degrees relative to each other,
- wherein an output signal of the ½ frequency divider is used as the local oscillation signal.
7 more elements
An I/Q demodulation circuit comprising:
- an I/Q signal generation circuit for producing an I/Q signal from an input signal;
- an offset amount detection circuit for detecting an offset amount of the I/Q signal;
- and
- a storage circuit for storing the offset amount or a value with which to correct for the offset amount,
- wherein an offset of the I/Q signal is corrected for based on data stored in the storage circuit, and
- wherein the offset amount detection circuit includes:
- a delay circuit for producing a delayed inverted signal by delaying, of two versions of the I/Q signal differentially fed thereto, an inverted I/Q signal by half a period;
- and
- a subtraction circuit for determining the DC offset amount by subtracting the delayed inverted signal from a non-inverted I/Q signal.
6 more elements
Dependencies are inferred from the claim text.