Low SNR simulations comparing the minimum-free-energy (MFE) spectral estimation algorithms of Silverstein and Pimbley (1988) with the reduced rank modified covariance eigenanalysis algorithm of Tufts and Kumaresan (1982) have been performed. Two different MFE algorithms are discussed and simulated. The results of the statistical analyses demonstrate that both MFE algorithms are robust, low-variance spectral estimators capable of making reliable frequency estimations of closely spaced sources at very low SNRs, from single snapshot data. They are applicable to the general domain of spectral estimation, while the eigenanalysis algorithms are primarily restricted to line spectra frequency estimation. Nonetheless, for simulations of closely spaced line spectra at low SNRs, the MFE estimations are considerably more robust than the Tufts-Kumaresan estimations.>

Some of the trends in integrated circuit process development are described. The motivations or technical reasons for this activity are discussed. This effort will continue to develop the downsizing that increases functional density and performance. Limiting factors are examined and new technical developments that could enable CMOS density to be comparable with NMOS density are explored. Various isolation techniques are described and the influence on performance of well profiles and doping concentrations are examined. These trends have a beating on the choice of gate electrode materials. Reliability factors governing the gate dielectric thickness are discussed briefly. MOSFET diode capacitance is shown to be the predominant limiting factor at the device level. Methodologies that could be used to reduce device parasitics are considered in detail. Device scaling below 1-µm calls for changes in contact metallization techniques. Trends in metallization technology and the various methods of fabricating multilevel interconnections when the via sizes become very small are described. The processing methods being investigated to overcome device limitations are examined and compared. In some cases, the present technical difficulties of these methods are discussed. The general conclusion of this work is that "downsizing" will continue, but advances will be more dependent upon innovative processes and device research, whereas in the past, scaling rules were adequate and progress was evolutionary.