A Method for Improving Modulation in NMR Using Harmonic Analysis

✍ Scribed by M. Izquierdo; J.M. Böhlen; H. Reutenauer; M. Décorps

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 196 KB
• Volume: 119
• Category: Article
• ISSN: 1064-1858
• DOI: 10.1006/jmra.1996.0045

✦ Synopsis

Modulated pulses designed for NMR often suffer from imperfecperformance of an RF modulator might easily be carried out tions arising from the pulse-shape modulator. This produces a noniusing harmonic analysis. The interest of such a method was deal magnetization distribution which may lead to the failure of the recently recalled in this journal (10). In this paper, we deexperiment. This paper describes how to perform quantitative analyscribe how to perform quantitative analysis of the imperfecsis of the imperfections of the RF modulator by harmonic analysis tions of the pulse-shape modulator by harmonic analysis of of the output wave form, using the NMR spectrometer itself. From the output wave form, using the NMR spectrometer itself.

these measurements, an analytical form of the transfer function is

We then propose a very simple and accurate method to reproobtained. The wave form which compensates for the distortion is then duce the desired modulation shape accurately. We demoncalculated by an iterative process. To demonstrate the performance strate the method with a transmitter equipped with a singleof the method, it was applied to representative pulse shapes. The side-band modulator, although its use can easily be generalcomparison of the experimental frequency profiles, obtained with and without correction, with the simulated profiles illustrates the ized for modulation based on other principles. reliability of the method.