Abstract: A 4-level direct conversion receiver demodulator 1 comprises an edge detector 2, a finite impulse response filter 3, an N-bit path 4, a data slicer 5 and automatic frequency control device 6. The edge detector 2 receives Limited I (LIMI) and Limited Q (LIMQ) signals on respective ones of first and second input leads 7 and 8 from a direct conversion receiver arrangement R. The edge detector 2 contains logic to provide an EDGE signal, comprising a short pulse when any edge is detected in either of the LIMI and LIMQ signals, on a line 9 and an I Lead Q (ILQ) signal, indicative of which of the LIMI and LIMQ signals has the leading phase, on a line 10 to the filter 3. The edge detector 2 thus determines both the frequency and the relative phase of the signals provided by the limited output direct conversion receiver R without the use of analogue to digital conversion circuitry. The N-bit path output 4 from the filter 3 is provided to both the data slicer 5 and to the AFC device 6.

Abstract: A method for quantitatively monitoring in situ by Raman spectrometry one or more selected constituents of a chemical composition comprises: simultaneously irradiating with a substantially monochromatic radiation source a reference material and a chemical composition containing one or more constituents, the radiation being transmitted from the source to the chemical composition by an excitation conduit connecting the source to an optical probe that interfaces with the composition; simultaneously acquiring at more than one wavelength convolved Raman spectra of the reference material and the chemical composition by means of a spectrograph, which is connected to the optical probe by a collection conduit; choosing the standard Raman spectrum of the reference material; determining the convolution function of the convolved spectra from the convolved Raman spectrum and the standard Raman spectrum of the reference material; applying the convolution function to adjust the convolved Raman spectrum of the composition to