Fabrication of lightweight targets for radar measurements

Abstract

ance connected to terminals of negative resistance. I 2 -r , -2 X Fig. 2-Wes equivalent circuit of Fig. 1. R I ' E i -< Fig. + -s e r i e s model of tunnel diode amplifier. G =(equal source and load impedances yield maximum gain for a given bandwidths).The gain a t wo is 2Ro ' Go = ( z R , r i i a ; > In order to calculate the bandwidth, we will make the assumption that (cw-l/LW)' <<g' for all frequencies of interest. Under these circumstances the 3 dB bandwidth is given by all frequencies. The approximation involved in the analysis, namelyis certainly true for moderate bandwidths and for center frequencies ( W O ) approaching the original cutoff frequency of the diode. If, since the effect of r, is entirely removed, the load and source impedances could also be connected to the terminals 34 of the diode, then (GI/*l)B =g/c.In practice, if access can be gained to the terminals 34 of the diode in microwave circuits, then the actual performance obtained should lie somewhere between the case where no access is obtained to the 34 terminals for resistive loading, and the case where complete access is obtained. However, the main feature brought out by the analysis is that operation is possible with improved performance at frequencies a p proaching the cutoff frequency. The analysis, as given, is also valid for narrow bandwidths a t frequencies above cutoff, and it is probable that an exact analysis would yield the same results for any frequency of operation. Experimental verification of the effect of mounting the diode, as described by Ishii and Hoffins,',' on amplifier performance is now required.

Guiding Canada's Girls Toward the Empire

“…2 Volunteer reform groups across Canada and the United States, such as the Hull House Reformers in Chicago, a group of White middle class volunteers, attempted to address the ills of urban life in the late 19th and early-20th centuries through education and youth programs, aimed at working class and immigrant communities. 3 Urban reformers offered free services for their working class communities and argued that as populations in urban centres grew, so did vices such as alcoholism, gambling, and prostitution. 4 Reformers stressed that unmarried urban girls were especially at risk of falling into a life of immorality and promiscuity, because they had access to the vices of the cities and the freedom to fraternize with young men.…”