Calibration method performing spectrum analysis upon test signal and associated apparatus for communication system

Abstract

A calibration method for calibrating a communication system includes: generating a test signal at a transmitter; configuring at least one calibration coefficient at the transmitter; configuring at least one calibration coefficient at the receiver; transmitting the test signal to a receiver via the calibration coefficient; performing a spectrum analysis upon the test signal received by the receiver to generate a spectrum analysis result; and adjusting the calibration coefficient according to the spectrum analysis result to calibrate the transmitter. In addition, a calibration method is also provided for calibrating a receiver of a communication system, and related calibration apparatuses are further provided.

What is claimed is: 
     
       1. A calibration method for a communication system, comprising:
 generating a test signal at a transmitter; 
 configuring at least one calibration coefficient at the transmitter; 
 transmitting the test signal from the transmitter to a receiver via the at least one calibration coefficient; 
 performing a spectrum analysis upon the test signal received by the receiver to generate a spectrum analysis result; 
 adjusting the test signal according to the spectrum analysis result; and 
 adjusting the at least one calibration coefficient according to the spectrum analysis result in order to calibrate the transmitter; 
 wherein when the spectrum analysis result indicates a power of the received test signal is less than a predetermined power, the transmitter is notified to increase the power of the test signal; and when the spectrum analysis result indicates a plurality of harmonic powers of the test signal are higher than the background noise, the transmitter is notified to decrease the power of the test signal. 
 
     
     
       2. The calibration method of  claim 1 , wherein the transmitter and the receiver perform a Quadrature Amplitude Modulation (QAM). 
     
     
       3. The calibration method of  claim 1 , wherein the at least one calibration coefficient includes at least a first coefficient and a second coefficient, the first coefficient being used for calibrating an in-phase signal path, and the second coefficient being used for calibrating a quadrature-phase signal path. 
     
     
       4. The calibration method of  claim 1 , wherein the step of transmitting the test signal from the transmitter to the receiver via the at least one calibration coefficient comprises:
 performing self-mixing upon the test signal which is transmitted by the transmitter and passes through the at least one calibration coefficient but does not pass through a power amplifier, to generate a self-mixing output; and 
 feeding the self-mixing output to the receiver without passing through a low-noise amplifier and a down-converter of the receiver. 
 
     
     
       5. The calibration method of  claim 1 , wherein the step of transmitting the test signal to the receiver via the at least one calibration coefficient comprises:
 performing self-mixing upon the test signal which is transmitted by the transmitter and passes through the at least one calibration coefficient and a power amplifier, to generate a self-mixing output; and 
 feeding the self-mixing output to the receiver without passing through a low-noise amplifier and a down-converter of the receiver. 
 
     
     
       6. The calibration method of  claim 5 , wherein a low-noise amplifier of the receiver switches between different gains for respectively calibrating corresponding paths. 
     
     
       7. The calibration method of  claim 3 , wherein the step of adjusting the at least one calibration coefficient of the transmitter according to the spectrum analysis result comprises:
 changing the first coefficient on basis of a specific step, to derive a relative minima of an image signal of the test signal. 
 
     
     
       8. The calibration method of  claim 3 , wherein the step of adjusting the at least one calibration coefficient of the transmitter according to the spectrum analysis result comprises:
 changing the second coefficient on basis of a specific step, to derive a relative minima of an image signal of the test signal. 
 
     
     
       9. The calibration method of  claim 1 , which is performed when the transmitter is activated. 
     
     
       10. The calibration method of  claim 1 , which is performed when the difference between a current temperature measured at the transmitter and a predetermined temperature exceeds a predetermined temperature difference. 
     
     
       11. The calibration method of  claim 1 , which is performed when the channel currently used by the transmitter alters. 
     
     
       12. The calibration method of  claim 1 , wherein the spectrum analysis is estimation of the power spectrum density. 
     
     
       13. A calibration method for a communication system, comprising:
 generating a test signal at a transmitter; 
 configuring at least one calibration coefficient at a receiver; 
 transmitting the test signal from the transmitter to the receiver via the at least one calibration coefficient; 
 performing a spectrum analysis upon the test signal received by the receiver to generate a spectrum analysis result; and 
 adjusting the at least one calibration coefficient according to the spectrum analysis result to calibrate the receiver; 
 before adjusting the at least one calibration coefficient of the transmitter according to the spectrum analysis result, adjusting the test signal according to the spectrum analysis result; 
 wherein when the spectrum analysis result indicates a power of the received test signal is less than a predetermined power, the transmitter is notified to increase the power of the test signal; and when the spectrum analysis result indicates a plurality of harmonic powers of the test signal are higher than the background noise, the transmitter is notified to decrease the power of the test signal. 
 
     
     
       14. The calibration method of  claim 13 , wherein the transmitter and the receiver perform a Quadrature Amplitude Modulation (QAM). 
     
     
       15. The calibration method of  claim 13 , wherein the at least one calibration coefficient includes at least a first coefficient and a second coefficient, the first coefficient is used to calibrate an in-phase signal path, and the second coefficient is used to calibrate a quadrature-phase signal path. 
     
     
       16. The calibration method of  claim 13 , wherein the step of transmitting the test signal from the transmitter to the receiver via the at least one calibration coefficient comprises:
 coupling the test signal transmitted from the transmitter to the receiver, wherein the test signal passes through the at least one calibration coefficient. 
 
     
     
       17. The calibration method of  claim 13 , wherein a calibration coefficient of the transmitter has been calibrated. 
     
     
       18. The calibration method of  claim 15 , wherein a low-noise amplifier of the receiver switches between different gains for respectively calibrating corresponding paths. 
     
     
       19. The calibration method of  claim 15 , wherein the step of adjusting the at least one calibration coefficient of the transmitter according to the spectrum analysis result comprises:
 changing the first coefficient on basis of a specific step, so as to derive a relative minima of an image signal of the test signal. 
 
     
     
       20. The calibration method of  claim 15 , wherein the step of adjusting the at least one calibration coefficient of the transmitter according to the spectrum analysis result comprises:
 changing the second coefficient on basis of a specific step, so as to derive a relative minima of an image signal of the test signal. 
 
     
     
       21. The calibration method of  claim 13 , which is performed when the transmitter is activated. 
     
     
       22. The calibration method of  claim 13 , which is performed when the difference between a current temperature measured at the transmitter and a predetermined temperature exceeds a predetermined temperature difference. 
     
     
       23. The calibration method of  claim 13 , which is performed when the channel currently used by the transmitter alters. 
     
     
       24. The calibration method of  claim 13 , wherein the spectrum analysis is estimation of the power spectrum density. 
     
     
       25. A calibration apparatus for a communication system, comprising:
 a transmitter; 
 a test signal generator, arranged for generating a test signal at the transmitter; 
 a receiver, coupled to the transmitter; 
 a calibration coefficient configuring unit, arranged for configuring at least one calibration coefficient at the receiver, and adjusting the at least one calibration coefficient according to the spectrum analysis result; and 
 a spectrum analysis unit, arranged for performing a spectrum analysis upon the test signal received by the receiver to generate a spectrum analysis result; 
 wherein the at least one calibration coefficient includes at least a first coefficient and a second coefficient, the first coefficient is used to calibrate an in-phase signal path, and the second coefficient is used to calibrate a quadrature-phase signal path, and the calibration coefficient configuring unit changes the first coefficient or the second coefficient on basis of a specific step, so as to derive a relative minima of an image signal of the test signal. 
 
     
     
       26. A calibration method for a communication system, comprising:
 generating a test signal at a transmitter; 
 configuring at least one calibration coefficient at the transmitter; 
 transmitting the test signal from the transmitter to a receiver via the at least one calibration coefficient; 
 performing a spectrum analysis upon the test signal received by the receiver to generate a spectrum analysis result; and 
 adjusting the at least one calibration coefficient according to the spectrum analysis result in order to calibrate the transmitter; 
 wherein the at least one calibration coefficient includes at least a first coefficient and a second coefficient, the first coefficient being used for calibrating an in-phase signal path, and the second coefficient being used for calibrating a quadrature-phase signal path; and the step of adjusting the calibration coefficient of the transmitter according to the spectrum analysis result comprises:
 changing the first coefficient on basis of a specific step, to derive a relative minima of an image signal of the test signal; and 
 changing the second coefficient on basis of a specific step, to derive a relative minima of an image signal of the test signal. 
 
 
     
     
       27. The calibration method of  claim 26 , wherein the step of transmitting the test signal to the receiver via the at least one calibration coefficient comprises:
 performing self-mixing upon the test signal which is transmitted by the transmitter and passes through the at least one calibration coefficient and a power amplifier, to generate a self-mixing output; and 
 feeding the self-mixing output to the receiver without passing through a low-noise amplifier and a down-converter of the receiver.