Abstract
Analog-to-digital converter (ADC) characterization is usually performed using stationary stimuli like sine waves. However, the use of a non-stationary stimulus, besides providing testing conditions closer to those found in real applications, can lead to interesting improvements in ADC testing speed, This kind of signal needs proper processing techniques in order to extract useful information. In this paper we propose the use of joint time-frequency analysis (JTFA) for this purpose. The basic principles of the technique, and how it can be used in ADC testing are presented. in particular, a method for characterising an ADC on its entire bandwidth using a single stimulus is described.

Abstract
We have flattened the gain spectrum of a commercial Erbium-doped fibre amplifier, obtaining a curve with approximately 3 dB of ripple, from 1524 nm to 1551 nm, using long-period fibre gratings as equalising optical filters. The fabrication principle of the long-period fibre grating is based on the electric arc technique.

Abstract
Recent research in high-quality audio coding seeks not only improved coding gains but also new functionalities, such as easy semantic access to compressed audio material and audio modification in the compressed domain. These objectives imply the decomposition of the audio signal into several components of specific semantic value, such as sinusoidal components, that take advantage of selective coding and parametrization tools. In this paper we presume an MDCT based audio coding environment and present a new technique combining spectral envelope normalization with accurate subtraction of sinusoidal components in the MDCT frequency domain. It is shown how a parametrization of L stationary sinusoids in the complex ODFT spectrum can lead to the effective subtraction in the real MDCT spectrum, of 3L spectral lines. A demonstration of the implementation of the technique is available on the Internet.

Abstract
This paper addresses the extraction of parametric information in an audio coder that uses the MDCT filter bank. The computation of the filter bank is reformulated as a function of the Odd-DFT, in order to allow the estimation of the frequency, the phase and the magnitude of stationary sinusoids. Closed expression delivering accurate estimates are derived and explained, and their implementation and accuracy are illustrated in a Web page that includes a demonstration Matlab M-file.

Abstract
A method for characterizing modulators is described which can be built in large integrated circuits or systems-on-chip. The method can be used to measure gain and phase, as well as, total harmonic distortion and signal to noise and harmonic distortion ratio parameters. It is prone to be built in circuit, when computational resources such as digital signal processors or re-programmable logic are available, but can also be used in computer simulations making it easier to compare expected with measured performances.

Abstract
In this paper an alternative technique for differential gain and phase testing of video ADCs based on the use of joint time-frequency analysis is presented. This technique can lead to a significant improvement in ADC testing time and in the amount of information provided by these specific tests.