Digital approach for image rejection correction in low intermediate frequency conversion tuner
View Patent ↗A method of processing an in-phase signal component and a quadrature signal component of a low intermediate frequency (LIF) signal includes estimating and correcting an amplitude imbalance between a digitized in-phase signal component and a digitized quadrature signal component at a first point in time, and estimating and correcting a phase imbalance between the digitized in-phase signal component and the digitized quadrature signal component at a second point in time in response to the correcting process. The digitized in-phase signal component corresponds to the in-phase signal component at the first point in time and the digitized quadrature signal component corresponds to the quadrature signal component at the first point in time. The second point in the time is subsequent to the first point in time.
1. A method of processing an in-phase signal component and a quadrature signal component of a low intermediate frequency (LIF) signal, said method comprising:
estimating and correcting an amplitude imbalance between a digitized in-phase signal component and a digitized quadrature signal component at a first point in time, wherein said digitized in-phase signal component corresponds to said in-phase signal component at said first point in time and said digitized quadrature signal component corresponds to said quadrature signal component at said first point in time; and
estimating and correcting a phase imbalance between said digitized in-phase signal component and said digitized quadrature signal component at a second point in time in response to the correcting process, wherein said second point in time is subsequent to said first point in time,
wherein the correcting of said amplitude imbalance comprises determining an amplitude offset between said digitized in-phase signal component at said first point in time and said digitized quadrature signal component at said first point in time.
2. The method of claim 1 , wherein said amplitude imbalance is determined as a function of at least one of a variance of said in-phase signal component and a variance of said quadrature signal component.
3. The method of claim 2 , wherein said amplitude imbalance is determined in accordance with equation:
α
=
Var
(
y
I
)
Var
(
y
Q
)
-
1
,
wherein α denotes said amplitude imbalance, Var denotes variance, y I denotes the in-phase component of a complex intermediate frequency (IF) signal output, and y Q denotes the quadrature component of said complex IF signal output.
4. A method of processing an in-phase signal component and a quadrature signal component of a low intermediate frequency (LIF) signal, said method comprising:
estimating and correcting an amplitude imbalance between a digitized in-phase signal component and a digitized quadrature signal component at a first point in time, wherein said digitized in-phase signal component corresponds to said in-phase signal component at said first point in time and said digitized quadrature signal component corresponds to said quadrature signal component at said first point in time; and
estimating and correcting a phase imbalance between said digitized in-phase signal component and said digitized quadrature signal component at a second point in time in response to the correcting process, wherein said second point in time is subsequent to said first point in time,
wherein a phase offset is determined as a function of at least one of an expected value of the digitized in-phase signal component at said second point in time, an expected value of the digitized quadrature signal component at said second point in time, and an expected value of an input signal at said second point in time.
5. The method of claim 4 , wherein the phase offset is determined in accordance with equation:
φ
=
-
2
E
(
y
I
·
y
Q
)
E
(
x
2
(
t
)
)
,
wherein φ denotes a phase imbalance, E denotes the expectation function, y I denotes the in-phase component of a complex intermediate frequency (IF) signal output, and y Q denotes the quadrature component of said complex IF signal output.
6. A method of processing an in-phase signal component and a quadrature signal component of a low intermediate frequency (LIF) signal, said method comprising:
estimating and correcting an amplitude imbalance between a digitized in-phase signal component and a digitized quadrature signal component at a first point in time, wherein said digitized in-phase signal component corresponds to said in-phase signal component at said first point in time and said digitized quadrature signal component corresponds to said quadrature signal component at said first point in time;
estimating and correcting a phase imbalance between said digitized in-phase signal component and said digitized quadrature signal component at a second point in time in response to the correcting process, wherein said second point in time is subsequent to said first point in time;
correcting a phase offset between the digitized in-phase signal component and the digitized quadrature signal component at a third point in time in response to the estimating said phase offset, wherein said third point in time is subsequent to said second point in time.
7. A method of processing an in-phase signal component and a quadrature signal component of a low intermediate frequency (LIF) signal, said method comprising:
correcting an amplitude imbalance between a digitized in-phase signal component and a digitized quadrature signal component at a first point in time, wherein said digitized in-phase signal component corresponds to said in-phase signal component at said first point in time and said digitized quadrature signal component corresponds to said quadrature signal component at said first point in time, wherein the correcting of said amplitude imbalance comprises calculating said amplitude offset between said digitized in-phase signal component at said first point in time and said digitized quadrature signal component at said first point in time;
estimating a phase imbalance between said digitized in-phase signal component and said digitized quadrature signal component at a second point in time in response to said correcting, wherein said second point in time is subsequent to said first point in time; and
correcting said phase imbalance between said digitized in-phase signal component and said digitized quadrature signal component at a third point in time in response to the estimating of said phase imbalance, wherein said third point in time is subsequent to said second point in time.
8. The method of claim 7 , wherein said amplitude imbalance is determined as a function of at least one of a variance of said in-phase signal component and a variance of said quadrature signal component.
9. The method of claim 8 , wherein said amplitude imbalance is determined in accordance with equation:
α
=
Var
(
y
I
)
Var
(
y
Q
)
-
1
,
wherein α denotes said amplitude imbalance, Var denotes variance, y I denotes the in-phase component of a complex intermediate frequency (IF) signal output, and y Q denotes the quadrature component of said complex IF signal output.
10. The method of claim 7 , wherein said phase imbalance is determined as a function of at least one of an expected value of the digitized in-phase signal component at said second point in time, an expected value of the digitized quadrature signal component at said second point in time, and an expected value of an input signal at said second point in time.
11. The method of claim 10 , wherein said phase imbalance is estimated in accordance with equation:
φ
=
-
2
E
(
y
I
·
y
Q
)
E
(
x
2
(
t
)
)
,
wherein φ denotes a phase imbalance, E denotes the expectation function, y I denotes the in-phase component of a complex intermediate frequency (IF) signal output, and y Q denotes the quadrature component of said complex IF signal output.
12. A circuit comprising:
an IQ mixer configured to provide a signal comprising in-phase (I) and quadrature (Q) components, wherein said in-phase and quadrature components comprise at least one of an input and an output signal;
a plurality of cycle counters operatively connected to said IQ mixer;
at least one loop gain unit operatively connected to said plurality of cycle counters, said loop gain unit comprising at least one predefined threshold; and
at least one round/clip component operatively connected to said at least one loop gain unit and adapted to remove an undesired signal and to correct a digitized in-phase signal component and a digitized quadrature signal component of said signal at a first point in time, wherein said digitized in-phase signal component corresponds to said in-phase signal component at said first point in time and said digitized quadrature signal component corresponds to said quadrature signal component at said first point in time, and a phase imbalance between said digitized in-phase signal component and said digitized quadrature signal component at a second point in time in response to said correct digitized in-phase signal component and a digitized quadrature signal component of said signal, wherein said second point in time is subsequent to said first point in time.
13. The circuit of claim 12 , wherein said plurality of cycle counters are adapted to determine the number of times said signal has a phase imbalance and an amplitude imbalance.
14. The circuit of claim 12 , wherein said predefined threshold is at least one of a 1 and 0.
15. The circuit of claim 14 , wherein said amplitude imbalance is determined in accordance with equation:
α
=
Var
(
y
I
)
Var
(
y
Q
)
-
1
,
wherein α denotes said amplitude imbalance, Var denotes variance, y I denotes the in-phase component of a complex intermediate frequency (IF) signal output, and y Q denotes the quadrature component of said complex IF signal output.
16. The circuit of claim 12 , wherein an amplitude imbalance is determined as a function of at least one of a variance of said in-phase signal component and a variance of said quadrature signal component.
17. The circuit of claim 12 , wherein said IQ mixer is adapted to mix said in phase and said quadrature components.
18. The circuit of claim 12 , wherein said phase imbalance is corrected based on a phase imbalance offset estimation.
19. The circuit of claim 12 , wherein a phase offset is determined as a function of at least one of an expected value of the digitized in-phase signal component at said second point in time, an expected value of the digitized quadrature signal component at said second point in time, and an expected value of an input signal at said second point in time.
20. The circuit of claim 19 , wherein said phase imbalance is estimated in accordance with equation:
φ
=
-
2
E
(
y
I
·
y
Q
)
E
(
x
2
(
t
)
)
,
wherein φ denotes a phase imbalance, E denotes the expectation function, y I denotes the in-phase component of a complex intermediate frequency (IF) signal output, and y Q denotes the quadrature component of said complex IF signal output.