Noise is a part of every electronic device and circuit. Electrons do not travel in perfectly controlled paths, and these random electron motions, along with the effects of temperature, result in a certain level of noise. Of course, noise can spring from outside sources, including the radiated electromagnetic forms from power lines that anyone with a car radio has suffered through while driving under or near those power lines. Noise can't be avoided, but it can be characterized. Knowing the level of noise in a device or circuit helps to work around it in a final design, and Agilent Technologies has made great strides recently in improving the quality of the measurements used to characterize noise.
Agilent author David Ballo has detailed these advances in noise-figure measurements in the latest addition to the company's Measurement Solution Series of educational White Papers. Entitled "Making Source-Corrected Noise-Figure Measurements," the four-page White Paper appears in both the September issue of Microwaves & RF as well as on the white-paper section of the magazine's website at www.mwrf.com. It discusses the use of an Agilent PNA-X vector network analyzer with an ECal calibration module. By essentially using the ECal module as an impedance tuner, and applying vector error correction, it is possible to use the analyzer for making source- corrected noise-figure measurements.
Since the impedance match at the source of a device under test (DUT) is critical to the accuracy of noise-figure measurements, this new approach can deliver accuracy that exceeds even dedicated noise-figure measurement receivers. It can't get rid of the noise, but knowing how much noise is there certainly helps in the overall design process. For more information, visit the white paper section of www.mwrf.com.
by Jack Browne, MWRF Technical Director