Phase detection using AD8302 evaluation board in the superheterodyne microwave interferometer for line average plasma electron density measurements

In this paper the use of AD8302 evaluation board from analog devices for phase detection and consequently line average electron density measurement in the superheterodyne microwave interferometer is described. The phase is directly measured from this board. This method is very cheap and easy to integrate. For the measurement, signals that were obtained from the IF of both the mixers in the interferometer were fed as inputs to the evaluation board. The output was connected to an oscilloscope to capture the voltage trace. The voltage reading was then converted to phase angle by using the calibration data provided with the evaluation board. The plasma used to test the phase detection system was a microwave plasma discharge. The phase measurements were obtained very quickly without the use of a computer. These were then translated to line average electron density. The values were agreeable to published results.