A system generating compacted physical layouts from MOS transistor netlists has been developed. It uses a novel graphtheoretical placement algorithm to simultaneously maximize diffusion sharing and minimize the wiring area. The algorithm is not limited to circuits that have equal numbers of NMOS and PMOS transistors. A special-purpose router using either onelayer or two-layer metal is described. Experimental results for area efficiency and run-time performance are very promising.

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Abstract. Using a wideband chirp sounder technique, the impulse response characteristics of a 500-km meteor burst channel were investigated for the purpose of studying the fine structure of meteor trails giving rise to multipath propagation, determining the channel delay spread statistics, and examining the correlation between multipath phenomena and meteor trail duration. To date, an analysis of these data has revealed that most of the time only a single dominant path exists between the transmitter and receiver. However, when multipath conditions are encountered, many paths varying in both strength and duration may exist and can adversely affect communications. Fortunately, multipath conditions were observed in only about 30% of all echoes and, while seen in both short-and long-duration trails, were found to occur most frequently during trails of longer temporal extent. In 90% of all measurements considered, the rms delay spread was found to be less than 100 ns. By observing the temporal spreading of vertical equalization pulses received from distant commercial TV transmitters, Weitzen et al. [1984] were able to make high-resolution measurements which showed the multipath spread to be typically less than 0.7 From these results it was concluded that signaling rates of the order of 500 kbit/s could generally be used and that the adverse effects arising from multipath propagation could be mitigated by employing advanced adaptive rate modulation techniques. Weitzen et al.[1987] also conducted channel measurements at 1525