Ultimate sensitivity of heterodyne spectrometers
- 39 Downloads
Low noise heterodyne receivers are now used in a large variety of instruments such as radiotelescopes, far infrared laser side bands spectrometers, supersonic nozzle beams Fourier transform spectrometers, lidars or plasmas diagnostics devices. Numerous papers have been devoted to the analysis of heterodyne receivers in the attempt to reach ultimate performances. These previous papers usually retain the restrictive hypothesis of vanishingly small signal powers. Such a condition occurs only in a restrictive number of applications, radioastronomic systems being probably among the most representative examples. Spectroscopic instruments operate usually in a different regime. The signal to be detected consists of a small variation in the source power. The absolute value of this source power largely depends on the available technology in the spectral range of interest. The purpose of this paper is to analyze the behavior of heterodyne detection in the general case. The results apply to a large category of systems including spectroscopic instruments. The influence of crucial parameters such as source power and predetection bandwidth is analysed in details. The theory is experimentally tested on an example of ultra low noise receiver designed for far infrared laser side bands spectroscopy. Some numerical calculations are proposed, illustrating methods for an optimal sizing of receiver's predetection bandwidth and the estimation of ultimate sensitivity of spectrometers.
KeywordsSource Power Lidar Restrictive Number Plasma Diagnostics Noise Receiver
Unable to display preview. Download preview PDF.
- P. VERHOEVE, E. ZWART, M. VERSLUIS, M. DRABBELS, J. J. TERMEULEN, W. L. MEERTS, A. DYMANUS, and D.B. McLAY Rev. Sci. Instrum.,61, 1612, (1990)Google Scholar
- G. A. BLAKE, K. B. LAUGHLIN, R. C. COHEN, K. L. BUSAROW, D.-H. GWO, C. A. SCHMUTTENMAER, D. W. STEYERT, and R. J. SAYKALLY Rev. Sci. Instrum.,62, 1701, (1991)Google Scholar
- G. SCHWAAB Ph. D. Thesis, Universität Bonn, (1990)Google Scholar
- B.M. OLIVER Proc. IEEE,53, 436, (1965)Google Scholar
- T.G. BLANEY Space Sci. Rev.,17, 691, (1975)Google Scholar
- A.I. HARRIS "Coherent and incoherent detection at submillimeter and farinfrared wavelengths" Proc. of the winter workshop held at les Houches, France, (1990, Nova Science Publishers - New - York, (1991)Google Scholar
- D. BOUCHER, R. BOCQUET and W. CHEN 16th Int. Conf. on IR & MM Waves, Lausanne, Switzerland, SPIE1576, 240, (1991)Google Scholar