Reducing image spectral leakage due to I-Q imbalance
View Patent ↗Methods of reducing spectral leakage due to I-Q imbalance within a transmitter are disclosed. The method includes the transmitter receiving a data stream of coefficients of a multi-carrier modulation signal. The data stream is pre-processed by processing a set of the coefficients that correspond with selected notch frequencies to reduce the effects of I-Q imbalance of the transmitter, wherein at least a portion of the set of coefficients corresponds to non-symmetrical notch frequencies. The pre-processed data stream is multi-carrier modulated. The multi-carrier modulated pre-processed data stream is I-Q modulated before transmission.
1. A method of reducing spectral leakage due to I-Q imbalance within a transmitter, comprising:
the transmitter receiving a data stream of coefficients of a multi-carrier modulation signal;
measuring I-Q imbalance of the transmitter;
pre-processing the data stream by processing a set of the coefficients that correspond with selected notch frequencies to reduce the effects of I-Q imbalance of the transmitter, wherein at least a portion of the set of coefficients corresponds to non-symmetrical notch freqencies, wherein the pre-processing of the data stream is based at least in part on the measured I-Q imbalance;
multi-carrier modulating the pre-processed data stream;
I-Q modulating the multi-carrier modulated pre-processed data stream.
2. A method of reducing spectral leakage due to I-Q imbalance within a transmitter, comprising:
the transmitter receiving a data stream of coefficients of a multi-carrier modulation signal;
pre-processing the data stream by processing a set of the coefficients that correspond with selected notch frequencies to reduce the effects of I-Q imbalance of the transmitter, wherein at least a portion of the set of coefficients corresponds to non-symmetrical notch frequencies, wherein the set of coefficients additionally corresponds to symmetrical notch frequencies;
multi-carrier modulating the pre-processed data stream;
I-Q modulating the multi-carrier modulated pre-processed data stream.
3. The method of claim 1 , wherein measuring I-Q imbalance of the transmitter comprises measuring the I-Q imbalance at a single frequency.
4. The method of claim 2 , further comprising pre-processing data stream coefficients corresponding to symmetric notch frequencies to affect a notch at a transmit carrier frequency f m .
5. A method of reducing spectral leakage due to I-Q imbalance within a transmitter, comprising:
the transmitter receiving a data stream of coefficients of a multi-carrier modulation signal;
pre-processing the data stream by processing a set of the coefficients that correspond with selected notch frequencies to reduce the effects of I-Q imbalance of the transmitter, wherein at least a portion of the set of coefficients corresponds to non-symmetrical notch frequencies;
multi-carrier modulating the pre-processed data stream;
I-Q modulating the multi-carrier modulated pre-processed data stream;
wherein pre-processing of the data stream comprises:
selecting a value for at least one data stream coefficient X m reducing leakage at transmit frequency f m due to data stream coefficient X -m , the leakage being caused by I-Q imbalance of the transmitter;
wherein selecting the value of the data stream coefficient X m is based at least in part on measured I-Q imbalance.
6. The method of claim 5 , wherein the measured I-Q imbalance is frequency dependent.
7. The method of claim 5 , wherein the measured I-Q imbalance is frequency independent.
8. The method of claim 5 , wherein the value for X m is determined by measuring spectral leakage at f m due to X -m when X m is zeroed, and by measuring spectral leakage at f m due to X m when X -m is zeroed.
9. The method of claim 5 , wherein reducing the leakage at the transmit frequency f m comprises canceling the leakage at the transmit frequency f m by proper selection of the value of X m .
10. A transmitter that includes means for reducing I-Q imbalance of the transmitter, comprising:
the transmitter receiving a data stream of coefficients of a multi-carrier modulation signal;
means for pre-processing the data stream by processing a set of the coefficients that correspond with selected notch frequencies to reduce the effects of I-Q imbalance of the transmitter, wherein at least a portion of the set of coefficients corresponds to non-symmetrical notch frequencies;
a multi-carrier modulator for multi-carrier modulating the pre-processed data stream;
an I-Q modulator for I-Q modulating the multi-carrier modulated pre-processed data stream;
means for measuring I-Q imbalance of the transmitter; and wherein
the pre-processing of the data stream is based at least in part on the measured I-Q imbalance.
11. The transmitter of claim 10 , wherein the set of coefficients additionally corresponds to symmetrical notch frequencies.
12. The transmitter of claim 10 , wherein measuring I-Q imbalance of the transmitter comprises measuring the I-Q imbalance at a single frequency.
13. The transmitter of claim 11 , further comprising pre-processing data stream coefficients corresponding to symmetric notch frequencies to affect a notch at a transmit carrier frequency f m .
14. The transmitter of claim 10 , wherein pre-processing of the data stream comprises:
selecting a value for at least one data stream coefficient X m reducing leakage at transmit frequency f m due to data stream coefficient X -m the leakage being caused by I-Q imbalance of the transmitter.
15. The transmitter of claim 14 , wherein selecting the value of the data stream coefficient X m is based at least in part on measured I-Q imbalance.
16. The transmitter of claim 14 , wherein the value for X m is determined by measuring spectral leakage at f m due to X -m when X m is zeroed, and by measuring spectral leakage at f m due to X m when X -m is zeroed.
17. The transmitter of claim 14 , wherein reducing the leakage at the transmit frequency f m comprises canceling the leakage at the transmit frequency f m by proper selection of the value of X m .