Quadrature demodulator for compensating for gain and phase imbalances between in-phase and quadrature-phase components

• US 7,010,059 B2
• Filed: 04/02/2003
• Issued: 03/07/2006
• Est. Priority Date: 10/07/2002
• Status: Expired due to Fees

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Nae-Soo, Oh, Deock-Gil, Kim, Young-Wan, Song, Yun-Jeong
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US10/406,094
• Publication Number:
  US 20040066861A1
• Time in Patent Office: 1,070 Days
• Field of Search: 375/316, 375/326, 375/345, 375/261, 375/340, 375/329, 375/332, 375/304, 375/279, 375/280, 375/355, 455/182.1, 4551921-1923, 455/232.1, 455/234.1, 4551931-1933, 329/304
• US Class Current: 375/316
• CPC Class Codes: H04L 2027/0028 at passband only
• CPC Class Codes: H04L 2027/0057 quadrature phase
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop
• CPC Class Codes: H04L 27/3809 Amplitude regulation arrangements

Abstract

Disclosed is a quadrature demodulator for high-speed wireless communication, which comprises: an A/D converter for converting received signals into digital signals; a signal recovery unit for recovering carriers and symbol timing from the signals converted by the A/D converter; a decision unit for detecting recovered signals output by the signal recovery unit, and performing a decision process on them; an I/Q gain imbalance detector for detecting gain imbalances of the I and Q-phase components from the recovered signals, and outputting an I/Q gain compensation value for compensating for the gain imbalances; and an I/Q gain compensator, provided between the A/D converter and the signal recovery unit, for reflecting the I/Q gain compensation value output by the I/Q gain imbalance detector to the received signals.

Claims

1. A quadrature demodulator for high-speed wireless communication, comprising:

an A/D converter for converting a received signals into a digital signal;

a signal recovery unit for recovering carriers and symbol timing from the signal converted by the A/D converter and outputting a recovered signal;

a decision unit for detecting the recovered signal output by the signal recovery unit, and performing a decision process on the recovered signal;

an I/Q gain imbalance detector for detecting gain imbalances of I and Q-phase components from the recovered signal, wherein the I/Q gain imbalance detector computes a ratio of the I and Q-phase components to generate an output of an I/Q gain compensation value for compensating for the gain imbalances; and

an I/Q gain compensator, disposed between the A/D converter and the signal recovery unit, for reflecting the I/Q gain compensation value output by the I/Q gain imbalance detector to the received signal.

2. The quadrature demodulator of claim 1, wherein the I/Q gain imbalance detector comprises:

an absolute value operator for performing an absolute value operation on the respective I-phase and the Q-phase components output by the signal recovery unit;

a mean value operator for performing a mean value operation on the respective I-phase and the Q-phase components output by the absolute value operator; and

a division operator for performing a division operation for dividing an I-phase mean value output provided by the mean value operator by a Q-phase mean value output, and outputting a result to the I/Q gain compensator.

3. A quadrature demodulator for high-speed wireless communication, comprising:

an A/D converter for converting a received signal into a digital signal;

a signal recovery unit for recovering carriers and symbol timing from the signal converted by the A/D converter and outputting a recovered signal;

a decision unit for detecting the recovered signal output by the signal recovery unit, and performing a decision process on the recovered signal;

an I/Q phase imbalance detector for applying a signal value difference between the recovered signal and a signal output by the decision unit to the respective I and Q-phase components by performing an AGC (automatic gain control) operation according to a code of the recovered signal to detect phase imbalances between the I and Q-phase components, and outputting an I/Q phase compensation value for compensating for the phase imbalances; and

an I/Q phase compensator, provided between the A/D converter and the signal recovery unit, for reflecting the I/Q phase compensation value output by the I/Q phase imbalance detector to the received signal.

4. The quadrature demodulator of claim 3, wherein the I/Q phase imbalance detector independently performs the AGC (automatic gain control) operation according to the code of the recovered signal to recognize the phase imbalance between the I-phase and the Q-phase components as a signal value difference format depending on the code of the recovered signal.

5. The quadrature demodulator of claim 3, wherein the I/Q phase imbalance detector comprises:

a first code determiner for determining the code for the recovered signal and outputting a first selection signal;

a demultiplexer for determining an output position of the recovered signal according to the first selection signal and outputting the output position;

an automatic gain controller for performing the AGC operation on the signal output by the demultiplexer according to the code of the recovered signal;

a second code determiner for determining the code of the received signal and outputting a second selection signal;

a time delay unit for delaying the second selection signal by a time when the automatic gain controller performs the AGC operation; and

a multiplexer for combining the signals output from the automatic gain controller, multiplexing the signals output from the automatic gain controller according to the signal output by the time delay unit, and outputting result signals to the I/Q phase compensator.

6. The quadrature demodulator of claim 5, wherein the code of the recovered signal has four categories according to the code of the I and Q phases, and the demultiplexer outputs the recovered signal as one of four outputs according to the first selection signal, and the automatic gain controller comprises four AGC modules for respectively performing AGC operations on the four outputs output by the demultiplexer.

7. The quadrature demodulator of claim 3, wherein the I/Q phase compensator comprises:

a time delay unit for delaying and outputting the time of the recovered signal; and

a multiplier for multiplying the signal output from the time delay unit by an I/Q phase compensation value output from the I/Q phase imbalance detector.

8. A quadrature demodulator for high-speed wireless communication, comprising:

an A/D converter for converting a received signal into a digital signal;

a signal recovery unit for recovering carriers and symbol timing from the signal converted by the AID converter and outputting a recovered signal;

a decision unit for detecting and determining the recovered signal output by the signal recovery unit;

an I/Q gain imbalance detector for detecting gain imbalances of the I and Q-phase components from the recovered signal, wherein the I/Q gain imbalance detector computes a ratio of the I and Q-phase components to generate an output of an I/Q gain compensation value for compensating for the gain imbalance;

an I/Q phase imbalance detector for applying a signal value difference between the recovered signal and a signal output by the decision unit to the respective I and Q-phase components according to a code of the recovered signal to detect phase imbalances between the I and Q-phase components, and outputting an I/Q phase compensation value for compensating for the phase imbalances;

an I/Q gain compensator, provided between the A/D converter and the signal recovery unit, for reflecting the I/Q gain compensation value output by the I/Q gain imbalance detector to the received signal; and

an I/Q phase compensator, provided between the I/Q gain compensator and the signal recovery unit, for reflecting the I/Q phase compensation value output by the I/Q phase imbalance detector to the received signal.