A pl asma s imulation techn iqu e has been d eve loped which ca n be used to s t udy the effec ts of homoge neou s or inh omoge neo us plasma s hea th on the radia ti on pa tt ern de te ri ora ti on a nd input im · peda nce of microwave antennas. A tan k has been des igned and cons tru cted for us e in the s imulation tec hn iq1le whi ch ca n re produ ce by mea ns of real di e lectri c mate ri als the dielectric co ns tant e nco unt· e red in plasma cove red a nte nn a re earc h.Th e radia ti on patte rn s and the input im pedances of an a nnular s lot and a thin and long rec tang ular s lot have been s uccessfull y measured in th e prese nce of a s imul ated loss less, homoge neo us, and iso· tropic plasma laye r of varie d thi c kn ess . Co mpariso n with the ava il ab le theore ti ca l d a ta indi cates a ge nerally good agreeme nt, alth ough so me differe nces e xist. In the case of th e radiation patterns th ese differences are attributed to the finit e di s tan ce be twee n t he radi ator and the rece ivin g a nt e nna on one hand a nd th e inh e re nt inaccu racy of th e saddle point method of int egrati on in ce rt a in reg ions on th e ot he r ha nd.

Hardcopy. t icrof.iche-GEORGE TYRAS THE UNIVERSITY OF ARIZO r J '

In the case of semi-infinite and finite-extent homogeneous plasma sheaths, the radiation pattern and the impedance characteristic are investigated with regard to the geometry of the discontinuity and its proximity to the slot antenna. It is found that the radiation pattern is unaffected by the discontinuity as long as the ratio of the distance between the source and the discontinuity to the sheath thickness is of the order of 20 or greater. When the sheath is made finite in extents with a discontinuity on each side of the slot, the resulting pattern is seen to be a superposition of the effects of each discontinuity acting separately. The input impedance of the slot exhibits only small variations when the ratio of the discontinuity separation to the sheath thickness is of the order of 4 or greater. For smaller separations, the impedance exhibits significant variations, strongly dependent on the geometry of the discontinuity. The effects produced Ly inhomogeneities are found to be similar to those of a homogeneous sheath with a certain equivalent dielectric constant.For both the homogeneous and inhomogeneous sheaths, favorable comparison with the available theory is obtained.

No abstract