Abstract: A method is provided for in-situ monitoring of etch uniformity during plasma etching, on the basis of the detection of interferometry patterns. The method is applicable to a reactor wherein a plasma is created in the area between the surface to be etched and a counter-surface arranged essentially parallel to the surface to be etched. The occurrence of interference patterns is detected at a location that is placed laterally with respect to the area between the surface to be etched and the counter-surface. The presence of an interference pattern at a particular wavelength is observed through the detection of oscillations of the light intensity measured by an optical detector, preferably by the standard Optical Emission Spectrometry tool of the reactor. When these oscillations are no longer detectable, non-uniformity exceeds a pre-defined limit. The counter surface is arranged such that the oscillations are detected.

Abstract: A method of determining IQ imbalance introduced on an RF multicarrier signal received via a channel on a direct conversion analog receiver is disclosed. In one embodiment, the method comprises i) receiving a training signal on the receiver, ii) demodulating the training signal on the receiver, iii) estimating a first frequency domain channel characteristic of the channel based on the demodulated training signal, iv) defining a predetermined relationship between a corrected frequency domain channel characteristic of the channel and the first channel characteristic, the predetermined relationship comprising at least one IQ imbalance parameter, and v) determining the at least one IQ imbalance parameter such that the corrected channel characteristic satisfies a channel constraint.