Vector network analyzer techniques to measure WR340 waveguide windows.

Abstract

In its fundamental form, network analysis involves the measurement of incident, reflected, and transmitted waves that travel along transmission lines. Measuring both magnitude and phase of components is important for several reasons. First, both measurements are required to fully characterize a linear network and ensure distortion-free transmission. To design effective matching networks, complex impedances must be measured. In the development of computer-aided-design (CAD) circuit simulation programs, magnitude and phase data are required for accurate models. In addition, time-domain characterization requires magnitude and phase information in order to perform an inverse Fourier transform [1]. To acquire accurate data using network analyzers special care must be taken when performing calibrations and measurements. Various calibrations and measurement techniques using a vector network analyzer (HP8510C) will be discussed. The design of a WR340 waveguide rf window will be used as an example for explaining some of these techniques. A major problem encountered when making network measurements is the need to separate the effects of the transmission medium from the device characteristics. While it is advantageous to be able to predict how a device will behave in the environment of its final application, it can be difficult to measure this way. In most microwave measurements, systematic errors are the most significant source of measurement uncertainty. Systematic errors are caused by imperfections in the test equipment and test setup. If these errors do not vary over time, they can be characterized through calibration and mathematically removed during the measurement process [2]. The process of removing systematic errors from the network analyzer S-parameter measurement is called ''measurement calibration.''