Multi-tap IQ imbalance estimation and correction circuit and method

Patent metadata

Field	Value
Publication number	US-8976914-B2
Application number	US-201213560020-A
Country	US
Kind code	B2
Filing date	Jul 27, 2012
Priority date	Jul 27, 2012
Publication date	Mar 10, 2015
Grant date	Mar 10, 2015

Abstract

A system for correcting gain imbalance and phase imbalance between first (I OUT ) and second (Q OUT ) signals which are 90° out of phase, including circuitry for estimating the phase mismatch (φ) and gain mismatch (Δ) between the first signal and the second signal signals in a plurality of frequency bands. An inverse fast Fourier transform is performed on each of a number of arrays of the phase mismatch estimates and the gain mismatch estimates to generate correction filter coefficients (h[N]) for a N tap correction filter. The N tap correction filter filters an uncorrected value of the second signal to generate a corrected value of the second signal.

First claim

What is claimed is:

1. A system for correcting gain imbalance and phase imbalance between first and second signals which are 90° out of phase, the system comprising:
(a) circuitry for estimating a phase mismatch and gain mismatch between the first signal and the second signal at a plurality of frequency bands;
(b) circuitry for performing an inverse fast Fourier transform (IFFT) on each of a number of arrays of the phase mismatch estimates and the gain mismatch estimates to generate correction filter coefficients for a N tap correction filter, N is a positive non-zero integer; and
(c) wherein the N tap correction filter filters an uncorrected value of the second signal to generate a corrected value of the second signal,
(d) circuitry for splitting each of the first and second signals into a predetermined number of frequency bands to provide a plurality of in-phase and quadrature-phase signals in the frequency bands, respectively, and
(e) the circuitry for estimating comprising circuitry for successively producing a phase mismatch estimate and a gain mismatch estimate corresponding to successive frequency bands, respectively, on the basis of samples of the in-phase and quadrature-phase signals in the frequency bands,
wherein the splitting circuitry includes
a bank of filters for splitting each of the first and second signals into the predetermined number of frequency bands, and
wherein the estimating circuitry operates to successively produce a plurality of pairs of mismatch estimates corresponding to the plurality of successive frequency bands, respectively, on the basis of samples of in-phase and quadrature-phase signal values generated by the bank of filters,
each pair including a phase mismatch estimate and a gain mismatch estimate, and
circuit for DC offset correction including a DC phase correction circuit including a mixer for mixing the first signal with a DC mismatch adjustment value and an adder for adding an output of the mixer to the second signal to generate the uncorrected value of the second signal such that the N tap filter essentially eliminates the gain imbalance and the phase imbalance between the first and second signals across all of the frequency bands.

2. The system of claim 1 wherein the estimating circuitry performs a function of distinguishing filter delay mismatches and mixer phase mismatches of the first signal and the second signal at the plurality of frequency bands.

3. The system of claim 1 wherein the phase mismatch estimates are determined in accordance with the equation

sin
⁡

(
φ
)

=

I
kc

⁢

Q
kc

+

I
ks

⁢

Q
ks

Q
ks
2

+

Q
kc
2

,

where φ is a phase mismatch estimate, I kc is a cosine-related in-phase signal in a predetermined frequency band produced by the bank of filters, Q kc is a cosine-related quadrature signal in the predetermined frequency band produced by the bank of filters, I ks is a sine-related in- phase signal in a predetermined frequency band produced by the bank of filters, and Q ks is a sine-related quadrature signal in the predetermined frequency band produced by the bank of filters.

4. The system of claim 1 wherein the gain mismatch estimates are determined in accordance with equation

2
⁢

⁢
Δ

=

∑

I
ks
2

-

∑

Q
ks
2

+

∑

I
kc
2

-

∑

Q
kc
2

∑

(

Q
ks
2

+

Q
kc
2

)

,

where Δ is a gain mismatch estimate, I kc is a cosine-related in-phase signal in a predetermined frequency band produced by the bank of filters, Q ks is a cosine-related quadrature signal in the predetermined frequency band produced by the bank of filters, I ks is a sine-related in-phase signal in the predetermined frequency band produced by the bank of filters, and Q ks is a sine-related quadrature signal in the predetermined frequency band produced by the bank of filters.

5. The system of claim 1 wherein the N tap filter includes a finite impulse response filter (FIR).

6. The system of claim 1 wherein the number of arrays of the phase mismatch estimates and gain mismatch estimates represent a mismatch estimate frequency response of an In-phase and Quandrature (IQ) system through which the first and second signals pass.

7. The system of claim 1 wherein the bank of filters includes a plurality of mixing and filtering circuits for mixing the first signal with a plurality of first reference signals and for mixing the second signal with a plurality of second reference signals which are shifted 90° relative to a corresponding first reference signal, respectively, and also includes low pass filtering outputs of the various mixed signals to provide the samples of the in-phase and quadrature-phase signal values generated by the bank of filters.

8. The system of claim 1 wherein the number of arrays are included in a primary feedback loop also including the bank of filters, the estimating ci

Assignees

• Viswanathan Nagarajan
• Texas Instruments Inc

Inventors

• Viswanathan Nagarajan

Classifications

• H03D3/009 Primary

  Compensating quadrature phase or amplitude imbalances · CPC title

• H04L2027/0016

  Stabilisation of local oscillators · CPC title