# US 7,412,222 B2 · Quadrature correction method for analog television reception using direct-conversion tuners

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- Number: US 7,412,222 B2
- Document ID: US7412222B2
- Status: Granted
- Kind: B2
- Application number: 10/441,057
- Filed: 2003-05-20
- Published: 2004-11-25
- Granted: 2008-08-12
- Earliest claimed: 2003-05-20
- Assignees: Broadcom Corporation
- Inventors: Ramon A Gomez
- Web page: https://patentgrep.com/patent/US7412222B2

## CPC

- H03D 3/009: {Compensating quadrature phase or amplitude imbalances}
- H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66)

## Abstract

A direct conversion radio frequency (RF) tuner includes a mixer generating I and Q quadrature components. A phase detection circuit generates a phase error measurement between the I quadrature component and the Q quadrature component. A phase correction circuit corrects a phase of the Q component based on the phase error measurement, and outputs a phase-corrected Q quadrature component. An I quadrature component gain control circuit receives the I quadrature component and outputting an amplitude corrected I quadrature component. A Q quadrature component gain control circuit receives the phase corrected Q quadrature component and outputs an amplitude corrected Q quadrature component.

## Claims

### Claim 1

A direct conversion radio frequency (RE) tuner for processing an input signal, comprising:
a mixer generating I and Q quadrature components;
a phase correction circuit generating a phase error measurement between the I quadrature component and the Q quadrature component, correcting a phase of the Q component based on the phase error measurement, and outputting a phase-corrected Q quadrature component;
an I quadrature component gain control circuit receiving the I quadrature component and outputting an amplitude corrected I quadrature component; and
a Q quadrature component gain control circuit receiving the phase corrected Q quadrature component and outputting an amplitude corrected Q quadrature component;
wherein respective gains of the I quadrature component gain control circuit and the Q quadrature gain control circuit are determined when the input signal includes one of a horizontal sync signal or vertical sync signal.

### Claim 2 (depends on 1)

The tuner of claim 1, wherein the phase correction circuit includes:
a first hard limiter receiving the Q quadrature component and outputting a first modified Q quadrature component;
a second hard limiter receiving the I quadrature component and outputting a first modified I quadrature component;
a phase detection circuit receiving the first modified Q quadrature component and the first modified I quadrature component and outputting an error signal;
a first loop filter filtering the error signal;
a circuit generating a product of the error signal and the I quadrature component; and
a summer receiving the Q quadrature component and the product of the error signal and the I quadrature component and outputting the phase corrected Q quadrature component.

### Claim 3 (depends on 1)

The tuner of claim 1, wherein the Q quadrature component gain control circuit includes a variable gain amplifier, and a power detection circuit and a loop filter connected to the variable gain amplifier in a feedback loop.

### Claim 4 (depends on 1)

The tuner of claim 1, wherein the I quadrature component gain control circuit includes a variable gain amplifier, and a power detection circuit and a loop filter connected to the variable gain amplifier in a feedback loop.

### Claim 5 (depends on 1)

The tuner of claim 1, wherein the I quadrature component gain control circuit outputs the amplitude corrected I quadrature component corrected relative to the phase corrected Q quadrature component.

### Claim 6 (depends on 1)

The tuner of claim 1, wherein the I quadrature component gain control circuit outputs the amplitude corrected I quadrature component corrected relative to a reference voltage; and
wherein the Q quadrature component gain control circuit outputs the amplitude corrected Q quadrature component corrected relative to the reference voltage.

### Claim 7 (depends on 1)

The tuner of claim 1, wherein the I quadrature component gain control circuit outputs the amplitude corrected I quadrature component that is corrected relative to the Q quadrature component.

### Claim 8

A direct conversion radio frequency (RF) tuner for processing an input signal, comprising:
a mixer generating I and Q quadrature components;
a phase correction circuit generating a phase error measurement between the Q quadrature component and the I quadrature component, correcting a phase of the I component based on the phase error measurement, and outputting a phase-corrected I quadrature component;
a Q quadrature component gain control circuit receiving the Q quadrature component and outputting an amplitude corrected Q quadrature component; and
an I quadrature component gain control circuit receiving the phase corrected I quadrature component and outputting an amplitude corrected I quadrature component;
wherein respective gains of the I quadrature component gain control circuit and the Q quadrature gain control circuit are determined when the input signal includes one of a horizontal sync signal or vertical sync signal.

### Claim 9 (depends on 8)

The tuner of claim 8, wherein the phase correction circuit includes:
a first hard limiter receiving the I quadrature component and outputting a first modified I quadrature component;
a second hard limiter receiving the Q quadrature component and outputting a first modified Q quadrature component;
a phase detection circuit receiving the first modified I quadrature component and the first modified Q quadrature component and outputting an error signal;
a first loop filter filtering the error signal;
a circuit generating a product of the error signal and the Q quadrature component; and
a summer receiving the I quadrature component and the product of the error signal and the Q quadrature component and outputting the phase corrected I quadrature component.

### Claim 10 (depends on 8)

The tuner of claim 8, wherein the I quadrature component gain control circuit includes a variable gain amplifier, and a power detection circuit and a loop filter connected to the variable gain amplifier in a feedback loop.

### Claim 11 (depends on 8)

The tuner of claim 8, wherein the Q quadrature component gain control circuit includes a variable gain amplifier, and a power detection circuit and a loop filter connected to the variable gain amplifier in a feedback loop.

### Claim 12 (depends on 8)

The tuner of claim 8, wherein the Q quadrature component gain control circuit outputs the amplitude corrected Q quadrature component corrected relative to the phase corrected I quadrature component.

### Claim 13 (depends on 8)

The tuner of claim 8, wherein the Q quadrature component gain control circuit outputs the amplitude corrected Q quadrature component corrected relative to a reference voltage; and
wherein the I quadrature component gain control circuit outputs the amplitude corrected I quadrature component corrected relative to the reference voltage.

### Claim 14 (depends on 8)

The tuner of claim 8, wherein the Q quadrature component gain control circuit outputs the amplitude corrected Q quadrature component that is corrected relative to the I quadrature component.

### Claim 15

A method of balancing I and Q quadrature components, comprising:
during a horizontal sync signal, adjusting an amplitude of the I quadrature component to a predetermined level using an automatic gain control circuit to generate a normalized I quadrature component;
during the horizontal sync signal, generating a phase error of the normalized I quadrature component and the Q quadrature component;
subtracting a product of the phase error and the I quadrature component from the Q quadrature component; and
during the horizontal sync signal, adjusting an amplitude of the Q quadrature component to an amplitude of the normalized I quadrature component.

### Claim 16

A method of balancing I and Q quadrature components, comprising:
during a vertical sync signal, adjusting an amplitude of the I quadrature component to a predetermined level using an automatic gain control circuit to generate a normalized I quadrature component;
during the vertical sync signal, generating a phase error of the normalized I quadrature component and the Q quadrature component;
subtracting a product of the phase error and the I quadrature component from the Q quadrature component; and
during the vertical sync signal, adjusting an amplitude of the Q quadrature component to an amplitude of the normalized I quadrature component.

### Claim 17

A direct conversion radio frequency (RF) tuner for processing an input signal, comprising:
a mixer generating I and Q quadrature components;
a phase correction circuit generating a phase error measurement between the I quadrature component and the Q quadrature component, correcting a phase of the Q component based on the phase error measurement, and outputting a phase-corrected Q quadrature component;
an I quadrature component gain control circuit receiving the I quadrature component and outputting an amplitude corrected I quadrature component; and
a Q quadrature component gain control circuit receiving the phase corrected Q quadrature component and outputting an amplitude corrected Q quadrature component;
wherein the phase correction circuit includes,
a first hard limiter receiving the Q quadrature component and outputting a first modified Q quadrature component;
a second hard limiter receiving the I quadrature component and outputting a first modified I quadrature component;
a phase detection circuit receiving the first modified Q quadrature component and the first modified I quadrature component and outputting an error signal;
a first loop filter filtering the error signal;
a circuit generating a product of the error signal and the I quadrature component; and
a summer receiving the Q quadrature component and the product of the error signal and the I quadrature component and outputting the phase corrected Q quadrature component.

### Claim 18

A direct conversion radio frequency (RF) tuner for processing an input signal, comprising:
a mixer generating I and Q quadrature components;
a phase correction circuit generating a phase error measurement between the Q quadrature component and the I quadrature component, correcting a phase of the I component based on the phase error measurement, and outputting a phase-corrected I quadrature component;
a Q quadrature component gain control circuit receiving the Q quadrature component and outputting an amplitude corrected Q quadrature component;
an I quadrature component gain control circuit receiving the phase corrected I quadrature component and outputting an amplitude corrected I quadrature component;
wherein the phase correction circuit includes,
a first hard limiter receiving the I quadrature component and outputting a first modified I quadrature component;
a second hard limiter receiving the Q quadrature component and outputting a first modified Q quadrature component;
a phase detection circuit receiving the first modified I quadrature component and the first modified Q quadrature component and outputting an error signal;
a first loop filter filtering the error signal;
a circuit generating a product of the error signal and the Q quadrature component; and
a summer receiving the I quadrature component and the product of the error signal and the Q quadrature component and outputting the phase corrected I quadrature component.