Using digital data processing to speed up radar phase noise measurements

Amplitude modulated noise and phase noise measurements for airborne radars have traditionally been performed by converting high frequency spectrums to the video range and measuring the analog noise and spurious parameters on conventional spectrum analyzers. The disadvantage of using spectrum analyzers is that test execution time is relatively long due to the slow sweep times required for selection of narrow resolution bandwidths. Also, since sweep times are long with spectrum analyzers, transient noise and other short time interval phenomena are difficult to detect (since they are usually "averaged out" due to the slow sweep). This has prompted the development of digital signal processing techniques to speed up the execution time and increase the accuracy of measurements. This paper describes an automated and efficient system that measures AM and PM response digitally. A digitizer is used to convert the analog signal to digital, whereupon a computer is used to process the digital data for noise and spurious response. This system allows for flexibility, since the processing may be altered by merely changing the computer software.<>