Y-factor method cannot measure the noise figure of RF module with Automatic Gain Control (AGC) because it will change the power gain of the module.A new method of noise figure measurement is presented.The method has two important features:estimation of Carrier-to-Noise Ratio (CNR) in front-end with the knowledge of error rate

thus the effect due to the inconstant amplitude versus frequency characteristic over the measurement bandwidth can be avoided;almost constant total power of signal and noise at input of AGC and constant gain of AGC during the measurement

hence the noise figure of RF module with AGC circuit can be measured accurately.The effects of random error

system error

ambient temperature and measurement times on the estimation of noise figure are analyzed by theoretical derivation and numerical simulation

and the results prove the validity of the method.The research result has been applied to the satellite navigation and positioning System.