Methods of weak signal detection in microwave power measurement and the implementations

The common techniques used for microwave power detection was firstly introduced. Then the issues of weak signal processing in microwave average power measurement based on thermocouple and diode were fully proposed. After the principles of chopping amplification and sigma-delta ADC were discussed, the actual practical circuit was presented. Emphasis was focused on the chopper, AC amplifier, de-chopping methods and the implementation of the sigma-delta ADC circuit. The results show that the techniques of chopping amplifier and sigma-delta data acquisition system can improve the SNR remarkably. And the dynamic range for RF/microwave power measurement can be expanded down to -67 dBm.